People who stay up late may have worse heart health, depending on their body clock

According to new research, early risers may not only catch the proverbial worm, but also have healthier hearts.

People who naturally stay up late, describing themselves as night owls, are more likely 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 results 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. The participants, whose average age was 57, completed a questionnaire about their chronotypes, a way of classifying people according to the time of day they are naturally most energetic and active.

“Research increasingly shows that when our internal body clock is out of sync with daily schedules, it can affect cardiometabolic health,” said lead author Sina Kianersi, a researcher in the division of sleep and circadian disorders at Brigham and Women’s Hospital and Harvard Medical School.

About 24% of those surveyed said they considered themselves a “morning person,” while 8% said they were an “evening person.” The majority of 67 percent, which researchers dubbed the “middle” group, said they fell somewhere in between.

Kianersi’s team used the American Heart Association’s Life’s Essential 8 measures to assign each participant a heart health score from zero to 100, with a higher score indicating a healthier heart. Behaviors that affect biological aging include sleep quality, weight, nutrition, blood sugar, blood pressure, cholesterol, smoking, 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 to the middle group, night owls had a 79% higher prevalence of poor heart health, defined as a score below 50. Meanwhile, early risers had a 5% lower prevalence.

Over a median follow-up period of 14 years, night owls had a 16% higher risk of heart attack or stroke than the middle group. Early risers were not 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 the chronotype alone has something that increases the risk of cardiovascular disease in night owls,” he said, “but it’s because of that profile, or that poor cardiovascular health, that it causes that increase. [heart disease] risk.”

Sleep is vital for heart health

Heart disease has been the leading cause of death in the United States for more than a century, killing one person every 34 seconds, according to the American Heart Association (AHA).

Although a number of studies have linked poor sleep hygiene to an increased risk of death, the AHA didn’t include sleep in its pillars of cardiovascular health until 2022. In an article published that year, the organization noted that too little sleep — or too much — was associated with coronary heart disease.

The AHA recommends adults get an average of seven to nine hours of quality sleep each night to maintain optimal heart health.

The purpose of sleep is to prepare the brain and body for wakefulness, said Dr. Maha Alattar, medical director of the VCU Health Center for Sleep Medicine in Richmond, Virginia. But this 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 was not part of the study. “Every biological cell and tissue in the body depends on sleep to sustain itself while awake.”

Over time, insufficient, irregular, or poor quality sleep can lead to a myriad of medical problems. For example, a person with a sleep deficit may have higher levels of stress hormones, such as cortisol, which can contribute to the formation of heart disease, Alattar said.

Previous research has estimated that 8% to 11% of middle-aged and older adults have the evening chronotype.

In the study, night owls had a higher likelihood of performing poorly in six of eight categories, including sleep. Additionally, researchers observed the strongest associations between evening chronotype and low scores in two categories: sleep and nicotine exposure.

Dr. Shady Abohashem is responsible for cardiac PET/CT imaging trials at Massachusetts General Hospital. Although he wasn’t involved in this study, he studies how lack of sleep affects heart health and says night owls shouldn’t panic.

Statistically, the link between evening chronotype and increased likelihood of poor heart health was “modest, not dramatic,” he said. Additionally, the study used relative risk, comparing the risk of night owls to that of the intermediate group. Absolute risk, on the other hand, reflects the risk of an entire population.

“Being a night owl is not going to condemn your heart,” Abohashem said.

How can night owls improve heart health?

Dr. Phyllis Zee, director of the Center for Circadian and Sleep Medicine at Northwestern University’s Feinberg School of Medicine, calls herself a “flexible owl.” In other words, she can go to bed late or wake up early depending on her needs.

The good news, Zee said, is that unhealthy behaviors common among night owls that contribute to poor heart health are changeable. The downside is that some of them are more difficult to modify than others.

Nicotine, for example, isn’t just bad for the heart, said Zee, who was not involved in the study. It is also a stimulant that can alter a person’s circadian rhythm.

“Get seven to eight hours of sleep, stop smoking, increase your level of physical activity during the day,” Zee said. “All of these things will help you maintain better quality sleep.”

She added: “Even for night owls, stop eating at 8 p.m., at least three hours before you go to sleep. »

Proper light exposure is also essential for sleep health, Zee said. Everyone, regardless of their chronotype, should be exposed to natural or blue light in the morning and subdued or amber light in the evening. Zee recommends turning off the lights two to three hours before bed to allow for a natural increase in the sleep hormone melatonin.

Aattar said exposure to sunlight in the morning helps trigger sleep about 16 hours later, which is why it can be difficult to get to bed on time after sleeping. She also advised quitting caffeine 12 hours before bed.

The observational study has several limitations. The study was limited to primarily white, middle-aged and older adults who self-reported their chronotypes. Additionally, heart health measurements represent a unique moment.

Kianersi is currently studying the genetics behind chronotypes and said more research is needed to understand why the link between chronotype and heart health was stronger in women.

Aattar said that evening sleep chronotype, or delayed sleep-wake syndrome, is not curable, but it is manageable. Such research can provide insight and help reduce stigma against night owls, who operate outside of societal norms.

“Society thinks about [night owls] like lazy,” said Alattar. “They are not lazy; it’s just that their rhythm is off.