The Association between Vitamin D Deficiency and Changes in Cognitive Functions in Chinese Older Adults: A Prospective Cohort Study

Background: Along with the problem of population aging, the prevalence of dementia is gradually increasing. Associations between vitamin D deficiency (VDD) and cognitive functions remain unclear.Objectives: We aimed to determine the relationship between VDD and changes in cognitive performance in community-dwelling older adults.Methods: In this longitudinal cohort study, participants aged >= 65 years were enrolled in March, 2016. The serum level of 25-hydroxy-vitamin D was analyzed by liquid-chromatography-tandem-mass-spectrometry at baseline. VDD was defined as less than 20 ng/mL. All participants completed a health status questionnaire. Cognitive functions were evaluated by the Wechsler Adult Intelligence Scale-Revised in China at baseline and each visit. The linear mixed-effects model was utilized to examine the association between baseline VDD and changes in cognitive functions.Results: In total, 866 participants were included in our study, with a mean duration of 3 years. VDD was markedly associated with lower full intelligence quotient (FIQ) (beta: -3.355, 95% confidence interval [CI]:-4.165,-2.545), verbal intelligence quotient (VIQ) (beta: -3.420, 95%CI: -4.193,-2.647), performance intelligence quotient (PIQ) (beta: -2.610, 95%CI: -3.683,-1.537), comprehension (beta: -0.630, 95%CI: -1.022,-0.238), information (beta: -0.354, 95%CI: -0.699,-0.008), arithmetic (beta: -1.065, 95%CI: -1.228,-0.902), digit span (beta: -0.370, 95%CI: -0.547,-0.192), vocabulary (beta: -0.789, 95%CI: -1.084,-0.493), picture completion (beta: -0.391, 95%CI: -0.761,-0.022), block design (beta: -0.412, 95%CI: -0.697,-0.127), picture arrangement (beta: -0.542, 95%CI: -0.909,-0.174), and object assembly (beta: -0.492, 95%CI: -0.818,-0.165) than those with adequacy.Conclusion: A higher frequency of VDD was associated with lower scores of FIQ, VIQ, PIQ and subtests on memory and executive function. Future randomized controlled trials are warranted to further verify the conclusions.