April 16, 2010 (Toronto) -- Two new studies add to evidence that older people with low levels of vitamin D may be more likely to suffer from cognitive impairment.
Vitamin D is best known for helping the body absorb calcium, which restores and strengthens bone, protecting against fracture.
But vitamin D also seems to have anti-inflammatory effects that may help keep blood vessels healthy, ensuring nutrient- and oxygen-rich blood flow to brain cells, says Amie Peterson, MD, of Oregon Health & Science University in Portland.
Testing Cognitive Impairment
Still, whether vitamin D has a role in memory and cognition is unclear at this point, Peterson says, and studies have had conflicting results.
To help answer the question, Peterson and colleagues studied about 150 people aged 70 and older living on their own. Their average age was 85, and about three-fourths were women.
Participants' vitamin D levels ranged from 9 to 90 nanograms per milliliter of blood. Levels of 30 or higher are considered normal, according to Peterson.
All participants were given a standard 30-point test that is used to screen for cognitive impairment.
Results showed that the lower their score on the test, the lower their vitamin D levels.
The average vitamin D level was 42.8 for the 42 participants with a perfect score of 30 on the test; 36.7 for the 89 participants who scored between 27 and 29 ("still normal but lower," says Peterson), and 34.8 for the 21 people with scores of 22 to 26 ("mild cognitive impairment").
The study also showed that lower vitamin D levels were associated with a greater risk of falling.
This summer, Peterson and colleagues plan to embark on a study of people with Parkinson's disease to look at the effect of vitamin D supplementation on cognition, balance, and gait. Still to be tested is whether the intervention will help older people who are otherwise healthy.
Vitamin D Deficiency Common in Elderly
The second study involved 752 women, aged 75 and older, in France.
A total of 129 of the women had vitamin D levels that were below 10 nanograms per milliliter, suggesting vitamin D deficiency, which is common among older women, says Cédric Annweiler, MD, of Angers University Hospital.
Compared to women with higher vitamin D levels, those with levels below 10 were about twice as likely to have cognitive impairment, as measured by a standard test of cognitive skills, he tells WebMD.
The researchers plan to follow the women for seven years to see whether those with low vitamin D levels are more likely to develop Alzheimer's disease or other dementia, Annweiler says.
Studies like that are needed to answer the question of which comes first: vitamin D deficiency or cognitive impairment, says David Knopman, MD, a neurologist at the Mayo Clinic in Rochester, Minn., who was not involved with the new work.
"People with dementia or cognitive impairment tend to become socially isolated and less physically active, so they’re less likely to get outside" to get the benefits of the sun's vitamin-D-producing ultraviolet light, he tells WebMD.
The studies were presented at the annual meeting of the American Academy of Neurology.