Hours of sleep as a risk factor for injury among adolescents in rural Minnesota

Background: The purpose of this study was to determine the relationship between injury and sleep hours among adolescents. Methods: Youth at Work, an open cohort from 41 rural Minnesota high schools, followed 15,002 students from 2001-2003. Data were collected through self-completed questionnaires four times during 2001-2002 and 2002-2003 school years. Questionnaire responses identified injury events and exposures in summer months (fall administration) and the school year (spring administration); 41,272 questionnaires were completed. Risk of injury was estimated using sleep patterns from both usual school nights (Sunday-Thursday) and usual weekend nights; >9 hours of sleep every night was the referent. Multivariate analyses were conducted using directed acyclic graphs to select potential confounders for each exposure of interest. Results: Risk of injury was increased for eight hours or less of sleep every night (OR = 1.25; CI = 1.08,1.45). Students obtaining eight hours or more during school nights, but less than eight hours on weekend nights, also had an increased risk (OR = 1.18; CI = 1.05,1.33), as did individuals who slept longer on weekend nights, but less than eight hours on school nights (OR = 1.13; CI = 1.01,1.27). Risk of injury increased further for seven and six hours or less of sleep on school nights, respectively (OR = 1.36; CI = 1.12, 1.64 and OR = 1.59; CI = 1.24, 2.05). Conclusions: Sleep may play an important role in the safety of adolescents. These findings serve as a basis for further research and consideration of relevant intervention efforts.