Type 2 Diabetes Associated With Increased Risk, Faster Progression of Parkinson Disease

Patients with type 2 diabetes (T2D) may be at greater risk for developing Parkinson disease (PD), with T2D also associated with faster disease progression in those with PD, according to study findings published this week in Movement Disorders.

As 2 prevalent diseases within an aging population, prior research has highlighted the biologic similarities between T2D and PD.

“Both are characterized by aberrant protein accumulation, lysosomal and mitochondrial dysfunction, and chronic systemic inflammation,” explain the study authors. “Insulin resistance is a hallmark of T2D and may be an important contributing factor to PD, too.”

In addition to studies on the relationship between the 2 diseases, prior systematic reviews and meta-analyses have investigated whether T2D may contribute to risk of developing PD. Although findings are conflicting, the researchers note that most of these studies recruited cohorts of patients with diabetes, as opposed to T2D, with this association also not explored via modern causal methods.

Seeking to further explore whether T2D may serve as a determinant of PD, the researchers from Queen Mary University of London (QMUL) conducted a systematic review of 33,408 articles, with 28 observational studies selected for a meta-analysis. Each study examined the association of T2D with PD risk and progression and came from 1 of 6 databases: PubMed, Web of Science, Scopus, Ovid, Rxiv, and medRxiv.

Leveraging mendelian randomization (MR), a method in genetic epidemiology that can be used to follow up observational associations for evidence of true causal effect, the researchers then gathered summary data from genome-wide association studies to assess the causal effects of genetic liability toward T2D on PD risk and progression.

In the meta-analysis, pooled effect estimates showed that T2D was associated with an increased risk of PD (odds ratio [OR], 1.21; 95% CI, 1.07-1.36), a causal relationship supported by MR (inverse‐variance weighted method [IVW] OR, 1.08; 95% CI, 1.02-1.14; P = .010).

Furthermore, the findings suggest that T2D is associated with faster progression of motor symptoms (standardized mean difference [SMD], 0.55; 95% CI, 0.39-0.72) and cognitive decline (SMD, −0.92; 95% CI, −1.50 to −0.34), although only motor progression was supported by MR (IVW OR, 1.10; 95% CI, 1.01-1.20; P = .032).

“This research brings together the results from many other studies to provide convincing evidence that T2D likely affects not only PD risk, but also PD progression,” said corresponding author Alastair Noyce, MD, clinical senior lecturer in the Preventive Neurology Unit at the Wolfson Institute of Preventive Medicine, QMUL, in a statement.

Addressing the study findings, the researchers said that the analysis did not consider the effect of antidiabetic drugs on PD risk and progression. Notably, prior studies on therapies for treatment of T2D have been shown to reduce PD severity and lower risk of PD.

“Treating T2D may slow down the progression of PD,” concluded the study authors. “Thus, careful screening for T2D and early treatment of T2D in patients with PD may be advisable.”

Reference

Chohan H, Senkevich K, Patel RK, et al. Type 2 diabetes as a determinant of Parkinson's disease risk and progression. Mov Disord. Published online March 8, 2021. doi:10.1002/mds.28551