SAN FRANCISCO, June 7 (UPI) -- A lack of sleep -- less than 6 hours a night -- increases a woman's risk of heart attack, but not a man's, U.S. researchers say.
Lead author Aric Prather, an assistant professor of psychiatry at the University of California, San Francisco, said poor sleep -- particularly waking too early -- appeared to play a significant role in raising unhealthy levels of inflammation among women with coronary heart disease.
However, the elevated inflammation affected only women, not men, even after adjusting for medical, lifestyle and demographic differences, Prather said.
"Inflammation is a well-known predictor of cardiovascular health," Prather said in a statement. "Now we have evidence that poor sleep appears to play a bigger role than we had previously thought in driving long-term increases in inflammation levels and may contribute to the negative consequences often associated with poor sleep."
The five-year study, which began in 2000, involved nearly 700 people -- average age of the men was 66 and age 64 in women.
The findings, published in the Journal of Psychiatric Research, found women who reported very poor or fairly poor sleep quality showed 2.5 times the level of inflammation then men who said they slept poorly.