Association between blood cadmium and the likelihood of developing human papillomavirus infection: A combination of NHANES and clinical study.

Human papillomavirus (HPV) is a virus characterized by a circular DNA structure with two strands and belongs to the papillomavirus family. 1 , 2 Transmission occurs through skin or mucosal contact, such as wounds on the skin or mucous membranes. Moreover, HPV is a prevalent sexually transmitted infection affecting both females and males, with the lifetime risk of acquiring HPV exceeding 80% and 90%, respectively. 3 , 4 Over 40 types of mucosal HPV exist, causing a significant burden of disease in both sexes. These types of HPV (such as 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, and 68) are responsible for causing cervical cancer as well as anal, vaginal, vulvar, penile, and oropharyngeal cancers. 5 Low-risk HPV (such as 6 and 11) primarily leads to the development of anogenital warts. 6 Cadmium (Cd), a heavy metal, is a toxic element. Contaminated food and water are the primary sources of Cd exposure, with cigarette smoke also playing a significant role. 7 , 8 Cd has a biological half-life of approximately 25–30 years in humans. Exposure to Cd in occupational and environmental settings poses substantial risks to human health. 9 Chronic exposure to Cd can lead to kidney and liver dysfunction, pulmonary edema, testicular damage, reproductive failure in males and females, osteomalacia, and harm to the adrenal system and hematopoiesis process. It can also result in various types of systemic cancers. 10 – 13 Furthermore, numerous studies have identified a correlation between indicators of Cd exposure (blood and urine) and the likelihood of various illnesses, including cerebrovascular accidents, diabetes, elevated uric acid levels, and endometriosis. 14 – 17 Emerging evidence highlights the detrimental effects of Cd exposure on reproductive health and immune function. Cd exposure can induce oxidative stress, disrupt hormonal balance, and promote apoptosis in reproductive tissues, 11 , 13 potentially influencing susceptibility to infections. Although epidemiological studies have established links between Cd exposure and diseases such as diabetes and hyperuricemia, its potential role in viral infections remains underexplored. Only a few studies have examined whether Cd exposure is related to HPV infection risk. Given the shared pathways of inflammation, oxidative stress, and immune modulation, we hypothesized that Cd body burden might be associated with HPV infection status. Within this framework, we investigated the correlation between blood Cd concentration and HPV infection status among participants in the National Health and Nutrition Examination Survey (NHANES) study from 2005 to 2016, with validation from an independent clinical cohort.

The reporting of this cross-sectional study conforms to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guidelines. 18 The NHANES survey collects health and dietary information from noninstitutionalized civilians within the United States. The National Center for Health Statistics (NCHS) Research Ethics Review Board approved the study procedure (Protocol #2005-06 and #2011-17). All survey procedures were conducted in accordance with the Helsinki Declaration of 1975, as revised in 2024. All participants at the time of recruitment provided written consent. Our study utilized the NHANES datasets from 2005 to 2016. Of the 60,936 participants, we excluded 30,152 males, 13,152 participants aged 59 years, 523 pregnant women, 1507 individuals without HPV status data, and 2014 participants without blood Cd data. In the final data analysis, 7815 individuals were included for studying the blood Cd levels and HPV infection status ( Figure 1 ). The NHANES website provides further details about the study samples, which can be accessed at https://www.cdc.gov/nchs/nhanes/ . Participant selection flow chart. NHANES: National Health and Nutrition Examination Survey; HPV: human papillomavirus. The blood Cd level was considered as the independent variable in this analysis. The National Center for Environmental Health’s Division of Laboratory Sciences used inductively coupled plasma mass spectrometry to analyze whole blood for blood Cd (ICP-MS; CDC method No. ITB0001A). The specific experimental methods have been described in detail in previous studies. 19 , 20 DNA extracted from self-collected vaginal swabs was used to determine the presence of HPV infection through HPV genotyping. A biotinylated set of PGMY09/11 primers was used in this assay as part of the Roche Linear Array HPV Genotyping test, which relies on HPV L1 consensus polymerase chain reaction. For short-term storage, DNA samples were maintained at a temperature of −20°C, and a freezer set at −80°C was employed for extended storage. The NHANES (HPVSWR) study recorded HPV infection as a binary variable (1 = HPV positive; 0 = HPV negative). 21 , 22 Age, race, level of education, insurance coverage, family income relative to poverty, body mass index (BMI), marital status, hypertension, diabetes, smoking history, age at menarche, age when had first sex, regular menstrual periods, pregnant times, trouble sleeping, sexual activity in the past year (either vaginal or anal), number of times had sex without condom in the past year, history of sexually transmitted diseases (STDs), contraceptive use, and female hormone supplementation were all covariates in this study. The measurement details are provided the NHANES official website ( https://wwwn.cdc.gov/nchs/nhanes/Default.aspx ). To validate our findings, we conducted a retrospective clinical study at Yuejianglou Community Health Center under the Medical Alliance of The Second Hospital of Nanjing. We retrospectively reviewed the patients from 2023 to 2025, randomly selecting 50 HPV-positive patients and 50 HPV-negative controls. The blood Cd level was compared between the two groups. The institutional validation study, which involved a retrospective study, was reviewed by the ethics board and received exemption. All patient data were de-identified prior to analysis to ensure confidentiality and comply with privacy regulations. The statistical software package R (version 4.2, http://www.R-project.org , The R Foundation) and EmpowerStates (version 4.1, http://www.empowerstats.com , X&Y Solutions, Inc. Boston, MA, USA) were utilized for all analyses. Participants’ demographic characteristics were analyzed using chi-square and independent two-sample t-tests based on HPV infection status. Using multivariate linear regression models, we examined the correlation between HPV infection status and blood Cd levels. The nonlinear association between HPV infection status and blood Cd level was examined using generalized weighted models and smoothed fitted curves. Furthermore, a subgroup analysis was conducted to establish the correlation between HPV infection status and blood Cd based on age, BMI, high blood pressure (HBP), diabetes, and trouble sleeping. An effect was considered statistically significant when it achieved a two-sided P  <   0.05.

Our study ultimately included a total of 7815 participants aged 20–59 years between the years 2005 and 2016. Based on their HPV infection status, 3453 individuals (44.18%) tested positive for HPV, while 4362 (55.82%) tested negative for HPV. Table 1 displays the attributes of the population based on their HPV infection status. HPV-positive participants exhibited elevated blood Cd levels (0.62 ± 0.74 vs. 0.48 ±0.53 µg/L, P  <   0.001). Moreover, HPV-positive individuals were younger (38.34 ±11.49 vs. 40.50 ± 10.89 years), were less educated, and had lower family income (2.21 ± 1.61 vs. 2.68 ± 1.67) and health insurance rates (70.37% vs. 74.68%). They were less likely to marry or live with a partner (46.83% vs. 67.86%), had a higher smoking rate (43.24% vs. 30.81%), and experienced more trouble sleeping (29.37% vs. 25.63%). Regarding reproductive health variables, compared with the HPV-negative group, HPV-positive individuals reported a younger age at menarche (12.54 ± 1.77 vs. 12.67 ± 1.75 years) and at first sexual intercourse (17.08 ± 4.64 vs. 18.29 ± 5.07 years). Regarding sexual behavior, HPV-positive individuals reported a higher frequency of vaginal and anal sex over the past year, and a higher proportion did not use condoms (55.52% vs. 45.20%). The prevalence of STDs (including genital herpes, genital warts, gonorrhea, and chlamydia) in HPV-positive women was higher than that in HPV-negative women (13.09% vs. 8.23%). Furthermore, HPV-positive participants were more likely to use contraceptives (77.30% vs. 73.38%) and less likely to use female sex hormones (9.83% vs. 11.48%) during their daily lives. Statistically significant differences ( P  < 0.05) were observed in all the above variables. Comparison of demographic characteristics between HPV-positive and HPV-negative participants. HPV: human papillomavirus; BMI: body mass index; SD: standard deviation; HBP: high blood pressure; STDs: sexually transmitted diseases. Three models were used to investigate the correlation between blood Cd levels and HPV infection status (odds ratio (OR) and 95% confidence interval (CI)). Three models are represented along with their OR, 95% CI, and P -values in Table 2 . Based on our unadjusted model (Model 1), a 1 µg/L increase in blood Cd level was associated with a 44% higher likelihood of HPV infection (OR: 1.44, 95% CI: 1.34–1.56, P  < 0.0001). Despite accounting for age, race, educational level, and health insurance in Model 2, a strong positive association persisted (OR: 1.45; 95% CI: 1.33–1.58; P  < 0.0001). After fully adjusting for all the covariates listed in Table 1 (Model 3), the overall association remained statistically significant (OR: 1.14; 95% CI: 1.01–1.27, P  =   0.0269). Overall, in all three models, the correlation between blood Cd levels and the risk of HPV infection was found to be positive. A significant trend was identified when the blood Cd level was converted to a categorical variable, divided into four groups (Q1, Q2, Q3, and Q4, P for trend <0.001 in Model 1 and 2). However, the trend across quartiles in Model 3 was nullified ( P for trend = 0.1612). Association between blood cadmium levels (ug/L) and HPV infection status. Model 1: No covariates were adjusted. Model 2: Age, race, educational level, and health insurance were adjusted. Model 3: Age, race, educational level, health insurance, ratio of family income to poverty, BMI, marital status, high blood pressure, diabetes, smoked at least 100 cigarettes in life, trouble sleeping, age at menarche, age when had first sex, regular menstrual periods, pregnant times, number of vaginal or anal sex in the past year, time had sex without condom in the past year, history of STDs, used contraceptives, and use of female sex hormones were adjusted. HPV: human papillomavirus; OR: odds ratio; CI: confidence interval; STDs: sexually transmitted diseases. Despite the nonsignificant linear association in the full model, a smoothed curve fitting analysis ( Figure 2 ) revealed a potential nonlinear relationship between blood Cd and the log-odds of HPV infection. The association between blood cadmium levels and human papillomavirus infection risk. Red solid lines represent smooth curves between variables. Blue bands represent the 95% confidence interval. To assess the potential modifying effect of demographic and clinical characteristics on the association between blood Cd levels and HPV infection status, we conducted subgroup analyses stratified by age, BMI, HBP, diabetes, and trouble sleeping ( Table 3 ). Subgroup analysis for the association between blood cadmium levels (µg/L) and HPV infection status. Each stratification was adjusted for the covariates listed in Table 1 except for the stratifying variable itself. HPV: human papillomavirus; OR: odds ratio; CI: confidence interval; BMI: body mass index; HBP: high blood pressure. The positive association between blood Cd and HPV infection was consistently observed across most subgroups, although the strength of association varied. Notably, a significant interaction was observed for HBP ( P for interaction = 0.0071), indicating that the effect of Cd on HPV infection may be modified by HBP status. Among individuals without HBP, blood Cd levels were significantly associated with increased odds of HPV infection (OR = 1.26; 95% CI: 1.09–1.45; P  =   0.0012), whereas no significant association was found in those with HBP ( P  =   0.2610). In contrast, no significant interactions were found for age, BMI, diabetes, or trouble sleeping, suggesting that the association between Cd and HPV infection was not significantly modified by these factors ( P  > 0.05). However, significant associations were observed in specific subgroups, such as participants aged 33–45 years (OR = 1.26; 95% CI: 1.04–1.52; P  =   0.0173), those without diabetes (OR = 1.16; 95% CI: 1.03–1.30; P  =   0.0145), and those without trouble sleeping (OR = 1.27; 95% CI: 1.08–1.49; P  =   0.0035). Additionally, we performed multiple regression analyses for HPV infection with blood Cd using age and BMI as stratifying factors ( Table 4 ). In Models 1 and 2, blood Cd levels were positively associated with HPV infection risk in all BMI groups aged 33–45 and 46–59 years ( P <0.05). Nevertheless, when accounting for all variables (Model 3), the risk of HPV infection in women aged 46–59 years with a BMI of ≥25 and <30 kg/m 2 increased by 34% for every incremental rise in blood Cd levels (OR: 1.34; 95% CI: 1.00–1.81, P  =   0.0495). No significant differences were observed in the other groups. Association between blood cadmium levels (ug/L) and HPV infection status stratified by age and BMI. Model 1: No covariates were adjusted. Model 2: race, educational level, and health insurance were adjusted. Model 3: Adjusted for age, race, educational level, health insurance, ratio of family income to poverty, BMI, marital status, high blood pressure, diabetes, smoked at least 100 cigarettes in life, trouble sleeping, age at menarche, age when had first sex, regular menstrual periods, pregnant times, number of vaginal or anal sex in the past year, time had sex without condom in the past year, history of STDs, used contraceptives, and use of female sex hormones. HPV: human papillomavirus; OR: odds ratio; CI: confidence interval; BMI: body mass index; STDs: sexually transmitted diseases. In a validation cohort of 50 HPV-positive individuals and 50 HPV-negative controls, no significant difference was observed in age (41.95 ± 6.47 vs. 41.52 ± 7.28 years). Additionally, the HPV-positive group exhibited significantly higher blood Cd levels than the control group (0.77 ± 0.33 vs. 0.62 ± 0.21 µg/L, P  < 0.05) ( Figure 3 ). Institutional validation cohort: blood cadmium in HPV-positive and HPV-negative individuals. HPV: human papillomavirus.

HPV infection can result in a wide range of pathologies. The German virologist Harald zur Hausen first described the association between HPV and cervical cancer in the 1970s. 23 , 24 HPV contributes to cervical cancer, vaginal cancer, penile cancer, anal cancer, and oropharyngeal cancer. 25 Furthermore, an HPV infection can cause benign cutaneous warts and juvenile respiratory papillomatosis. Studies on HPV infection risk factors focus on sexual behavior and gynecological factors. Lifestyle factors, dietary habits, and other diseases with a history of infection are also taken into account in some cross-sectional studies. 26 , 27 During cervical cancer progression from pre-cancerous to metastatic, the levels of trace elements (copper, selenium, zinc, iron, arsenic, manganese, and Cd) fluctuate. 28 Cd, one of the trace elements, has been categorized as a type I carcinogen. The presence of Cd potentially plays a role in the development of certain types of cancer in women, including endometrial cancer, epithelial ovarian cancer, and breast cancer. 29 – 33 However, no studies have been conducted on the correlation between the blood Cd levels and the HPV infection status in females. In this nationally representative cross-sectional study of US women aged 20–59 years, we observed a positive association between blood Cd levels and the likelihood of HPV infection. In the fully adjusted model, each 1 μg/L increase in blood Cd was associated with a 14% increased odds of HPV infection (OR: 1.14; 95% CI: 1.01–1.27; P  =   0.0269). This finding was further corroborated by an independent clinical validation cohort, in which HPV-positive women exhibited significantly higher blood Cd levels than HPV-negative controls ( P  <   0.05). These results suggest that Cd exposure may represent an underrecognized environmental factor associated with HPV infection susceptibility. The observed association between Cd levels and HPV infection warrants careful interpretation. Although the overall effect size was modest in the fully adjusted model, the consistency of the positive direction across all three analytical models strengthens the credibility of the finding. Notably, the smoothed curve fitting analysis revealed a potential nonlinear relationship between blood Cd levels and the log-odds of HPV infection. This nonlinearity may explain why the trend across Cd quartiles was attenuated after full adjustment, as the relationship may plateau or even diminish at higher exposure levels. Such a pattern could reflect a threshold effect, beyond which cadmium-induced cytotoxicity or immune suppression reaches a ceiling, or may be attributable to unmeasured confounding in individuals with extremely high Cd burden, such as heavy smokers or those with occupational exposure. Furthermore, the stratified analysis by age and BMI revealed that the strongest association was observed in women aged 46–59 years who were overweight (BMI 25–30 kg/m 2 ), in whom each unit increase in blood Cd conferred a 34% higher risk of HPV infection (OR: 1.34; 95% CI: 1.00–1.81; P  =   0.0495). This finding is clinically relevant, as perimenopausal and postmenopausal women may exhibit heightened susceptibility to persistent HPV infection due to age-related immune senescence and hormonal changes. 34 – 36 The accumulation of Cd in the body over decades, combined with its long half-life (approximately 25–30 years), may render older women particularly vulnerable to its immunotoxic effects. Furthermore, adipose tissue can serve as a reservoir for lipophilic environmental toxicants, and overweight individuals may experience chronic low-grade inflammation that synergizes with cadmium-induced immune dysregulation to facilitate HPV acquisition or persistence. 37 – 39 These observations align with previous research demonstrating that heavy metal toxicity can disrupt reproductive and immune function through multiple pathways. 40 – 42 Several biological mechanisms may underpin the cadmium–HPV association. Cd is a well-characterized immunotoxicant that can impair both innate and adaptive immune responses. Experimental studies have shown that Cd exposure suppresses natural killer cell activity, disrupts cytokine signaling, and induces apoptosis in lymphocytes, thereby compromising host defense against viral pathogens. 11 , 13 Cd generates oxidative stress and DNA damage, which may create a permissive microenvironment for HPV integration and persistence. Given that HPV relies on epithelial differentiation for its life cycle, cadmium-induced disruption of epithelial barrier integrity in the cervicovaginal mucosa may further enhance viral entry and replication. Notably, Cd has also been shown to exhibit estrogenic activity, and its interaction with estrogen receptor signaling could modulate HPV gene expression and immune evasion, particularly in hormone-sensitive tissues such as the cervical epithelium. 43 Recent advances in understanding heavy metal toxicity have elucidated the molecular pathways through which Cd induces cellular damage, including mitochondrial dysfunction, endoplasmic reticulum stress, and activation of apoptotic cascades. 44 These mechanisms may collectively contribute to impaired antiviral defense and increased susceptibility to HPV infection. Our findings carry potential public health implications. If confirmed prospectively, reducing Cd exposure—via smoking cessation and dietary modifications—could represent a novel HPV prevention strategy. Identification of susceptible subgroups, such as perimenopausal overweight women, may inform targeted screening. Clinically, these findings underscore the importance of considering environmental exposures in assessing the risk of sexually transmitted infections, an aspect often overlooked in routine gynecological care. However, this study has several limitations. First, the cross-sectional design precludes causal inference, and reverse causation cannot be entirely excluded. Second, blood Cd reflects recent exposure, whereas HPV infection may be transient or persistent; longitudinal data are needed to establish temporality. Third, the nonsignificant quartile trend in the fully adjusted model suggests that the linear association may not be robust across the exposure distribution, and the observed nonlinear relationship requires confirmation. Finally, subgroup findings should be considered exploratory due to multiple comparisons. Future research should prioritize large-scale, multicenter prospective cohort studies with repeated measurements to establish causality, clarify dose–response relationships, and validate these findings across diverse populations.

This study provides evidence of a positive association between blood Cd levels and HPV infection among US women, with the relationship appearing nonlinear and potentially modified by hypertension status. The strongest association was observed in perimenopausal women who were overweight, suggesting a susceptible subgroup that may benefit from targeted prevention efforts. Although these findings are preliminary and require confirmation in longitudinal studies, they underscore the need for greater attention to environmental determinants of HPV infection and highlight Cd exposure as a potentially modifiable risk factor. If causally validated, integrating environmental exposure assessment into HPV prevention strategies could complement existing vaccination and screening programs to reduce the burden of HPV-related disease.