Researchers report that news in the Archives of Neurology.
Vitamin D deficiency, in which people have even less vitamin D than people who have vitamin D insufficiency, was also more common among the Parkinson's patients (23%), compared to the Alzheimer's patients (16%) and the healthy participants (10%).
The findings held regardless of people's age, gender, and presence or absence of an Alzheimer's-related mutation in the APOE gene.
The study was a snapshot in time -- it doesn't prove that low levels of vitamin D cause Parkinson's disease or that taking vitamin D would help prevent Parkinson's.
But those possibilities should be studied, note the researchers, who included Emory University's Marian Evatt, MD, MS.