Background: Vitamin D insufficiency has been reported to be more common in patients with Parkinson disease (PD) than in healthy control subjects, but it is not clear whether having a chronic disease causing reduced mobility contributes to this relatively high prevalence.
Objective: To examine the prevalence of vitamin D insufficiency in a cohort of untreated patients with early PD (diagnosed within 5 years of study entry). DESIGN, SETTING, AND PATIENTS The Deprenyl and Tocopherol Antioxidative Therapy of Parkinsonism (DATATOP) cohort is a well-characterized cohort of subjects with early, nondisabling PD. The cohort is well suited for examining the prevalence of vitamin D insufficiency early in the course of the disease. We conducted a survey study of vitamin D status in stored blood samples from patients with PD enrolled in the placebo group of the DATATOP trial. Samples from baseline visits and end point/final visits (mean [SD], 18.9 [13.1] months) were analyzed for 25-hydroxyvitamin D (25[OH]D) concentration in blinded fashion.
Main outcome measures: The mean vitamin D concentration and the prevalence of vitamin D insufficiency at baseline and end point/final visits.
Results: Among 199 subjects, 170 (85.4%) had samples from the baseline and end point visits available for analysis; 13 were excluded (10 with low probability of having PD and 3 with 25[OH]D concentrations>3 SDs above the mean). In the remaining 157 subjects, the mean (SD) 25(OH)D concentrations at the baseline and end point visits were 26.3 (8.6) ng/mL and 31.3 (9.0) ng/mL, respectively (to convert to nanomoles per liter, multiply by 2.496). The prevalence of vitamin D insufficiency (25[OH]D concentration<30.0 ng/mL) was 69.4% at baseline and 51.6% at the end point.
Conclusions: The prevalence of vitamin D insufficiency in patients with early PD was similar to or higher than those reported in previous studies. Vitamin D concentrations did not decline during progression of PD. Further studies are needed to elucidate the natural history and significance of vitamin D insufficiency in PD.