Irregular bedtimes in midlife may increase the risk of cardiovascular disease. A new study from the University of Oulu suggests that large variations in bedtime can double the risk of serious cardiac events, especially for people who sleep less than eight hours.
Researchers found that irregular bedtimes and high variability in sleep timing were strongly associated with a higher risk of serious cardiovascular events, especially when sleeping for less than 8 hours. The risk for this group was about twice that of people with more regular sleep patterns. In contrast, irregular wake times showed no clear association with cardiac events. In this study, major cardiovascular events were defined as conditions requiring specialized medical care, such as myocardial infarction or cerebral infarction.
Previous studies have linked irregular sleep patterns to heart health risks, but this is the first to separately examine the independent associations between bedtime, wake time, mid-sleep variation, and major cardiac events. ”
Laura Nauha, Postdoctoral Researcher, University of Oulu
Sleep duration and duration were estimated using activity monitors that tracked participants’ bedtimes.
“Our findings suggest that bedtime regularity, in particular, may be important for heart health, reflecting the rhythm of daily life and the degree to which it fluctuates,” says Nauha.
The study followed 3,231 people born in northern Finland in 1966. Their sleep patterns were recorded over a one-week period at age 46, and their health was tracked for more than 10 years using health record data.
According to Nauha, many aspects of heart health are shaped by daily habits. “Maintaining a regular sleep schedule is one factor most of us can influence.”
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Reference magazines:
Naha, L. Others. (2026). Irregular sleep timing in midlife: Association with serious adverse cardiac events and cardiovascular mortality over 10 years of follow-up. BMC cardiovascular disorders. DOI: 10.1186/s12872-026-05762-4https://link.springer.com/article/10.1186/s12872-026-05762-4
