Experts recommend that adults get between seven and nine hours of sleep each night or risk developing health problems, especially heart disease. Women report sleep disturbances more often than men, and inflammatory responses and cardiovascular risks in women have been found to be associated with sleep loss.
The endothelium is the layer of cells that makes up the lining of blood vessels. It has been suggested that a major function of healthy sleep is to protect against oxidative stress, which can lead to endothelial inflammation and dysfunction, which is associated with cardiovascular diseases such as atherosclerosis and hypertension.
Most research on sleep examines the physiological effects of a few nights of sleep deprivation. However, in a new study, researchers at Columbia University Irving Medical Center examined the effects of long-term mild sleep deprivation on blood vessels in women.
"But this isn't how people behave night after night," said Sanja Jelic, corresponding author of the study. "Most people wake up at the same time every day, but tend to push their bedtime by one to two hours. We wanted to mimic this behavior, which is the sleep pattern we see most commonly 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 had their bedtime 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 is verified with a wrist-worn sleep tracker.
When examining the participants' endothelial cells, they found that endothelial oxidative stress levels increased by 78% after sleep restriction compared with adequate sleep, suggesting that mild, prolonged sleep restriction promotes oxidative stress in healthy women.
The researchers found that despite a significant increase in oxidative stress, there was a complete lack of antioxidant response. In other words, mild sleep deprivation can lead to cellular inflammation and dysfunction, which are early stages in the development of cardiovascular disease.
"This is the first direct evidence that mild chronic sleep deprivation causes heart disease," Yelich said. "So far, we have only seen a link between sleep and heart health in epidemiological studies, but these studies may be affected by many confounding factors that cannot be identified and adjusted for. Only randomized controlled studies can determine whether this link is real and what changes in the body occur due to short sleep periods that increase the incidence of heart disease."
The researchers say their findings highlight a simple message: Make sure you get enough sleep. If people sleep at least 7 to 8 hours every night, many problems can be solved. Young, healthy people need to know that if they consistently sleep less than this, they are increasing their cardiovascular risk.
They plan to next investigate whether changes in bedtime have the same impact on blood vessel cells as long-term but regular sleep shortening.
The research was published in the journal Scientific Reports.