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Irregular sleep patterns may raise risk of heart disease

Like not getting enough good sleep, not having a regular sleep schedule could also be unhealthy. Sturti / E+ via Getty Images

Getting enough sleep is important for good health. Experts recommend that most adults get seven to nine hours of quality sleep a night. Sleep helps support healthy brain function and important aspects of our metabolism, like controlling appetite and blood sugar. Research has linked insufficient sleep to health conditions such as obesity and diabetes.

Studies have also found that insufficient sleep and poor sleep quality have negative effects on heart health. However, scientists had not examined the effects of irregular sleeping patterns—going to sleep and waking at different times each day or getting varying amounts of sleep.

A research team led by Dr. Tianyi Huang at the Brigham and Women's Hospital set out to explore whether irregular sleep patterns increased the risk of heart attack, stroke, and other cardiovascular events. The study was supported by NIH’s National Heart, Lung, and Blood Institute (NHLBI) and National Center for Advancing Translational Studies (NCATS). Findings appeared on March 10, 2020, in the Journal of the American College of Cardiology.

The research team analyzed data from nearly 2,000 men and women, ages 45 to 84, who were enrolled in NHLBI’s Multi-Ethnic Study of Atherosclerosis. None of the participants had cardiovascular disease at the start of the study.

Participants had their sleep-wake patterns tracked for seven days using a device called an actigraph, which resembles a smart watch. The actigraph measures periods of activity and rest to estimate waking and sleep. They also underwent an at-home sleep test and completed a questionnaire about their sleep habits.

The researchers then followed the study participants for about five years to see whether they developed cardiovascular disease. Over this time, 111 participants had cardiovascular events, including heart attack, stroke, or death from a cardiovascular cause.

Participants with the most irregular sleep schedules were nearly twice as likely to develop cardiovascular disease as those with more regular sleep patterns. This remained true even after adjusting for factors that affect heart disease or sleep, such as the breathing disorder sleep apnea. The association between irregular sleep and cardiovascular disease was stronger among minority populations, particularly African Americans, than white participants.

The findings suggest that an irregular sleep pattern may be a new and independent risk factor for cardiovascular disease. Maintaining regular sleep patterns could help prevent heart disease just as physical activity, a healthy diet, and other lifestyle measures do.

It’s unclear why irregular sleep patterns may have this effect. It may be due in part to disruptions to the body’s natural sleep-wake cycles, called circadian rhythms. Heart rate, blood pressure, and other cardiovascular functions follow circadian patterns. Studies have shown that night shift workers, with disrupted circadian rhythms, have a moderate increase in heart disease and stroke.

“We hope that our study will help raise awareness about the potential importance of a regular sleep pattern in improving heart health. It is a new frontier in sleep medicine,” Huang says.

Future studies will focus on confirming these results and understanding the underlying causes linking irregular sleep and cardiovascular disease risk.