Researchers from the National Institute for Health and Welfare in Helsinki analysed data from 3,173 Finnish men and women aged between 50 and 79. Over an impressive 29 years of follow-up, the researchers documented 50 cases of Parkinson's disease.
The study is reported to be the first longitudinal analysis of vitamin D status and the risk of Parkinson's disease.
Writing in the Archives of Neurology, the authors note that the exact mechanism is unknown, but postulated that vitamin D may be exerting a benefit through antioxidant activities, regulation of calcium levels, detoxification, modulation of the immune system and enhanced conduction of electricity through neurons.
“Our results are in line with the hypothesis that low vitamin D status predicts the development of Parkinson disease,” write the researchers. “Because of the small number of cases and the possibility of residual confounding, large cohort studies are needed. In intervention trials focusing on effects of vitamin D supplements, the incidence of Parkinson disease merits follow up.”
In an accompanying editorial, Marian Leslie Evatt, MD, MS, from Emory University in Atlanta described the study as “the first promising human data to suggest that inadequate vitamin D status is associated with the risk of developing Parkinson's disease”.
Evatt cautioned however that “further work is needed in both basic and clinical arenas to elucidate the exact role, mechanisms and optimum concentration of vitamin D in Parkinson's disease."
Parkinson's disease is a degenerative condition affecting movement and balance in more than one million Americans each year, a figure expected to rise due to ageing populations. The disease affects nerve cells in several parts of the brain, particularly those that use the chemical messenger dopamine to control movement.
Previous studies have shown that the part of the brain affected most by Parkinson's, the substantia nigra, contains high levels of the vitamin D receptor, which suggests vitamin D may be important for normal functions of these cells.
The new study involved the measurement of vitamin D levels in over 3,000 people. The data showed that people with the lowest levels of vitamin D were three times more likely to develop Parkinson's, compared to the group with the highest levels.
In the editorial, Evatt added that “it seems prudent to confirm the findings presented in this issue and investigate whether the apparent dose-response relationship observed in the current study maintains its slope, levels off or becomes negative with higher 25-hydroxyvitamin D concentrations.
“In the interim, data from interventional studies of fractures and falls appear to justify optimizing vitamin D levels to greater than 30 to 40 nanograms per millilitre,” she concluded
Source: Archives of Neurology
Volume 67, Issue 7, Pages 808-811
"Serum Vitamin D and the Risk of Parkinson Disease"
Authors: P. Knekt, A. Kilkkinen, H. Rissanen, J. Marniemi, K. Saaksjarvi, M. Heliovaara
Editorial: Archives of Neurology
Volume 67, Issue 7, Pages 795-797, doi:10.1001/archneurol.2010.123
“Beyond Vitamin Status – Is There a Role for Vitamin D in Parkinson Disease?”
Author: M.L. Evatt