In a new study, researchers found that older adults with irregular sleep patterns—meaning they have no regular bedtime and wakeup schedule, or they get different amounts of sleep each night—are nearly twice as likely to develop cardiovascular disease as those with more regular sleep patterns.
They suggest that an irregular sleep pattern may be a novel and independent risk factor for heart disease and that maintaining regular sleep patterns could help prevent heart disease just as physical activity, a healthy diet, and other lifestyle measures do, the researchers said.
It is the first study believed to link sleep irregularity to the development of heart disease.
The research was conducted by a team at Brigham and Women’s Hospital in Boston.
Previous studies have linked insufficient amounts of sleep to a higher risk of obesity, diabetes, and heart disease, which is among the reasons doctors emphasize the importance of getting seven to eight hours of sleep per night.
Although researchers have suspected that high day-to-day variability in sleep duration and timing might also have negative effects on heart health, its effect remained unclear.
In the study, the researchers tested 1,992 men and women, 45-84 years old, who did not have heart disease at the start of the study.
The participants lived in communities across the United States. They were followed for about five years (2010-2016) after having a sleep examination.
To measure sleep irregularity, the participants wore actigraph devices on their wrists to closely track sleep and wake activity for seven consecutive days, including weekends.
The actigraphs resemble smart watches but are designed to specifically measure whether a person is active or at rest, which correlates to wakefulness and sleep.
They also underwent one-night at-home polysomnography—a comprehensive sleep test—at the beginning of the study and took a questionnaire-based sleep assessment.
During the five-year follow-up period, 111 participants developed heart disease events, including heart attack and stroke, or died from related causes.
The researchers found that participants with the most irregular sleep duration or timing had more than double the risk of developing a heart disease event compared to those with the most regular sleep patterns.
They suspect that multiple factors, including harmful disturbances in the body’s circadian rhythm—the 24-hour internal body clock which controls the sleep-wake cycle—may be in play.
Recent studies by the same researchers linked irregular sleep patterns to harmful metabolic changes associated with obesity, diabetes, and high cholesterol, and they suspect similar processes might also influence heart disease risk.
In future studies, the researchers say they will look for blood biomarkers that may help explain the apparent link. Larger studies with longer follow-up will also be important to confirm these findings.
The lead author of the study is Tianyi Huang, Sc.D, an epidemiologist with the Channing Division of Network Medicine at Brigham and Women’s Hospital in Boston.
The study is published in the Journal of the American College of Cardiology.
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