Cadmium exposure and incidence of all-cause dementia and Alzheimer's disease in US adults

BackgroundWhile longitudinal studies aid in understanding and preventing long-latency disorders like dementia, evidence for cadmium's role in these conditions is still limited.ObjectiveWe evaluated the association between cadmium exposure, Alzheimer's disease (AD) and all-cause dementia incidence in US adults.MethodsNational Health and Nutrition Examination Survey (NHANES) III (1988-1994) and continuous NHANES (1999-2016) data were linked with Medicare claims to identify incident AD and dementia cases through 2018. Urinary and/or blood cadmium were measured during NHANES. We used covariate-adjusted, survey-weighted Cox proportional hazard models to evaluate the associations between cadmium exposure biomarkers and AD/dementia over follow-up.ResultsIn NHANES III (N = 6122), mean baseline age was 53.9 years and urinary cadmium was 0.76 µg/L. Over a mean follow-up of 20.4 years, 743 AD and 1508 all-cause dementia cases occurred. Urinary cadmium was not associated with AD (HR: 1.01, 95% CI: 0.9-1.0) nor all-cause dementia incidence (HR: 1.02, 95% CI: 0.96-1.08). In continuous NHANES (urinary cadmium N = 2833; blood cadmium N = 8038), mean baseline age was 64.1 years, urinary cadmium was 0.49 µg/L, and blood cadmium was 0.55 µg/L. Over mean 9.5 years, 587 AD and 1260 all-cause dementia cases occurred. Urinary and blood cadmium showed no associations with AD (HR [95% CI]: 1.09 [0.9, 1.4]; 1.06 [0.9, 1.2]) nor all-cause dementia (HR [95% CI]: 1.07 [0.9, 1.3]; 1.06 [0.95, 1.2]).ConclusionsNo association between cadmium exposure and dementia incidence was observed. Our null findings should be interpreted in the context of potential methodological issues and should be verified by subsequent studies.