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19 March 2011

Vitamin D insufficiency could play a role in the development of Parkinson's disease

Researchers at Emory University report in the March, 2011 issue of Archives of Neurology the finding of a correlation between insufficient levels of vitamin D and the development of early Parkinson's disease (PD).

In the article's background information, Marian L. Evatt, MD, MS of Emory University School of Medicine and the Atlanta Veterans Affairs Medical Center and colleagues remark that "Vitamin D insufficiency has been reported to be more common in patients with Parkinson's disease than in healthy control subjects, but it is not clear whether having a chronic disease causing reduced mobility contributes to this relatively high prevalence."

The study included 157 placebo recipients who participated in The Deprenyl and Tocopherol Antioxidative Therapy of Parkinsonism (DATATOP) trial of men and women with early, untreated Parkinson's disease. Blood samples obtained upon enrollment and at the final visit after 13 months were analyzed for levels of 25-hydroxyvitamin D, the active form of the vitamin.

A high percentage of subjects had vitamin D insufficiency or deficiency at both points of the study. While 69.4 percent had vitamin D insufficiency defined as levels of less than 30 nanograms per milliliter (ng/mL) at the beginning of the study, 26.1 percent were classified as deficient with levels of less than 20 ng/mL. The prevalence of insufficiency at the final visit was 51.6 percent, and deficiency occurred in 7 percent.

"Previous studies in Asian populations reported a higher prevalence of hypovitaminosis D (deficiency or insufficiency) in patients with more advanced disease, suggesting that long-term effects of Parkinson's disease may contribute to the development of insufficient vitamin D concentrations," the authors write. "Contrary to our expectation that vitamin D levels might decrease over time because of disease-related inactivity and reduced sun exposure, vitamin D levels increased over the study period. These findings are consistent with the possibility that long-term insufficiency is present before the clinical manifestations of Parkinson's disease and may play a role in the pathogenesis of PD."

"To our knowledge, the study cohort is the largest and most well-characterized cohort of patients with PD in whom vitamin D status has been investigated," they observe. "We confirm a high prevalence of vitamin D insufficiency in patients with recent onset of PD, during the early clinical stages in which patients do not require symptomatic therapy."

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