Decade-Long Study Links Irregular Bedtimes to Higher Risk of Heart Attack, Stroke - Video

A long-term study suggests that irregular sleep timing-especially inconsistent bedtimes-may significantly increase the risk of cardiovascular disease. Conducted by researchers at the University of Oulu and published in BMC Cardiovascular Disorders, the study followed more than 3,000 individuals over a decade, offering new insights into how daily sleep habits influence heart health.

The findings revealed that people with highly variable bedtimes in midlife faced up to double the risk of major cardiovascular events, including Myocardial Infarction and Cerebral Infarction. Interestingly, irregular wake-up times did not show a similar association, suggesting that bedtime plays a more critical role in maintaining cardiovascular stability.

Researchers tracked 3,231 participants born in Northern Finland in 1966. At age 46, their sleep patterns were recorded over a week using wearable activity monitors. These data were then linked to national health records over the following 10+ years to identify heart-related outcomes.

The study also examined “sleep midpoint”-the halfway point between falling asleep and waking up-and found that greater variability in this measure was also linked to increased cardiovascular risk.

The underlying mechanism appears to involve disruption of the body’s Circadian Rhythm. Irregular sleep schedules can disturb this internal clock, affecting key physiological processes such as blood pressure regulation, metabolism, and inflammation-all of which are known contributors to heart disease.

Notably, the highest risk was observed in individuals who combined irregular bedtimes with shorter sleep duration, particularly those sleeping less than eight hours per night. This suggests that both sleep quality and consistency are crucial for long-term cardiovascular health.

Overall, the study highlights bedtime regularity as a simple yet powerful lifestyle factor. Maintaining a consistent sleep schedule may help protect heart health and reduce the risk of serious cardiovascular conditions over time.

REFERENCE: Nauha, L., Niemelä, M., Azadifar, S. et al. Sleep timing irregularity in midlife: association with incident major adverse cardiac events and cardiovascular disease mortality over a 10-year follow-up. BMC Cardiovasc Disord (2026). https://doi.org/10.1186/s12872-026-05762-4