SOPHIA ANTIPOLIS, France — Bedtimes are probably something many people only associate with children. However, a new study reveals that adults should be just as strict with their own sleep cycles as well. Researchers find that going to bed between 10 p.m. and 11 p.m. local time lowers the risk of developing heart disease compared to any other time of night.
While bedtimes after midnight resulted in the highest increase in heart-related declines in health, the team finds that even bedtimes earlier than 10 p.m. increased the risk of cardiovascular disease in adults.
“The body has a 24-hour internal clock, called circadian rhythm, that helps regulate physical and mental functioning,” says study author Dr. David Plans from the University of Exeter in a media 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.”
Study authors add that there has been plenty of research into the link between how long people sleep and the impact it has on their hearts. However, the relationship between bedtimes and heart disease has remained unclear.
Researchers studied over 88,000 participants from the UK Biobank, recruited between 2006 and 2010. These individuals ranged between 43 and 79 years-old, with nearly 60 percent being women. The team collected data on their sleep habits through wrist monitors for seven days and gathered information on each person’s health history and lifestyle habits through a questionnaire.
Over the next six years, 3.6 percent of the group (3,172 participants) developed cardiovascular disease — experiencing various heart-related events like stroke, heart failure, heart attacks, and chronic ischemic heart disease.
Remember the sweet spot
The results show that the highest rates of heart disease were among people going to sleep after midnight. Conversely, the lowest were among those falling asleep each night between 10 p.m. and 10:59 p.m.
Overall, people who fell asleep after midnight had a 25-percent higher chance of developing heart disease compared to those in the bedtime sweet spot. Those going to bed between 11 p.m. and midnight had a 12-percent greater risk of developing heart issues. Meanwhile, people with a bedtime earlier than 10 p.m. also had a 24-percent higher risk for heart disease than those going to bed after 10.
When researchers delved deeper into the results, they found that the link between bedtime and heart disease appears to be stronger in women than men. However, scientists discovered that men who go to bed before 10 p.m. continued to display a higher risk for cardiovascular disease.
“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. The riskiest time was after midnight, potentially because it may reduce the likelihood of seeing morning light, which resets the body clock,” Dr. Plans reports.
Why does a bedtime matter more for women’s health?
“It may be that there is a sex difference in how the endocrine system responds to a disruption in circadian rhythm. Alternatively, the older age of study participants could be a confounding factor since women’s cardiovascular risk increases post-menopause – meaning there may be no difference in the strength of the association between women and men,” Dr. Plans explains.
“While the findings do not show causality, sleep timing has emerged as a potential cardiac risk factor – independent of other risk factors and sleep characteristics. If our findings are confirmed in other studies, sleep timing and basic sleep hygiene could be a low-cost public health target for lowering risk of heart disease.”
The findings are published in the European Heart Journal – Digital Health.