Scientists pinpoint how many hours’ sleep will increase your risk of heart disease

We have known for a long time that a lack of sleep is bad for the heart – but scientists are now starting to understand exactly how it causes damage.

In a study by the University of Uppsala in SuedeThe researchers found that only three nights of limited sleep – approximately four hours per night – triggered changes in the blood linked to a higher risk of heart disease.

Researchers examined inflammatory proteins in the blood. These are molecules that the body produces when it is under stress or the fight against disease. When these proteins remain high for a long time, they can damage blood vessels and raise the risk of problems as heart failurecoronary disease and atrial fibrillation (irregular heart rate).

The study involved 16 young healthy men who spent several days in a laboratory, where everything, from their meals at their activity levels and exposure to light, was carefully controlled.

The participants followed two routines: three nights of normal sleep (8.5 hours) and three nights of sleep restriction (4.25 hours). After each sleep phase, the men finished a short and high intensity cycling training and their blood was tested before and after.

The researchers measured nearly 90 different proteins in blood samples. They found that sleep deprivation has caused a clear increase in inflammatory markers linked to heart disease. And although the exercise generally stimulates healthy proteins such as interleukin-6 and BDNF (which support brain and heart health), these responses were lower after bad sleep.

Surprisingly, changes have occurred even in young healthy adults, and after only a few nights of bad sleep. This is worrying since it is common for adults to feel bad sleep from time to time – and about one in four people work changes that disrupt sleep habits.

The researchers also discovered that the blood time of the day was taken into account: the protein levels varied between morning and evening, and even more when sleep was limited. This suggests that sleep affects not only what is in your blood, but when these changes are most visible.

Although modern life often encourages us to exchange sleep for productivity, socialization or screen time, studies like this remind us that the body maintains the score – quietly, chemically and without compromise.

Annie Curtis is a professor (partner) at the school of pharmacy and biomolecular sciences (PBS) at the RCSI University of Medicine and Health Sciences.

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