You may have heard that sleep is described as a kind of magic pill for the body. With the right amount, timing and quality, it can work wonders – boosting the immune system, improving blood sugar levels and even lowering the risk of heart attacks and strokes. Sleep differences in men and women have been reported for some time, but it is not known whether the characteristics of sleep in one sex serve different functions than in the other, especially in relation to the heart. New research is seeking answers.

Numerous studies over decades have documented a critical role for sleep in heart health. For example, sleep duration is essential to maintaining healthy blood pressure. In 2018, a study funded by the NHLBI found that people who slept less than seven hours had higher blood pressure than those who slept at least seven hours.

Blood Pressure and Deep Sleep: Differences Between Men and Women

“Sleep is essential to overall health and well-being,” said Dr. Marishka Brown, director of the National Center on Sleep Disorders Research at the NHLBI. ”Research is beginning to uncover how sleep characteristics, such as the time spent in each sleep stage or how often one wakes up at night, contribute to blood pressure control and also how sex and gender may affect these outcomes, but there are still many unanswered questions.” According to Kristen Knutson, Ph.D., associate professor of neurology and preventive medicine at the Feinberg School of Medicine at Northwestern University and an NHLBI-funded researcher, sleep is very important for heart health. That is why researchers are trying to find out more about this connection and how sleep may be related to the gender differences observed in cardiovascular disease. For example, high blood pressure in women is more strongly associated with heart attacks than in men.

Knutson and her team recently published a study that focused on different sleep stages and characteristics, as opposed to sleep duration, to see what factors, if any, were associated with blood pressure in men and women. The study found that women who spent more time in deep sleep—the third and deepest stage of sleep—tend to have lower blood pressure than women who spent less time in this stage. However, no comparable link between blood pressure and deep sleep was found in men. At the same time, men who woke more often after falling asleep had higher blood pressure than men who woke less often, while in women waking after falling asleep showed no comparable link with blood pressure.

The researchers conducted home sleep studies on more than 1,100 adults in Brazil who did not have moderate to severe sleep apnea—a condition known to be associated with high blood pressure, although some participants had mild sleep apnea. The study participants were between the ages of 18 and 91, and 64% were women. Researchers recorded one night of sleep using polysomnography, a diagnostic test that measures various bodily functions such as brain waves and heart rate during sleep using sensors placed all over the body. The next morning, blood pressure was measured and fasting blood samples were taken to measure lipid levels, specifically total cholesterol, HDL cholesterol, LDL cholesterol, and triglycerides. The data were analyzed collectively and also by gender.

Specific Changes in Sleep Habits Linked to Improvements in Blood Pressure

They found differences in blood pressure when they compared sleep experiences of men and women only, and also when they compared men and women. The results are fascinating, but they are only a starting point for further research, according to Knutson. For example, the researchers did not take into account multiple time points for sleep and blood pressure, so they could not determine whether someone got more or less sleep at a particular time or whether waking up during the night actually made blood pressure better or worse.

Future studies would need to examine whether changing these sleep phases in men and women results in changes in blood pressure. Nevertheless, the results of the current study could serve as a guide for future work exploring the underlying mechanisms that could make deep sleep in particular more valuable for women, according to Knutson. This in turn could lead to novel therapies that improve this sleep stage in women. She also explained that experimental studies could test whether certain changes in sleep habits can lead to improvements in blood pressure and ultimately heart health.