In the October, 2008 issue of the American Medical Association journal Archives of Neurology, researchers from Emory University School of Medicine in Atlanta report that men and women with Parkinson’s disease have a greater incidence of vitamin D insufficiency compared with Alzheimer’s disease patients and healthy people. The discovery adds another disease to the growing list of the conditions that have been recently associated with reduced levels of the vitamin.
Assistant professor of neurology Marian L. Evatt, MD, MS and associates measured 25-hydroxyvitamin D [25(OH)D] levels in stored plasma samples from 100 hundred Parkinson’s disease patients, 97 patients with Alzheimer’s disease, and 99 healthy older participants in Emory’s Clinical Research in Neurology database.Alzheimer’s disease patients were included in the current study in order to better examine the possibility that neurodegenerative diseases in general (and not just Parkinson’s disease) might be associated with vitamin D insufficiency.
While 36 percent of the plasma samples from healthy subjects contained insufficient levels of vitamin D (defined as 30 nanograms per milliliter or less), 41 percent of the Alzheimer’s disease patients and 55 percent of those with Parkinson’s disease had insufficient levels of the vitamin. Outright deficiency, defined as having less than 20 nanograms vitamin D per milliliter, was also more prevalent in Parkinson’s disease patients. Twenty-three percent of the Parkinson’s disease group was found to be deficient in vitamin D, compared with 16 percent of the Alzheimer’s disease patients and 10 percent of the healthy population.
"We found that vitamin D insufficiency may have a unique association with Parkinson's, which is intriguing and warrants further investigation," Dr Evatt stated.
Studies have shown that the area of the brain that is most affected by Parkinson's disease, known as the substantia nigra, has high vitamin D receptor levels, indicating that the vitamin may be important for the normal function of these cells. Emory University researchers are investigating whether vitamin D plays a causative role in the disease by testing varying doses of the vitamin in Parkinson’s disease patients.
“These findings support the previously suggested need for further studies to assess what contribution a low 25(OH)D concentration adds to the risk of developing Parkinson’s disease (vs other neurodegenerative disorders) and to determine whether correction of vitamin D insufficiency and deficiency will improve motor or nonmotor symptoms in Parkinson’s disease,” the authors conclude. “The finding of a high incidence of vitamin D deficiency in the Parkinson's disease and other cohorts highlights the importance of routinely checking the level of 25(OH)D, particularly in elderly patients, since deficiency is strongly correlated with a higher incidence of osteoporosis, falls and hip fractures and has been associated with a higher incidence of several forms of cancer and autoimmune disorders."