People Who Sleep Too Much, or Too Little, at Heightened Risk of Heart Attack

Both insufficient (<6 hours) and longer (>9 hours) sleep durations are associated with greater risk of myocardial infarction (MI), according to a study published this week in the Journal of American College of Cardiology.

The prospective cohort analysis examined correlations between sleep duration and incident MI by utilizing Mendelian randomization (MR) to determine causality. Genetic risk of coronary artery disease (CAD) and joint effects with other sleep traits, such as insomnia, daytime napping, and sleep quality, were accounted for as well. Researchers aimed to not only determine the causal contribution of sleep to MI, but to assess its potential in mitigating genetic predisposition to CAD.

Self-reported sleep durations and medical records were derived from 461,347 UK Biobank participants aged 40 to 69 with no relevant cardiovascular disease:

• Single nucleotide polymorphisms (SNP) were used as proxies for lifetime exposure to longer (>9 hours) and shorter (<6 hours) sleep durations
• 2-sample MR was conducted by the authors in which short sleep duration patients (24 SNPs) and longer sleep duration patients (71 SNPs) were examined for causality with MI

Assessments revealed a stark multivariable-adjusted risk of incidence for MI in both patient groups reported shorter and longer sleep durations. Compared with patients who slept 6 to 9 hours a night, short sleepers had a significant 20% higher risk of incident MI (hazard ratio [HR], 1.20; 95% CI, 1.07-1.33), while longer sleepers exhibited a heightened 34% risk (HR,1.34; 95% CI, 1.13-1.58). For patients who reported short or long sleep durations, and have a high genetic risk (top 25%) for CAD, a 130% higher risk of MI (HR, 2.30; 95% CI, 1.88-2.82) was found when compared with patients with a low genetic risk who slept for the optimal amount of time—6 to 9 hours.

Senior study author Celine Vetter, PhD, assistant professor of Integrative Physiology at the University of Colorado Boulder, emphasized the correlation between sleep duration and CAD found in the study. “This provides some of the strongest proof yet that sleep duration is a key factor when it comes to heart health, and this holds true for everyone,” said Vetter. For patients who have a high genetic liability for CAD, optimal sleep duration mitigated MI risk by 18% (HR, 0.82; 95% CI, 0.68-0.998). This substantial difference in MI risk for patients with high genetic risk of CAD highlights the importance of achieving an optimal sleep duration.

“Just as working out and eating healthy can reduce your risk of heart disease, sleep can too,” said Vetter. Duration of sleep plays a vital role as a either too little or too much sleep can increase MI risk. The further one gets from the optimal window of sleep duration, the higher that risk becomes compared to optimal sleepers in the unadjusted model:

• 4 hours of sleep (96% increase; HR, 1.96; 95% CI, 1.57-2.43)
• 5 hours of sleep (52% increase; HR, 1.52; 95% CI, 1.35-1.70)
• 10 hours of sleep (107% increase; HR, 2.07; 95% CI, 1.73-2.46)
• 11 hours of sleep (178% increase; HR, 2.78; 95% CI, 1.59-4.51)

“This gives us even more confidence that there is a causal relationship here - that it is sleep duration, not something else, influencing heart health,” said Vetter. The authors noted that investigation of sleep extension to prevent MI may be warranted.

Reference

Daghlas I, Dashti HS, Lane J, et al. Sleep duration and myocardial infarction. [published online September 2, 2019]. Journal of the American College of Cardiology. doi: 10.1016/j.jacc.2019.07.022.