Men's Osteoporosis Support Group
Vitamin D, sunshine and hip fracture in people with Parkinson's disease
Parkinsonism Relat Disord. 2010 Nov 1. [Epub ahead of print]. Amelioration of osteoporosis and hypovitaminosis D by sunlight exposure in Parkinson's disease. Sato Y, Iwamoto J, Honda Y. PMID: 21050796. This Japanese study of Parkinson's disease patients with low levels of serum vitamin D included 162 people who were given 3221 minutes of sunlight exposure per year and compared to 162 controls who weren't exposed to sunlight. The results after two years showed, "BMD increased by 3.8% in the sunlight-exposed group and decreased by 2.6% in the usual lifestyle group (p<.0001)." The serum vitamin D levels increased from 27 nmol/L to 52 nmol/L. The control individuals had 11 hip fractures and the test individuals had 3 fractures. The authors concluded, "Sunlight exposure can increase the BMD of vitamin D deficient bone by increasing 25-OHD concentration and leads to the prevention of hip fracture."
Editor's comments. A recent Update discussed the problems with low bone mineral density (BMD), increased falls, and fractures in people with Parkinson's disease. The Sato study shows that sunlight will increase serum vitamin D levels and BMD, which leads to decreased fracture risk in Parkinson's patients. The amount of time in the sun for the two years was about one hour per week. Based upon the latitude of the study's location, that might have involved more time in winter/summer when ultraviolet B (UVB) rays are not filtered out by the low angle of the incident sunlight. But that isn't stated in the abstract, so we don't know for sure.
The increase in BMD is very significant in this study, similar to what is gained with one of the bisphosphonates, especially if you consider that the test subjects not only gained 3.8% of BMD, they didn't lose the 2.6% that the controls did. That means a real net gain of over 6% in BMD. I don't have the full study, but I wonder if there wasn't some benefit from the exercise involved in getting the test individuals out to the sunlight. If it involved several days a week of walks to an outside area where sunlight was available, that could be the case. For more information on vitamin D and BMD/fractures, see the Osteoporosis Issues article on that topic.
Not tested or discussed is the possibility that oral vitamin D supplements would have the same effect as the sunlight. A future study will have to be done comparing the two methods of increasing serum vitamin D to see if one is more effective than the other.
The bottom line from this study is that Parkinson's patients should include some time in the sun if they are in a latitude where seasonal sunlight will stimulate formation of serum vitamin D. For those in a more polar latitude where there is no UVB radiation much of the year, they should probably take vitamin B supplements and have their serum vitamin D levels tested to be sure they are maintaining normal levels: 30 ng/mL (75 nmol/L). Note that participants in the above study had BMD improvement with a mean increase of serum vitamin D to less than normal, 52 nmol/L.