Abstract
To investigate the association between serum vitamin D (25-hydroxy-cholecalciferol) (25(OH)D) concentrations and cognitive impairment in older adults living in Southern Brazil. Cross-sectional analysis using data from the second follow-up wave of the populational-based EpiFloripa Aging Cohort Study was collected in 2013-2014. Cognitive impairment was evaluated using the Mini-Mental State Examination (MMSE). Blood samples were collected to measure serum vitamin D concentrations using a chemiluminescent microparticle immunoassay. Vitamin D concentrations were distributed in quartiles (Q1: 4·0-20·7 ng/ml; Q2: 20·8-26·6 ng/ml; Q3: 26·7-32·0 ng/ml and Q4: 32·1-60·1 ng/ml), and its association with cognitive impairment was tested by crude and adjusted logistic regression (sociodemographic, behavioural and health aspects) using Q4 as a reference group. 200 men and 371 women aged 60 years or older participated in this study. The prevalence of probable cognitive impairment was 21·7 %. Those without cognitive impairment had a higher mean of vitamin D serum concentrations (26·8 v. 24·6, P = 0·014). In the crude analysis, only individuals in Q2 of vitamin D presented an increased risk for probable cognitive impairment compared with Q4 (highest quartile) (OR 2·65, 95 % CI 1·46, 4·81), remaining significant in the adjusted analysis (OR 6·04, 95 % CI 2·78, 13·13). While Q1 (lowest quartile) was not associated in the crude analysis, but when adjusted, an increased risk of cognitive impairment was observed. The lowest quartile of vitamin D was directly associated with probable cognitive impairment in older adults in Southern Brazil. More studies are needed to investigate whether maintaining adequate serum levels may represent a significant factor in preventing age-related neurological disorders as well as to verify the need for new cutoff points for this age group.
Highlights
Regarding the characteristics of the sample according to the presence and absence of probable cognitive impairment, there was a difference for almost all aspects, except for gender (P = 0·171), smoking (P = 0·551) and the number of morbidities (P = 0·286)
The prevalence of cognitive impairment was higher among the older adults over 80 years of age (P < 0·001), with an income of up to 3 minimum wages (MW) (P < 0·001), with less than 4 years of schooling (< 0·001), who are widowed (P = 0·0016), who never consumed alcohol (P < 0·001), who are physically inactive (P < 0·001) and with eutrophic BMI (P = 0·003)
The main finding of this study is the association between lower concentrations of serum vitamin D and cognitive impairment independent of vitamin D supplementation and season, a statistically significant result even after adjusting for potential confounding factors
Summary
Study design and population This is a cross-sectional analysis of data collected in 2013– 2014 from the database of household populational-based EpiFloripa Aging Cohort Study (www.epifloripa.ufsc.br). All the older adults in the follow-up were invited to provide blood samples for analysis of biochemical markers, including vitamin D (n 604, response rate of 50·5 %)(24). 572 older adults who participated in the second follow-up wave with complete data to assess cognitive impairment and vitamin D were included in the analysis.
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