Sleeping Too Much Or Little Affects Risk For Heart Attack

Those that are at a high genetic risk for heart attack were found to be able to offset the risk by sleeping between 6-9 hours a night in the study published in the Journal of the American College of Cardiology.

"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 senior author Celine Vetter, an assistant professor of Integrative Physiology.

Genetic information, self reported sleep habits, and medical records were analyzed from 461,000 UK Biobank participants who were between the ages of 40-69 with no history of heart attack, and were followed for 7 years. 

Those who slept less than 6 hours a night were 20% more likely to have a heart attack during the study period than those who slept 6-9 hours; those sleeping more than 9 hours were found to be 34% more likely to have a heart attack. When analyzing only those with genetic predisposition to heart disease sleeping between 6-9 hours a night was found to reduce their risk of having a heart attack by 18%. 

"It's kind of a hopeful message, that regardless of what your inherited risk for heart attack is, sleeping a healthy amount may cut that risk just like eating a healthy diet, not smoking, and other lifestyle approaches can," said lead author Iyas Daghlas, a medical student at Harvard.

Many factors influence heart health and sleep, making it difficult to determine cause and effect. The UK Biobank was used in this study to combine observational and genetic research to investigate in a different way, and after taking 30 other factors into account such as mental health, socioeconomics, body composition, and physical activity sleep duration, in and of itself, was found to influence risk of heart attack independently of other factors. 

The risk was found to increase the further people fell outside of the 6-9 hours of sleep range; those sleeping 5 hours per night had 52% higher risk of heart attack than those sleeping 7-8 hours, and those sleeping 10 hours a night were twice as likely to have a heart attack. 

Using Mendelian randomization the team examined genetic profiles to determine if those who were genetically predisposed to short sleep were more likely to suffer a heart attack; 27 genetic variants are associated with short sleep, similar patterns emerged to find that genetically influenced short sleep duration was also a risk factor for heart attack.

"This gives us even more confidence that there is a causal relationship here—that it is sleep duration, not something else, influencing heart health. Just as working out and eating healthy can reduce your risk of heart disease, sleep can too." Vetter said.

The team did not explore the mechanism by which short/long sleep may increase the risk for heart attack in this study. Past research suggests that sleeping too little can impact artery linings, bone marrow development of inflammatory cells, and lead to poor dietary choices which impacts weight and heart health, while sleeping too much increases inflammation in the body which is associated with cardiovascular disease.