Prospective study on the components of metabolic syndrome and the incidence of Parkinson's disease.

INTRODUCTION: Inconsistent results regarding the association between the components of metabolic syndrome and Parkinson's disease (PD) have been reported. We investigated whether the metabolic syndrome or its components, or serum total cholesterol, predict PD incidence in a prospective cohort study design. METHODS: The study was based on the Mini-Finland Health Survey including 6641 individuals aged 30-79 and free from PD at baseline (1978-1980). During 30 years of follow-up, 89 incident PD cases occurred. RESULTS: After adjustment for sociodemographic and lifestyle factors, the relative risk (RR) of PD was 0.50 (95% confidence interval (CI): 0.30, 0.83) for individuals with the metabolic syndrome compared to those without. This association was especially due to elevated serum triglyceride concentration (≥1.7 vs.<1.7 mmol/L, RR = 0.52, 95%CI: 0.30-0.89, P for trend 0.02) and elevated plasma fasting glucose concentration (≥5.6 vs.<5.6 mmol/L, RR = 0.56 0.32, 0.98, P for trend 0.05). Elevated serum triglyceride and plasma fasting glucose concentration predicted lower PD risk even after excluding the first 10 years of follow-up. After this exclusion and further adjustment for other components of the metabolic syndrome, a suggestively increased PD risk was observed in overweight individuals (≥25 kg/m(2) vs.<25 kg/m(2), RR = 1.75, 95%CI: 1.00, 3.07, P for trend 0.22). Blood pressure, serum HDL cholesterol, or serum total cholesterol carried no prediction of PD risk. CONCLUSION: Elevated serum triglyceride and plasma fasting glucose concentrations predict low PD incidence whereas high BMI seems to be suggestively related to an increased PD risk.