People who miss many hours of sleep are more likely to develop hardening of their arteries, a precursor to heart disease, research suggests.
Calcified arteries were found in nearly a third of people who slept fewer than five hours a night.
This dropped to around one in 10 for those who slept an extra hour, the Journal of the American Medical Association study of 495 adults found.
Experts said getting enough sleep was important for good heart health.
In the study, the volunteers underwent two CT scans, designed to assess the build-up of calcium in the heart’s arteries, five years apart. Although this single study does not prove that short sleep leads to coronary artery disease, it is safe to recommend at least six hours of sleep a night
They also filled out sleep questionnaires, kept a sleep diary and wore a wrist monitor for six nights that measured movement to give an estimate of how long they were actually lying still and asleep.
At the first scan, none of the volunteers had any calcification in their arteries but five years later 61 of them did.
The risk was lowest for those who regularly had more than seven hours sleep each night.
Lead researcher Dr Diane Lauderdale, of the University of Chicago, said there were several possible explanations for the link that they found.
Firstly, there may be some factor not yet identified that can both reduce sleep duration and increase calcification.
Or it might be down to blood pressure – high blood pressure increases the likelihood of calcification and blood pressure goes down during sleep.
Alternatively, stress or a stress hormone like cortisol, which has been tied to decreased sleep and increased calcification, may play a role.
She said: "Although there are constant temptations to sleep less, there is a growing body of evidence that short sleep may have subtle health consequences.
"Although this single study does not prove that short sleep leads to coronary artery disease, it is safe to recommend at least six hours of sleep a night."
Ellen Mason, of the British Heart Foundation, said "It is not yet clear quite how sleep affects our heart disease risk, but this study adds to previous research suggesting that getting enough sleep may help to keep our hearts and circulation healthy.
"Sleep is essential for our body’s ability to repair itself and with the party season in full flow, it is important to try and get enough rest.
"Drinking alcohol late at night and getting up early can mean we’re not getting enough quantity or quality of sleep."