Table 1.
Association of Vitamin D with Parkinson's disease risk and symptoms.
| Study findings | References | |
|---|---|---|
| Parkinson's Disease Risk | ||
| Vitamin D and Parkinson's Disease Risk | Findings are mixed. A study in Finland found an association between vitamin D level and future PD risk while a study in the United States did not. Differences in the populations studied may play a role | (31–36) |
| Vitamin D Receptor and Parkinson's Disease Risk | The SNP FokI is associated with a decreased risk of PD in Asian populations but not in Caucasian populations | (37–40) |
| Motor Symptoms | ||
| Disease Severity | Lower serum vitamin D levels are consistently associated with higher motor symptom severity in PD, however, reduced mobility in advanced disease may result in limited sun exposure and lower vitamin D levels | (22, 41–47) |
| Disease Progression | Findings are mixed. In two studies, lower baseline vitamin D level was a predictor of increased motor severity, while two other studies found no association. There is risk for confounding due to limited mobility and sun exposure as the disease progresses | (22, 48–53) |
| Balance and Falls | Lower vitamin D levels are associated with falls. High dose vitamin D supplementation may improve balance in younger PD patients. More recent data in the general population suggests there is a U-shaped response curve to vitamin D supplementation | (45, 54–75) |
| Non-motor Symptoms | ||
| Cognition | In PD without dementia, higher plasma vitamin D levels are associated with better verbal fluency and verbal memory. The VDR FokI AA genotype is associated with faster cognitive decline and lower VDR activity | (44, 50, 76, 77) |
| Mood | There is limited evidence of an association between depression and lower serum vitamin D levels in PD. Data is inconsistent in the general population, however, a meta-analysis of 31,000 participants found lower vitamin D levels in participants with depression compared to controls | (44, 73, 78–84) |
| Orthostatic hypotension | Lower serum vitamin D levels were associated with orthostatic hypotension in one study involving PD patients and multiple studies involving the general population, however, the findings have been inconsistent | (85–90) |
| Olfactory function | One study in PD reported a negative correlation between odor identification scores and serum vitamin D level. More studies are needed | (91) |
UPDRS, Unified Parkinson's Disease Rating Scale; H&Y, Hohn and Yahr; SNP, Single Nucleotide Polymorphism.