Irregular bedtime linked to high risk of heart attack, stroke: Decade-long study

A new long-term study suggests that going to bed at different times every night could harm your heart. Researchers have found that people in midlife who have irregular bedtimes may face a much higher risk of major heart problems later.

The study, conducted by researchers at the University of Oulu, followed more than 3,000 people for over a decade. It found that large changes in bedtime—especially among people who sleep less than eight hours a night—can double the risk of serious cardiovascular events such as a Myocardial Infarction (heart attack) or Cerebral Infarction (a type of stroke).

BEDTIME MATTERS MORE THAN WAKE-UP TIME

Researchers say the findings show that the time people go to sleep may be more important for heart health than the time they wake up.

While irregular bedtimes were strongly linked to heart problems, inconsistent wake-up times did not show a clear connection to cardiovascular disease.

“Previous research has shown that irregular sleep patterns can affect heart health, but this is the first study to examine bedtime, wake-up time and the midpoint of sleep separately,” said Laura Nauha, a postdoctoral researcher at the University of Oulu.

The results suggest that bedtime may act as the main “anchor” for the body’s daily rhythm.

A DECADE-LONG FOLLOW-UP

The study followed 3,231 people born in Northern Finland in 1966. When the participants were 46 years old, researchers recorded their sleep patterns for a



week using activity trackers that monitored the time they spent in bed.

The participants’ health records were then followed for more than 10 years using national healthcare registries to identify major cardiovascular events.

Researchers also examined something called the sleep midpoint, the halfway point between when a person falls asleep and when they wake up. Greater variability in this midpoint was also linked to a higher risk of heart disease.

Scientists believe that irregular sleep schedules can disrupt the body’s internal clock, also known as the circadian rhythm.

This disruption may affect metabolism, blood pressure, and inflammation, all factors linked to heart disease.

The study also found that the risk was highest among people who had both irregular bedtimes and shorter sleep duration, particularly those who slept less than eight hours.

A LIFESTYLE FACTOR PEOPLE CAN CHANGE

Researchers say the findings highlight how everyday habits can influence long-term heart health.

“Our results suggest that maintaining a regular bedtime may be important for protecting heart health,” Nauha said. “It reflects the rhythms of daily life and how much they fluctuate.”

In other words, it may not only be about getting enough sleep, but also about going to bed at roughly the same time every night. Small changes in daily routines could make a meaningful difference to cardiovascular health over time.