Effect of diabetes control status on the progression of Parkinson’s disease: A prospective study

OBJECTIVE: To evaluate whether the control status of type 2 diabetes mellitus (DM) influences the progression of Parkinson’s disease (PD). METHODS: We conducted a prospective cohort study from March 2009 to August 2020. Patients at baseline were categorized into DM and non‐DM groups, and those with DM were further classified into the well and poorly controlled DM groups based on the 7.0% of glycated hemoglobin (HbA1C) levels. Multivariate Cox proportional hazards regression models were used to explore the predictors for PD‐related outcomes by hazard ratios (HRs) and 95% confidence intervals (CIs). RESULTS: Of the 379 patients enrolled, 49 (12.9%) had DM, and 22 of DM (44.9%) were poorly controlled. The adjusted HRs were 2.060 (95% CI 1.165‐3.641) for United Rating Scale (UPDRS) III score increased ≥14 in the poorly controlled‐DM group, and 1.066 (95% CI 0.572‐1.986) in the well‐controlled DM group, relative to the non‐DM group (p trend = 0.025), after adjusting for sex, age, age of onset, body mass index, and UPDRS III and Montreal Cognitive Assessment (MoCA) scores at baseline. The adjusted HRs were 2.079 (95% CI 1.212‐3.566) for reaching Hoehn & Yahr stage ≥3 in the poorly controlled DM group, and 0.879 (95% CI 0.413‐1.871) in the well‐controlled DM group, compared with the non‐DM group (p trend = 0.021). Time to death or time to MoCA 3‐point decrease were not significantly different among the three groups. INTERPRETATION: Poorly controlled DM is an independent risk factor contributing to motor progression in PD. Our study highlights the importance of adequate control of diabetes in PD.