The association between type 2 diabetes mellitus and Parkinson's disease; a systematic review and meta-analysis

Abstract

Type 2 Diabetes Mellitus (T2DM) may be a novel risk factor for Parkinson's Disease (PD). Due to the mechanistic plausibility and conflicting reports in clinical studies of an association between PD and T2DM, we conducted a systematic review and meta-analysis to further investigate the relationship between the two conditions. We searched EMBASE, MEDLINE, and Scopus databases from database inception to July 8, 2022 for English-language articles that explored the risk relationship between T2DM and PD. R project was used to estimate the pooled odds ratio (OR) and 95 % confidence interval (CI) (PROSPERO registration number: CRD42022353804). Seventeen observational studies were analysed, including a total of 32,551,133 participants, of whom 48,609 (0.15 %) were diagnosed with both T2DM and PD. The analysis revealed that T2DM increased the likelihood of PD development [OR = 1.59 (CI; 1.30, 1.95)], the odds were not significantly influenced by age, sex, or diabetes duration. The odds of developing PD were higher in participants with T2DM complications compared to those without complications [OR = 1.62 (CI; 1.24, 2.12)]. T2DM was associated with more severe motor decline evidenced by higher Unified Parkinson's Disease Rating Scale scores, but not for developing cognitive impairment. All outcomes were assessed to be of very low certainty, due to high risk of bias and significant heterogeneity. Further studies are required to understand this relationship between T2DM and PD, particularly with a focus on exploring the potential of repurposing antidiabetic medications as disease-modifying treatments for PD.