We all feel better after a good night’s shut-eye - but there could be an even more imperative reason for clocking up those eight hours.
Regularly experiencing disrupted sleep can have long-term consequences for health, say scientists.
A new study has found it can clog arteries - leading to an increased risk of heart disease.
Poor sleeping habits have long been linked to unhealthy hearts, but scientists have not fully grasped why.
Now, global sleep expert Professor Matthew Walker and his team have discovered that plaque accumulates inside the arteries of poor sleepers, causing inflammation.
Two white cells - called neutrophils and monocytes - gather in the arteries of those with disrupted sleep.
The team at the University of California, Berkeley discovered that the consequent inflammation, known as atherosclerosis, leads to a higher risk of strokes and dangerous heart conditions.
Given the new findings, the team now hope to bolster public awareness into the dangers of poor sleep.
Professor Walker, the author of Why We Sleep, said: "Improving sleep may offer a novel way to reduce inflammation and thus reduce the risk of atherosclerosis.
"These findings may help inform public health guidelines that seek to increase the continuity of sleep as a way to improve health and decrease the burden of heart disease on society."
To measure sleep disruption, the researchers used both lab-based polysomnography, which records brain waves, blood oxygen level and heart rate during sleep, and a simple movement detector worn on the wrist over multiple nights.
The team used standard blood cell counts to measure levels of neutrophils and monocytes.
They discovered that fragmented sleep, as measured by the wrist detector, predicted higher neutrophil counts and higher coronary artery calcium, a measure of inflamed arteries.
In short, poor sleep led to increased neutrophils, which in turn caused inflamed arteries and worsened atherosclerosis.
Even after accounting for known contributors to artery disease, including age, sex, and body mass index, sleep disruption was still found to aggravate inflammation.
Professor Walker added: “These results provide a mechanism to explain the long-standing observation that poor sleep increases the risk of heart disease and stroke, and suggest simple and direct ways to reduce such risk.”
No association was found in participants who reported their own poor sleep when prompted, suggesting that asking patients about their sleep may not be a useful tool for assessing their sleep-related risk of heart disease.