Fasting Plasma Glucose Levels and Longitudinal Motor and Cognitive Outcomes in Parkinson’s Disease Patients

Objective Hyperglycemia and diabetes mellitus have been identified as poor prognostic factors for motor and nonmotor outcomes in patients with Parkinson’s disease (PD), although there is some controversy with this finding. In the present study, we investigated the effects of fasting plasma glucose (FPG) levels on longitudinal motor and cognitive outcomes in PD patients. Methods We included a total of 201 patients who were diagnosed with PD between January 2015 and January 2020. The patients were categorized based on FPG level into euglycemia (70 mg/dL < FPG < 100 mg/dL), intermediate glycemia (100 mg/dL ≤ FPG < 126 mg/dL), and hyperglycemia (FPG ≥ 126 mg/dL), and longitudinal FPG trajectories were analyzed using group-based trajectory modeling. Survival analysis was conducted to determine the time until motor outcome (Hoehn and Yahr stage ≥ 2) and the conversion from normal cognition to mild cognitive impairment. Results Among the patient cohort, 82 had euglycemia, 93 had intermediate glycemia, and 26 had hyperglycemia. Intermediate glycemia (hazard ratio 1.747, 95% confidence interval [CI] 1.083–2.816, p = 0.0221) and hyperglycemia (hazard ratio 3.864, 95% CI 1.996–7.481, p < 0.0001) were found to be significant predictors of worsening motor symptoms. However, neither intermediate glycemia (hazard ratio 1.183, 95% CI 0.697–2.009, p = 0.5339) nor hyperglycemia (hazard ratio 1.297, 95% CI 0.601–2.800, p = 0.5078) demonstrated associations with the longitudinal progression of cognitive impairment. Diabetes mellitus, defined by self-reported medical history, was not related to poor motor or cognitive impairment outcomes. Conclusion Our results suggest that both impaired glucose tolerance and hyperglycemia could be associated with motor progression in PD patients.