Suicide and unintentional injury mortality among homeless people: A Danish nationwide register-based cohort study

Background: Homeless people have elevated mortality, especially due to external causes. We aimed to examine suicide and unintentional injury mortality levels and identify predictors in the homeless population. Methods: A nationwide, register-based cohort study of homeless people aged 16 years and older was carried out using the Danish Homeless Register, 1999-2008. Results: In all, 32 010 homeless people (70.5% men) were observed. For men, the mortality rate was 174.4 [95% confidence interval (CI) = 150.6-198.1] per 100 000 person-years for suicide and 463.3 (95% CI = 424.6-502.0) for unintentional injury. For women, the corresponding rates were 111.4 (95% CI = 81.7-141.1) for suicide and 241.4 (95% CI = 197.6-285.1) for unintentional injury. Schizophrenia spectrum, affective, personality and substance use disorders were strongly associated with increased risk of suicide; the highest risk estimates were found for schizophrenia spectrum disorders among both men [hazard ratio (HR) = 3.1, 95% CI = 2.0-4.9] and women (HR = 15.5, 95% CI = 4.5-54.0). Alcohol and drug use disorders were predictors of death by unintentional injury for both men and women, whereas schizophrenia spectrum disorders and personality disorders were only significant predictors among men; the highest risk estimates were found for drug use disorders among men (HR = 2.2, 95% CI = 1.8-2.8) and women (HR = 3.1, 95% CI = 1.8-5.4). A history of psychiatric admission and emergency room contact were predictors for dying by suicide and unintentional injury. Conclusion: People in the homeless shelter population with a history of a psychiatric disorder constitute a high-risk group regarding the elevated suicide and unintentional injury mortality.