Background: Few prospective studies have investigated insomnia in relation to risk for coronary heart disease. We assessed insomnia symptoms and risk of acute myocardial infarction (AMI) in a large, population-based study.
Methods and results: A total of 52 610 men and women were followed up for a first AMI, and 2368 incident AMIs occurred during 11.4 years of follow-up, either identified at hospitals or by the National Cause of Death Registry. In our analyses, we adjusted for age, sex, marital status, education, shift work, blood pressure, lipids, diabetes mellitus, body mass index, physical activity, smoking, and alcohol consumption. Difficulties initiating and maintaining sleep and having a feeling of nonrestorative sleep were associated with a moderate increase in AMI risk. The multiadjusted hazard ratios for AMI were 1.45 (95% confidence interval 1.18-1.80) for people with difficulties initiating sleep almost every night, 1.30 (1.01-1.68) for those with difficulties maintaining sleep almost every night, and 1.27 (1.03-1.57) for those with a feeling of nonrestorative sleep more than once a week compared with people who never experienced these sleep difficulties. When we combined the symptoms, a dose-dependent association was seen between the number of insomnia symptoms and AMI risk (P for trend 0.003). Alternative multivariable models and different sensitivity analyses suggest that the results were robust, especially concerning difficulties initiating sleep.
Conclusions: Insomnia is associated with a moderately increased risk for AMI.