February 24, 2023 – Irregular sleep, akin to having an irregular bedtime each night or falling asleep at different times, may increase the danger of developing atherosclerosis, or hardening of the arteries, in adults over 45, a brand new study suggests.
In particular, a deviation in sleep duration of greater than two hours per night in the identical week has been related to the event of arteriosclerosis.
“Poor sleep is linked to several cardiovascular diseases, including heart disease, high blood pressure and type 2 diabetes,” says study creator Kelsie Full, PhD, assistant professor of drugs at Vanderbilt University Medical Center.
“Overall, we found that participants who slept different hours throughout the week (that is, sleeping one night less and one night more) were more likely to develop atherosclerosis than participants who slept about the same amount of time each night,” she says.
The results were published within theJournal of the American Heart Association.
Atherosclerosis is the buildup of fatty deposits, also called plaque, on the partitions of arteries. This can result in narrowed arteries and reduced blood flow and oxygen to the body. The plaque may rupture and form a blood clot that blocks the artery, which may result in a heart attack or stroke.
To investigate the sleep-related associations, Full and colleagues examined observational data from greater than 2,000 participants within the Multi-Ethnic Study of Atherosclerosis (MESA) Sleep Ancillary Study. The study included adults aged 45 to 84 years in six U.S. Communities: St. Paul, MN; Baltimore City and Baltimore County, MD; Chicago; Forsyth County, NC; Los Angeles County, CA; and Northern Manhattan and the Bronx, NY.
For seven days in a row between 2010 and 2013, study participants wore a wrist-worn device that detected after they were awake and asleep and kept a seven-day sleep diary. They also participated in a one-day sleep study to measure sleep disturbances affecting respiratory, sleep stages and heart rate.
The research team checked out sleep duration, which is the whole time spent sleeping in bed at night, and sleep timing, which was defined because the time the person fell asleep each night. They measured the presence of plaque within the arteries by searching for coronary calcification (or calcified plaque deposits in arteries), carotid plaque (or fatty plaque deposits in carotid arteries), carotid intima-media thickness (or the thickness of the 2 inner layers of the carotid arteries), and ankle-brachial index (or narrow peripheral arteries), all of which indicate the presence of atherosclerosis.
Overall, the typical age of respondents was 69 years old and 54% were women. About 38% identified as white, 28% as black or African American, 23% as Hispanic, and 11% as Chinese.
Over the 7-day period, sleep duration modified by greater than 90 minutes for about 38% of participants and by greater than 120 minutes for 18%. Those who had irregular sleep were more more likely to be non-white, to be a current smoker, to have a lower average annual income, to work shifts or not, and to have a better average body mass index.
Participants whose sleep duration was more irregular and varied by greater than 2 hours throughout the week were 1.4 times more more likely to have high levels of coronary calcium than those whose sleep duration was more regular and varied by 60 minutes or less. They were also more more likely to have carotid plaque formation and an abnormal ankle-brachial index.
Individuals with irregular sleep times (fluctuating by greater than 90 minutes throughout the week) were 1.43 times more more likely to have high coronary calcium burden than individuals with more regular sleep times (fluctuating by half-hour or less).
“The biggest surprise for me was that 30% of study participants had a total sleep time of more than 90 minutes over the course of the week,” says Full. “This is consistent with previous studies that suggest that a large portion of the general population has irregular sleep patterns, not just shift workers.”
Further studies are needed to know the mechanisms, write the study authors. Nighttime fluctuations in sleep duration and sleep time can result in desynchronization of the sleep-wake rhythm and disruption of the circadian rhythm.
“Sleep is a naturally recurring phenomenon, and maintaining regularity provides stability and predictability to the body,” says Michael Grandner, M.D., associate professor of psychiatry and director of the Sleep and Health Research Program on the University of Arizona College of Medicine.
“When people have very irregular sleep patterns, it can be harder for the body to make the most of sleep because it's such a moving target.”
Grandner, who was not involved on this study, has researched sleep irregularities and their connection to heart problems, diabetes, obesity and plenty of other negative outcomes.
“Healthy sleep means more than just getting enough sleep,” he says. “It also means getting quality sleep at the right times on a regular basis.”