Associations Between Hair Heavy Metal Concentrations and Frailty in Mexican Adults: a Cross-Sectional Study

Exposure to heavy metals is increasingly recognized as a potential risk factors for health conditions and its accumulation across life has become of interes in older adults. Older adults may be susceptible because of accumulated exposure, reduced clearance, and greater vulnerability. Whether heavy metals contribute to frailty in community-dwelling adults, and whether their effect is modified by social vulnerability or sex, remains unclear.

Cross-sectional analysis of 2018 wave of the Mexican Health and Aging Study (MHAS). Hair samples from 2,671 participants aged 18 to 99 years were analyzed (EPA method 6020B). Frailty was operationalized with a 60-item frailty index (FI). Associations between each log-metal and FI were estimated with crude and covariate-adjusted linear (OLS) regression with heteroscedasticity-consistent (HC3) standard errors, and with fractional-logit regression. False-discovery-rate correction was applied. Effect modification by SVI and by sex was assessed.

2,590 participants had a valid FI. In crude analyses, most metals were inversely associated with the FI. After adjustment, only cobalt retained inversely associated, which did not survive FDR correction. No metals were significant in multivariable models. Inverse association of vanadium and copper with the FI was confined to participants with higher social vulnerability; at low SVI these slopes were null or positive.

In this sample, individual hair concentrations of heavy metals were not robustly associated with frailty after adjustment. The results suggest that the relationship between trace metals and frailty may be small and highly context-dependent.