Abstract

Objective: Previous observational studies reported inconsistent results on the association between diabetes and Parkinson's disease (PD), and data on the risk of developing incident diabetes in relation to PD are scarce. We aimed at comparing the diabetes prevalence between patients with or without PD, and at exploring the risk of developing incident diabetes associated with PD.

Research Design and Methods: We used the UK-based General Practice Research Database (GPRD) to a) compare the diabetes prevalence between PD cases and a matched comparison group free of PD between 1994 and 2005, and to b) conduct a follow-up study with a nested case-control analysis to quantify the risk of developing new onset diabetes in association with PD.

Results: The diabetes prevalence was similar in PD patients and in PD-free patients (adjusted odds ratio [OR] 0.95, 95% CI 0.80-1.14). In the cohort analysis (incidence rate ratio [IRR] 0.55, 95% CI 0.38-0.81) and in the nested case-control analysis (adjusted OR 0.53, 95% CI 0.33-0.87), the risk of developing diabetes was lower in PD patients than in subjects without PD. The adjusted OR for PD patients who were current levodopa users of ≥ 5 prescriptions was 0.22 (95% CI 0.10-0.48), and 1.11 (95% CI 0.50-2.45) for PD patients not using levodopa.

Conclusions: In this observational study the diabetes prevalence was closely similar between PD cases and patients without PD. The risk of developing incident diabetes was lower for PD patients than for patients without PD, a finding which was limited to PD patients using levodopa.