Type 2 Diabetes Risk among Incident Parkinson’s Disease Patients: A 20-Year Retrospective Population-Based Cohort Study

INTRODUCTION: Parkinson's disease (PD) and type 2 diabetes mellitus (T2DM) are common chronic conditions that may share biological mechanisms such as inflammation and insulin resistance. While T2DM is associated with increased PD risk, evidence for T2DM risk in newly diagnosed PD patients remains limited. This study was designed to estimate the risk of T2DM among incident PD patients and assess the effect of T2DM on PD patient mortality. METHODS: A population-based retrospective cohort study was conducted in 7,976 incident PD patients without prior T2DM according to a validated registry in Maccabi Health Services medical data (2000-2019). Cox regression models, adjusted for age, sex, and comorbidities, were used to estimate hazard ratios (HRs) for both T2DM onset and the effect of T2DM on mortality risk among PD patients. RESULTS: During a mean follow-up of 7.1 years, 666 patients (8.4%) developed T2DM. Male sex was significantly associated with a reduced risk of T2DM onset (HR = 0.77; 95% CI: 0.66-0.89) compared to females. Furthermore, patients with T2DM but without complications had a significantly lower risk of mortality than those without T2DM (HR = 0.70; 95% CI: 0.62-0.78). CONCLUSION: The risk of developing T2DM was relatively low in male PD patients without pre-existing diabetes. Moreover, PD patients with uncomplicated T2DM had a lower mortality risk than nondiabetic individuals. These findings highlight the importance of considering the timing of comorbidities and suggest sex-specific mechanisms linking PD and T2DM that warrant further investigation.