Higher vitamin D levels are associated with better thinking and mood in people with Parkinson's disease, a new study suggests.
The finding may lead to new ways to delay or prevent the onset of thinking problems and depression in people with the progressive neurodegenerative disease, the researchers said.
Their analysis of nearly 300 Parkinson's disease patients revealed that higher blood levels of vitamin D -- the "sunshine vitamin" -- were associated with less severe physical symptoms, better thinking abilities and lower risk of depression.
This link was especially strong in patients without dementia, according to the study in the current issue of the Journal of Parkinson's Disease.
"About 30 percent of persons with [Parkinson's disease] suffer from cognitive impairment and dementia, and dementia is associated with nursing home placement and shortened life expectancy," study author Dr. Amie Peterson, of the Oregon Health and Sciences University, said in a journal news release.
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"We know mild cognitive impairment may predict the future development of dementia," she added. Preventing the development of dementia in these patients may potentially improve rates of illness and death related to Parkinson's disease, Peterson suggested.
However, the study doesn't show whether low vitamin D dulls thinking or if the opposite is true -- that people with more advanced Parkinson's disease get less sun exposure because of their limited mobility and have lower levels of vitamin D as a result. The study also did not ask if patients were taking vitamin D supplements. While the study showed an association between vitamin D levels and thinking problems, it did not prove a cause-and-effect link.
Vitamin D is absorbed by the body from sunlight. It is also found in foods such as fatty fish and in supplements.
Low levels of vitamin D increase the risk of type 2 diabetes, multiple sclerosis, high blood pressure, cancer and infections, the study authors noted in the news release.
Parkinson's disease affects about 1 million Americans and 5 million people worldwide. Its prevalence is expected to double by 2030.