Data from sleep tracking devices worn by 10,000 Americans for six months has revealed that irregular sleep patterns, often caused by weekend lie-ins, are linked to a 20%-23% higher risk of heart attack, stroke and heart failure.
Scientists analysed more than one million nights of sleep data, examining both duration and quality. Changes in sleep timing from night to night over about a six-month period were associated with the increased cardiovascular risk.
Every Half Hour of Variation Raises Risk
Every half hour increase in how much a person's sleep length varied from night to night was associated with a 29% higher risk of having a disease of the heart muscle, which leaves the heart unable to pump enough blood through the body, as well as a 20% higher risk of heart failure.
Lead researcher Dr Nguyen Minh Tuan Viet, of Harvard Medical School in the US, said: "Sleep irregularity is often due to weekends - we get to sleep a little bit later on a Friday night; or people have shift work. This may not be good for your heart health."
"Sometimes the quality of sleep is something we cannot control but the regularity, consistent bedtimes throughout the week and waking up at the same time every morning, is something some people can control," he added.
Study Tracked Sleep Cycles
The study, being presented at the American Heart Association's Scientific Sessions 2026 in Chicago, tracked sleep for six months before following participants for four years to see if they suffered heart issues. It also looked at how much of participants' night was spent in light, deep and rapid eye movement (REM) sleep.
REM sleep is periods of rapid brain activity when people have dreams and it makes up around a quarter of our night's sleep. The study measured participants' number of "sleep cycles" each night, which is the interval from the end of one REM period to the end of the next, including the light and deep sleep stages in between.
Catch-Up Sleep Could Help
Having a greater number of complete "sleep cycles" each night led to a 28% lower risk of atrial arrhythmia, a common type of irregular heartbeat. An unusually long sleep cycle was linked to a 55% higher risk of heart attack or stroke.
Dr Minh Tuan Viet, who also works as a neuroscientist at Boston Children's Hospital, said: "While we often focus on getting a full eight hours of sleep every night, having a regular sleep schedule - consistent bedtimes, wake times, and sleep duration from night to night - is a practical, actionable step anyone can take that may help protect their heart and blood vessels."
Previous research has shown going to bed late, alcohol near bedtime and certain medications can disrupt the restorative periods of REM sleep.
The average British adult gets between 6 and 6.4 hours of sleep per night, below the recommended 7 to 9 hours. Scientists behind a seven-year study of 41,000 adults presented at the European Society of Cardiology's annual congress in Munich said people should not feel guilty about sleeping in at the weekend, as it could be the body's way of recovering. Their analysis identified the perfect amount of catch-up sleep, with a one hour and 27 minute lie-in resulting in the most benefit, and someone getting this amount of extra sleep being 9% less likely to have high blood pressure.
