Atherosclerosis: Irregular sleeping habits may increase risk

• A new study finds a link between irregular sleeping patterns and subclinical symptoms of atherosclerosis in older people.
• Atherosclerosis-related diseases are the leading cause of death in the United States.
• The study underscores the importance of establishing regularity in one’s sleep routine.

A recent study explores a connection between atherosclerosis, not maintaining a regular bedtime, and sleeping for inconsistent periods of time.

The study found that older people who varied sleep time by an average of two hours within a single week and those who changed their bedtimes by an hour and a half were significantly more likely to exhibit subclinical symptoms of atherosclerosis.

According to a press release, here’s what the researchers measured to investigate the presence of plaque in the arteries:

• calcified fatty plaque buildup in arteries — coronary artery calcium
• fatty plaque buildup in neck arteries — carotid plaque presence
• thickness of the inner two layers of the neck arteries — carotid intima-media thickness
• narrowed peripheral arteries — the ankle brachial index

They detected calcified plaque in arteries, the primary underlying cause of strokes and heart attacks. When they measured participants’ blood pressure at their arms and compared that figure to blood pressure at their ankles, the resulting high ankle brachial indexes indicated stiffness in their blood vessels. Both symptoms may be signs of developing atherosclerosis.

People who significantly varied their bedtimes by more than 90 minutes within a week had high levels of coronary artery calcium — compared with those who varied their bedtimes by 30 minutes or less.

Atherosclerosis is a condition in which cholesterol, fatty deposits, and cellular waste products in your blood form sticky plaques on the insides of your arteries. The plaques thus thicken artery walls and can cause them to harden. The condition inhibits blood flow, preventing sufficient oxygen from being delivered to your organs.

According to the United States National Institutes of Health (NIH), half of Americans aged 45-84 have atherosclerosis without knowing it, and the disease linked to atherosclerosis is the leading cause of death in the U.S.

The study appears in the Journal of the American Heart Association.

Large study on sleep and disease risks

The study involved 2032 participants in the separate community‐based MESA (Multi‐Ethnic Study of Atherosclerosis). MESA aimed to investigate the characteristics and risk factors of subclinical symptoms of atherosclerosis across a diverse population of older people.

To that end, just over half of the participants in MESA were women. Thirty-eight percent of the participants self-identified as White, 28% as Black or African American, 23% as Hispanic, and 11% as Chinese. They were also geographically diverse, recruited from St. Paul, MN; Baltimore City and Baltimore County, MD; Chicago, IL; Forsyth County, NC; Los Angeles County, CA; Northern Manhattan and the Bronx, NY.

The participants ranged from 45 to 84 years old, with an average age of 69, and all were free of diagnosed cardiovascular disease.

Each participant wore a wrist device for seven days that tracked their periods of being awake or asleep. They also completed sleep diaries.

Finally, each individual participated in one night of in-home sleep monitoring that measured their breathing, sleep stages, sleep duration, heart rate, and the time they went to bed.

In the current study, people whose sleep duration varied by an average of two hours per week were 1.33 times more likely to have high coronary artery calcium scores than those with more regular sleep patterns. They were also 1.75 times more likely to have abnormal ankle brachial indexes.

When assessing people whose bedtimes varied by an average of 90 minutes over the course of a week, researchers found a 1.39 times increase in the likelihood of calcified artery plaques.

“Our results add to growing evidence from recent studies that have connected irregular sleep patterns to cardiovascular risk,” said the study’s lead author, Dr. Kelsie M. Full of Vanderbilt University.

Other studies, Dr. Full noted, already connect poor sleep to cardiovascular conditions such as hypertension, type 2 diabetes, and heart disease.

The connection between sleep and atherosclerosis

“Our bodies have a natural 24-hour internal clock, known as the circadian rhythm, that regulates many physiological processes, including sleep-wake cycles. When we consistently go to bed and wake up at different times, it can disrupt our circadian rhythm and lead to what’s called ‘social jet lag,’” said Dr. José M. Ordovás of Tufts University, who was not involved in the study.

Interventional cardiologist Dr. Hoang Nguyen, not involved in the study, told Medical News Today:

“The authors suggested that disturbance in sleep regularity promotes cardiovascular disease by disturbing the natural circadian rhythm of the body, thereby affecting inflammation, glucose metabolism and sympathetic neurohormal response. All of these factors are known to cause cardiovascular disease.”

“During sleep, the sympathetic nervous system (SNS) activity is typically reduced, allowing the body to rest and recover,” Dr. Ordovás explained.

“However, sleep disorders such as sleep apnea can lead to increased SNS activity, which can cause hypertension and other CVD risk factors,” he added.

The press release noted that due to the limitation of sleep and atherosclerosis being measured simultaneously, the researchers were unable to assess “if greater sleep irregularity causes the development of atherosclerosis.”

Too little sleep, too much, and just right

Dr. Full noted that their study tracked people who often got less or more sleep than usual and found no difference in their atherosclerosis indicators.

The NIH recommends that older adults, like all other adults, get between seven and nine hours of sleep each day.

It is possible to get too much sleep, according to other research. Dr. Ordovás reported that both a short sleep duration of fewer than 7 hours per night and a long sleep duration of more than 9 hours per night have both been associated with an increased risk of CVD.

“What is interesting about this study is that the authors went beyond the quality of sleep, and investigated the regularity of sleep,” said Dr. Nguyen.

“I find this part interesting, as it opens up a myriad of questions on the underlying reasons for this, and has implications on possible interventions from a health care provider standpoint to improve cardiovascular health.”

“Addressing sleep issues,” said Dr. Ordovás, “and promoting healthy sleep habits may help to reduce the risk of CVD by reducing inflammation, oxidative stress, and other risk factors associated with sleep disturbances.”

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