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Study links low vitamin D levels in older adults to cognitive decline

Older adults with low levels of vitamin D experience faster cognitive decline, a new study found.

Researchers from Rutgers University in New Jersey and the University of California at Davis followed a racially diverse group of 382 older adults for an average of five years. The study subjects underwent cognitive testing and vitamin D testing once a year during the study. Participants ranged in age from their 60s to their 90s, but the average age at the beginning of the study was 75.5. Almost two-thirds of the participants were women.

About half of the study group was cognitively normal, and about one-third had mild cognitive impairment. About 18 per cent of the participants had dementia.

Low vitamin D levels were common in the study group: 61 per cent had either deficient (less than 12 ng/ml) or insufficient (between 12 and 20 ng/ml) vitamin D levels. Those with dementia had lower average vitamin D levels compared to those with mild cognitive impairment or normal cognitive function.

Over the followup period, decline in executive function and episodic memory was significantly faster in people with low vitamin D levels compared to those with adequate levels. The rate of cognitive decline was two to three times faster in people with low vitamin D, regardless of whether they had cognitive impairment or dementia at the start of the study.

Even when participants who had dementia at the start of the study were left out of the calculations, low vitamin D was still associated with faster rates of cognitive decline.

These results highlight the importance of identifying low vitamin D levels in older adults. Further research is needed to investigate whether vitamin D supplements might help slow the rate of cognitive decline.

The study, which was led by Joshua W. Miller, PhD of Rutgers University, was published online in JAMA Neurology on Sept. 14, 2015.

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  • A publication of:
  • Women's College Hospital