Vitamin D insufficiency and cognitive impairment in Asians: a multi-ethnic population-based study and meta-analysis.

Abstract

The relationship between vitamin D insufficiency and cognitive impairment remains equivocal in Asians. We examined the association between circulating 25-hydroxyvitamin D (25OHD) concentration and cognitive performance in a large multi-ethnic Singaporean population-based study. We also conducted a meta-analysis of 25OHD concentrations amongst cognitively impaired older adults in Asia. Our population-based cross-sectional study included 2273 persons ≥60years of age from the Singapore Epidemiology of Eye Diseases (SEED) study (mean±SD age 70.4±6.2years; 44.7% female), who were categorized according to 25OHD concentration (i.e. ≤10, 10.1-20 and >20ngmL(-1) ). The 25OHD concentration was measured and adjusted to reflect a deseasonalized value. Cognition was assessed using the total and domain scores of the Abbreviated Mental Test (AMT). Global cognitive impairment was defined as AMT score of ≤6 if 0-6years of education and AMT score of ≤8 if >7years of education. Fully adjusted multivariate models were used. We included seven studies in a meta-analysis of 25OHD and cognition in Asia (6068 participants; 1179 cognitively impaired cases). Participants with 25OHD levels >20ngmL(-1) (n=1302) had higher AMT total scores (mean±SD 8.5±1.9) and were less likely to have cognitive impairment (14.1%) than participants with lower 25OHD levels (overall P<0.001, P-trend<0.001). Deseasonalized 25OHD concentration was associated with AMT score (β=0.10 per 10ngmL(-1) , P=0.035). Vitamin D insufficiency (25OHD ≤20ngmL(-1) ) was associated with global cognitive impairment (OR 1.56, P=0.028). Specifically, 25OHD concentration correlated with semantic memory (r=0.08, P=0.009) and orientation in time (r=0.09, P=0.003). In the meta-analysis, the pooled mean 25OHD difference was -6.83ngmL(-1) (95% confidence interval -11.36; -2.30), indicating lower 25OHD concentrations amongst cognitively impaired compared to cognitively healthy participants in Asia. Vitamin D insufficiency is associated with a greater likelihood of and more severe cognitive impairment in Asian populations.