Diabetes and risk of Parkinson's disease: a systematic review and meta-analysis.
Level 3 - non-randomized controlled study
Systematic review and meta-analysis of observational cohort and case-control studies.
PubMed 22110170 · doi:10.2337/dc11-1584
What was done
A systematic review and meta-analysis investigated the association between pre-existing diabetes and Parkinson's disease (PD). Electronic databases (PubMed, Embase, Scopus) and reference lists were searched through May 10, 2011, for English-language prospective cohort and case-control studies. Nine studies out of 1,947 citations met inclusion criteria (4 prospective cohort studies and 5 case-control studies).
What was found
In prospective cohort studies, diabetes preceding PD onset was associated with an increased risk of future PD (relative risk [RR] = 1.37, 95% CI 1.21–1.55; P < 0.0001). This association remained after excluding participants with vascular disease at baseline or during follow-up (RR = 1.34, 95% CI 1.14–1.58; P < 0.001). Conversely, case-control studies showed no significant association (odds ratio [OR] = 0.75, 95% CI 0.50–1.11; P = 0.835), which persisted after adjustment for BMI (OR = 0.56, 95% CI 0.28–1.15; P = 0.089).
Why it matters
This review highlights a consistent link between pre-existing diabetes and Parkinson's disease risk in prospective longitudinal data, though divergence from case-control studies precludes a definitive conclusion.
Limits
The meta-analysis included only 9 studies (4 prospective cohorts). Findings differed substantially by study design, the search was restricted to English-language publications, and the abstract notes residual confounding was not fully controlled.
Cited by
- supports Type 2 diabetics have approximately a 40% increased risk of developing Parkinson's disease.