Three measures of sleep, sleepiness, and sleep deprivation and the risk of injury: A case-control and case-crossover study

Abstract

Purpose: Sleepiness and sleep deprivation are associated with injury, but few case-control studies have addressed them. We sought to add to the body of analytic observational studies. Methods: Case-control and case-crossover study of 2517 injured patients interviewed in person in 3 emergency departments and matched by age, sex, rural versus urban, day of week, and hour of day with 1856 controls. Sleep constructs were measured by the following: (1) self-perceived sleepiness at injury or matched control time using 3 adjectives (tired, sleepy, drowsy); (2) usual sleep quality and quantity, and differences in those in the past 7 days; and (3) hours of sleep in the 24 hours before injury and the 24 hours before that. Results: Better sleep quality in the past 7 days was associated with a lower risk of injury (odds ratio (OR) 0.88, 95% confidence interval (CI) 0.80 to 0.97). Self-reported sleepiness just before injury compared with control time was associated with a lower risk of injury, with ORs of 0.82 per unit on a 0-to-12 scale (95% CI 0.78 to 0.86) in case-control analysis and 0.76 (0.73 to 0.80) in case-crossover analysis. In case-crossover analysis, additional sleep in the 24 hours before injury compared with the 24 hours before that was associated with an increased risk of injury (OR 1.06 per hour, 95% CI 1.03 to 1.09), but this effect disappeared when we controlled for activity, location, and recent alcohol consumption. Conclusions: Better recent sleep quality was associated with a lower risk of injury, but surprisingly, feeling sleepy was also.