Sleep & Relaxation

Experts recommend that adults should get between seven and nine hours of sleep a night or risk developing health problems, especially heart disease. Women report sleep disorders more often than men, and inflammatory responses and cardiovascular risk have been found to be linked to sleep deprivation in women.

A new study has found that healthy women are at risk of developing cardiovascular disease with as little as an hour and a half less sleep per night over the long term. This finding reinforces an important message: make sure you get enough sleep.

The endothelium is the layer of cells that make up the inner walls of blood vessels. It is thought that a major function of healthy sleep is to prevent oxidative stress, which leads to endothelial inflammation and dysfunction, which has been linked to cardiovascular diseases such as atherosclerosis and hypertension.

Most research on sleep has examined the physiologic effects of a few nights of sleep deprivation. However, in a new study, researchers at Columbia University Irving Medical Center examined the effects of chronic light sleep deprivation on women's blood vessels.

Sanja Jelic, the study's corresponding author, said, "But it's not a manifestation of people going night after night. Most people get up at the same time every day, but tend to delay bedtime by one to two hours. We wanted to mimic this behavior, which is the most common sleep pattern we see in adults."

The researchers recruited healthy female participants who habitually slept seven to nine hours a day and randomly divided them into two groups. The control group slept the same amount of time as usual; the other group's bedtime was delayed by an hour and a half, but their wake-up time remained the same. After completing six weeks of training in one group, participants completed six weeks of training in the other group. Sleep duration was verified by a wrist-worn sleep tracker.

When examining the participants' endothelial cells, they found a 78 percent increase in endothelial oxidative stress levels after sleep restriction compared to adequate sleep, suggesting that mild, prolonged sleep restriction promotes oxidative stress in healthy women.

The researchers found that despite the apparent increase in oxidative stress, there was a complete lack of antioxidant response. In other words, mild sleep deprivation leads to cellular inflammation and dysfunction, an early stage in the development of cardiovascular disease.

"This is the first time there is direct evidence that mild chronic sleep deprivation leads to heart disease," says Yelich." So far, we've only seen a link between sleep and heart health in epidemiologic studies, but these studies can be affected by many confounding factors that can't be identified and adjusted for. Only randomized controlled studies will be able to determine whether the link is real and what changes in the body result from short sleep that increase the incidence of heart disease."

The researchers say their findings underscore a simple message: make sure you're getting enough sleep. Many of these problems can be solved if people get at least seven to eight hours of sleep a night. Young, healthy people need to know that if they consistently sleep less than that, they are at increased cardiovascular risk.

They plan to study next whether changes in bedtime have the same effect on blood vessel cells as a prolonged but regular shortening of sleep time.