Risks of road injuries in patients with bipolar disorder and associations with drug treatments: A population-based matched cohort study

Objective Using a nation-wide, population-based dataset, we aimed to investigate the risk of road injury among individuals with bipolar disorder (BD) compared to individuals without BD. In addition, we investigated the putative moderating effects of prescription for lithium, anticonvulsants, antidepressants, and/or first- or second-generation antipsychotic agents on the association between BD and risk of road injury. Method As part of an16-year longitudinal cohort study, we compared the risk of road injuries among study subjects aged 16 and above with a diagnosis of BD, with ten age- and sex-matched sample of individuals without BD. Individuals were compared on measures of incidence on road injuries using medical claims data based on the ICD-9-CM codes: E800~807, E810~817, E819~830, E840~848. Time dependent Cox regression models were used to adjust for time-varying covariates such as age, and medication uses. Hazard ratios before and after adjusting for age, sex, other comorbidities, and drug use were calculated. Results 3953 people with BD were matched with 39,530 controls from general population. Adjusted hazard ratios revealed a 1.66-fold (95% CI 1.40–1.97) increase in risk of road injuries among bipolar subjects when compared to controls. Female gender, older age (i.e. over 80), residence in areas of highest levels of urbanization, and use of antidepressants were associated with a lower risk of road injuries. Conclusions In this large, national, population-based cohort, BD was associated with an elevated risk of road injuries. However, prescriptions of antidepressants might help mitigate the foregoing risk.