Low levels of vitamin D increase the risk of cognitive impairment in the elderly, according to findings from the nationally representative, population-based Health Survey for England 2000.

Despite the theoretical support for the role of vitamin D in maintaining brain function in old age, clinical data are lacking, the researchers note.

Therefore, Dr. David J. Llewellyn and his associates studied 1766 adults, aged 65 or older, from whom blood samples were obtained to measure circulating vitamin D levels.

Cognitive function was measured using the Abbreviated Mental Test, which includes 10 questions to assess attention, orientation in time and space, and memory.

Based on scores of 70 percent or less, 212 subjects (12 percent) were deemed to be cognitively impaired.

The researchers found a significant association between lower levels of vitamin D and cognitive impairment.

After adjusting for factors that could influence the association, including co-existing illnesses, older adults with the lowest levels of vitamin D were more than twice as likely to be cognitively impaired as those with the highest levels.

Llewellyn, of the University of Cambridge and his colleagues suggest that vitamin D concentrations may help doctors in screening for cognitive impairment.

"Further research," they conclude, "is needed to investigate whether vitamin D supplementation is a cost effective way of reducing the incidence of cognitive impairment with few adverse events."

SOURCE: Journal of Geriatric Psychology and Neurology, February 2009