A new study has found that healthy women risk future cardiovascular disease by reducing their sleep time by as little as one-and-a-half hours a night over the long term. The finding reinforces an important message: make sure you get enough sleep.
Experts recommend that adults have between seven and nine hours of sleep a night, or they risk developing health issues, especially heart disease. Compared to males, females more frequently report sleep disturbances and have been found to have a more profound inflammatory response and cardiovascular risk associated with insufficient sleep.
The endothelium is the layer of cells that makes up the inner lining of blood vessels. It's been suggested that a major function of healthy sleep is the prevention of oxidative stress, which contributes to the endothelial inflammation and dysfunction that are implicated in cardiovascular diseases such as atherosclerosis and high blood pressure.
Most studies into sleep have examined the physiological effects of a few nights of deprivation. However, in a new study, researchers at Columbia University Irving Medical Center looked at what happens to women’s blood vessels during longer-term mild sleep deprivation.
“But that’s not how people behave night after night,” said Sanja Jelic, corresponding author of the study. “Most people get up around the same time each day but tend to push back their bedtime one to two hours. We wanted to mimic that behavior, which is the most common sleep pattern we see in adults.”
The researchers recruited healthy female participants with a habitual sleep duration of seven to nine hours daily and randomized them into two groups. The control group slept for the usual amount of time; the other group’s bedtime was delayed by one-and-a-half hours, but their wake time remained the same. After six weeks in one group, participants completed six weeks in the alternate group. Sleep time was verified using wrist-worn sleep trackers.
Examining the participants’ endothelial cells, they found that endothelial oxidative stress levels increased by 78% after sleep restriction compared with adequate sleep, indicating that mild, prolonged sleep restriction promoted oxidative stress in healthy women.
The researchers found that despite markedly increased oxidative stress, antioxidant responses were completely lacking. In other words, mild sleep deprivation led to cells that were inflamed and dysfunctional, an early step in the development of cardiovascular disease.
“This is some of the first direct evidence to show that mild chronic sleep deficits cause heart disease,” Jelic said. “Until now, we’ve only seen associations between sleep and heart health in epidemiological studies, but these studies could be tainted by many confounders that cannot be identified and adjusted for. Only randomized controlled studies can determine if this connection is real and what changes in the body caused by short sleep could increase heart disease.”
The researchers say their findings highlight a simple message: make sure you get enough sleep.
“Many problems could be solved if people sleep at least seven to eight hours per night,” Jelic said. “People who are young and healthy need to know that if they keep getting less sleep than that, they’re aggravating their cardiovascular risk.”
They plan to examine next whether bedtime variability affects vascular cells the same way as chronic but regular, shortened sleep does.
The study was published in the journal Scientific Reports.
