Experts say we should sleep for eight hours a night
Lack of sleep raises a woman's risk of heart disease more than it does for a man, research suggests.
Sleeping less than the recommended eight hours a night has been linked to a raised risk of heart problems.
Researchers found levels of inflammatory markers - indicators of heart disease - vary significantly with sleep duration in women, but not men.
The study, by University College London and the University of Warwick, appears in the journal Sleep.
Previous research has suggested people who sleep less than five hours a night have an increased risk of dying from cardiovascular disease, compared to those who get the full eight hours.
The latest study found levels of a molecule called interleukin-6 (IL-6), which is known to trigger inflammation, were much lower in women who reported sleeping eight hours, compared to those who slept for seven hours.
Levels of another molecule, high-sensitivity C-reactive protein (hs-CRP) - which is linked to heart problems - were significantly higher in women who reported sleeping for five hours or less.
Researcher Dr Michelle Miller said the findings added to the growing body of evidence suggesting that sleep duration played a key role in heart health.
She said: "The results also are consistent with the idea that sleeping seven or eight hours per night appears to be optimal for health."
Dr Miller said more work was required to pin down why lack of sleep potentially had a greater effect on women.
However, she said differences in hormone levels might be key. There is work to suggest that inflammatory marker levels are different in pre- and post-menopausal women.
The study was based on data from more than 4,600 London-based civil servants aged 35 to 55, of which 73% were men.
Dr Janet Mullington, of Harvard Medical School, said there were many questions still to be answered about the effect of sleep deprivation.
She said it was possible that the change to inflammatory markers produced in sleep deprivation experiments were merely short-term reflections of the battle against sleepiness.
They might also be influenced by the unusual conditions, such as the interaction between the participants and the researchers.
June Davison, a cardiac nurse at the British Heart Foundation, said: "Previous research suggests that a good night's sleep may help to keep our heart and circulation healthy, and this study could point to an underlying reason behind that finding.
"We should all try to get enough sleep - as it's likely to be good for heart health as well as overall health."