STUDY OBJECTIVES: Impaired sleep is an established risk factor for the development of cardiovascular disease, whereas less is known about how impaired sleep affects cardiovascular prognosis. The aim of this study is to determine how different aspects of impaired sleep affect the risk of case fatality and subsequent cardiovascular events following first-time acute myocardial infarction (AMI). DESIGN: Prospective cohort study. SETTING: The Stockholm Heart Epidemiology Program, Sweden. PARTICIPANTS: There were 2,246 first-time AMI cases. MEASUREMENTS AND RESULTS: SLEEP IMPAIRMENT WAS ASSESSED BY THE KAROLINA SLEEP QUESTIONNAIRE, WHICH COVERS VARIOUS INDICES OF IMPAIRED SLEEP: disturbed sleep, impaired awakening, daytime sleepiness, and nightmares. Case fatality, defined as death within 28 days of initial AMI, and new cardiovascular events within up to 10 y of follow-up were identified through national registries. In women, disturbed sleep showed a consistently higher risk of long-term cardiovascular events: AMI (hazard ratio [HR] = 1.69; 95% confidence interval [CI] 0.95-3.00), stroke (HR = 2.61; 95% CI: 1.19-5.76), and heart failure (HR = 2.43; 95% CI: 1.18-4.97), whereas no clear effect of impaired sleep on case fatality was found in women. In men, a strong effect on case fatality (odds ratio = 3.27; 95% CI: 1.76-6.06) was observed in regard to impaired awakening; however, no consistent effect of impaired sleep was seen on long-term cardiovascular prognosis. CONCLUSION: Results suggest sex-specific effects of impaired sleep that differ by short- and long-term prognosis. Sleep complaints are frequent, easily recognizable, and potentially manageable. Evaluation of sleep complaints may, even if they represent prognostic markers rather than risk factors, provide additional information in clinical risk assessment that could benefit secondary cardiovascular prevention. CITATION: Clark A, Lange T, Hallqvist J, Jennum P, Rod NH. Sleep impairment and prognosis of acute myocardial infarction: a prospective cohort study. SLEEP 2014;37(5):851-858.