Study Links Irregular Bedtimes to Doubled Heart Risk

A new study from researchers at the University of Oulu in Finland has found that irregular bedtimes, particularly among those who sleep less than eight hours a night, may double the risk of major cardiovascular events such as heart attacks and strokes over a decade.

The research, published in BMC Cardiovascular Disorders, analyzed sleep patterns from 3,231 midlife adults, primarily women, drawn from the Northern Finland Birth Cohort 1966. At around age 46, participants wore accelerometers for seven days between 2012 and 2014 to track sleep timing. Follow-up data through 2023, sourced from national medical registries, recorded health outcomes until a cardiovascular event, death, or loss to follow-up occurred. Major adverse cardiovascular events included heart attacks, strokes, unstable angina, heart failure hospitalizations, and cardiovascular deaths. Over the study period, 128 participants experienced such events.

Key findings centered on bedtime consistency. Participants were grouped into tertiles based on variability in bedtime, wakeup time, and sleep midpoint—the halfway point between bedtime and waking. Those with irregular bedtimes, averaging 108 minutes of variation across...