The study found a strong connection between irregular bedtimes and an increased likelihood of major heart-related events. People whose time in bed was under eight hours and whose sleep schedules varied widely faced about twice the risk compared to those with more consistent routines. In contrast, irregular wake-up times did not show a clear association with heart issues.

Major cardiovascular events in this research included conditions that require specialized medical care, such as myocardial infarction or cerebral infarction.

“Previous research has linked irregular sleep patterns to heart health risks, but this is the first time we’ve looked separately at variability in bedtime, wake-up time and the midpoint of the sleep period — and their independent associations with major cardiac events,” says postdoctoral researcher Laura Nauha from the University of Oulu.

Tracking Sleep Patterns and Long-Term Health

Researchers measured sleep duration and timing using activity monitors, which recorded how long participants stayed in bed. The results pointed to bedtime consistency as a particularly important factor.

“Our findings suggest that the regularity of bedtime, in particular, may be important for heart health. It reflects the rhythms of everyday life — and how much they fluctuate,” Nauha says.

Long-Term Study Reveals Lasting Impact

The research followed 3,231 individuals born in Northern Finland in 1966. Their sleep habits were tracked over a one-week period at age 46, and their health outcomes were monitored for more than ten years using healthcare register data.

According to Nauha, everyday routines play a major role in shaping heart health over time. “Maintaining a regular sleep schedule is one factor that most of us can influence.”