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Another Vitamin to Test?

Low vitamin D levels are associated with impaired cognition.

Vitamin D is important in the regulation of multiple brain processes, and studies have suggested a possible association between low concentrations of 25-hydroxyvitamin D [25(OH)D] and impaired cognition. Researchers in France examined data on 752 women (mean age, 80) participating in a larger, cross-sectional, population-based study of risk factors for hip fractures in women aged 75 or older.

The researchers measured serum 25(OH)D and parathyroid hormone (PTH) levels, assessed global cognitive function through a 10-item screening test, and controlled for many variables (e.g., age, education level, hypertension, depression). Of the sample, 17% had low 25(OH)D concentrations (<10 ng/mL). Compared with the normal-level (10 ng/mL) group, the low-level group had significantly lower mean cognitive scores and a significantly higher prevalence of scores below the cut-off for cognitive impairment (17%, vs. 9% in the normal-level group). Depression scores and other clinical characteristics did not differ between the two groups. Serum PTH levels were significantly higher in the group with low 25(OH)D levels.

Comment: In this study, as in others, cognitive problems were more prevalent in elders with low vitamin D levels (here, almost twice as prevalent) as in those with normal levels. The authors discuss several possible mechanisms for this finding, including the role of vitamin D in neuronal functioning. Why some individuals have low vitamin D levels (diet, sunlight exposure, etc.) remains unknown, as does whether vitamin D₃ supplements would prevent or reverse this problem. Dietary changes and occasionally getting out in the sun may be helpful. Testing 25(OH)D levels in our patients with cognitive problems seems reasonable, but the value of routine testing to determine the need for preventive supplementation in those with normal cognition is unclear.

— Jonathan Silver, MD

Published in Journal Watch Psychiatry November 23, 2009

Citation(s):

Annweiler C et al. Association of vitamin D deficiency with cognitive impairment in older women: Cross-sectional study. Neurology 2009 Sep 30; [e-pub ahead of print]. (http://dx.doi.org/10.1212/WNL.0b013e3181beecd3)

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