A new study conducted by researchers at Duke University Medical Center seems to have found why poor sleep does more harm to cardiovascular health in women than in men.
In the study, the researchers found that poor sleep is linked to greater psychological distress and higher levels of biomarkers, which is linked to an increased risk of heart disease and type 2 diabetes.
They also found that these links are much stronger in women than in men.
"The study suggests that poor sleep - measured by the total amount of sleep, the degree of awakening during the night, and most importantly, how long it takes to get to sleep - may have more serious health consequences for women than for men," said Edward Suarez, an associate professor in the department of psychiatry and behavioral sciences at Duke and the lead author of the study.
For the study, researchers examined 210 apparently healthy, middle-aged men and women without any history of sleep disorders.
None of the participants smoked or took any medications on a daily basis and researchers expelled women who were on hormone therapy, as it has been shown to alter sleep patterns in some women.
Researchers used a standardized sleep quality questionnaire, with which participants rated various dimensions of their sleep during the previous month.
Besides this, additional measures assessed the extent of any depression, anger, hostility and perceived social support from friends and family.
Researchers also took blood samples from the volunteers and they were measured for levels of biomarkers linked to elevated risk of heart disease and diabetes, including insulin and glucose levels, fibrinogen (a clotting factor) and two inflammatory proteins, interleukin-6 and C-reactive protein.
Suarez and his colleagues found that about 40 percent of the men and the women were classified as poor sleepers - defined as having frequent problems falling asleep, taking 30 or more minutes to fall asleep or awakening frequently during the night.
They also found while their sleep quality ratings were similar; men and women had dramatically different risk profiles.
"We found that for women, poor sleep is strongly associated with high levels of psychological distress, and greater feelings of hostility, depression and anger. In contrast, these feelings were not associated with the same degree of sleep disruption in men," Suarez said.
Furthermore, the researchers found that women who reported higher degree of sleep disruption also had higher levels of all the biomarkers tested.
For women, poor sleep was linked to higher levels of C-reactive protein and interleukin-6, measures of inflammation that have been associated with increased risk of heart disease, and higher levels of insulin.
Suarez said that the findings were so dramatic that of those women considered poor sleepers, 33 per cent had C-reactive protein levels linked to high risk of heart disease.
"Interestingly, it appears that it's not so much the overall poor sleep quality that was associated with greater risk, but rather the length of time it takes a person to fall asleep that takes the highest toll. Women who reported taking a half an hour or more to fall asleep showed the worst risk profile," Suarez said.
The study is published online in the journal Brain, Behaviour and Immunity.