Going to bed at different times each night in midlife could be an early signal of future cardiovascular risk.
Findings from researchers at the University of Oulu suggest that inconsistent bedtimes, especially when combined with shorter sleep duration, may significantly increase the chance of serious heart related events later on.
The study points to a clear pattern in that those with highly variable bedtimes and fewer than eight hours in bed per night had roughly double the risk of major cardiovascular problems compared to those with more stable sleep routines.
Interestingly, irregular wake-up times didn’t show the same strong link to heart risk.
Earlier studies already connect poor sleep patterns with heart risk, but this newer research breaks things down further by looking separately at bedtime, wake time and sleep midpoint.
That separation helped show that bedtime variability stood out as a particularly strong factor.
How the Study Measured Sleep Patterns
Researchers used activity-monitoring devices to track participants’ sleep behavior in a real-world setting.
These devices recorded how long individuals stayed in bed and how consistent their sleep timing was.
The focus wasn’t just on total sleep, but on how stable daily routines were from night to night.
The findings reinforced the idea that rhythm and consistency in sleep schedules are important in long-term health outcomes.
The study followed 3,231 people born in Northern Finland in 1966. Their sleep habits were recorded when they were 46 years old using a one-week monitoring period.
Researchers then tracked their health outcomes for more than a decade using national healthcare registry data.
This long follow-up period helped reveal how midlife sleep patterns might connect to later cardiovascular events.
The study did not look at cause and effect; it shows only an association.
This leaves open the possibility that people who have inconsistent bedtimes might also be more likely to engage in lifestyle habits that have been connected to poor heart health such as drinking, smoking, a diet high in salt or processed foods, and lack of exercise.
