The Impact of Type 2 Diabetes in Parkinson's Disease

Abstract

Background: Type 2 diabetes (T2DM) is an established risk factor for developing Parkinson's disease (PD), but its effect on disease progression is not well understood.

Objective: The aim of this study was to investigate the influence of T2DM on aspects of disease progression in PD.

Methods: We analyzed data from the Tracking Parkinson's study to examine the effects of comorbid T2DM on PD progression and quality of life by comparing symptom severity scores assessing a range of motor and nonmotor symptoms.

Results: We identified 167 (8.7%) patients with PD and T2DM (PD + T2DM) and 1763 (91.3%) patients with PD without T2DM (PD). After controlling for confounders, patients with T2DM had more severe motor symptoms, as assessed by Movement Disorder Society Unified Parkinson's Disease Rating Scale, Part III (25.8 [0.9] vs. 22.5 [0.3] P = 0.002), and nonmotor symptoms, as assessed by Non-Motor Symptoms Scale total (38.4 [2.5] vs. 31.8 [0.7] P < 0.001), and were significantly more likely to report loss of independence (odds ratio, 2.08; 95% confidence interval [CI]: 1.34-3.25; P = 0.001) and depression (odds ratio, 1.62; CI: 1.10-2.39; P = 0.015). Furthermore, over time, patients with T2DM had significantly faster motor symptom progression (P = 0.012), developed worse mood symptoms (P = 0.041), and were more likely to develop substantial gait impairment (hazard ratio, 1.55; CI: 1.07-2.23; P = 0.020) and mild cognitive impairment (hazard ratio, 1.7; CI: 1.24-2.51; P = 0.002) compared with the PD group.

Conclusions: In the largest study to date, T2DM is associated with faster disease progression in Parkinson's, highlighting an interaction between these two diseases. Because it is a potentially modifiable metabolic state, with multiple peripheral and central targets for intervention, it may represent a target for alleviating parkinsonian symptoms and slowing progression to disability and dementia. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Keywords: Parkinson's; cognitive impairment; disease progression; type 2 diabetes.

FIG 1

Flow diagram of the study population. DM, diabetes mellitus; PD, Parkinson's disease; T2DM, type 2 diabetes mellitus.

FIG 2

Likelihood of complications or reaching disease milestones in patients with Parkinson's disease (PD), according to type 2 diabetes mellitus (T2DM) status. Patients with T2DM were significantly more likely to have depression, substantial gait impairment, and loss of independence and were significantly less likely to have dopamine dysregulation than patients without T2DM. MCI, mild cognitive impairment; H&Y, Hoehn & Yahr; ICD, impulse control disorder; ICDs‐RD, impulse control and related disorders; OR, odds ratio; SE‐ADL, Schwab and England Activities of Daily Living Scale.

FIG 3

Timeline for the development of mild cognitive impairment (MCI) and substantial gait impairment, comparing Parkinson's disease (PD) cases with and without type 2 diabetes mellitus (T2DM). Kaplan–Meier curves show the significantly shorter time to develop both of these complications in patients with T2DM. [Color figure can be viewed at wileyonlinelibrary.com]

FIG 4

Time course of features in patients with Parkinson's disease (PD) comparing those with and without type 2 diabetes mellitus (T2DM). Progression was significantly faster for several domains. *P < 0.05. MDS‐UPDRS, Movement Disorder Society Unified Parkinson's Disease Rating Scale; NMSS, Non‐Motor Symptoms Scale; SE‐ADL, Schwab and England Activities of Daily Living Scale. [Color figure can be viewed at wileyonlinelibrary.com]