The Hidden Heart Risk of Irregular Sleep

New research suggests that when you sleep (and how consistent your sleep schedule is) may play an important role in your heart health. Investigators from the University of Oulu in Finland explored how sleep timing patterns, tracked using wearable devices, relate to the risk of serious heart problems, known as cardiovascular disease.

Sleep timing refers to your usual bedtime, wake-up time, and the midpoint of your sleep (the halfway point between falling asleep and waking up). These patterns are closely tied to your body’s internal clock, or circadian rhythm, which helps regulate key processes like blood pressure, heart rate and hormone levels.

“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,” said lead investigator Laura Nauha, Ph.D., a researcher from the University of Oulu.

The study, published in BMC Cardiovascular Disorders, followed more than 3,200 adults for up to 10 years. Participants wore devices that tracked their sleep habits over a one-week period, allowing researchers to measure how regular (or irregular) their sleep schedules were. People were then grouped based on how consistent their sleep timing was, from very regular to highly irregular.

Over the course of the study, about 4% of participants experienced a major heart-related event, such as a heart attack, stroke, heart failure hospitalization or death related to cardiovascular disease. These are often grouped together as major adverse cardiac events.

One of the most important findings was that irregular sleep timing was linked to a higher risk of these serious heart events — but only in people who were not getting enough sleep overall. Specifically, among individuals sleeping less than about eight hours per night, those with inconsistent bedtimes had about double the risk of experiencing a major cardiac event compared with those with regular sleep schedules. Similarly, people with irregular sleep midpoints (meaning their sleep timing varied significantly from day to day) also had about twice the risk.

Interestingly, variability in wake-up time alone did not appear to increase risk. This suggests that going to bed at consistent times may be more important than waking up at the exact same time every day when it comes to heart health.

For people who slept longer, closer to or above eight hours, irregular sleep timing did not show the same strong link to heart risk. This highlights that both sleep duration and sleep consistency likely work together to influence overall health.

The takeaway for patients is that healthy sleep isn’t just about how much you sleep; it’s also about maintaining a consistent routine. Going to bed at roughly the same time each night, especially if you’re not getting a full eight hours of sleep, may help reduce your risk of serious heart problems.

While more research is needed to confirm these findings, this study adds to growing evidence that simple lifestyle habits, such as regular sleep schedules, can have meaningful impacts on long-term cardiovascular health.

“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 said. “Maintaining a regular sleep schedule is one factor that most of us can influence.”