Llewellyn DJ, et al.
"Our results suggest that high levels of serum 25-hydroxyvitamin D are associated with lower odds of cognitive impairment," the researchers said. As patients age, however, the capacity of their skin to absorb vitamin D from sunlight decreases, often requiring they obtain it from other sources, they said. Evidence from in vitro and animal studies suggests vitamin D may be neuroprotective, but there is a "paucity of reliable evidence" from clinical and population studies, the researchers said.
So to examine the association between serum vitamin D and cognitive impairment, the researchers conducted a cross-sectional study of 1,766 persons 65 and older in the Health Survey for England 2000. Each participant had a serum vitamin D measurement and each had a cognitive impairment assessment via the Abbreviated Mental Test Score. Of the total study population, 212 patients (12%) were cognitively impaired. The researchers found that vitamin D levels were higher in those with normal cognition than in those who were cognitively impaired. About half of patients with cognitive impairment had the lowest serum levels of the vitamin. In a multivariate analysis, those with the lowest levels of vitamin D were 2.3-fold more likely to be cognitively impaired than those with the highest levels (95% CI 1.4 to 3.8, P=0.001).
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