Getting enough sleep doesn't ensure heart health without having a regular sleep schedule. (Maridav/Shutterstock)
In a nutshell
- People with irregular sleep schedules had a 26% higher risk of major cardiovascular events—including heart attacks, strokes, and heart failure—even if they got the recommended amount of sleep.
- Sleep regularity may matter just as much as sleep duration: going to bed and waking up at consistent times was linked to significantly better heart health outcomes.
- The study found a clear dose-response relationship, with higher sleep regularity scores tied to lower cardiovascular risk; an SRI score of 77.1 or above was associated with a 15–18% risk reduction.
OTTAWA, Canada — Even if you’re getting enough sleep overall, inconsistent bedtimes and wake-up times might be putting your heart at serious risk. An international study shows that people with irregular sleep schedules face a significantly higher risk of heart attacks, strokes, and heart failure, regardless of whether they clock the recommended seven to nine hours of sleep each night.
The research, published in the Journal of Epidemiology and Community Health, followed more than 72,000 adults for nearly eight years and discovered that those with the most chaotic sleep patterns had a 26% higher risk of major cardiovascular events compared to people who maintained regular sleep schedules.
They also found that getting the recommended amount of sleep didn’t protect irregular sleepers from heart problems. For millions of Americans whose work schedules, family responsibilities, or lifestyle habits lead to erratic sleep patterns, this could be a wake-up call about a previously underappreciated heart risk factor.
Researchers from institutions including the Children’s Hospital of Eastern Ontario Research Institute and the University of Sydney used data from the UK Biobank, analyzing information from 72,269 adults aged 40-79 who wore wrist accelerometers for a week to precisely measure their sleep patterns. The team calculated each participant’s “Sleep Regularity Index” (SRI), a measure that captures day-to-day consistency in bedtime, wake-up time, sleep duration, and awakenings during sleep.
The SRI is scored from 0 (completely random sleep-wake times) to 100 (perfectly consistent sleep patterns). Participants were divided into three groups: those with regular sleep (SRI above 87.3), moderately irregular sleep (SRI between 71.6 and 87.3), and irregular sleep (SRI below 71.6).
After following participants for an average of 7.8 years, researchers documented 4,887 major adverse cardiovascular events (MACE)—a measure that includes heart attacks, strokes, and heart failure. Even after accounting for numerous factors like age, physical activity, diet, smoking, alcohol consumption, and existing health conditions, the findings remained accurate.
Heart Risks and Irregular Sleep
People with irregular sleep patterns had a 26% higher risk of experiencing a MACE event compared to regular sleepers. Even those with moderately irregular sleep patterns showed an 8% increased risk. This connection was particularly strong for heart failure, with irregular sleepers facing a 45% higher risk compared to consistent sleepers.
Researchers also looked at the combination of sleep regularity and sleep duration. Conventional wisdom might suggest that as long as you’re getting enough sleep, some irregularity wouldn’t matter. This data shows that might not be the case.
People with irregular sleep patterns faced an elevated cardiovascular risk even if they slept the recommended 7-9 hours (for adults under 65) or 7-8 hours (for those 65 and older). While sufficient sleep partially offset the risk for moderately irregular sleepers, it didn’t help those with the most erratic patterns.
The relationship between sleep irregularity and cardiovascular problems appears to follow a dose-response pattern. This means that the more irregular your sleep, the higher your risk. However, the researchers identified a threshold: an SRI score of at least 77.1 was associated with a 15% reduction in cardiovascular risk, while the median score of 80.8 correlated with an 18% risk reduction.
Why Inconsistent Sleep Hurts Your Heart
What explains this connection? When sleep patterns vary widely, it causes circadian misalignment, essentially throwing off the body’s internal clock. This disruption can cascade into various physiological changes that stress the cardiovascular system.
These disruptions can lead to problems with glucose and lipid metabolism, insulin resistance, and increased activation of the sympathetic nervous system, all factors that contribute to cardiovascular disease.
Irregular sleep patterns were more common among certain groups in the study. People who reported mental health issues, those taking medications for cholesterol, diabetes, or blood pressure, and individuals working night shifts were all more likely to have irregular sleep patterns. Current smokers also tended to have less regular sleep compared to non-smokers.
Recommendations about sleep duration have become common in recent years, with the American Heart Association even adding sleep duration to its “Life’s Essential 8” metrics for cardiovascular health in 2022, but sleep regularity has received far less attention.
For those looking to improve sleep regularity, experts suggest maintaining a consistent sleep schedule (even on weekends), establishing a relaxing bedtime routine, and creating a sleep-conducive environment. How consistently we sleep may be just as important as how long we sleep—and for your heart’s sake, sticking to regular bedtimes might matter more than we previously thought.
Paper Summary
Methodology
The researchers conducted a prospective cohort study using data from the UK Biobank, focusing on 72,269 adults aged 40-79 who wore wrist accelerometers for 7 days. They calculated a Sleep Regularity Index (SRI) for each participant using validated algorithms that measure consistency in sleep-wake patterns. Participants were categorized as having irregular sleep (SRI <71.6), moderately irregular sleep (SRI 71.6-87.3), or regular sleep (SRI >87.3). They also classified participants based on whether they met age-specific sleep duration recommendations (7-9 hours for ages 18-64, 7-8 hours for those 65+). Information on major adverse cardiovascular events (MACE) was obtained from hospitalization and death records, with participants followed for an average of 7.8 years. The researchers excluded participants with previous history of MACE or who had an event in the first year of follow-up to reduce reverse causation. They used Cox proportional hazards regression models adjusted for numerous confounders including age, sex, ethnicity, socioeconomic status, physical activity, screen time, diet, coffee intake, alcohol consumption, smoking, mental health, medication use, family history, shift work, and self-reported sleep problems.
Results
The study found that irregular sleepers had a 26% higher risk of MACE (HR 1.26, 95% CI 1.16-1.37) and moderately irregular sleepers had an 8% higher risk (HR 1.08, 95% CI 1.01-1.70) compared to regular sleepers. When examining MACE subtypes, irregular sleep was associated with a 45% higher risk of heart failure, 23% higher risk of myocardial infarction, and 22% higher risk of stroke. The relationship between SRI and MACE risk was near-linear, with steeper risk reduction at higher SRI scores. An SRI score of at least 77.1 was associated with a 15% reduction in MACE risk. Joint analyses of sleep regularity and duration showed that meeting sleep duration recommendations offset MACE risk for moderately irregular sleepers (HR 1.07, 95% CI 0.96-1.18), but not for irregular sleepers (HR 1.19, 95% CI 1.06-1.35), indicating that adequate sleep duration cannot compensate for highly irregular sleep patterns.
Limitations
The study has several limitations. The UK Biobank had a low response rate (5.5%), which may affect representativeness of the broader population. Covariate assessments were conducted at a single time point rather than treated as time-varying factors, with a median lag of 5.5 years between baseline measurements and the accelerometry sub-study. While the study design allows for assessing associations, randomized experiments would be needed for stronger causal inference. Sleep was measured over only a single week, which may not fully capture long-term sleep patterns. The accelerometry method has limitations in distinguishing between quiet wakefulness and sleep, potentially leading to misclassification. Additionally, the SRI algorithm did not detect napping, only the longest sleep period of the day.
Funding and Disclosures
The research was conducted using the UK Biobank Resource and funded through Dr. Stamatakis’ Australian National Health and Medical Research Council Investigator Grant. Several authors disclosed potential conflicts of interest: Dr. Cistulli has an endowed Academic Chair at the University of Sydney created from ResMed funding (though he receives no personal fees) and has received research support from ResMed, SomnoMed, and Bayer, and serves as consultant to these companies. Dr. Rajaratnam declared grants from Vanda Pharmaceuticals, WA Police, and the CDC, consulting fees from Roche and Circadian Therapeutics, honoraria from Roche, and holds a patent for a digital application for sleep in shift workers. Other authors declared no competing interests.
Publication Information
The study titled “Sleep regularity and major adverse cardiovascular events: a device-based prospective study in 72,269 UK adults” was published in the Journal of Epidemiology and Community Health in 2025 (Vol. 79, pages 257-264). The authors included Jean-Philippe Chaput, Raaj Kishore Biswas, Matthew Ahmadi, Peter A. Cistulli, Shantha M.W. Rajaratnam, Wenxin Bian, Marie-Pierre St-Onge, and Emmanuel Stamatakis, representing institutions in Canada, Australia, and the United States.
