The early bird may not only catch the proverbial worm but also have a healthier heart, new research suggests.
People who naturally stay up late, self-described night owls, are likelier to have poor heart health than people with more traditional sleep-wake schedules, according to a study published Wednesday in the Journal of the American Heart Association.
The findings were particularly strong among women.
Researchers assessed the health and behaviors of nearly 323,000 adults in the UK Biobank, a comprehensive research database that recruited people from 2006 to 2010. Participants, whose average age was 57, completed a questionnaire about their chronotypes, a way of categorizing people by the time of day when they're naturally most energetic and active.
“Research is increasingly showing that when our internal body clock is out of sync with daily schedules, it can affect cardiometabolic health,” said lead author Sina Kianersi, a research fellow in the division of sleep and circadian disorders at Brigham and Women’s Hospital and Harvard Medical School.
About 24% of respondents said they considered themselves to be a “morning person,” while 8% said they were an “evening person.” The 67% majority, which researchers dubbed the “intermediate” group, said they fell somewhere in between.
Kianersi’s team used the American Heart Association’s Life’s Essential 8 metrics to award each participant a heart health score from zero to 100, with a higher score indicating a healthier heart. The behaviors that affect biological aging are sleep quality, weight, nutrition, blood sugar, blood pressure, cholesterol, smoking status and physical activity.
The average heart health score for all participants was 67.4. Women had better heart health than men, with scores of 70 and 65, respectively.
Compared with the intermediate group, night owls had a 79% higher prevalence of poor heart health, defined by a score below 50. Meanwhile, early birds had a 5% lower prevalence.
Across a median follow-up period of 14 years, night owls had a 16% higher risk of having heart attacks or strokes compared with the intermediate group. Early birds weren’t at increased risk.
Kianersi said his research is unique in that it explores chronotype in relation to multiple facets of a person’s heart health.
“It’s not just that chronotype alone has something that raises night owls’ risk for cardiovascular disease,” he said, “but it is through that profile, or that poor cardiovascular health, that it causes that increased [heart disease] risk.”
Sleep is vital for heart health
Heart disease has been the leading cause of death in the U.S. for more than a century, killing one person every 34 seconds, according to the American Heart Association (AHA).
Though a number of studies have tied poor sleep hygiene to an increased risk of death, the AHA didn’t incorporate sleep into its pillars of cardiovascular health until 2022. In a paper that year, the organization noted that too little sleep — or too much — is associated with coronary heart disease.
The AHA recommends adults get an average of seven to nine hours of quality sleep every night to maintain optimal heart health.
The purpose of sleep is to prepare the brain and the body for wakefulness, said Dr. Maha Alattar, medical director of the VCU Health Center for Sleep Medicine in Richmond, Virginia. But that deep rest goes beyond keeping a person alert the next day.
“When we go to sleep, we go into physiological processes that actually help us regenerate some of our tissues, brain neurotransmitters — we kind of reset ourselves,” said Alattar, who wasn’t part of the study. “Every single biological cell and tissue in the body depends on sleep to be able to maintain itself during wakefulness.”
Over time, insufficient, inconsistent or low-quality sleep may lead to myriad medical problems. For example, a person operating on a sleep deficit may have higher levels of stress hormones, such as cortisol, which can contribute to the formation of heart disease, Alattar said.
