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Diabetes mellitus, prediabetes and the risk of Parkinson's disease: a systematic review and meta-analysis of 15 cohort studies with 29.9 million participants and 86,345 cases.
Aune, D, Schlesinger, S, Mahamat-Saleh, Y, Zheng, B, Udeh-Momoh, CT, Middleton, LT
European journal of epidemiology. 2023;38(6):591-604
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Plain language summary
Diabetes mellitus and prediabetes may increase an individual’s risk for Parkinson’s disease (PD), however the research completed to date has been controversial. This meta-analysis of 15 observational studies with 86,345 individuals with PD aimed to update the research on PD risk for individuals with diabetes or prediabetes and determine possible reasons for the ambiguity of previous research. The results showed that compared to people without diabetes, those with, were at a 27% increased relative risk of PD and a 4% increase amongst those with prediabetes. Individuals with a history of complications alongside diabetes were at a higher risk than those without. It was concluded that the risk of developing PD is increased amongst individuals with diabetes. This study could be used by healthcare professionals to understand that individuals with diabetes may be at an increased risk for PD and should be monitored. However, as this is based on observational studies, there is a chance that PD increases the risk for diabetes and not the reverse.
Abstract
A diagnosis of diabetes mellitus and prediabetes has been associated with increased risk of Parkinson's disease (PD) in several studies, but results have not been entirely consistent. We conducted a systematic review and meta-analysis of cohort studies on diabetes mellitus, prediabetes and the risk of PD to provide an up-to-date assessment of the evidence. PubMed and Embase databases were searched for relevant studies up to 6th of February 2022. Cohort studies reporting adjusted relative risk (RR) estimates and 95% confidence intervals (CIs) for the association between diabetes, prediabetes and Parkinson's disease were included. Summary RRs (95% CIs) were calculated using a random effects model. Fifteen cohort studies (29.9 million participants, 86,345 cases) were included in the meta-analysis. The summary RR (95% CI) of PD for persons with diabetes compared to persons without diabetes was 1.27 (1.20-1.35, I2 = 82%). There was no indication of publication bias, based on Egger's test (p = 0.41), Begg's test (p = 0.99), and inspection of the funnel plot. The association was consistent across geographic regions, by sex, and across several other subgroup and sensitivity analyses. There was some suggestion of a stronger association for diabetes patients reporting diabetes complications than for diabetes patients without complications (RR = 1.54, 1.32-1.80 [n = 3] vs. 1.26, 1.16-1.38 [n = 3]), vs. those without diabetes (pheterogeneity=0.18). The summary RR for prediabetes was 1.04 (95% CI: 1.02-1.07, I2 = 0%, n = 2). Our results suggest that patients with diabetes have a 27% increased relative risk of developing PD compared to persons without diabetes, and persons with prediabetes have a 4% increase in RR compared to persons with normal blood glucose. Further studies are warranted to clarify the specific role age of onset or duration of diabetes, diabetic complications, glycaemic level and its long-term variability and management may play in relation to PD risk.