Evaluation of motor vehicle crashes between scooter riders and car drivers after diagnosis of type 2 diabetes in Taiwan

Background: Despite the plausibility that diabetes may increase the risk of motor vehicle crashes (MVCs) due to various diabetes related complications and co-morbidity, findings from epidemiological studies on the relationship between diabetes and MVCs remained inclusive mainly due to heterogeneity in the study design and failure to complete consideration of potential confounders. This study re-visited this putative association with an improved study design. Method: This study employed a controlled before–after study design and included 1,264,280 people aged 18–75 years with T2D newly diagnosed from 2009–2014 and an equal number of age-, sex-, and time-matched controls. The rate ratios (RRs) of vehicle type–specific incidence rates of MVCs in the 1 and 2 years before and after diabetes diagnosis (or the matched dates) were compared between the individuals with type 2 diabetes (T2D) and their matched controls. Results: The rate of MVCs increased slightly among people with T2D over 1 and 2 years following diabetes diagnosis, with RRs of 1.04 (95% confidence interval [CI]=1.02–1.07) and 1.11 (95% CI=1.09–1.13), respectively. These RRs were comparable to those obtained for controls (1.06 and 1.12, respectively). By contrast, the RRs of scooter crashes were significantly higher in the T2D group than in the control group during the 1 year (1.28 vs. 1.08, p < 0.001) and 2 years (1.32 vs. 1.08, p < 0.001) following diabetes diagnosis. Conclusion: : T2D diagnosis was associated with a moderate but significant increase in the risk of MVCs among scooter drivers, but not among car drivers.