Irregular sleep linked to higher cardiovascular risk
Each 29-minute increase in night-to-night sleep-duration variability was linked to higher cardiovascular risk, with a hazard ratio (a relative risk measure) of 1.24.
The catch: Early cardiovascular disease can disrupt sleep, so the order may be reversed
Edited by Boris Djordjevic · AgingResearch.News
In a cohort study of 10,362 US adults with linked Fitbit and electronic health records, the median age was 53 and 70% were female. Researchers analyzed sleep over a 180-day baseline with at least 90 valid nights per participant. Over a median follow-up of 3.7 years, 230 participants developed a combined cardiovascular outcome: heart attack, heart failure, heart muscle disease or stroke caused by blocked blood flow.
Greater night-to-night variation in sleep duration, bedtime and waking time was associated with higher risk of this outcome after adjustment for demographic, socioeconomic, lifestyle and health factors. Average sleep duration was not associated with this outcome. Sleep-duration variability was also linked to heart failure, high blood pressure and type 2 diabetes.
Why it matters
Heart disease and stroke are major concerns in later life. The results bear on whether sleep-health assessments should consider regularity alongside duration.
Caveats
This observational study could not establish cause and effect. The findings may not extend to children or populations unlike these US adults with linked Fitbit and health records, most of whom were female.
The paper
Circulation Population Health and Outcomes, Nov 2, 2026
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