Your heart is at risk if you go to bed at different times: just 29 minutes can make all the difference
Getting eight hours’ sleep a night might not be enough. Because, as well as the quantity and quality of sleep, there is a third factor that should not be underestimated: regularity
Key points
Sleep can be a panacea, but it can also be a risk factor for cardiovascular disease and metabolic disorders (particularly diabetes and obesity). However, it is not just how much we sleep, or the structure and quality of our sleep, that matters. The time at which we turn off the light each evening is also crucial. A study covering over a million nights, due to be presented in the coming days at the American Heart Association’s conference, has found a link between going to bed at different times each night and an increased risk of heart attack, stroke and heart failure.
Sleeping eight hours a night may therefore not be enough to protect the heart. This is because, in addition to the quantity and quality of sleep, there is a third factor that should not be underestimated: the regularity with which we close our eyes each evening to drift off into the arms of Morpheus. Going to bed at a different time every evening, indulging in long sleeps at the weekend under the illusion of making up for lost sleep during the week, or alternating between nights of short sleep and very long ones could have consequences for cardiovascular health. What’s more, even seemingly insignificant variations can make a difference: every 29-minute increase in the irregularity of sleep duration results in a 24 per cent increase in the risk of cardiovascular events.
This is suggested by a study carried out by researchers at Boston Children’s Hospital and Harvard Medical School, which will be presented at the American Heart Association’s Scientific Sessions 2026, due to take place in Chicago from 7 to 9 November.
The Stars and Stripes Sleep Study
American researchers have analysed over a million nights’ sleep from 10,362 adults, with an average age of 53, who were monitored using wearable devices as part of the ‘All of Us’ Research Programme run by the US National Institutes of Health . Over a period of approximately six months, the researchers analysed not only the hours spent sleeping, but also the times at which participants fell asleep and woke up (sleep regularity), the quality of sleep (i.e. how much of the night was spent in REM, light or deep sleep, and how long a person remained awake after first falling asleep), the number of sleep cycles completed each night and the duration of each cycle. The participants, who were in good health at baseline and had no cardiovascular or metabolic diseases, were followed for a median of 3.7 years.
Turning off the light at different times each evening increases the risk of heart problems
The findings of this research should serve as a wake-up call for those with particularly irregular sleeping patterns. Variations in sleep times from one night to the next were found to be associated with a 20–23 per cent increase in the risk of serious cardiovascular events, such as heart attacks, strokes and heart failure. Every 29-minute increase in the variability of sleep duration was associated with a 24 per cent increase in overall cardiovascular risk, a 29 per cent increase in heart muscle disease and a 20 per cent increase in heart failure.
