Lower Plasma Vitamin B-6 is Associated with 2-Year Cognitive Decline in the Boston Puerto Rican Health Study

Background: Despite its important role in cognitive development and regulation of nervous system function, vitamin B-6 has been under-studied in relation to cognitive aging. Objective: We investigated whether plasma pyridoxal-5'-phosphate (PLP, vitamin B-6) concentrations were associated with cognitive function and subsequent cognitive decline. Methods: In a longitudinal study of 949 participants (aged 45-75 y at baseline; 70% women) from the Boston Puerto Rican Health Study cohort, we examined the association between baseline plasma PLP and baseline cognitive function and 2-y cognitive decline. Cognitive function was assessed with an in-person 7-test cognitive battery, at baseline and 2-y follow-up. We also used logistic regression to estimate the odds of major 2-y decline in global cognitive function (defined as decline >= 1 SD below the mean), as well as decline in executive function and memory. We also used multivariable linear regression to calculate adjusted mean differences in cognitive scores, and 95% CIs, across tertiles of plasma PLP at baseline, as well as cross-sectional and longitudinal associations with individual test scores. Results: In analyses adjusted for potential confounders, the OR of having a major 2-y decline in global cognitive function was 2.46 (95% CI: 1.49, 4.05; P-trend: 0.001) among participants in the lowest tertile of PLP compared with those in the top tertile of PLP. The association of PLP with cognition was stronger in participants older than 55 y at baseline (OR for bottom to top tertile: 4.58; 95% CI: 2.02, 10.35; P-interaction: 0.01) compared with those 55 y old or younger, as well as in ever smokers (OR for bottom to top tertile: 2.99; 95% CI: 1.45, 6.19; P-interaction: 0.02) compared with never smokers. Conclusions: Lower baseline plasma PLP was associated with increased odds of 2-y cognitive decline in a cohort of Boston area Puerto Ricans. The association was stronger among older participants and among ever smokers.