The riskiest time to head to bed is after midnight, study finds

Your risk of developing cardiovascular disease depends on what time you hit the sack — and don't assume that getting there earlier is a good thing.

Chris Arnold 3 minute read November 11, 2021
Red alarm clock

Thirty-three per cent of Canadians don't get the proper amount of sleep. GETTY

The time you head to bed could be putting you at risk for heart disease, according to a study of more than 88,000 people by British health-tech company Huma. 

For six years, researchers tracked the sleep of the participants and found a 12 per cent greater risk of developing cardiovascular disease among those who fell asleep between 11 p.m. and midnight, compared to those who fell asleep between 10 p.m. and 11 p.m. That risk more than doubled to 25 per cent for participants who fell asleep at midnight or later. 

“Our study indicates that the optimum time to go to sleep is at a specific point in the body’s 24-hour cycle and deviations may be detrimental to health,” said Dr. David Plans of the University of Exeter and the author of the study. “The riskiest time was after midnight, potentially because it may reduce the likelihood of seeing morning light, which resets the body clock.”

Falling asleep too early could be an issue as well, since research suggests that dozing off before 10 p.m. is associated with a 24 per cent increased risk for developing cardiovascular disease. 

Because of the increased risks on both sides, the sweet spot for sleep in adults is between 10 and 11 p.m.

The findings were first published in the European Heart Journal-Digital Health. 

In order to find how varying bedtimes may influence heart health, researchers used  UK Biobank, a biomedical database from just outside of Manchester, England. 

UK Biobank keeps in-depth information on genetics and health from more than half a million volunteers ages 37 to 73, collected between 2006 and 2010. Of those 500,000 volunteers, roughly 88,000 were focused on during the study. 

Participants wore devices to track their movements on their wrists for one week so researchers could determine when they hit the hay each day. 

“The body has a 24-hour internal clock, called circadian rhythm, that helps regulate physical and mental functioning,” Plans said in a release. “While we cannot conclude causation from our study, the results suggest that early or late bedtimes may be more likely to disrupt the body clock, with adverse consequences for cardiovascular health.”

After following up with participants, and having them fill out a questionnaire to determine if they smoke, were overweight, had health conditions such as diabetes or high blood pressure, and if they consider themselves to be a morning person or night person, researchers found that the optimum time to go to bed is determined by the body’s internal clock.  

In Canada, 90 per cent of people have at least one risk factor which could contribute to heart disease, according to the Heart and Stroke Foundation. Risk factors include an unhealthy diet, unhealthy weight, stress, alcohol or drug abuse, smoking, and lack of exercise. 

Between 25 and 33 per cent of adults in Canada are not getting enough sleep, reports the Public Health Agency of Canada. That could be nearly 10 million people. 

Sleep deprivation’s effects on the body are not just limited to cardiovascular issues. People who do not get a sufficient amount of rest are more likely to crave sweet, salty, ann starchy food, and are at a 50 per cent higher risk for obesity, according to Johns Hopkins Medicine. Those that don’t get enough sleep are also at a 33 per cent higher risk of dementia, three times more likely to catch a cold, and 36 per cent more at risk for colorectal cancer.