Effects of an early water, sanitation, hygiene, and nutritional intervention on child development at school age: a 7-year follow-up of a cluster-randomized trial in rural Bangladesh

58

59 A previous cluster-randomized controlled trial in Bangladesh found that individual or 60 combined water, handwashing, sanitation, and nutrition interventions during pregnancy 61 and after birth improved developmental outcomes of children at 1 and 2 years of age. 62 We aimed to determine if these intervention effects were sustained at school-age. 63 64

and Findings 65 Pregnant women were enrolled between May 2012 and July 2013 and randomized into 66 chlorinated drinking water (W); improved sanitation (S); handwashing with soap (H); 67 combined WSH; nutrition counselling and provision of lipid-based supplements (N); 68 combined WSH+N, or a passive control arm (C) (N=5,551). We followed-up enrolled 69 mothers and children 5 years after intervention completion. Primary outcomes were 70 child cognition, fine motor abilities, behaviour, school achievement, and executive 71 function; secondary outcomes were maternal mental health and the home environment. 72 We conducted intention to treat analyses using generalized linear models to determine 73 unadjusted and adjusted comparisons between each arm and the control, accounting 74 for pair-matching and block level clustering. 75 76 Between September 2019 and February 2021, we re-enrolled 3,832 children. Children 77 in the WSH+N, N, and S arms had improved cognitive scores on one or more domains 78 compared to the control arm, with adjusted effect sizes between 0.10 (95%CI: 79 0.00, 0.20) and 0.15 (0.03, 0.27). Children in all arms except S had improved prosocial 80 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 4 behaviour, with effect sizes between 0.21 (0.07, 0.34) and 0.33 (0.17, 0.49). No 81 intervention effects were observed for fine motor, difficult behaviours, executive 82 functioning, or school achievement. Maternal depressive symptoms were improved in 83 the WSH+N, H, and N arms, and the stimulating home environment was improved in all 84 intervention arms. Data collection for this study was interrupted by a 6-month pause at 85 the start of the COVID-19 pandemic. 86 87

88 At 7 years of age, we found small, sustained impacts of early water, sanitation, hygiene, 89 and nutrition interventions on child cognitive and social-emotional outcomes, the 90 stimulating home environment, and maternal mental health. Future work to determine 91 the mechanisms underlying these intervention effects will further inform the design of 92 early interventions to improve child health and development. 93 94 Trial registration 95 Follow-up trial: ClinicalTrials.gov, NCT04443855 96 Original WASH-Benefits Bangladesh (WASH-B): ClinicalTrials.gov, NCT01590095 97 98 99 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 5

100 In low- and middle-income countries (LMICs) it is estimated that one-third of three and 101 four-year-olds fail to meet basic milestones in cognitive or socioemotional 102 development.[1] Early measures of motor, cognitive, and socioemotional development 103 are predictive of later life outcomes, including educational attainment, economic 104 earnings, and socio-emotional behaviour in early adulthood.[2–4] During early 105 childhood, the brain undergoes rapid structural and functional changes; positive 106 experiences are more likely to contribute to the development of synaptic connections 107 important for optimal developmental trajectories and resilience, and negative 108 experiences can shift a child off the optimal developmental trajectory.[5] Thus, 109 interventions to reduce risk factors for impaired development in early life are critical to 110 promoting positive developmental trajectories and later life outcomes. 111 112 Similar to classification of nutrition interventions, interventions targeting child 113 development can be classified as development-specific interventions (i.e. those 114 addressing immediate determinants of nutrition and child development, such as 115 inadequate nutrient intake and unsupportive caregiving practices), or development-116 sensitive interventions (i.e. those addressing the underlying causes of undernutrition or 117 poor development such as poverty, food insecurity, or poor water and sanitation).[6] 118 Development-specific interventions focused on teaching caregivers about the 119 developmental importance of responsive caregiver-child interactions or the provision of 120 nutrition supplements or education have been shown to impact immediate early child 121 development outcomes.[7,8] 122 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 6 123 Development-sensitive interventions include those that provide nutritional 124 supplementation in early childhood, as well as those that aim to improve water, 125 sanitation, and handwashing (WASH) conditions. Nutrition interventions, which provide 126 the nutrients required for brain development have been shown to improve child 127 development outcomes early in life when delivered in the first 1000 days.[8] WASH 128 interventions aim to reduce the burden of enteric pathogens in the environment. Enteric 129 infections, including intestinal worms caused by poor sanitation, can result in iron 130 deficiency, and have negative consequences for child development outcomes.[9] 131 Observational studies have demonstrated associations between diarrhoea or other 132 infectious diseases and impaired cognitive outcomes.[10] Though observational 133 research demonstrates associations between improved water and sanitation 134 infrastructure and early child development outcomes,[11] few randomized-controlled 135 trials evaluated the independent effects of early WASH interventions on child 136 development outcomes. Three interventions, including the one followed up as part of 137 this study have evaluated the immediate post intervention impact of development-138 sensitive interventions targeting improvements in WASH on child development 139 outcomes.[12–14] An early WASH intervention in rural Zimbabwe found no effect on 140 child development outcomes. [12] Individual or combined WASH and nutrition 141 interventions improved early child development in Bangladesh, but not in Kenya.[13,14] 142 143 Despite robust evidence for the early effects of both development-specific interventions, 144 very few studies have investigated the medium or long-term impacts of early 145 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 7 interventions to promote child development on outcomes in middle and late-146 childhood.[15] There is even less evidence for the medium- or long-term effects of 147 development-sensitive interventions. A follow-up of the early WASH intervention in rural 148 Zimbabwe that had no impact on development outcomes in early childhood found no 149 impacts on cognitive development at 7 years of age, and small impacts of WASH on 150 socioemotional function.[16] Another cRCT in Pakistan found that children whose 151 households received a handwashing promotion and drinking water treatment for 9 152 months in the first 30 months of life had improved child development at 5-7 years of 153 age.[17] Our team was unable to find any studies that evaluated the later impact of an 154 early combined Nutrition and WASH intervention that previously demonstrated an early 155 impact on child development outcomes. 156 157 Our previous cluster-randomized controlled trial (cRCT) in Bangladesh evaluated the 158 impact of water quality, handwashing, sanitation (WASH), and nutrition interventions, 159 when delivered either individually or in combination during pregnancy through 18 160 months after birth, on diarrhoea, growth, and developmental outcomes in 161 children.[13,18] It was hypothesized that the WASH intervention had the potential to 162 positively benefit the developmental trajectories of children by reducing enteric infection, 163 improving child nutritional status and health, and altering parental interaction and care 164 practices. At the immediate post-intervention evaluation at the age of approximately 2-165 years, there were immediate benefits on one or more domains of child development in 166 all intervention arms, with the greatest benefit in the combined intervention arm (WASH 167 and nutrition), with effect sizes ranging from 0·13 to 0·35 SDs.[13] Additionally, mothers 168 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 8 in all intervention groups reported fewer depressive symptoms compared to mothers in 169 the control households (effect sizes ranged between -0·19 to -0·31 SDs). To better 170 understand how early water, sanitation, and hygiene interventions can impact child 171 development over the life course, we aim to evaluate the effects of individual and 172 combined water, sanitation, hygiene, and nutrition interventions on primary outcomes of 173 child development, school achievement, executive functioning, fine motor development, 174 and socio-emotional development, and secondary outcomes of maternal mental health 175 and stimulation in the home environment at 7 years of age. 176 177

178 Original study design and participants 179 The parent cluster-randomized controlled trial (WASH-Benefits, or WASH-B, 180 ClinicalTrials.gov Identifier: NCT01590095) was conducted in the rural villages of four 181 districts (Gazipur, Kishoreganj, Mymensingh, and Tangail) of central Bangladesh. The 182 parent trial began in 2011 when there were no major water, sanitation, or focused 183 nutrition programmes in the study area. The details about randomization, study design, 184 intervention, methods, and rationale are described elsewhere.[18,19] In brief, pregnant 185 women were randomized to one of six intervention arms: chlorinated drinking water (W); 186 improved sanitation (S); handwashing with soap (H); combined water, sanitation, and 187 handwashing (WASH); improved nutrition through counselling and provision of lipid-188 based nutrient supplements (N); and combined water, sanitation, handwashing, and 189 nutrition (WASH+N) or into a double-sized, passive, control arm (C) through 190 geographically pair-matched randomization (Table S1). The intervention continued for 191 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 9 two years. A total of 5,551 pregnant women were enrolled, among them, 4,757 live 192 births were assessed at 1 year and 4,403 at 2 years of age.[13] 193 194 Procedure at long term follow-up 195 Between September 2019 and February 2021, 7 years following intervention initiation, 196 and 5 years following intervention completion, we re-visited the households of all live 197 births who had not been reported to have passed away at any previous time point. 198 Trained enumerators evaluated children, mothers, and the home environment through 199 two separate household visits around a week apart. The visits took 1.5 and 2.5 hours, 200 respectively. During the initial visit (Day-1), trained enumerators obtained written 201 consent and collected information on sociodemographic factors, and data regarding- 202 water supply, sanitation, faecal disposal methods, hand washing conditions, latrine 203 infrastructure, and other facilities. Additionally, they evaluated the home environment, 204 children’s behaviour, and anthropometry. In the subsequent visit (Day-2), enumerators 205 assessed the developmental outcomes of the children and evaluated the depressive 206 symptoms of their mothers. 207 208 On Day-1, 10 university graduate enumerators conducted data collection and 209 assessments. On Day-2, 12 enumerators, who had degrees in social sciences or 210 psychology and experiences in child development assessments, conducted 211 developmental evaluations. The Day-1 and Day-2 enumerators underwent a 2 (for day 212 1) and 4 (for day 2) training programs, which included theoretical instruction, mock 213 practice, and hands-on practice with non-study participants/children in the community, 214 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 10 under supervision. For Day-2 enumerators inter-observer reliability assessments were 215 conducted between testers and enumerators where each enumerator conducted at 216 least 10 tests. Enumerators were only allowed to participate in the main study once they 217 achieved over 90% agreement with the trainers. During the data collection phase, a 218 supervisor evaluated 10% of all tests to ensure satisfactory ongoing reliability (kappa > 219 0.90). Refresher training sessions were held once in October 2020 for both data 220 collection teams. Enumerators were blinded to intervention status. Up to three attempts 221 were made to find each household. Children who were vision or hearing impaired or had 222 a severe developmental disability were excluded from the assessment. 223 224 The study protocol was approved by human subjects committees at icddr,b (PR-19025), 225 and the University of California, Berkeley (2018-12-11672). 226 227 Measurement 228 Primary outcomes: 229 To measure child cognitive development, we selected 9 subtests of the Wechsler Pre 230 and Primary School Intelligence – Fourth Edition (WPPSI-IV) developed in the United 231 States.[20] This test aims to assess the intellectual ability of children aged 4 to 7.5 years 232 of age. Previous versions of WPPSI have been widely implemented in Bangladesh, and 233 went through rigorous cultural adaptations before use.[21] Our cultural adaptations 234 focused on modifying individual items and pictures that were unfamiliar in the rural 235 Bangladeshi context (e.g. we replaced the image of “Red Fire Hydrant” with “local Red 236 Gas Cylinder”, “Life Jacket” with “Normal Jacket”, “Hour Glass” with “Table-Clock”) while 237 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 11 maintaining the underlying intent of the question. We followed standard instructions for 238 administration and scoring of evaluations. Using the 9 subtests we constructed 239 subscales for the Full Scale IQ (FSIQ); 3 Primary Index Scores: Verbal Comprehension 240 Index (VCI), Fluid Reasoning Index (FRI), Working Memory Index (WMI); 3 Ancillary 241 Index Score: General Ability Index (GAI), Nonverbal Index (NVI), and the Cognitive 242 Proficiency Index (CPI). 243 244 To assess children’s fine motor ability we used three measures of manual dexterity 245 following the second edition of the Movement Assessment Battery for Children.[22] 246 These tests have been previously used in Bangladesh.[23] To assess children’s 247 behaviour we used the parent-reported Strengths and Difficulties Questionnaire 248 (SDQ).[24] The standard Bengali language (Bangla) version of SDQ has been used 249 previously in Bangladesh.[25] We assessed three areas of children’s executive 250 functioning. Working memory, attention, and memory (short and delayed) were 251 evaluated using forward Digit span, Corsi-blocks, and a narrative memory test, 252 respectively. These tests were chosen from neuropsychological[26] and preschool 253 assessment tools[27] after piloting on 50 children. We piloted a battery of executive 254 function tests previously implemented in South Asia and selected the tests that showed 255 variability for children of the age group assessed in the current study. Finally, we 256 evaluated academic achievement (reading, spelling, and mathematics) using a locally 257 developed tool based on the Wide Range Achievement Test (WRAT).[28] It has 258 individually administered reading, spelling, and arithmetic questions in Bengali which 259 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 12 are ranked with increasing difficulty. It has previously been used in Bangladesh with 260 primary school children.[29] 261 262 We internally age-standardized all primary outcomes to the control group separately for 263 data collected prior to the COVID pandemic and data collected during the COVID 264 pandemic. We used local mean standardization with 2-month age bands. We had 265 originally planned to use 4-month age bands but had sufficient sample size to reduce 266 the size of the age band. To construct WPPSI-IV and fine motor subtest scores, we first 267 internally standardized each subscale, then averaged the internally standardized scores 268 across relevant subtest for each subscale, and finally constructed a z-score with respect 269 to the control group. We conducted supplementary analyses with externally 270 standardized scores for the WPPSI-IV subscales. 271 272 Secondary outcomes: 273 We measured maternal depressive symptoms of mothers with the 20-item Center for 274 Epidemiologic Studies Depression Scale (CESD).[30] The 20-item CESD has been 275 used widely in Bangladesh and other South-East Asian countries.[31] We evaluated the 276 home environment and amount of stimulation at home with an adapted version of the 277 Middle childhood Home Observation Measurement (HOME), which has been used 278 previously in Bangladesh.[29,32] 279 280 Other measurements 281 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 13 We collected information on the sustained presence of technologies distributed during 282 the initial intervention following protocols used at the 1 and 2 year follow up time 283 points.[18] 284 285 Statistical Analysis 286 The sample size for the original trial was calculated to detect a difference of 0.15 in the 287 length-for-age Z score (LAZ) when comparing each intervention arm to the control, 288 accounting for repeated measures within clusters.[19] In this follow-up, for each 289 outcome, we compared the control arm to each intervention arm, and also compared 290 the WSH+N vs. Nutrition, and WSH+N vs WSH to isolate the additive effects of WSH 291 and N, respectively. We first calculated unadjusted mean differences using generalized 292 linear models accounting for pair matching and block-level clustering, to account for the 293 original randomization procedure.[18] We then calculated adjusted mean differences 294 controlling for time of assessment (pre-COVID or during COVID) and concurrent child 295 age along with a set of prognostic baseline characteristics. The covariates for potential 296 inclusion in each model were assessed with a likelihood ratio test, and covariates with 297 p>0.20 were included. All analyses were intention to treat. 298 We conducted subgroup analyses by maternal primary education status at baseline, 299 child sex at birth, measurement before or during the COVID-19 pandemic, and 300 socioeconomic status at baseline (wealth index split at the median). and We had 301 originally planned to conduct additional stratified analyses by household distance from 302 Dhaka (split at the median distance) but found that there was large overlap between 303 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 14 distance from Dhaka and measurement pre vs. post COVID, so we did not conduct this 304 analysis. 305 All analyses were done in R, version 4.3.3.[33] The pre-analysis plan for this study is 306 posted on OSF (https://osf.io/jgh7y/?view_only=ca62a737fc3a443f859e83eb6cc9ad13). 307 In the pre-analysis plan, we specified that we would additionally do subgroup analysis 308 by child age at assessment, but the lack of full age overlap across assessment periods 309 made this not viable as an independent analysis. 310 311 The follow-up is registered with ClinicalTrials.gov, NCT04443855. 312 313

314 Between September 2019 and February 2021, enumerators attempted to locate 4,961 315 children in 4,932 households (Figure 1). Assessments were paused during the initial 316 phases of the COVID-19 pandemic from March 15th to October 13th, 2020. The 317 assessment took place over two days, which aimed to be conducted within 3 weeks. 318 Due to COVID-19 pandemic related disruptions as well as households that were 319 unavailable for a second assessment within 3 weeks, 23% of assessments were 320 conducted over 3 weeks apart. A total of 4,175 (84% of those attempted) children 321 completed the first assessment, with the most common reasons for not completing the 322 assessment were that the family had migrated (n=543, 11% of those attempted) or the 323 child was absent from household (n=173, 3%) (Figure 1). At the second assessment, 324 which included the child development assessment, an additional 340 (8% of the sample 325 attempted) did not complete the assessment, with the most common reason being that 326 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 15 the child was absent from the household at the second visit (n=281, 7% of those 327 attempted for visit 2) (Figure 1). Complete assessments for both days were performed 328 for 3,833 (69% of the initially enrolled sample, 77% of the sample that was attempted at 329 follow-up) children in 3,812 households (21 pairs of twins) (Figure 1). Participants 330 followed-up were similar to those who were lost to follow-up across a range of 331 characteristics (Table S2). 332 333 Baseline characteristics of the sample are similar across study arm for those in the 334 completely assessed group at the 7-year follow-up (Table 1). Children had a mean age 335 of 83.5 months (Range: 74.4-92.2, SD: 3.5) at the child development assessment. 336 337 338 Figure 1. Flow diagram 339 Follow up #1: Included water, sanitation and hygiene infrastructure, school attendance information, 340 HOME assessment, Strengths and difficulties questionnaire, anthropometry; Follow up #2: included all 341 direct cognitive, motor and school achievement assessments, and maternal mental health. 342 343 344 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 16 Table 1. Baseline characteristics of the re-enrolled populations 345 346 Data are n (%) or mean (s.d.); No. of participants includes 21 sets of twins 347 348 At the 7-year follow-up, households in intervention arms that received the sanitation 349 intervention were more likely to have a latrine with a functional water seal (Sanitation: 350 83%, WSH: 78%, and WSH+N: 83%) compared to the control arm (48%) and other 351 arms without sanitation (Sanitation: 51%, WSH: 50%, WSH+N: 51%) (Table 2). The 352 proportion of households in the Sanitation arms with a latrine with a functional water 353 seal was lower than at the 2-year endline (Table 2). Other indicators of intervention 354 adherence including the presence of stored drinking water, visible faeces on the latrine 355 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 17 slab or floor, and the presence of soap at the handwashing station were not 356 substantially different across arms (Table 2). 357 Table 2. Sustained adoption of behavioural recommendations and continued presence of 358 technologies promoted or distributed during the period of project implementation 359 360 Data are n(%); Intervention began after enrolment and continued until the Year 2 assessment. No 361 intervention was implemented between Year 2 and Year 7. Participants without a latrine are included in 362 the denominator of the latrine-related adherence measures, and those without a handwashing statement 363 are included in the denominator of the handwashing location with soap adherence measure. 364 365 WPPSI-IV 366 Compared to children in the control arm, children in the WSH+N arm had better FSIQ 367 scores (adjusted mean difference: 0.12 (95% CI: 0.02, 0.23)) (Figure 2, Table S3). 368 Children in all other arms did not have differences in FSIQ scores compared to children 369 in the control arm that were statistically significant at p<0.05 (Figure 2, Table S3). 370 Compared to children in the control arm, children had better FRI scores in the WSH+N 371 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 18 (0.15 (0.03, 0.27)), Sanitation (0.12 (0.00, 0.24)), and Nutrition arms (0.12 (0.01, 0.23)) 372 (Figure S1, Table S3). Children also had better WPPSI-IV GAI scores in the WSH+N 373 (0.12 (0.03, 0.22)), Sanitation (0.12 (0.01, 0.23)), and Nutrition (0.11 (0.01, 0.20)) arms, 374 better NVI scores in the WSH+N (0.13 (0.03, 0.24)) and Sanitation (0.11 (0.00, 0.22)) 375 arm, and better VCI scores in the nutrition arm (0.10 (0.00, 0.20)) (Figure S1, Table S3). 376 There were no differences between any intervention arm and the control arm for the CPI 377 or WMI scores (Figure S1, Table S3). 378 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 19 Figure 2. Differences in child development and school achievement by control versus intervention 379 arm. SDQ: strengths and difficulties questionnaire, Narrative memory: Sum of free and cued recall scores 380 from a narrative memory test 381 382 Fine motor, executive functioning, academic achievement, difficult and prosocial 383 behaviour 384 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 20 There were no differences between the control arm and any intervention arm for fine 385 motor development, executive functioning, or the spelling, math, or reading domains of 386 the school achievement test (Figure 2, Table S4, Figure S2). The measure of social 387 emotional development showed that difficult behaviours were not different between any 388 intervention arm when compared to the control arm, but prosocial behaviour scores 389 were higher for children in all intervention arms except for the sanitation arm compared 390 to the control arm (Water: 0.19 (0.06, 0.32), Hygiene: 0.21 (0.08, 0.34), WSH: 391 0.29 (0.15, 0.43), Nutrition: 0.21 (0.07, 0.35), WSH+N: 0.32 (0.16, 0.48) (Figure 2, Table 392 S4). 393 394 Compared to caregivers of control children, caregivers had fewer depressive symptoms 395 in the WSH+N (-0.15 (-0.27, -0.02)), Handwashing (-0.14 (-0.24, -0.03)), and Nutrition (-396 0.21 (-0.31, -0.11)) arms. Compared to children in the control arm, children in all 397 intervention arms had more stimulating home environments ((Water: 0.19 (0.03, 0.35), 398 Sanitation: 0.17 (0.00, 0.35), Hygiene: 0.26 (0.11, 0.42), WSH: 0.31 (0.15, 0.48), 399 Nutrition: 0.24 (0.08, 0.41), WSH+N: 0.41 (0.24, 0.57)) (Figure 3, Table S5). 400 401 402 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 21 Figure 3. Differences in secondary outcomes by arm. CES-D: Center for epidemiologic studies 20-403 question depression measure; HOME: Middle childhood Home Observation Measurement of the 404 Environment 405 406 In subgroup analyses there was no consistent heterogeneity in intervention effects on 407 FSIQ by assessment timing (prior to or during the COVID pandemic), or maternal 408 education status (mother had completed secondary school prior to pregnancy) (Figure 409 4). Families with higher wealth indices at baseline, and those with male children tended 410 to have larger effect sizes on the FSIQ (Figure 4). There were no consistent patterns 411 across other outcomes for heterogeneity analyses (Figures S3-S12). There were no 412 differences between WSH+N vs nutrition or WSH+N vs WSH for any outcomes (Tables 413 S1-S4). 414 415 416 Figure 4. Subgroup analysis for FSIQ outcome. FSIQ: Full Scale IQ 417 418 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 22 419 420

421 This medium-term follow up showed that 5 years after intervention completion single or 422 combined water, handwashing, sanitation, and nutritional interventions had small but 423 significant sustained impacts on one or more domains of child development, the home 424 environment, and caregiver mental wellbeing. At approximately 7 years of age, we 425 found that children who received the WSN+N, Nutrition, or Sanitation intervention had 426 improved cognitive development in three of the six WPPSI-IV subscales when 427 compared to control children, and children in all arms except for the Sanitation arm had 428 improved prosocial behaviours. Children in all intervention arms had more stimulating 429 home environments compared to the control arm. Caregiver-related outcomes were 430 also improved, with caregivers in the WSH+N, Handwashing, and Nutrition arms having 431 fewer depressive symptoms. There were no improvements in fine motor, executive 432 functioning or academic achievement for children in any of the intervention arms. 433 Impacts across domains did not substantially differ by assessment timing (prior to or 434 during the COVID-19 pandemic), maternal education status, child sex, or wealth status. 435 436 Our intervention was unique in that it followed up an early WASH intervention that 437 improved child development at 2 years of age. Two other randomized controlled trials 438 have evaluated the impact of early WASH interventions on early child development 439 outcomes immediately post intervention, and neither found any improvements for 440 children who received the interventions. [12,14] One previous study in Pakistan 441 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 23 evaluated later, but not immediate impacts of a handwashing and water intervention on 442 child development. In Pakistan, children who were randomized to receive either hand 443 washing promotion or hand washing promotion plus water treatment interventions 444 during the first 30 months of life were followed up between 5-7 years of age. Children 445 who received the intervention were found to have improvements on a composite 446 measure of development equivalent to an effect size of 0.4 standard deviations.[17] 447 Other interventions have evaluated a combination of sanitation or hygiene interventions 448 with stimulation on outcomes later in childhood, and found improved child development 449 and caregiver mental health amongst families who received the intervention.[34,35] 450 However, these interventions are unable to untangle the impact of the water, sanitation 451 and hygiene component from the psychosocial stimulation component. 452 453 In contrast to the evidence for early WASH interventions, there is evidence for the 454 impact of early nutrition supplementation on immediate child development. A recent 455 systematic review and meta-analyses,[8] examined the impact of early small-quantity 456 lipid-based multiple micronutrient supplements delivered within the first 1000 days on 457 short-term child-development outcomes in LMICs. They found that 11 out of 13 458 interventions showed moderate post-intervention benefits to language, social-emotional, 459 motor, and executive function. However, few of these studies followed up with children. 460 In rural Pakistan a nutrition education and multiple micronutrient powder 461 supplementation intervention for children 6-24 months of age was found to improve 462 motor development, but not WPPSII-III FSIQ, executive functioning, pre-academic skills 463 or behavioural problems at 4 years of age.[36] In Ghana, lipid-based nutrient 464 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 24 supplements provided between 6-24 months reduced social emotional difficulties 465 amongst children at 4-6 years of age, but weren’t found to impact cognitive or fine motor 466 development outcomes.[37] These impacts on social emotional difficulties did not 467 persist to 9-11 years of age.[38] A micronutrient supplementation trial in Indonesia 468 found improved procedural memory in children at 9-12 years of age, and enrolled 469 children born to anaemic mothers had improved general intellectual ability.[39] Finally, a 470 small factorial designed nutrition and stimulation intervention provided in Jamaica found 471 no impact of 2 years of early supplementation with milk-based formula on child 472 development outcomes at 7-8 years of age except a subset of children with mothers 473 who had higher verbal intelligence quotients, and no impact was found from 474 supplementation at later time points.[40] 475 476 In this follow-up, we found small but sustained benefits in Full Scale IQ for children in 477 the Sanitation and WSH+N arms. We also found improvements in three out of six total 478 WPPSI sub-domains for the WSH+N, Nutrition, and Sanitation arms, and improved 479 prosocial behaviours in all intervention arms. The intervention was given during the first 480 1000 days of life, a critical and sensitive window of development.[5,41] There are two 481 primary pathways through which we hypothesize these interventions could have had 482 sustained impacts. The first is through reduced enteric infections, as the initial 483 interventions reduced diarrhoea at 2 years of age in all intervention arms except for the 484 Water arm.[18] Inflammation associated with diarrhoea limits the absorption of key 485 nutrients, and repeated episodes of diarrhoea before age two are associated with 486 poorer cognitive development outcomes, so this may also be a mechanism by which the 487 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 25 early intervention had sustained effects.[42,43] Additionally, the two previous WASH 488 interventions that did not find impacts on child development at intervention completion 489 also did not find impacts on diarrhoea.[44,45] Another potential pathway of intervention 490 effect could be through support of caregivers and improved caregiving practices, which 491 was higher in the WASH-Benefits Bangladesh intervention than in the previous WASH 492 interventions. In all intervention arms community health promotors were instructed to 493 visited intervention households weekly for the first 6 months, and then every 2 weeks for 494 the subsequent 18 months, the actual number of visits per month were an average of 5-495 7 throughout the intervention period.[46] These visits started during the 1st and 2nd 496 trimester of pregnancy and continued for almost two years after birth. Although support 497 for caregiver mental wellbeing or child stimulation was not explicitly provided, maternal 498 depressive symptoms were significantly reduced in the WSH+N, H, and N arms, and the 499 stimulating home environment was improved in all intervention arms. Caregiver mental 500 health and the caregiving environment were also improved at the 2-year endline 501 assessment reported previously.[13] The impacts on child development may be due to 502 increased attention to the child and social support provided to the caregiver during the 503 frequent household visits leading to both improved mental health of caregivers and 504 more attention to and investment in the child’s physical and social environment. 505 Improvements in home stimulation is a target of many child development-specific 506 interventions.[47] 507 508 While we found impacts on some measures of child development, for multiple measures 509 we did not identify any impacts. For example, we found impacts on narrative memory for 510 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 26 children in the WSH+N arm, but did not find any impacts for any other intervention arms 511 or any other measures of executive functioning. To evaluate executive functioning, we 512 chose tests that focused on memory and attention but did not include a test that 513 evaluated inhibitory control as it was not adequately adapted to the population (we 514 observed ceiling effects during piloting). The chosen tests may not have been sensitive 515 enough to evaluate the intervention’s impact. We also did not find impacts on fine 516 motor, problematic behaviours, or academic achievement. A lack of effects on school 517 achievement may be because most children have only been exposed to one fewer 518 years of formal schooling at this age. As intervention effects did not differ between 519 children assessed prior to and during the COVID-19 pandemic, educational interruption 520 during the early COVID-19 pandemic period was not likely to have affected this finding. 521 522 Our study has several strengths including its basis on a large RCT design with well-523 balanced intervention arms and a double-sized control. We delivered both individual 524 and combined interventions to understand the unique and combined impacts of each 525 intervention. The enumerators went through a rigorous training for developmental 526 assessments and monitored for 10% quality-check throughout the study period. There 527 were direct assessments for children’s development and observation for home 528 environment, and all analyses were prespecified. Our outcome measures had good 529 psychometric properties. However, this study also has several weaknesses. We applied 530 child development assessment tools that were not initially developed or standardized for 531 use in LMIC settings. We culturally adapted all measures for use in our study setting in 532 Bangladesh and conducted rigorous piloting. To further mitigate this issue, instead of 533 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 27 using standardized scores from external high-income populations, we used internally 534 standardized z-scores. Further, our data collection period was interrupted by the 535 COVID-19 pandemic, and paused between March and September 2020, which may 536 have affected the results. We adjusted for assessment time period (before or during the 537 COVID-19 pandemic) within the standardization of outcomes, controlled for it in all 538 analyses, and conducted sub-group analyses to examine differences. Finally, we were 539 unable to assess 31% of children from the original study. However, we did not find 540 major differences in baseline characteristics between participants who lost to follow and 541 those followed up, reducing the potential bias induced by loss to follow up. 542 543 We found that an early water, sanitation, hygiene, and nutrition interventions had 544 sustained impacts on child development, caregiver mental health, and the stimulating 545 home environment. Future work to elucidate the mechanisms of these impacts will help 546 to isolate the key components of these interventions. 547 548 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 28

549 1. McCoy DC, Peet ED, Ezzati M, Danaei G, Black MM, Sudfeld CR, et al. Early 550 Childhood Developmental Status in Low- and Middle-Income Countries: National, 551 Regional, and Global Prevalence Estimates Using Predictive Modeling. PLoS Med. 552 2016;13: e1002034. doi:10.1371/journal.pmed.1002034 553 2. Gertler P, Heckman J, Pinto R, Zanolini A, Vermeersch C, Walker S, et al. Labor 554 market returns to an early childhood stimulation intervention in Jamaica. Science. 555 2014;344: 998–1001. doi:10.1126/science.1251178 556 3. Peet ED, McCoy DC, Danaei G, Ezzati M, Fawzi W, Jarvelin M-R, et al. Early 557 Childhood Development and Schooling Attainment: Longitudinal Evidence from 558 British, Finnish and Philippine Birth Cohorts. PLOS ONE. 2015;10: e0137219. 559 doi:10.1371/journal.pone.0137219 560 4. Black MM, Walker SP, Fernald LCH, Andersen CT, DiGirolamo AM, Lu C, et al. 561 Early childhood development coming of age: science through the life course. The 562 Lancet. 2017;389: 77–90. doi:10.1016/S0140-6736(16)31389-7 563 5. Bhutta ZA, Guerrant RL, Nelson CA. Neurodevelopment, Nutrition, and 564 Inflammation: The Evolving Global Child Health Landscape. Pediatrics. 2017;139: 565 S12–S22. doi:10.1542/peds.2016-2828D 566 6. Ruel MT, Alderman H. Nutrition-sensitive interventions and programmes: how can 567 they help to accelerate progress in improving maternal and child nutrition? The 568 Lancet. 2013;382: 536–551. doi:10.1016/S0140-6736(13)60843-0 569 7. Aboud FE, Yousafzai AK. Global Health and Development in Early Childhood. 570 Annu Rev Psychol. 2015;66: 433–457. doi:10.1146/annurev-psych-010814-015128 571 8. Prado EL, Arnold CD, Wessells KR, Stewart CP, Abbeddou S, Adu-Afarwuah S, et 572 al. Small-quantity lipid-based nutrient supplements for children age 6-24 months: a 573 systematic review and individual participant data meta-analysis of effects on 574 developmental outcomes and effect modifiers. Am J Clin Nutr. 2021;114: 43S-67S. 575 doi:10.1093/ajcn/nqab277 576 9. Prado EL, Dewey KG. Nutrition and brain development in early life. Nutr Rev. 577 2014;72: 267–284. doi:10.1111/nure.12102 578 10. Pinkerton R, Oriá RB, Lima AAM, Rogawski ET, Oriá MOB, Patrick PD, et al. Early 579 Childhood Diarrhea Predicts Cognitive Delays in Later Childhood Independently of 580 Malnutrition. Am J Trop Med Hyg. 2016;95: 1004–1010. doi:10.4269/ajtmh.16-0150 581 11. Dearden KA, Brennan AT, Behrman JR, Schott W, Crookston BT, Humphries DL, 582 et al. Does household access to improved water and sanitation in infancy and 583 childhood predict better vocabulary test performance in Ethiopian, Indian, Peruvian 584 and Vietnamese cohort studies? BMJ Open. 2017;7: e013201. 585 doi:10.1136/bmjopen-2016-013201 586 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 29 12. Gladstone MJ, Chandna J, Kandawasvika G, Ntozini R, Majo FD, Tavengwa NV, et 587 al. Independent and combined effects of improved water, sanitation, and hygiene 588 (WASH) and improved complementary feeding on early neurodevelopment among 589 children born to HIV-negative mothers in rural Zimbabwe: Substudy of a cluster-590 randomized trial. PLOS Med. 2019;16: e1002766. 591 doi:10.1371/journal.pmed.1002766 592 13. Tofail F, Fernald LC, Das KK, Rahman M, Ahmed T, Jannat KK, et al. Effect of 593 water quality, sanitation, hand washing, and nutritional interventions on child 594 development in rural Bangladesh (WASH Benefits Bangladesh): a cluster-595 randomised controlled trial. Lancet Child Adolesc Health. 2018;2: 255–268. 596 doi:10.1016/S2352-4642(18)30031-2 597 14. Stewart CP, Kariger P, Fernald L, Pickering AJ, Arnold CD, Arnold BF, et al. Effects 598 of water quality, sanitation, handwashing, and nutritional interventions on child 599 development in rural Kenya (WASH Benefits Kenya): a cluster-randomised 600 controlled trial. Lancet Child Adolesc Health. 2018;2: 269–280. doi:10.1016/S2352-601 4642(18)30025-7 602 15. Jeong J, Pitchik HO, Fink G. Short-term, medium-term and long-term effects of 603 early parenting interventions in low- and middle-income countries: a systematic 604 review. BMJ Glob Health. 2021;6: e004067. doi:10.1136/bmjgh-2020-004067 605 16. Piper JD, Mazhanga C, Mwapaura M, Mapako G, Mapurisa I, Mashedze T, et al. 606 School-age growth and development following infant feeding and/or water, 607 sanitation, and hygiene interventions in rural Zimbabwe: long-term follow-up of a 608 cluster-randomised trial. eClinicalMedicine. 2024;78. 609 doi:10.1016/j.eclinm.2024.102946 610 17. Bowen A, Agboatwalla M, Luby S, Tobery T, Ayers T, Hoekstra RM. Association 611 between intensive handwashing promotion and child development in Karachi, 612 Pakistan: a cluster randomized controlled trial. Arch Pediatr Adolesc Med. 613 2012;166: 1037–1044. doi:10.1001/archpediatrics.2012.1181 614 18. Luby SP, Rahman M, Arnold BF, Unicomb L, Ashraf S, Winch PJ, et al. Effects of 615 water quality, sanitation, handwashing, and nutritional interventions on diarrhoea 616 and child growth in rural Bangladesh: a cluster randomised controlled trial. Lancet 617 Glob Health. 2018;6: e302–e315. doi:10.1016/S2214-109X(17)30490-4 618 19. Arnold BF, Null C, Luby SP, Unicomb L, Stewart CP, Dewey KG, et al. Cluster-619 randomised controlled trials of individual and combined water, sanitation, hygiene 620 and nutritional interventions in rural Bangladesh and Kenya: the WASH Benefits 621 study design and rationale. BMJ Open. 2013;3: e003476. doi:10.1136/bmjopen-622 2013-003476 623 20. Wechsler D. Wechsler preschool and primary scale of intelligence—fourth edition. 624 Psychol Corp San Antonio TX. 2012. 625 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 30 21. Ruan-Iu L, Pendergast LL, Rasheed M, Tofail F, Svensen E, Maphula A, et al. 626 Assessing Early Childhood Fluid Reasoning in Low- and Middle-Income Nations: 627 Validity of the Wechsler Preschool and Primary Scale of Intelligence Across Seven 628 MAL-ED Sites. J Psychoeduc Assess. 2019; 0734282919850040. 629 doi:10.1177/0734282919850040 630 22. Henderson SE, Sugden D, Barnett AL. Movement Assessment Battery for 631 Children-2. APA PsycTests. 2007 [cited 27 Jun 2024]. doi:10.1037/t55281-000 632 23. Ali H, Hamadani J, Mehra S, Tofail F, Hasan MI, Shaikh S, et al. Effect of maternal 633 antenatal and newborn supplementation with vitamin A on cognitive development 634 of school-aged children in rural Bangladesh: a follow-up of a placebo-controlled, 635 randomized trial. Am J Clin Nutr. 2017;106: 77–87. doi:10.3945/ajcn.116.134478 636 24. Goodman R. Psychometric Properties of the Strengths and Difficulties 637 Questionnaire. J Am Acad Child Adolesc Psychiatry. 2001;40: 1337–1345. 638 doi:10.1097/00004583-200111000-00015 639 25. Gustin K, Tofail F, Vahter M, Kippler M. Cadmium exposure and cognitive abilities 640 and behavior at 10 years of age: A prospective cohort study. Environ Int. 2018;113: 641 259–268. doi:10.1016/j.envint.2018.02.020 642 26. Korkman M, Kirk U, Kemp S. NEPSY - Second Edition. APA PsycTests. 2007 643 [cited 27 Jun 2024]. doi:10.1037/t15125-000 644 27. Obradović J, Portilla XA, Boyce WT. Executive functioning and developmental 645 neuroscience: Current progress and implications for early childhood education. 646 Handb Early Child Educ. 2012; 324–351. 647 28. Wilkinson GS. Wide range achievement test 3: WRAT3. Wilmington, DE: Wide 648 Range, Inc.; 1993. Available: 649 https://search.library.wisc.edu/catalog/999714707202121 650 29. Hossain SJ, Tofail F, Mehrin SF, Hamadani JD. Six-Year Follow-up of Childhood 651 Stimulation on Development of Children With and Without Anemia. Pediatrics. 652 2023;151: e2023060221E. doi:10.1542/peds.2023-060221E 653 30. Radloff LS. The CES-D Scale: A Self-Report Depression Scale for Research in the 654 General Population. Appl Psychol Meas. 1977;1: 385–401. 655 doi:10.1177/014662167700100306 656 31. Black MM, Baqui AH, Zaman K, Arifeen SE, Black RE. Maternal depressive 657 symptoms and infant growth in rural Bangladesh. Am J Clin Nutr. 2009;89: 951S-658 957S. doi:10.3945/ajcn.2008.26692E 659 32. Bradley RH, Caldwell BM, Rock SL, Hamrick HM, Harris P. Home Observation for 660 Measurement of the Environment: Development of a Home Inventory for use with 661 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 31 families having children 6 to 10 years old. Contemp Educ Psychol. 1988;13: 58–71. 662 doi:10.1016/0361-476X(88)90006-9 663 33. R Core Team. R: A language and environment for statistical computing. R 664 Foundation for Statistical Computing, Vienna, Austria; 2022. 665 34. Kakwangire P, Muhoozi G, Ngari M, Matovu N, Westerberg AC, Iversen PO, et al. 666 8-Year Follow-up of a Maternal Education Trial in a Low-Resource Setting. 667 Pediatrics. 2024; e2023063352. doi:10.1542/peds.2023-063352 668 35. Kakwangire P, Atukunda P, Ngari M, Westerberg AC, Iversen PO, Muhoozi G. 669 Long-term effects on depressive symptoms among Ugandan mothers – Findings 670 from a follow-up of a cluster-randomized education trial in a rural low-resource 671 setting. J Affect Disord. 2024;351: 598–606. doi:10.1016/j.jad.2024.01.263 672 36. Yousafzai AK, Obradović J, Rasheed MA, Rizvi A, Portilla XA, Tirado-Strayer N, et 673 al. Effects of responsive stimulation and nutrition interventions on children’s 674 development and growth at age 4 years in a disadvantaged population in Pakistan: 675 a longitudinal follow-up of a cluster-randomised factorial effectiveness trial. Lancet 676 Glob Health. 2016;4: e548-558. doi:10.1016/S2214-109X(16)30100-0 677 37. Ocansey ME, Adu-Afarwuah S, Kumordzie SM, Okronipa H, Young RR, Tamakloe 678 SM, et al. Prenatal and postnatal lipid-based nutrient supplementation and 679 cognitive, social-emotional, and motor function in preschool-aged children in 680 Ghana: a follow-up of a randomized controlled trial. Am J Clin Nutr. 2019;109: 322–681 334. doi:10.1093/ajcn/nqy303 682 38. Prado EL, Adu-Afarwuah S, Arnold CD, Adjetey E, Amponsah B, Bentil H, et al. 683 Prenatal and postnatal small-quantity lipid-based nutrient supplements and 684 children’s social–emotional difficulties at ages 9–11 y in Ghana: follow-up of a 685 randomized controlled trial. Am J Clin Nutr. 2023;118: 433–442. 686 doi:10.1016/j.ajcnut.2023.05.025 687 39. Prado EL, Sebayang SK, Apriatni M, Adawiyah SR, Hidayati N, Islamiyah A, et al. 688 Maternal multiple micronutrient supplementation and other biomedical and 689 socioenvironmental influences on children’s cognition at age 9–12 years in 690 Indonesia: follow-up of the SUMMIT randomised trial. Lancet Glob Health. 2017;5: 691 e217–e228. doi:10.1016/S2214-109X(16)30354-0 692 40. Grantham-McGregor SM, Walker SP, Chang SM, Powell CA. Effects of early 693 childhood supplementation with and without stimulation on later development in 694 stunted Jamaican children. Am J Clin Nutr. 1997;66: 247–253. 695 doi:10.1093/ajcn/66.2.247 696 41. Cusick SE, Georgieff MK. The Role of Nutrition in Brain Development: The Golden 697 Opportunity of the “First 1000 Days.” J Pediatr. 2016;175: 16–21. 698 doi:10.1016/j.jpeds.2016.05.013 699 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint 32 42. Niehaus MD, Moore SR, Patrick PD, Derr LL, Lorntz B, Lima AA, et al. Early 700 childhood diarrhea is associated with diminished cognitive function 4 to 7 years 701 later in children in a northeast Brazilian shantytown. Am J Trop Med Hyg. 2002;66: 702 590–593. doi:10.4269/ajtmh.2002.66.590 703 43. Petri WA, Miller M, Binder HJ, Levine MM, Dillingham R, Guerrant RL. Enteric 704 infections, diarrhea, and their impact on function and development. J Clin Invest. 705 2008;118: 1277–1290. doi:10.1172/JCI34005 706 44. Rogawski McQuade ET, Platts-Mills JA, Gratz J, Zhang J, Moulton LH, Mutasa K, 707 et al. Impact of Water Quality, Sanitation, Handwashing, and Nutritional 708 Interventions on Enteric Infections in Rural Zimbabwe: The Sanitation Hygiene 709 Infant Nutrition Efficacy (SHINE) Trial. J Infect Dis. 2020;221: 1379–1386. 710 doi:10.1093/infdis/jiz179 711 45. Null C, Stewart CP, Pickering AJ, Dentz HN, Arnold BF, Arnold CD, et al. Effects of 712 water quality, sanitation, handwashing, and nutritional interventions on diarrhoea 713 and child growth in rural Kenya: a cluster-randomised controlled trial. Lancet Glob 714 Health. 2018;6: e316–e329. doi:10.1016/S2214-109X(18)30005-6 715 46. Parvez SM, Azad R, Rahman M, Unicomb L, Ram PK, Naser AM, et al. Achieving 716 optimal technology and behavioral uptake of single and combined interventions of 717 water, sanitation hygiene and nutrition, in an efficacy trial (WASH benefits) in rural 718 Bangladesh. Trials. 2018;19: 358. doi:10.1186/s13063-018-2710-8 719 47. Jeong J, Pitchik HO, Yousafzai AK. Stimulation Interventions and Parenting in Low- 720 and Middle-Income Countries: A Meta-analysis. Pediatrics. 2018; e20173510. 721 doi:10.1542/peds.2017-3510 722 723 . CC-BY 4.0 International licenseIt is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review) The copyright holder for this preprint this version posted February 26, 2025. ; https://doi.org/10.1101/2025.02.25.25321966doi: medRxiv preprint