A new large-scale study has found that irregular sleep-wake cycles can significantly increase the risk of serious cardiovascular events, including heart attack and stroke — even for individuals who meet recommended sleep duration guidelines.
Published in the Journal of Epidemiology & Community Health, the research tracked over 72,000 adults in the UK Biobank cohort.
As reported by Healthline, participants wore activity monitors to objectively measure sleep duration and consistency over seven days.
Sleep Regularity May Matter More Than Duration
Researchers developed a Sleep Regularity Index (SRI) to score participants' consistency in going to bed and waking up at the same time daily. They found:
Those with irregular sleep patterns (SRI below 71.6) had a 26% higher risk of major cardiovascular events.
Moderately irregular sleepers saw an 8% increased risk.
A more regular sleep pattern, with an SRI over 77.1, was linked to up to 18% reduced risk.
Notably, even when individuals in the study got the recommended amount of sleep for their age, those with inconsistent schedules still faced elevated risks.
“Meeting sleep duration recommendations alone does not eliminate the increased MACE [major adverse cardiovascular event] risk for those with irregular sleep schedules,” said lead author Jean-Philippe Chaput, PhD, of the Children’s Hospital of Eastern Ontario.
Circadian Disruption and Health Consequences
Experts believe irregular sleep disrupts the body’s circadian rhythm — the internal 24-hour clock that regulates vital physiological functions.
This disruption may lead to widespread impacts across systems, including metabolism, hormone production, and cardiovascular function.
Andrew J. K. Phillips, MD, a sleep scientist at Flinders University, noted that this study aligns with previous findings linking irregular sleep with higher mortality, mental health issues, and poor academic performance.
“What we are seeing is that sleep regularity touches on a wide range of health outcomes,” he told Healthline.
How to Improve Sleep Regularity
Experts recommend several strategies to build a consistent sleep schedule:
Wake up at the same time every day, including weekends.
Set a bedtime alarm and establish a consistent wind-down routine.
Limit screen time and caffeine before bed.
Create a sleep-friendly environment: dark, quiet, and cool.
Even those with variable work shifts are encouraged to find overlapping sleep windows to maintain some level of consistency.
In short, while getting enough sleep is critical, how consistently you sleep may be just as important for your heart health.
