Type 2 diabetes (T2DM) may increase the risk of Parkinson’s disease (PD). This cohort study evaluated the role of oral anti-hyperglycemic agents (OAA) in any diabetes-PD linkage. A representative cohort of 800,000 was obtained from the Taiwan National Health Insurance database. Those with T2DM were matched with those diabetes-free by birth-date and gender for the comparison of PD incidence. Related to diabetes-free, the hazard ratio (HR) was 2.18 (95% CI 1.27-3.73) for T2DM without OAAs and 1.30 (95% CI 0.77-2.19) with OAAs. For sulfonylurea alone, the PD incidence densities (PID, per 10,000 person-years) increased from 58.3 (95% CI 46.6-70.1) to 83.2 (95% CI 68.6-97.7), with similar findings by gender, but little difference if metformin was used. The metformin-alone HR was 0.95 (95% CI 0.53-1.71), sulfonylurea-alone 1.57 (95% CI 1.15-2.13), and combined therapy 0.78 (95% CI 0.61-1.01) and these differences persisted when incident PD was excluded for four years after T2DM diagnosis. The use of metformin first, in those without insulin, provided an HR of 0.40 (0.17-0.94). The authors concluded that incident PD risk in T2DM increases 2.2-fold and sulfonylureas further increase risk by 57%, which is avoided by combination with metformin. Parkinsonism Relat Disord. 2012 Apr 10. PMID: 22498320
