Association of Serum Antioxidant Vitamins and Carotenoids With Incident Alzheimer Disease and All-Cause Dementia Among US Adults

Background and ObjectivesSerum antioxidant vitamins and carotenoids may protect against neurodegeneration with age. We examined associations of these nutritional biomarkers with incident all-cause and Alzheimer disease (AD) dementia among US middle-aged and older adults.MethodsUsing data from the third National Health and Nutrition Examination Surveys (1988–1994), linked with Centers for Medicare & Medicaid follow-up data, we tested associations and interactions of serum vitamins A, C, and E and total and individual serum carotenoids and interactions with incident AD and all-cause dementia. Cox proportional hazards regression models were conducted.ResultsAfter ≤26 years follow-up (mean 16–17 years, 7,283 participants aged 45–90 years at baseline), serum lutein+zeaxanthin was associated with reduced risk of all-cause dementia (65+ age group), even in the lifestyle-adjusted model (per SD: hazard ratio [HR] 0.93, 95% CI 0.87–0.99;p= 0.037), but attenuated in comparison with a socioeconomic status (SES)–adjusted model (HR 0.92, 95% CI 0.86–0.93;p= 0.013). An inverse relationship was detected between serum β-cryptoxanthin (per SD increase) and all-cause dementia (45+ and 65+) for age- and sex-adjusted models (HR 0.86, 95% CI 0.80–0.93;p< 0.001 for 45+; HR 0.86, 95% CI 0.80–0.93;p= 0.001 for 65+), a relationship remaining strong in SES-adjusted models (HR 0.89, 95% CI 0.82–0.96;p= 0.006 for 45+; HR 0.88, 95% CI 0.81–0.96;p= 0.007 for 65+), but attenuated in subsequent models. Antagonistic interactions indicate putative protective effects of 1 carotenoid may be observed at lower levels other carotenoids or antioxidant vitamin.DiscussionIncident all-cause dementia was inversely associated with serum lutein+zeaxanthin and β-cryptoxanthin levels. Further studies with time-dependent exposures and randomized trials are needed to test neuroprotective effects of supplementing the diet with select carotenoids.Classification of EvidenceThis study provides Class II evidence that incident all-cause dementia was inversely associated with serum lutein+zeaxanthin and β-cryptoxanthin levels.