💤 Going to bed at irregular times leads to serious heart problems!

A team from the University of Oulu in Finland followed more than 3,200 people born in 1966 for over a decade. At the age of 46, these volunteers wore activity sensors for a week. The scientists thus obtained precise measurements of their nighttime habits, which they then compared with medical data from health registries.

The results obtained are striking. In people sleeping less than eight hours per night, highly irregular bedtimes double the probability of experiencing a major cardiovascular event, such as a myocardial infarction or a stroke. Conversely, an irregular wake-up schedule would not have the same influence on heart health.


This research distinguishes itself from previous work by isolating the impact of three key moments: going to bed, waking up, and the midpoint of the sleep period. Postdoctoral researcher Laura Nauha indicates that this is the first time these three aspects have been examined independently and linked to serious heart problems. According to her, the observations indicate that bedtime regularity, in particular, has a significant impact on the heart.

Sleep measurement was performed using activity monitors, small devices that record movements to estimate time spent in bed. This method proves more reliable than a simple questionnaire. It allowed the researchers to gather accurate information on the duration and timing of rest for each participant.

Beyond the numbers, this study reminds us that our body appreciates regularity. Our internal rhythms, aligned with the day-night cycle, function optimally when they follow a consistent schedule. Disrupting this rhythm with random bedtimes could, over time, deregulate certain biological processes and increase pressure on the cardiovascular system.

Circadian rhythms and health

Our body operates on a cycle of approximately 24 hours, guided by an internal clock located in the brain. This clock regulates numerous functions like body temperature, hormone release, and blood pressure. It synchronizes primarily with natural light, but also with our habits, such as mealtimes or bedtime.

When we go to bed at very irregular times, we send conflicting signals to this internal clock. It can then become deregulated, a phenomenon sometimes called "desynchronization." This deregulation can disrupt the production of cortisol, the stress hormone, or melatonin, the sleep hormone, which has repercussions throughout the body.

Research on night shift work has already demonstrated that shifting sleep schedules increases the risks of certain health problems. The Finnish research extends this observation to everyday life, even without shift work. It indicates that simply having an irregular bedtime on weekdays or weekends can be enough to create an imbalance.

Understanding this link paves the way for simple solutions. Going to bed at roughly the same time each evening, including on weekends, helps keep the internal clock well-regulated. This can contribute to better regulation of blood pressure and metabolism, two important elements for heart health.