Vitamin D supplementation — or just getting more time in the sun — may help stave off cognitive decline in older adults, according to a study recently published in the Journal of the American Geriatrics Society.
The study was conducted by researchers from Wake Forest Baptist Medical Center, the University of Alabama-Birmingham, the University of California-San Francisco, the University of Pittsburgh and the National Institute on Aging (NIA). It received funding from the NIA and the National Institute of Nursing Research.
Researchers have known for some time that both cognitive impairment and vitamin D deficiency are common in the elderly.
“This study provides increasing evidence that suggests there is an association between low vitamin D levels and cognitive decline over time,” lead author Valerie Wilson, MD, said.
Lower vitamin D, worse cognitive performance
The researchers analyzed data on 2,777 well-functioning adults between the ages of 70 and 79 who were enrolled in the Dynamics of Health, Aging and Body Composition (Health ABC) study. The participants were all Medicare-eligible, community-dwelling white or black adults from Pittsburgh, Pa., and Memphis, Tenn., who joined the study between April 1997 and June 1998.
Participants underwent tests of their cognitive function at the beginning of the study and had their vitamin D levels measured 12 months later. Three years after that, participants underwent another cognitive test.
“With just the baseline observational data, you can’t conclude that low vitamin Dcauses cognitive decline,” Wilson said. But “[w]hen we looked four years down the road, low vitamin D was associated with worse cognitive performance on one of the two cognitive tests used.”
“It is interesting that there is this association and ultimately the next question is whether or not supplementing vitamin D would improve cognitive function over time,” he said.
It would take randomized, controlled studies to determine for sure whether vitamin D supplementation could stave off cognitive decline, however.
“Although this study cannot establish a direct cause and effect relationship, it would have a huge public health implication if vitamin D supplementation could be shown to improve cognitive performance over time because deficiency is so common in the population,” Wilson said.
She noted that further research could also determine whether specific cognitive abilities are more or less affected by vitamin D deficiency.
“Doctors need this information to make well-supported recommendations to their patients,” she said. “Further research is also needed to evaluate whether specific cognitive domains, such as memory versus concentration, are especially sensitive to low vitamin D levels.”
Sunlight for brain health
An increasing body of research is linking vitamin D to cognitive function. In a study conducted by researchers from the Peninsula Medical School in Exeter, the University of Cambridge and the University of Michigan, and published in theJournal of Geriatric Psychology in 2009, elderly adults with lower vitamin D blood levels also scored lower on tests of memory, attention and orientation in space and time. Studies have also shown that dementia patients tend to have lower vitamin D levels than their cognitively healthy peers.
Scientists have long known that vitamin D builds and maintains healthy bones and teeth, but they have only recently begun to explore the role that it plays in cognitive health. Research has also shown that the vitamin plays an important role in immune function and the prevention of autoimmune disorders, cancer and other chronic diseases.
Vitamin D, nicknamed the “sunshine vitamin,” is produced naturally by the skin upon exposure to sunlight. It takes just 15 to 30 minutes of sunlight on the unprotected face and hands for the average light-skinned person to get optimal levels; darker skin requires greater time in the sun.