A major new study has found that failing to maintain a regular sleep pattern—going to bed and waking up at different times each day—increases the risk of stroke, heart attack, and heart failure by 26%, even for those who get a full night's sleep. The research, published in the Journal of Epidemiology and Community Health, is the most comprehensive of its kind to examine the link between sleep regularity and cardiovascular health.
The study involved 72,269 participants aged 40 to 79 from the UK Biobank. Each wore an activity tracker for seven days to record sleep patterns, which were then scored using a sleep regularity index (SRI) from 0 (very irregular) to 100 (perfectly regular). Participants were grouped into irregular (SRI below 71.6), moderately irregular (SRI 71.6–87.3), or regular sleepers (SRI above 87.3) and followed for eight years.
Even after adjusting for other factors, irregular sleepers were 26% more likely to suffer a major adverse cardiovascular event, while moderately irregular sleepers had an 8% higher risk compared to regular sleepers. The risk increased with greater irregularity. Notably, getting the recommended seven to nine hours of sleep did not offset the harm for irregular sleepers, though it did reduce risk for the moderately irregular group.
Lead author Jean-Philippe Chaput of the University of Ottawa advised aiming to wake up and go to sleep within 30 minutes of the same time each day, including weekends. “Waking up at different times each morning really messes with your internal clock,” he said, adding that consistency in wake-up time is more important than bedtime. He cautioned that while occasional irregularity is not dangerous, chronic irregularity—five or six days a week—poses a significant health risk.
The researchers acknowledged the study is observational and cannot prove cause and effect, but concluded that irregular sleep is strongly associated with a higher risk of cardiovascular events in adults, regardless of sleep duration.
