Irregular sleep patterns are a stronger predictor of mortality risk than sleep duration.

New study showed that irregular sleep patterns increase the risk of mortality by up to 48%.

People with regular sleep patterns have up to 48% lower mortality risk, with regular sleep patterns being a stronger predictor of mortality than sleep duration

We all know getting enough sleep is important for health and longevity. But a new study finds that the regularity of your sleep may matter even more than sleep duration when it comes to mortality risk.

The large prospective study from researchers at Monash University, Brigham and Women's Hospital, University of Manchester and other institutions analyzed over 10 million hours of wrist accelerometer data from nearly 61,000 participants in the UK Biobank study. They developed a novel "sleep regularity index" (SRI) metric to precisely quantify night-to-night changes in sleep patterns, accounting for variability in sleep onset, offset timing, duration and fragmentation.

Participants with an SRI score above 80 (indicating highly regular sleep) faced meaningfully lower mortality risk compared to those with scores below 72 (representing irregular sleep patterns). Those in the top 20% of sleep regularity had a 20-48% reduced risk of all-cause mortality over the 6-7 year follow-up after adjusting for multiple factors. The protective effects of consistent sleep timing extended across multiple causes of death. Compared to the bottom 20%, those in the top quintile of sleep regularity (SRI above 87) had 16-39% lower cancer mortality risk and 22-57% lower risk of fatal cardiometabolic diseases like heart conditions and diabetes.

The study's key finding was that sleep regularity as measured by SRI outperformed self-reported and accelerometer-estimated sleep duration as a predictor of mortality risk. Statistical models based solely on the SRI score better explained mortality risk than models using sleep duration alone. Remarkably, adding sleep duration to the SRI models did not significantly improve their predictive ability.

Irregular sleep patterns can disrupt the body's circadian rhythms governing sleep/wake, metabolism, hormone release and other cyclic processes aligned to the 24-hour light/dark cycle. This circadian misalignment may trigger inflammation, oxidative stress, metabolic dysfunction and drive disease development.

Overall, this is yet another study showing how important, yet often neglected, regular sleep timing is. So next time you try to improve your sleep quality, try starting with having a consistent sleep and wake schedule.