Cadmium Exposure and Incidence of All-Cause Dementia and Alzheimer's Disease in US Adults

IntroductionWhile longitudinal studies aid in understanding and preventing long-latency disorders like dementia, evidence for cadmiums role in these conditions is still limited. We evaluated associations between cadmium exposure and incident Alzheimers disease (AD) and all-cause dementia 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=6,122), baseline age was 53.9{+/-}0.5 years and urinary cadmium was 0.8{+/-}0.02 ug/L. Over a follow-up of 20.4{+/-}0.3 years, 743 AD and 1,508 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=2,833; blood cadmium N=8,038), baseline age was 64.1{+/-}0.2 years, urinary cadmium was 0.5{+/-}0.03 ug/L, and blood cadmium was 0.6{+/-}0.01 ug/L. Over 9.5{+/-}0.1 years, 587 AD and 1,260 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]). ConclusionNo association between cadmium exposure and dementia incidence was observed. Our null findings should be interpreted while considering potential methodological issues and verified by subsequent studies.