A Protocol to Acquire Infant Heart Rate Variability in the Rohingya Camps and Surrounding Communities in Cox's Bazar, Bangladesh

A Protocol to Acquire Infant Heart Rate Variability in the Rohingya Camps and Surrounding Communities in Cox's Bazar, Bangladesh | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 27 February 2025 V1 Latest version Share on A Protocol to Acquire Infant Heart Rate Variability in the Rohingya Camps and Surrounding Communities in Cox's Bazar, Bangladesh Authors : Elisa Ugarte 0000-0003-1803-9619 [email protected] , Paul Hastings , Eamam Hossain , Md Shakil Ahamed , Rahim AK , Mahbub Elahi , Md Sajjadur Rahman , Fahmida Tofail , and Alice J. Wuermli Authors Info & Affiliations https://doi.org/10.22541/au.174065820.02352697/v1 380 views 86 downloads Contents Abstract Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract Regulation of autonomic arousal during infancy is critical for the development of self-regulation, socioemotional development and cognitive functioning. High frequency heart rate variability (HF-HRV), a key indicator of parasympathetic nervous system function, supports physiological regulation and emerging behaviors that foster social engagement during this critical developmental period. However, research on HF-HRV has largely been confined to controlled settings with highly resourced populations, limiting its applicability to culturally and contextually diverse populations. This study presents a protocol for collecting HF-HRV data from one-month-old infants in remote and low-resource field contexts, specifically, the Rohingya camps and surrounding host communities in Cox’s Bazar, Bangladesh. We present a three-step process to address challenges inherent to working in such contexts while ensuring ecological validity and cultural sensitivity, navigating logistical challenges, and optimizing data quality. Data quality metrics in 148 infants showed high usability, with 86% of data being usable when infants were held by their mothers (joint condition), and 80% when they were alone (solo condition). Aligning with theoretical expectations, higher respiratory sinus arrythmia (RSA, extracted from HRV) was negatively correlated with behavioral arousal (e.g., more alert, exhibiting motor activity) in both conditions. RSA also remained stable across 30-second segments within each baseline condition, indicating no systematic change in mean RSA levels across time. This study demonstrates a scalable, ethical approach to collecting HRV data in remote field settings, providing a foundation for exploring how early autonomic development intersects with proximal processes such as caregiving across diverse cultural contexts. This protocol aims to advance equity and inclusivity in developmental psychophysiology while maintaining rigorous scientific standards. A Protocol to Acquire Infant Heart Rate Variability in the Rohingya Camps and Surrounding Communities in Cox’s Bazar, Bangladesh Elisa Ugarte, Ph.D. 1 , Paul D. Hastings, Ph.D. 2,3 , Eamam Hossain 4 , Md Shakil Ahamed, M.D. 4 , AK Rahim 1 , Mahbub Elahi 4 , Md Sajjadur Rahman 4 , Fahmida Tofail, Ph.D. 4 , & Alice J. Wuermli, Ph.D. 1 1 Global TIES for Children, New York University 2 Department of Psychology, University of California, Davis 3 Center for Mind & Brain, University of California Davis 4 icddr,b The authors thank all the families who have supported and contributed to the the iRRRd study. The establishment of this cohort involved a number of organizations, including partners on the Play to Learn initiative: Sesame Workshop, BRAC Bangladesh, International Rescue Committee (IRC), and the Humanitarian Assistance Program (HAP). We thank the Data Team at NYU-Global TIES for Children, in particular Patrick Anker and Duja Michael for their leadership in developing data management solutions. We also thank Scarlett Lopez Aguilar for leading HRV data editing. We thank survey enumerators, medical technicians, porters, and Rohingya volunteers who demonstrated tremendous dedication and resolve to making this study a success. We extend our sincere gratitude to the Governments of Bangladesh for its essential core and unrestricted contributions. Data and Code Availability Statement The code used for the analysis will be made available upon acceptance of the manuscript. Due to ongoing data collection, the iRRRd study data are not yet publicly available. However, the project team is working on protocols for proposal-based access to the recruitment data in collaboration with project investigators. Funding Statement Funding for this study was provided by the LEGO Foundation through the Play to Learn initiative. Conflict of Interest Disclosure The authors declare no conflicts of interest. Ethics Approval Statement The study was approved by the ethical review committee of icddr,b (PR-22064) and by the New York University Institutional Review Board (IRB-FY2021-4875). CRediT Contributor Statement Elisa Ugarte: Conceptualization, Methodology, Formal analysis, Investigation, Writing – original draft. Paul D Hastings: Conceptualization, Supervision, Methodology, Writing – review & editing, Validation. Eamam Hossain: Investigation, Methodology, Supervision, Writing – original draft, Writing – review & editing. Md Shakil Ahamed: Supervision, Investigation, Writing – original draft, Writing – review & editing. AK Rahim: Writing – review & editing, Investigation, Resources. Mahbub Elahi: Data curation, Formal analysis. Md Sajjadur Rahman: Supervision, Investigation, Resources, Data curation. Fahmida Tofail: Writing – review & editing, Supervision. Alice J Wuermli: Conceptualization, Funding acquisition, Writing – review & editing, Supervision. Permission to Reproduce Material from Other Sources No material from other sources was reproduced in this study. Clinical Trial Registration Not applicable Abstract Regulation of autonomic arousal during infancy is critical for the development of self-regulation, socioemotional development and cognitive functioning. High frequency heart rate variability (HF-HRV), a key indicator of parasympathetic nervous system function, supports physiological regulation and emerging behaviors that foster social engagement during this critical developmental period. However, research on HF-HRV has largely been confined to controlled settings with highly resourced populations, limiting its applicability to culturally and contextually diverse populations. This study presents a protocol for collecting HF-HRV data from one-month-old infants in remote and low-resource field contexts, specifically, the Rohingya camps and surrounding host communities in Cox’s Bazar, Bangladesh. We present a three-step process to address challenges inherent to working in such contexts while ensuring ecological validity and cultural sensitivity, navigating logistical challenges, and optimizing data quality. Data quality metrics in 148 infants showed high usability, with 86% of data being usable when infants were held by their mothers (joint condition), and 80% when they were alone (solo condition). Aligning with theoretical expectations, higher respiratory sinus arrythmia (RSA, extracted from HRV) was negatively correlated with behavioral arousal ( e.g., more alert, exhibiting motor activity) in both conditions. RSA also remained stable across 30-second segments within each baseline condition, indicating no systematic change in mean RSA levels across time. This study demonstrates a scalable, ethical approach to collecting HRV data in remote field settings, providing a foundation for exploring how early autonomic development intersects with proximal processes such as caregiving across diverse cultural contexts. This protocol aims to advance equity and inclusivity in developmental psychophysiology while maintaining rigorous scientific standards. A Protocol to Acquire Infant Heart Rate Variability in the Rohingya Camps and Surrounding Communities in Cox’s Bazar, Bangladesh Regulation of autonomic arousal during infancy is foundational for the development of self-regulation, executive, verbal, socioemotional and motor functioning (Field & Diego, 2008; Scarpa, 2015). The autonomic nervous system (ANS), comprising the parasympathetic (PNS; “rest and digest”) and the sympathetic nervous system (SNS; “fight or flight”), regulates non-conscious physiological processes vital for essential survival (Berntson et al., 1993; Harteveld et al., 2021; Zisner & Beauchaine, 2016). After considerable prenatal development, the ANS continues to develop rapidly during the neonatal period and early infancy (DiPietro et al., 2007; Harteveld et al., 2021; Patural et al., 2019). Similar to other neurobiological systems during this developmental stage, cardiac parasympathetic control is highly sensitive to environmental influences, both social and non-social (Alkon et al., 2012; Mulkey & du Plessis, 2018; Propper & Holochwost, 2013). Early measures of the PNS provide insights into possible life-span neurodevelopmental trajectories (Aldrete-Cortez & Tafoya, 2024), allowing for investigations into factors supporting healthy PNS development and regulation at a very early stage with potentially life-long implications for health and wellbeing (Thayer et al., 2012). HRV is commonly measured via electrocardiography (ECG) and is widely used to assess PNS function (Berntson et al., 1997). Recent advancements in mobile ECG collection techniques have allowed researchers to explore PNS activity as a biomarker for biobehavioral regulation. Despite this progress, much of this knowledge has been derived from controlled environments such as laboratories or hospitals and have been largely concentrated in high-income countries (HICs; Cerritelli et al., 2021; Maitha et al., 2022; Mishra et al., 2023; Troller-Renfree et al., 2021; Zisner & Beauchaine, 2016;). This gap limits our understanding of HRV in low- and lower middle-income countries (LMICs), undermining our efforts toward a more diverse and inclusive science of developmental psychophysiology (BLINDED). There is a scarcity of recommendations on conducting mobile ECG research with infants in remote, low-resource settings, particularly around selecting and introducing field-friendly devices to participants and ensuring data quality under challenging acquisition conditions. By low-resource, we refer to home and community environments that often lack reliable access to electricity, cell phone coverage or Wi-Fi, and where conditions vary widely in terms of size, temperature, noise, and crowding. The present study addresses this gap by outlining the steps we have taken to develop a protocol for acquiring heart rate variability from one-month-old infants and their caregivers in a challenging field setting: the Rohingya camps and surrounding host communities in Cox’s Bazar, Bangladesh. By detailing the modifications made to typical laboratory or clinic-based procedures in HICs in order to optimize data quality in a low-resource field setting, and assessing the protocol’s feasibility and validity, we offer insights and recommendations for researchers interested in conducting psychophysiological data collection in previously neglected ”real-world” settings. The role of infants’ HRV in early development Existing theory and empirical evidence show that during infancy, social behavior emerges as a result of complex interactions between physiology and behavior (Feldman, 2015; Porges & Furman, 2011; Stallworthy et al., 2024). The PNS is a widely studied physiological system due to its role in promoting affiliative behaviors and social engagement in mammals (Porges, 2007). It achieves this by maintaining homeostasis of vital physiological systems and down-regulating the SNS, thereby supporting adequate physiological arousal and adjusting responses towards environmental demands (Porges, 2007; Porges & Furman, 2011). The PNS has garnered significant attention within scientific and medical communities due to its pivotal role in supporting and safeguarding overall health and well-being, given its central role in facilitating recovery from stressful and metabolically taxing experiences (Kemp et al., 2017; O’Connor et al., 2021). Specifically, the myelinated vagus nerve (X th cranial nerve), the longest parasympathetic nerve in the body, swiftly connects and transmits information between the brainstem and PNS-innervated peripheral tissue in various organs throughout the body, including the cardiopulmonary system (Berntson et al., 1993; Zisner & Beauchaine, 2016). Experimental studies involving humans and animals have demonstrated that the vagus nerve makes up 75% of PSN activities and possesses extensive projections throughout the brain, spanning cortical and subcortical networks (George et al., 2004; Schuerman et al., 2021). Vagal activity is commonly assessed through respiratory sinus arrhythmia (RSA), which measures the high-frequency variation in beat-to-beat intervals corresponding with spontaneous respiration (Poliakova et al., 2014; Zisner & Beauchaine, 2016). RSA can be extracted from HRV by breaking it down into frequency components using the Fast Fourier Transform algorithm (for details, see Bernston et al., 1993). In infants and young children, higher baseline RSA and RSA reactivity to stimuli are believed to collectively reflect the capacity for flexible physiological self-regulation and distress regulation (Beauchaine, 2001; BLINDED et al., 2013; Perry et al., 2018; Porges, 2003, 2007). Beyond self-regulation, a recent systematic review found that baseline PNS functioning during the neonatal period and early infancy (< 2 months) was positively associated with neurodevelopment during later infancy (6-36 months; Aldrete-Cortez & Tafoya, 2024). This highlights the broader implications of early PNS activity, not just for self-regulation, but also for long-term developmental trajectories (Beauchaine, 2015; Thayer et al., 2012). Human infants do not possess a fully developed myelinated vagus nerve at birth. Instead, the number of myelinated vagal fibers increases between 30-32 weeks of gestational age and six months postpartum (Cerritelli et al., 2021; Patural et al., 2019; Porges & Furman, 2011). Consequently, baseline RSA steadily rises during this period with more significant advancements in overall autonomic maturation and PNS activity overshadowing SNS activity by the age of two (Cerritelli et al., 2021; Izard et al., 1991). According to Polyvagal Theory, the mammalian myelinated vagus plays a central role in a biobehavioral social engagement system that connects autonomic regulation with social behavior early in development. Given the vagus’ innervation of facial, neck, and head muscles and its rapid operational timescale relative to other physiological systems (e.g., the SNS), parasympathetic control in newborns and infants is crucial for flexible social engagement (Field & Diego, 2008; Stallworthy et al., 2024; Porges & Furman, 2011). The current study Frameworks for selecting mobile devices in psychophysiological research provide comprehensive conventions for evaluating accuracy while considering feasibility (Kleckner et al., 2021; Quigley et al., 2024). However, transitioning from mobile ECG acquisition systems which are often designed for adults in HICs, to those intended for infants in low-resource, remote settings requires reevaluating these conventions to ensure that the devices are both feasible to use and provide sufficiently accurate data. This paper outlines the steps we followed to develop a home-based protocol for acquiring baseline HRV data from one-month-old infants and their primary caregivers (biological mothers). Additionally, we present preliminary data regarding the usability and validity of our protocol with one-month-old infants. We acquired baseline data in two conditions: While infants were held by their mothers (joint) and when infants were alone (i.e., not in contact with their mothers). Studies have shown that maternal touch increases RSA (Van Puyvelde, Gorissen, et al., 2019) and infants adjust their RSA levels to their mothers during the first two months of life (Van Puyvelde et al., 2015). To assess usability, we evaluated data quality and examined whether factors such as infant and maternal behaviors during recording systematically impacted data usability. To test the protocol’s validity, we examined the degree to which infants exhibited expected associations between RSA and participant characteristics theoretically and empirically linked to RSA levels. First, we hypothesized that infants who were more aroused during baseline (e.g., more alert, exhibiting motor activity, or fussing) would exhibit lower RSA compared to infants in calmer states, such as being drowsy or half-asleep. As arousal increases, RSA typically decreases, reflecting a shift toward sympathetic activation to support physiological mobilization (Porges, 2022). This relationship has been consistently documented: RSA is higher during quiet sleep compared to active sleep and shows a mild decrease as infants exhibit orienting responses (Porges et al., 2003; Porges et al., 2007). Second, we expected that there would be no systematic change in baseline RSA within and across infants, as baseline conditions were designed to minimize external stimuli and maintain a consistent measurement context across participants. Methods Project context Data for this study comes from the BLINDED study, an ongoing longitudinal birth and early years cohort study of 2,323 pregnant Rohingya women (and other members of their household) living in camps along the southeast coast of Bangladesh, as well as 566 pregnant women (and members of their households) from the local host community. Since the 1970s, this region of Bangladesh has hosted multiple waves of Rohingya refugees who have fled discrimination, persecution, and systematic violence in their home country of Myanmar. The most recent and most substantial displacement occurred in August 2017, increasing the population from approximately 250,000 to over 700,000 (and currently over 900,000; Hasnat & Ahmed, 2023). Over the course of 12 months, pregnant women were enrolled in the study at different stages of pregnancy. Birth follow-up included two visits: one brief visit within 72 hours of delivery to collect anthropometrics and birth information and another at one month postpartum, from which the data in this paper are drawn. For further details on the cohort, see BLINDED (under review). Protocol development steps Developing a protocol for HRV data collection in a low-resource field setting required balancing ethical considerations, cultural appropriateness, and logistical feasibility while prioritizing data quality. The following section outlines the steps we took to create a protocol that met these criteria. Designing an ethical and feasible pilot protocol Conducting biomedical research in low- and middle-income countries, particularly with vulnerable populations like the Rohingya in Bangladesh, involves navigating significant ethical and cultural challenges. These challenges stem from financial and regulatory disparities, along with pronounced power imbalances between researchers (often from HICs institutions) and populations of interest. A separate paper on the ethical considerations in biomarker research and the development of our biomedical protocols is currently in preparation (BLINDED, under review). To ensure the protocol was both ethical and feasible, we evaluated methods and measures based on logistical constraints, human resource availability, participant acceptability, cultural appropriateness, and cost-effectiveness. We prioritized devices that could function independently of electricity, Wi-Fi, or cell service, featured extended battery life, and allowed offline data storage. Additional considerations included selecting devices that were quick to set up, minimally intrusive, and respectful of cultural and religious norms regarding modesty and body placement. For example, women in the study population wear clothing that covers most of their bodies, and it we assumed that it would not be appropriate to ask them to expose large areas of skin, such as removing their shirts for a chest band or a three-lead electrode configuration. To address this, we prioritized devices that required as minimal skin exposure as possible, allowing data collection without compromising participants’ comfort. Between 2019 and 2022, we engaged the local community through focus group discussions and key informant interviews to test different devices and refine our protocol. Partnering with a community-based organization, local leaders, and a sociocultural linguist, we conducted six key informant interviews to explore participants’ past experiences with research, family decision-making processes regarding research participation, and the type of biomedical information they found valuable. Larger focus groups (disaggregated by gender) further addressed participant concerns, gauged their understanding of the proposed methods, and built trust by emphasizing confidentiality. To facilitate understanding and build trust, we included hands-on demonstrations, allowing participants to examine potential instruments and different devices, ask questions, and try devices on themselves and their children. Overall, participants expressed strong interest in new technologies and enthusiasm for gaining insights into their own and their children’s health. The primary concern among female participants was obtaining permission from husbands or male guardians. Rohingya men, as community gatekeepers, initially expressed reservations about the research. However, after discussions with various demographic groups of Rohingya men, there was an understanding of the importance of supporting research that benefits the most vulnerable members of their community, particularly women and children. Adapting our protocol to cultural and contextual constraints Our goal was to acquire baseline HRV data for mothers and infants to understand whether trauma before pregnancy and prenatal mental health “got under the skin”. However, defining a suitable “baseline” in this context presented unique challenges. One of them is the degree to which recording environments vary. Unlike laboratory environments where testing rooms are shielded and have consistent features (e.g., furniture, space, ventilation), home environments in the camps and surrounding Bangladeshi villages vary in size, temperature, and number of people. Data collectors set up in a quieter corner of the household, working as a two-person team; one enumerator focused on maintaining as calm an environment as possible among household members while the medical technician acquired biomedical data. Standardizing solo baseline measures for children posed another challenge. In this setting, children are rarely separated from their mothers or other adults and are often in physical contact even while seated. While most studies measure baseline HRV in children using cribs, baby seats, or swaddling, these options were unavailable. Cribs and baby seats are not typically present, and swaddling is uncommon, especially in hotter months when temperatures can reach 40°C or over. The supine position without maternal contact is unfamiliar and uncomfortable for these children. Nevertheless, mother-child touch had to be minimized to avoid influencing children’s HRV levels. As we moved from planning to implementation, our initial field tests in October 2023 revealed additional challenges in obtaining high-quality baseline data and ensuring participant comfort and engagement. Our first procedure involved simultaneous baseline measurements of mother and child separately, followed by a joint baseline with mothers holding their infants. However, the solo baseline segment often led to child distress and was challenging for enumerators to implement, resulting in data that was inconsistent with a true “baseline” state, in both infants and mothers. To address these issues, we adjusted the protocol by reorganizing the task order, extending visit times to allow enumerators to follow the natural pace of mother and child, scheduling visits during calmer periods of the day (typically after naps), and reinforcing the importance of a calm environment to enumerators to minimize the impact of arousal levels on HRV data quality. Data from approximately 25% of participants reported in this paper was acquired during these initial visits. We also faced limitations related to scheduling access. US-based researchers had to seek authorization from the Refugee Relief and Repatriation Commissioner (RRRC; an office of the Bangladeshi Government designated to control camp access) to enter the camps each time they needed to do so for training, observation of data collection, etc. Though understandable and not uncommon in humanitarian settings, it added time and resource constraints nonetheless. Additionally, access to the camps for any outside person was constrained to 9:00 am to 3:00 pm every day. This scheduling restriction occasionally conflicted with infants’ schedules and routines, requiring careful planning and flexibility from the logistics team to maximize efficiency (i.e., number of visits per day) within these constraints. Furthermore, we were keenly aware of certain ethical considerations of working in this (and other vulnerable) populations, importantly that, due in part to power dynamics between participants and higher educated Bangladeshi data collectors, participants might feel hesitant to stop a session. In response, we took an iterative and adaptive approach to training, working with enumerators over multiple sessions to recognize discomfort or confusion with participants and to give participants multiple opportunities to pause or stop the data collection if either they or their child was experiencing any sort of discomfort or distress beyond occasional fussiness or movement. Optimizing data quality To ensure data quality in this field setting, we evaluated several devices for HRV acquisition, including electrocardiography and photoplethysmography based systems. We ultimately selected the FirstBeat R BodyGuard 3.0 (BG3). This ECG device offers a practical balance of acceptable sampling rate (256 Hz), reliability, and affordability while accommodating the logistical constraints of fieldwork in low-resource settings, including the need for long battery life and independent operation without requiring a power source or internet. This was particularly critical in the camps as internet is extremely limited and there is no electricity beyond individual household solar panels. The BG3 records the full ECG waveform, enabling visual validation of inter-beat interval (IBI) data during data cleaning—an advantage over previous models that only provided IBI data, thereby improving overall data quality (Gamelin et al., 2006; Marchant-Forde et al., 2004; Palmer et al., 2021). To validate the device, we conducted in-lab testing, comparing the BG3’s performance to a gold-standard device (Mindware R ) under synchronized conditions. In tests with three adults, the BG3 demonstrated high reliability, with RSA correlations ranging from 0.99 in seated conditions to 0.95 during active conditions. Additional out-of-lab testing with six children (ages 5- to 54 months, mean = 25.8, three of them visited twice) further confirmed its usability across a range of activities. Data quality metrics included low error rates (<10% miscalculated R spikes), high inter-rater reliability in data editing, and minimal editing time. Despite the strengths of the BG3, it lacks integrated event markers, which signal the start and end of each activity and are critical for editing data from individual and dyadic (caregiver-child) sessions. To address this limitation, collaborators from the BLINDED lab developed an event marker feature tailored to our project called “Mirage”, a custom app for Android tablets, with data uploaded to a cloud (once back at a location with Wi-Fi) for later editing. Thirteen medical technicians underwent extensive training to ensure procedural consistency and maximize data quality. Training sessions included expert-led instruction by individuals from US Universities, and hands-on practice, focusing on proper electrode placement, device operation, and troubleshooting common challenges in field settings, such as crowding, device malfunctions, and child behavioral issues. Medical technicians had been collecting ECG from the mothers during recruitment and were well versed using the BG3 with adults, but received extra training for the infant protocol. Every week, supervisors led debriefing sessions to discuss and mitigate potential issues with participants and devices. In the field, supervisors oversaw protocol adherence, confirmed accurate device placement, and monitored baseline recordings, intervening as necessary to address interruptions or setup issues. As a result, medical technicians received timely feedback to refine their skills, enabling high-quality and consistent HRV data collection. To further ensure data quality, we systematically assessed behavioral indicators of infant arousal and mother-infant interactions during data acquisition. Due to cultural constraints, participants were uncomfortable with videotaping, so we needed a way to have “eyes and ears” from miles away, where the HRV data would later be reviewed and analyzed. We identified behavioral indicators that assess infant arousal states using modified items from the Neonatal Behavioral Assessment Scale (Brazelton et al., 1987). These state indicators (e.g., alert, crying, see Table 2) and eight movement and attention-inducing behaviors from mothers during joint baseline (e.g., rocking, face-to-face orientation) capture information that may influence HRV data quality and HRV levels, providing important context for data editing and interpretation. Participants For this paper specifically, participants were 148 mothers (median age at recruitment = 19 years; range: 14–37 years; 77% Rohingya, 32% primiparous) and their infants (median age: = 43 days; range: 25–96 days; 82% assessed before day 50, 60% male, median gestational age = 39; range: 30–42). Since cardiac data editing is ongoing, this group represents a subsample of the larger study cohort. Ethical approval for the study was granted by the Institutional Review Boards at the BLINDED (protocol # PR-22064) and BLINDED (protocol # FY2021-4875). In this subsample, over half of the pregnant women (53%) reported being unable to read in any language, 5% reported having a chronic disease such as diabetes, tuberculosis, or hepatitis, and 7% and 14% scored above the PTSD diagnostic threshold during pregnancy and 28 days postpartum, respectively. Although Rohingya and Bangladeshi women generally do not have a culture of smoking, 46% of participants lived in homes where someone smoked inside every day, and 51% lived in homes where wood was the primary or secondary cooking fuel. Most children (95%) were reported to be healthy within 72 hours of birth. However, at the one-month visit, 75% of mothers reported that their children were experiencing illness symptoms, the most common being a common cold (63%), fever (25%), and colics (21%), among others. Procedure Figure 1 Protocol summary What follows is our standardized procedure tailored to the unique setting and needs of our study population (see Figure 1 for a concise summary). Each step was designed to optimize data quality while minimizing participant burden and ensuring a comfortable environment for both mothers and infants. Preparation and Equipment Setup All families were attended by a primary survey enumerator with previous experience working in the camps, in addition to the medical technician. Surveys and tests are generally conducted inside the participants’ shelters, which are often small and constructed of bamboo panels and tarpaulin, with a size of 188 sq. feet for covered living space. The enumerators, technicians, and participants all sit on the floor on bamboo or plastic mats to create an equal environment. Linguistic particulars of working with Rohingya require enumerators to be from the area of Bangladesh where the local dialect (Chittagonian) has a significant overlap with the Rohingya language, whereas the medical technicians were from Dhaka (Bangladesh capital), and did not speak the local dialect. Therefore, enumerators conducted surveys and often served as translators and relationship managers. All visits with female participants were conducted exclusively by female data collectors to maintain purdah , the socio-religious practice of gender segregation. Notably, this was the third interaction mothers had with the research team and their second or third HRV assessment, while it was the first HRV assessment for the infants. Prior to data acquisition, medical technicians and survey enumerators explained the HRV assessment procedure to participants and then asked for verbal consent. Afterward, they instructed family members to keep a quiet environment if possible. Participants were advised to put away any electronic devices or materials that could interfere with HRV. Pre-acquisition questions included verifying when the infant last napped and ate, whether they were being more or less fussy than usual that day, and checking for any signs of illness in the infant. HRV Acquisition Protocol Mother’s Solo Baseline. Medical technicians cleaned the bodyguard attachment areas (right collar bone and left bottom rib) using an alcohol wipe. While the areas dried, they attached two disposable electrodes to the Bodyguard and then attached them in a bipolar configuration to the mother’s torso. Once attached, the mother was instructed to sit comfortably, close her eyes, and avoid talking or moving during a 5-minute solo baseline recording. During the recording, infants were held by enumerators or other family members, ensuring the child was quiet and calm. Since over a half of shelters have at least one internal partition to provide privacy, infants sometimes were kept in an adjacent room. Technicians used the Mirage app’s “event” feature to log any disturbances (e.g., external noise, movement). Joint Mother and Child Baseline. For the joint baseline condition, technicians attached a second BG3 device using infant electrodes to the infant’s torso in the same manner as the mother Then, the child was transferred to the mother’s lap, and the mother was asked to avoid moving or talking to the baby for another 5-minute session. Medical technicians logged interruptions or disturbances. Infant’s Solo Baseline. Finally , the child was placed supine on a soft mat, while either asleep or calm, for a 3-minute baseline recording. Enumerators instructed mothers to remain neutral and avoid engaging with the child. If the child was slightly upset, enumerators distracted babies and allowed them to move, wiggle, or roll slightly. Data collection was paused or terminated if the child displayed excessive movement or distress, and behavioral observations were logged in the Mirage app. Behavioral Observations and Data Management While data was being acquired, enumerators recorded in the survey primary and secondary predominant states and behaviors that could interfere with data quality (Table 1). At the end of each day, enumerators returned HRV equipment to the field data managers, who uploaded the data to secure servers. Bodyguard data was downloaded using the Bodyguard 3 Exporter software, renamed by participant ID, and Mirage app data was synchronized daily. With the data collected through these standardized procedures, we processed and analyzed ECG signals in BLINDED. Below, we outline the methods used for data processing, inclusion criteria, and analyses for this study. Measures ECG data processing Infant and maternal ECG data were processed offline at BLINDED using Mindware’s Heart Rate Variability Analysis Software. Data were divided into 30-second segments (10 for joint baseline, 6 for solo baseline). All ECG files were visually inspected for general usability, with files deemed unusable if the entire recording was too noisy to identify R peaks. ECG signals were cleaned through visual inspection and manual editing to address artifacts caused by movement or other interference. Erroneous beats were deleted, and missing beats were interpolated when necessary. Segments with fewer than 20 seconds of usable data or more than 5% estimated beats were excluded from analyses. Segments with 1–5% estimated beats were flagged as requiring high editing but were retained for HRV calculations. Baseline inclusion required a minimum of 4 usable segments for solo baseline and 6 usable segments for joint baseline. RSA for each segment was calculated as the natural log of high-frequency heart rate variability (0.24–1.04 Hz; Bar-Haim et al., 2000). Baseline RSA and heart rate (HR) were computed as the average of usable segments. Segments with RSA values exceeding 2.5 standard deviations from the participant’s intraindividual mean were excluded (n = 4 in joint and n = 3 in solo baseline). If the exclusion of outlier segments resulted in fewer than the required threshold of usable segments, the baseline was deemed unusable and excluded from further analysis. Analysis We assessed the usability and validity of the HRV data collected through descriptive and inferential statistics. Usability was evaluated by calculating the percentages of usable HRV data during solo and joint baselines. Independent sample t-tests compared usability improvements across data collection months (e.g., October to January). Additional analyses examined whether factors such as infant illness, arousal states, time since last nap and last meal, perception of daily fussiness (less than usual, as usual, more than usual), and maternal behaviors during recordings (e.g., rocking, breastfeeding, fussiness) systematically influenced usability using t-tests and chi-square tests. When cell count for chi-square test were less than 5, we also conducted Fisher’s Exact Test. To assess validity, we calculated Pearson correlations between infants’ arousal states and RSA. A mean arousal score was computed for each condition based on primary and secondary states. Finally, we probed for systematic time changes in RSA within and between participants conducting mixed-effects models in each baseline condition. We expected that there would be no systematic change in baseline RSA within and across infants, as baseline conditions were designed to minimize external stimuli and maintain a consistent measurement context across participants. These models included random intercepts for each participant to account for individual differences and modeled RSA as a function of segments. We also conducted exploratory analyses to test whether the association between RSA and segments varied across arousal levels. Fixed effects estimates were reported for each model, and significance was assessed using Wald t-tests with Satterthwaite approximations for degrees of freedom. Random effects were evaluated to determine the extent of variability attributable to individual differences versus residual error. Missing data for covariates ranged from 0% to 4.05% across all participants in the sample (N = 148). The variable with the highest missingness were arousal state data (4.05%). Other variables, such as maternal behaviors during HRV acquisition (1.35%), had minimal missingness. To assess potential bias, we compared RSA levels between children with missing data and those with complete data for variables with >4% missingness (arousal state data). No significant differences in RSA were observed (all p > .05). Missing data were handled using listwise deletion. All statistical analyses were performed using R Version 4.4.1 and RStudio 06.1 using the packages within easystats (Lüdecke et al., 2023), lessR (Gerbing, 2024), and lme4 (Bates et al., 2015). Results Table 1 Usability metrics for solo and joint baseline (usable and usable data) Category Joint Baseline Solo Baseline Usable 127 (85.8%) 118 (79.7%) Unusable 12 (8.1%) 14 (9.5%) Missing 9 (6.1%) 16 (10.8%) Table 2 Arousal State Frequencies Across Joint and Solo Baseline Conditions Arousal state Joint Baseline Solo Baseline Primary Secondary Primary Secondary State 1: Eyes closed, regular breathing, no activity 23 (16.2%) 27 (19%) 26 (18.3%) 24 (16.9%) State 2: Eyes closed, irregular respiration, small movements 14 (9.9%) 18 (12.7%) 11 (7.7%) 17 (12%) State 3: Drowsy; minimal activity 37 (26.1%) 39 (27.5%) 25 (17.6%) 21 (14.8%) State 4: Alert, orienting to mother or object 12 (8.45%) 5 (3.5%) 15 (10.6%) 13 (9.2%) State 5: Medium motor activity, brief fussiness 41 (28.9%) 38 (26.8%) 52 (36.6%) 60 (42.3%) State 6: Crying; high motor activity 15 (9.2%) 15 (10.6%) 13 (9.2%) 7 (5%) Joint baseline behaviors Yes No Breastfeeding 7 (4.7%) 139 (93.9%) Face-to-face position 15 (10.1%) 131 (88.5%) Kissing 4 (2.7%) 142 (95.9%) Rocking 77 (52%) 69 (46.6%) Stroking 16 (10.8%) 130 (87.8%) Talking to the child 14 (9.5%) 132 (89.2%) Tapping 3 (2%) 143 (96.6%) Note. Kissing and tapping were not included in the analysis due to low base rates. Data Usability Table 1 shows usability rates and missing data for joint and solo baseline conditions and Table 2 details descriptions and rates of behavioral indicators of infant arousal and mother-infant interactions. Missing data stemmed from technical errors or protocol interruption during data acquisition, leading to the absence of raw data altogether. There were no systematic differences in the proportions of data usability and missingness across collection dates (76 participants were assessed in October, and 72 participants were assessed in January). Although not statistically significant, the proportion of missing data in solo baseline was higher in October (14.5%) than in January (7%). For joint baseline arousal states, ANOVA tests revealed no significant differences across usability categories. However, a t-test comparing usable and unusable joint RSA data showed a significant difference, with higher arousal levels in the unusable group (Mean = 4.29, SD = 1.44) compared to the usable group (Mean = 3.38, SD = 1.47), t (131)=2.05, p=.043, Cohen’s d=0.62, suggesting that arousal during joint baseline was significantly higher in infants with unusable data. In contrast, no significant differences in arousal states were observed between usable and unusable data during the solo baseline condition ( p s > 0.05). We also examined whether data usability and missingness differed between Rohingya and Host participants for joint and solo baseline conditions. No significant differences were found across most usability categories, although there were significantly higher rates of missing data among Host participants during the solo baseline condition ( X 2 (1) = 6.425 p = .076, Cramér’s V=0.20), indicating that they had a higher proportion of missing data compared to Rohingya participants (22% vs. 7%). For fussiness, no significant associations were observed between data usability categories during either joint or solo baseline conditions ( p >.05). However, in the solo baseline condition, a significant association was found between fussiness and missing data ( X 2 (2) = 6.66, p = 0.036, Cramér’s V=0.214), indicating that infants who were less fussy than usual that given day were more likely to have missing data. Of note, this question, being more or less fussy than usual, was asked before data acquisition. T-tests comparing usability and missing data during the joint and solo baseline condition showed no significant differences for time since last nap or last feeding ( p s >.05). For child illnesses, we found no significant differences between usability categories across infants who currently had colds, skin diseases, and colics in either baseline condition. For fever, however, a trend was observed for missing data during the solo baseline condition (χ2(1)=3.53, p=.060, Cramér’s V=0.155), with a higher proportion of fever cases reported in the missing group compared to the usable group (19.4% vs. 8.2%). For respiratory issues, a significant association was observed for unusable data during the solo baseline condition (χ2(1)=8.192, p=.004 Cramér’s V=0.251, OR = 6.08), with respiratory issues more frequently reported in the unusable group (36.4%) compared to the usable group (6.4%). No significant differences were found for respiratory issues in the joint baseline condition or for missing data during either baseline condition. Lastly, regarding associations between data usability and maternal behaviors during the joint baseline (Table 1), no significant differences were observed across most maternal behaviors. However, there was a trend for higher rates of missing data among infants of mothers that talked (21%) versus those that did not talk (7%) during the joint baseline condition ( X 2 (1) = 3.13, p = .077, Cramér’s V=0.151, OR = 3.41). We examined RSA differences based on the number of usable segments (6–10 for joint baseline and 4–6 for solo baseline) and segments requiring high editing (1%–5%). For the joint baseline, 85% of infants had ten segments, 12.6% had nine, and 2.36% had fewer than nine. Additionally, 84.25% had no highly edited segments, 6.3% had one, 4% had two, and 5.5% had three or more. For the solo baseline, 77.12% had six segments, 17.8% had five, and 5.08% had four. Most (86%) had no highly edited segments, while 7.63% had one, 1.69% had two, and 5.92% had three or more. Neither the number of usable segments nor the number requiring high editing was significantly associated with RSA in either condition (ps > .05). Validity Table 3 Pearson correlation coefficients and descriptive statistics of age, arousal, and RSA Child Age Joint Arousal Solo Arousal Joint RSA Solo RSA Child Age Joint Arousal 0.19* Solo Arousal 0.11 0.57*** Joint RSA 0.06 -0.33*** -0.26** Solo RSA 0.10 -0.30** -0.35*** 0.68*** Mean (SD) 44.86 (13.49) 3.47 (1.53) 3.65 (1.58) 2.48 (0.98) 2.50 (1.04) Min - Max 25 - 96 1 - 6 1 - 6 0.08 - 4.64 0.40 - 5.46 Note. * p <.05, ** p <.01, *** p <.001. Child age correspond to days since birth. Table 3 shows correlation coefficients and descriptive statistics for age, arousal, and RSA. Figure 2 shows scatterplots depicting the association between arousal and RSA. In line with our hypothesis, children who were more aroused had lower RSA across both conditions. Joint and solo RSA were negatively correlated with joint arousal (r = -0.33, p < .001) and solo arousal (r = -0.35, p < .001), respectively. There were also cross correlations, such that joint arousal was negatively associated with solo RSA (r = -0.26, p < .01). There was a significant positive association between joint arousal and solo arousal (r = 0.57, p < .001). Further, joint RSA and solo RSA were strongly and positively correlated (r = 0.68, p < .001), indicating consistency in RSA measures across both conditions. Figure 2 Scatterplots of arousal states and RSA Mixed-effects models were used to examine the influence of segment on RSA in each condition. The fixed effects estimates indicated that RSA did not systematically vary across segments, both in the joint and solo conditions. None of the pairwise comparisons between segments were statistically significant after adjusting for multiple comparisons (e.g., Segment 1 vs. Segment 2 alone: t (553) = −0.82, p = 0.96). Thus, RSA levels remained stable across the six segments, indicating consistent physiological regulation during the baseline recordings. The random effects revealed substantial variability attributable to individual differences across participants (SD alone =0.90, SD togerther = 0.88) compared to residual error (SD alone =0.82, SD togerther = 0.95, 95% confidence intervals did not include 0) in the alone condition. For solo RSA, variability was mainly attributable to individual differences across participants. For joint RSA, the higher residual error suggests more unexplained variability in this condition, which could potentially be attributable to the fact that they were being held by their caregivers and therefore adjusting their parasympathetic cardiac activity to those of their mothers. Associations between RSA, arousal and other acquisition covariates We examined associations between RSA, arousal, data collection date, population, illness, and other acquisition covariates. As shown in Figure 3, arousal levels decreased from October 2023 to January 2024, with a statistically significant reduction observed only for joint baseline arousal (Mean difference = 0.67, t (140) = 2.66, p = .009, Cohen’s d = 0.45). As such, adjustments to the protocol and increased familiarity of data collectors with the procedure likely contributed to making children (and mothers) more comfortable during the assessments. Notwithstanding, there were no significant differences in joint and solo RSA between October and January (all p s >.05). Figure 3 Changes in sample wide arousal levels between our two data collection dates Of all caregiver behaviors, only those involving stroking and face-to-face positioning were significantly associated with differences in RSA during the joint condition. Infants who were stroked by their mothers had lower RSA (M = 1.70, SD = 0.66) compared to no stroking (M = 2.56, SD = 0.97, t (123) = 3.12, p = .002, Cohen’s d = 0.92), as well as elevated arousal levels (M = 5.12, SD = 0.82) compared to no stroking (M = 3.30, SD = 1.49), t (140) = 4.32,p <.001, Cohen’s d=1.26. Occasions of face-to-face positioning were associated with lower RSA (M = 2.00, SD = 0.68) compared to infants who were not positioned face-to-face (M = 2.53, SD = 0.99, t (123) = 1.96, p =.052, Cohen’s d = 0.56). However, face-to-face positioning was not associated with differences in arousal. Rocking was linked to significantly higher arousal (M = 3.81, SD = 1.48) compared to no rocking (M = 3.11, SD = 1.51, t( 140)= 2.10, p =.038, Cohen’s d=0.47), but no differences emerged for RSA. RSA and arousal levels were not significantly related to mothers’ perceptions of daily fussiness, and time since last feeding and last nap. Children whose mothers reported they had fever symptoms had lower solo RSA (M = 2.08, SD = 1.02), t (140) = 2.42,p =.017, Cohen’s d=0.54, compared to those with no fever (M = 2.63, SD = 1.02), and children with respiratory issues (M = 4.33, SD = 1.25) had higher arousal during joint baseline in comparison to children without respiratory issues (M = 3.39, SD = 1.53, t (140) = 2.07,p =.040, Cohen’s d=-0.62). Discussion This study demonstrated the feasibility and preliminary validity of a cultural- and contextually adapted protocol to collect infant HRV in a very low-resource setting. We detailed the steps taken to create an ethical protocol, including identifying field-friendly devices, adapting to cultural and contextual constraints, and optimizing data quality. The majority of visits yielded usable infant physiological data across both joint and solo conditions. Additionally, we emphasized the importance of capturing arousal and behavioral indicators, demonstrating that most infants exhibited the expected RSA decrease in response to higher arousal. Lastly, RSA did not systematically vary across segments in either condition. Individual differences accounted for a substantial portion of variability in baseline RSA, particularly in the solo condition. These findings underscore the stability of RSA across segments within our sample. Usability Our protocol demonstrated notable strengths in usability, achieving high rates of usable data across both joint and solo baseline conditions. As shown in Table 2, usable data were collected from 85.8% of participants during the joint baseline and 79.7% during the solo baseline, indicating the protocol’s robustness in a resource-constrained setting. These rates are consistent with or exceed those reported in prior studies with infants of similar age in an at-home-assessment (approximately 75%; Tabachnick et al., 2022), and in hospital/lab settings (91-83.6%; Della Longa et al., 2021; Longin et al., 2005; Moore & Calkins, 2004). Furthermore, the average RSA levels observed in our study (M RSA = 2.49) are comparable to another study reporting RSA in six week old infants (Jewell et al., 2017). Despite challenges inherent in the field, the protocol proved effective in collecting reliable physiological data for the majority of the sample. A key strength of the protocol lies in its adaptability and ecological validity. Data were collected in naturalistic settings, which likely decreased burden for participants. The high proportion of usable data, even in the solo baseline condition, underscores the feasibility of implementing a protocol designed to accommodate cultural and logistical constraints. Importantly, a majority of the data required minimal editing, with over 85% of joint and solo baseline recordings containing no highly edited segments. This indicates that the raw signal quality was generally high, validating the device, training and expertise of the enumerators and technicians in managing the BG3 device. Additionally, the protocol successfully incorporated behavioral and contextual indicators, enabling a more precise interpretation of RSA data within the environmental and physiological states of the infants. The analyses revealed a few notable factors affecting data usability. Missing data, although low, were slightly higher during the solo baseline condition (10.8%) compared to the joint baseline (6.1%), with technical errors or protocol interruptions being the primary causes. Higher arousal levels during the joint baseline were associated with unusable data, suggesting that infants in more activated states posed greater challenges for signal acquisition. Furthermore, respiratory issues were significantly associated with unusable data in the solo baseline, with a sixfold higher likelihood of unusable data among infants with respiratory symptoms. For joint baseline conditions, a trend indicated higher rates of missing data when mothers talked during the recordings, which may have introduced noise or interruptions. Despite its strengths, the protocol faced a few challenges that merit consideration. Infants with higher arousal during the joint baseline were less likely to yield usable data, highlighting the potential need for strategies to mitigate physiological and behavioral activation during recordings. Notably, changes in arousal between October 2023 and January 2024 shows that protocol changes and increased familiarity of data collectors with the procedure likely contributed to making children and their mothers more comfortable. While maternal behaviors like talking did not significantly affect most usability outcomes, they may introduce variability in signal quality, particularly in the joint baseline condition. Finally, the absence of systematic differences in RSA across segments requiring high editing shows that the protocol effectively minimizes the impact of artifact correction, though this requires continued monitoring in future applications. Validity Our findings support the preliminary validity of the protocol in capturing expected associations between RSA and arousal states, with significant negative correlations between RSA and arousal observed in both joint and solo conditions. These results align with previous studies demonstrating that higher arousal is associated with a decrease in RSA, reflecting a shift in autonomic regulation to support physiological mobilization in neonates and infants (Cerritelli et al., 2021; Groh & Narayan, 2019; Latremouille et al., 2021; Porges, 2007; Tabachnick et al., 2022; Van Puyvelde, Collette, et al., 2019). This is also in line with studies examining changes in RSA in infants as a function to their emotional distress within a paradigm, where lower RSA was related to infant negative affect in the moment (Qu & Leerkes, 2018; Weiss et al., 2024). The consistency across both conditions as well as the strong positive correlation between joint and solo RSA (r = 0.68) highlights the reliability of the RSA measure and the robustness of the protocol across different contexts and arousal levels. The stability of RSA across all segments highlights the robustness of the protocol in capturing consistent measures of baseline autonomic regulation. Unlike reactivity paradigms, which often show initial RSA declines followed by recovery (Jones-Mason et al., 2018; Qu & Leerkes, 2018), our baseline design ensures that measurements reflect stable physiological regulation across the procedure. This indicates the protocol’s reliability and its potential for capturing meaningful individual differences in parasympathetic cardiac control. The random effects analyses revealed substantial variability in RSA attributable to individual differences across participants, particularly in the solo condition. In the joint condition, the higher residual error likely reflects increased variability due to caregiver influences, such as touch or positioning, which are not fully accounted for in the current models. Future studies could examine how caregiver behaviors, arousal, and RSA levels during joint baseline may contribute to RSA variability in their infants. Associations between RSA, arousal and other acquisition covariates Our efforts to examine contextual and individual factors influencing RSA and arousal during physiological data collection revealed some key findings. While arousal levels significantly decreased from October 2023 to January 2024, likely reflecting procedural improvements and increased data collector familiarity, RSA remained stable across this period, suggesting it was less sensitive to immediate procedural changes than arousal. As such, the protocol might be reliably capturing more trait-like differences in cardiac parasympathetic control. One study found that stroking increased RSA in infants when they were in a quiet, resting state (Van Puyvelde, Collette, et al., 2019). In our study, stroking was linked to both lower RSA and elevated arousal, indicating it may reflect a maternal response to heightened infant distress. It is likely that the observed reduction in RSA during stroking could reflect infant states rather than directly modulating RSA. Similarly, rocking was associated with higher arousal but showed no effect on RSA, further supporting the idea that caregiving behaviors often mirror responses to infant states rather than directly altering cardiac parasympathetic control. In contrast, face-to-face positioning was associated with lower RSA but did not affect arousal, potentially engaging infants’ attentional processes without significantly influencing their emotional arousal (Stallworthy et al., 2024). Future analyses with our larger sample will investigate RSA in response to variations in caregiver responses to infant arousal. Infant health status during data collection also influenced physiological measures. Solo RSA was significantly lower in infants with fever symptoms, likely reflecting the physiological toll of illness (Chong et al., 2021), while higher arousal during joint baseline was observed in infants with respiratory issues, perhaps due to discomfort when held closely by their mothers. Importantly, of the 26 tests conducted to examine potential confounders, only three yielded statistically significant results. This finding suggests that the protocol effectively captures more stable, trait-like differences in RSA rather than transient variations driven by contextual or behavioral states. Limitations Findings should be considered in light of limitations. While RSA is commonly used as an index of parasympathetic control, our protocol did not include respiration data. As highlighted by Quigley and colleagues (2024), inferring RSA from HRV metrics such as high-frequency HRV (HF-HRV) without access to respiratory signals must be interpreted with caution. This limitation arises because the respiratory bandwidth may exceed the predefined HRV frequency band for infants (e.g., 1.04 Hz), potentially affecting the validity of HF-HRV as a pure marker of RSA. By acknowledging this limitation, we emphasize that while HF-HRV provides a useful approximation of RSA, its interpretation as a precise measure of respiratory-related vagal activity should be approached with caution. Further, the relatively low sampling rate of 250 Hz, may not fully capture rapid changes in cardiac intervals, limiting the granularity of our RSA analyses. Thus, this protocol will likely prove more useful for capturing broad or bigger picture parasympathetic control. Further, more specific behaviors such as vocalizations and movements, while integral to the ecological validity of field-based research, may have influenced RSA by introducing transient cardiac responses unrelated to baseline parasympathetic control. Future studies should integrate portable respiration sensors or synchronized audio recordings to refine RSA interpretation, especially in naturalistic settings, if possible. Combining wearable ECG devices with video or audio recordings in remote settings could offer a richer understanding of caregiver-infant interactions while preserving ecological validity. These multimodal approaches can contextualize physiological data within observed behaviors, providing a more comprehensive picture of the infant’s environments (Maitha et al., 2020). The BG3 system offered several advantages over traditional lab-based methods. It is a self-contained, portable device that is easily managed by enumerators and technicians, well tolerated by infants, and comparatively cost-effective. However, these benefits come with trade-offs. One key limitation is the inability to monitor data quality in real-time during collection. Nevertheless, with sufficient training and practice, data loss can be minimized. A significant challenge for our study has been the lack of event-marking capabilities and difficulties synchronizing cardiac data between caregivers and infants. Synchronizing devices requires periodically connecting the BG3 and tablet to a central computer to align their internal clocks. Even after synchronization, variations in internal clocks across devices can lead to misalignment of signals. While most data align correctly, additional time and effort are needed for precise matching of signals between the tablet and the two BG3 units. Strengths and conclusion This protocol represents a significant advancement in the collection of infant and caregiver psychophysiological data in remote, low-resource and culturally diverse settings. By conducting data acquisition within participants’ homes, we prioritized ecological validity while reducing the barriers to participation for families facing significant logistical challenges. The protocol’s design reflects thoughtful consideration of cultural and ethical constraints, emphasizing minimal intrusion and participant comfort. Selecting minimally intrusive devices and engaging the community ensured respect for local norms, building trust and fostering participation. Our iterative development process highlights the importance of collaboration and adaptability in field research. Extensive community engagement, including focus groups and key informant interviews, informed protocol refinement, while hands-on demonstrations build participant understanding and enthusiasm. Adjustments to task order, extended visit times, and scheduling during calmer periods improved both data quality and participant experience. These steps, combined with robust training for field staff in charge of ECG acquisition, in our case, medical technicians, and systematic supervision, facilitated consistent and reliable data collection, even under challenging conditions. Notably, this protocol provides a scalable framework for collecting baseline data that captures stable, trait-like differences in parasympathetic cardiac control while respecting participants’ dignity. Given that HF-HRV research increasingly informs developmental, clinical, and intervention science, the failure to diversify psychophysiological research can reinforce inequities in how physiological regulation is studied, understood, and applied across populations. By integrating culturally sensitive practices, rigorous training, and research-informed decisions, this work demonstrates how psychophysiological research on early development of the autonomic nervous system can be conducted ethically and effectively in remote (and vulnerable) populations. 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Authors Affiliations Elisa Ugarte 0000-0003-1803-9619 [email protected] New York University View all articles by this author Paul Hastings University of California Davis Department of Psychology View all articles by this author Eamam Hossain International Centre for Diarrhoeal Disease Research Bangladesh View all articles by this author Md Shakil Ahamed International Centre for Diarrhoeal Disease Research Bangladesh View all articles by this author Rahim AK New York University View all articles by this author Mahbub Elahi International Centre for Diarrhoeal Disease Research Bangladesh View all articles by this author Md Sajjadur Rahman International Centre for Diarrhoeal Disease Research Bangladesh View all articles by this author Fahmida Tofail International Centre for Diarrhoeal Disease Research Bangladesh View all articles by this author Alice J. Wuermli New York University View all articles by this author Metrics & Citations Metrics Article Usage 380 views 86 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Elisa Ugarte, Paul Hastings, Eamam Hossain, et al. A Protocol to Acquire Infant Heart Rate Variability in the Rohingya Camps and Surrounding Communities in Cox's Bazar, Bangladesh. Authorea . 27 February 2025. DOI: https://doi.org/10.22541/au.174065820.02352697/v1 If you have the appropriate software installed, you can download article citation data to the citation manager of your choice. Simply select your manager software from the list below and click Download. For more information or tips please see 'Downloading to a citation manager' in the Help menu . Format Please select one from the list RIS (ProCite, Reference Manager) EndNote BibTex Medlars RefWorks Direct import Tips for downloading citations document.getElementById('citMgrHelpLink').addEventListener('click', function() { popupHelp(this.href); return false; }); $(".js__slcInclude").on("change", function(e){ if ($(this).val() == 'refworks') $('#direct').prop("checked", false); $('#direct').prop("disabled", ($(this).val() == 'refworks')); }); Cited by Alice J Wuermli, Ashraf Haque, Caroline M Hiott, Elisa Ugarte, Kazi Istiaque Sanin, Fahmida Tofail, Paul D Hastings, Ethical and culturally responsive biomarker research in the majority world, Child Development Perspectives, (2026). https://doi.org/10.1093/cdpers/aadag003 Crossref Loading... View Options View options PDF View PDF Figures Tables Media Share Share Share article link Copy Link Copied! Copying failed. 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