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.