New research suggests that irregular sleep patterns—such as sleeping and waking up at different times—may increase the risk of heart attack and stroke, even for individuals who get the recommended amount of sleep.
While previous studies have focused primarily on the impact of sleep duration, there has been less research on how changes in the sleep cycle affect health, according to the scientists behind the new study.
To explore this, the researchers tracked activity data from 72,269 participants aged 40 to 79 over a period of seven days. These participants had no prior history of major cardiovascular events.
The study calculated each participant’s Sleep Regularity Index (SRI), with higher scores indicating more consistent sleep patterns. Over the next eight years, the researchers monitored incidents of cardiovascular death, heart attacks, heart failure, and stroke. The findings revealed that those with irregular sleep patterns were 26% more likely to experience one of these events compared to those with regular sleep cycles. Irregular sleep refers to variations in the times at which a person goes to bed and wakes up.
The 26% increase in risk took into account factors such as age, physical activity, alcohol consumption, and smoking, which could have influenced the results. However, as an observational study, the research cannot definitively establish cause and effect, meaning it cannot conclusively prove that irregular sleep patterns directly cause the increased risk.
The study also found that individuals with a higher SRI (more regular sleep) were more likely to get the recommended seven to nine hours of sleep per night for those aged 18-64, and seven to eight hours for those over 65. Sixty-one percent of regular sleepers met these guidelines, compared to only 48% of irregular sleepers.
Even among those with irregular sleep who met the recommended sleep duration, the risk of cardiovascular events remained higher.
The researchers concluded that “sleep regularity may be more relevant than sufficient sleep duration” when it comes to heart health.
Jean Pierre Chaput, the lead study author and a professor of pediatrics at the University of Ottawa, explained that growing research suggests that sleep irregularity might be a stronger predictor of mortality risk than insufficient sleep.
To mitigate the risk of cardiovascular events, Chaput emphasized the importance of managing high blood pressure, a leading risk factor. He advised readers to prioritize seven to nine hours of consistent, restorative sleep each night, as poor sleep can contribute to high blood pressure.
“While bedtimes and wake-up times don’t have to be exactly the same every day, it’s best to keep them within 30-60 minutes of your usual schedule to support your body’s natural circadian rhythm,” Chaput said. “Small variations are fine, but consistent sleep patterns improve sleep quality, enhance mood and cognitive function, and reduce the risk of conditions like heart disease and diabetes.”
Chaput also cautioned against relying on weekend sleep catch-ups, noting that while extra sleep may temporarily improve mood and cognitive function, it cannot reverse the negative effects of chronic sleep deprivation during the week. Irregular sleep patterns can disrupt the body’s natural rhythm, leading to long-term health issues like obesity, diabetes, and heart disease.
Naveed Sattar, a professor of cardiometabolic medicine at the University of Glasgow, who was not involved in the study, expressed caution about attributing causality. He noted that other factors, such as late-night alcohol consumption, might contribute to health issues, rather than sleep irregularity alone.
The study was published in the Journal of Epidemiology & Community Health.
