Association between blood heavy metals and fecal incontinence in American adults: A population-based study

Previous studies have revealed the impact of heavy metals (HMs) on gut microbiota and intestinal structure. However, the relationship between HMs and fecal incontinence (FI) remains unclear. Therefore, this study aims to evaluate the association between blood HMs exposure and FI.

Data for this study were obtained from the 2005-2010 cycles of National Health and Nutrition Examination Survey (NHANES). Information regarding FI was retrieved from the Bowel Health Questionnaire, while data on HMs were collected through laboratory examinations. Weighted logistic regression, two-indices weighted quantile sum (2iWQS), quantile g-computation (qgcomp), and restricted cubic splines (RCS) were employed to explore the relationships between blood levels of cadmium (Cd), lead (Pb), and mercury (Hg) and FI. Additionally, Subgroup analyses were conducted to discern specific associations within distinct populations.

A total of 12,142 participants aged 20 years and above were included in this study. Weighted logistic regression indicated a positive association between Cd (Crude model: OR = 1.21, 95% CI: 1.09-1.35, p < 0.001) and Pb (Crude model: OR = 1.01, 95% CI: 1.01-1.02, p < 0.001) with FI. After adjusting for all covariates, the positive associations remained significant for Cd (Model 2: Q1 vs. Q3, OR = 1.38, 95% CI: 1.04-1.83, p = 0.026) and Pb (Model 2: OR = 1.01, 95% CI: 1.00-1.01, p = 0.004). The 2iWQS regression analysis demonstrated a positive correlation between the mixture of three blood HMs and FI (OR = 1.18, 95% CI: 1.05-1.32, p = 0.005), with Cd having the highest weight among the metals (0.76). The qgcomp analysis confirmed this finding (OR = 1.12, 95% CI: 1.01-1.26, p = 0.036; weight = 0.72). Subgroup analysis revealed that the positive association between Cd and FI was more pronounced among males; Mexican Americans; those with a poverty income ratio (PIR) > 2; individuals with college or above education; overweight participants; never-smokers; heavy drinkers; those with hypertension; and non-diabetes individuals. Conversely, the association between Pb and FI was stronger among participants aged 40-60, overweight participants, and never-smokers.

Exposure to blood HMs, particularly Cd, is associated with FI in American adults. Future research should focus on elucidating the causal relationships and underlying mechanisms.