Sticking to a consistent sleeping routine may help keep your arteries clear as you age, new research suggests.

Conversely, older adults who slept for a varying number of hours each night and tended to fall asleep at different times were more likely to develop hardening of the arteries, which can lead to heart attack or stroke, the researchers reported.

“Sleep is super important to our overall health and well-being, and anything we can do to improve sleep will improve our [heart health] and overall well-being and happiness,” said study author Kelsie Full. She is an assistant professor of medicine in the division of epidemiology at Vanderbilt University Medical Center in Nashville, Tenn.

The study wasn’t designed to show how sleep irregularity causes heart disease, but researchers have some theories.

“One potential mechanism is that sleep irregularity may lead to a disruption of our circadian function, which can lead to inflammation, a known risk for heart disease,” Full said. (Circadian rhythm is the 24-hour internal clock that controls the release of the hormone melatonin to encourage sleep.)

What’s more, irregular sleep patterns may also travel with unhealthy behaviors such as late-night eating, poor diet or lack of exercise, she noted.

Her advice? “Set a regular bedtime, and just pay attention to how much you are sleeping each night, and strive for sleep that is as regular and routine as possible,” she said.

If you really struggle with sleep, bring it up with your doctor. “You may have an underlying sleep disorder that needs further treatment,” Full said.

For the study, researchers monitored sleep in more than 2,000 adults (average age, 69) for one week. People wore watch-like devices that detected when they were asleep and awake. They also completed a sleep diary for seven consecutive days and did an in-home sleep study to check for underlying sleep disorders. No one in the study had been diagnosed with heart disease.

Sleep duration was defined as the total amount of time spent in bed fully asleep, while sleep timing was described as the time a person falls asleep each night.

The results were telling.

When sleep duration varied by more than two hours within a week, folks were 40% more likely to have high coronary artery calcium scores compared to those with more consistent sleep patterns, the study showed. This score reflects the amount of calcified plaque that lines the arteries.

When plaque builds up in the artery walls, it sets the stage for a heart attack and stroke.

People whose sleep duration varied by more than two hours within a week were also 12% more likely to have plaque in their carotid artery and nearly twice as likely to have abnormal results on an ankle-brachial index test that measures stiffness in the blood vessels. Blood flow is reduced when blood vessels become stiff and narrow.

Meanwhile, those with the greatest irregularity in sleep timing varied the time they fell asleep by more than 90 minutes within one week. They were 43% more likely to have high coronary artery calcium scores than those whose regular sleeping time varied by 30 minutes or less within a week.

The findings were published online Feb. 15 in the Journal of the American Heart Association.

Sleep regularity may be a modifiable heart disease risk factor, said sleep expert Dr. Raj Dasgupta, an associate professor of clinical medicine at the Keck School of Medicine at the University of Southern California in Los Angeles.

“If you have any risk factors for [heart disease] such as high blood pressure, diabetes, high cholesterol, family history of heart disease, or are overweight, having a regular sleep schedule should be a priority along with addressing other modifiable risk factors to reduce your chance of developing atherosclerosis, which can lead to a heart attack or stroke,” said Dasgupta.

Having an irregular sleep pattern might contribute to heart disease because your cardiovascular system relies on many of the functions of healthy sleep to maintain optimal functioning, said Michael Grandner. He is director of the Sleep Health Research Program and the Behavioral Sleep Medicine Clinic at the University of Arizona in Tucson. He is also an American Heart Association volunteer spokesman.

For that reason, an irregular sleep schedule might impact things like blood pressure across the day, metabolism and energy levels. “The irregularity adds uncertainty and noise into the system, which might reduce the efficiency of those processes,” said Grandner.

If your sleep is very irregular, ask yourself why, Grandner suggested.

“If it is because you often are not able to sleep at the right time or not able to get enough sleep, consider the impacts of those on your health,” he said. “Consider addressing any underlying sleep disorders you might have or stresses that may get in the way of healthy, restful sleep that your body can rely on.”

More information

The American Heart Association has more on the importance of good quality sleep.

SOURCES: Kelsie Full, PhD, MPH, assistant professor, medicine division of epidemiology, Vanderbilt University Medical Center, Nashville, Tenn.; Raj Dasgupta, MD, associate professor, clinical medicine, Keck School of Medicine, University of Southern California, Los Angeles; Michael Grandner, PhD, director, Sleep Health Research Program, director, Behavioral Sleep Medicine Clinic, associate professor, department of psychiatry, University of Arizona, and volunteer expert, American Heart Association; Journal of the American Heart Association, Feb. 15, 2023