It’s not uncommon to see people twitch and move around in response to noises, temperature changes or light when snoozing away; it’s a normal part of sleep called unconscious wakefulness that most aren’t aware of or recall when the sun rises.
In some cases, these sleep disruptions can cause people to feel exhausted in the morning or even lead to serious health problems if they happen consistently enough over time.
Now, a new study of 8,000 people has, for the first time, found a “clear link” between the frequency and duration of these unconscious episodes and an increased risk of dying from any cause and of heart disease, especially in women.
Compared to women without sleep issues, women who experience unconscious wakefulness during the night had nearly double the risk of dying from heart disease in the six to 11 years of the study’s follow-up period. Men, on the other hand, faced a risk of death from cardiovascular illness that was just over a quarter compared to men with no sleep disruptions.
The researchers say their study highlights the importance of detecting and assessing arousals during sleep as a way to reduce the risk of heart disease, such as with wearable devices that can monitor breathing patterns. However, the study was conducted mostly on older, white people, so the findings cannot be applied to people of other races and ethnicities or younger ages.
The study was published Tuesday in the European Heart Journal.
“It is unclear why there is a difference between men and women in the associations, but there are some potential explanations. The triggers causing an arousal or the body’s response to arousal may differ in women compared to men,” study co-author Dr. Dominik Linz, an associate professor of cardiology at Maastricht University Medical Center in The Netherlands, said in a statement. “Women and men may have different compensatory mechanisms for coping with the detrimental effects of arousal. Women may have a higher arousal threshold and so this may result in a higher trigger burden in women compared to men.”
The team looked at data from sleep monitors worn overnight by 8,001 men and women who were part of one of three studies. Participants were, on average, above the age of 65.
After adjusting for age, medical history, body mass index, total time spent sleeping and smoking habits, the researchers learned the frequency of sleep arousals was lower in women than in men, but the association with mortality was stronger in women.
Women who experienced arousals for more than 6.5% of their night’s sleep had a 12.8% risk of dying from heart disease, compared to 6.7% for women of similar ages in the general population. Meanwhile, the risk of dying from any cause in the same group of women with disrupted sleep was 31.5%, compared to women without it (21%).
Men with an arousal burden of more than 8.5% of their night’s sleep had a risk of 13.4% and 33.7% of dying from heart disease or any cause, respectively. Men of similar ages without disrupted sleep faced risks of death from heart disease or any cause of 9.6% and 28%, respectively.
Despite the association found between more sleep arousal and increased risk of death, the results do not mean disrupted sleep causes the increased risk, the researchers said. The team also did not consider the effects of medications on sleep arousal and only monitored people’s sleep for one night.
Disrupted sleep is known to be involved in the development of fat in arteries, according to Borja Ibáñez, the clinical research director at the Spanish National Cardiovascular Research Centre in Spain, who was not involved in the study. This may explain why people who experience unconscious wakefulness may have greater risks for heart problems.
Past research has revealed that how long a person sleeps is associated with increased risks of death in general, but it wasn’t as clearly understood whether there was a link with unconscious wakefulness and risk of death.
“A high arousal burden helps to identify patients who may be at higher risk of cardiovascular disease. We need to advise our patients to take care of their sleep and practice good sleep ‘hygiene,’” Linz said. “Measures to minimize noise pollution during the night, lose weight and treat sleep apnoea could also help to reduce the arousal burden.”