Women who experience more frequent and longer periods of cortical arousal during night-time sleep have an increased risk of dying from diseases of the heart and blood vessels, researchers report today.
A Dutch study, published in the European Heart Journal, found that women who experienced cortical arousal, also known as unconscious wakefulness, most often and for longer periods of time had nearly double the risk of dying from cardiovascular disease when compared to the risk in general female population.
The association was less clear in men, with their risk of cardiovascular death increasing by just over a quarter compared to the general male population.
Dominik Linz, associate professor in the cardiology department at Maastricht University Medical Centre, The Netherlands, said: “A common trigger for nocturnal arousals is obstructive sleep apnoea when breathing stops and the arousal system ensures the activation of our body to change our sleep position and to reopen the upper airway.
“Another cause of arousals can be ‘noise pollution’ during the night by, for example, night-time aircraft noise. Depending on the strength of the arousal, a person might become consciously aware of the environment, but often that is not the case.
“Typically, people will feel exhausted and tired in the morning because of their sleep fragmentation but will not be aware of the individual arousals.”
Although previous studies have shown that too little or too much sleep is associated with increased risks of death from cardiovascular or other causes, it was unclear if there was also a link with the arousal burden during a night’s sleep and the risk of death.
Professor Linz, working with a team from the University of Adelaide, Australia, led by associate professor Mathias Baumert from the School of Electrical and Electronic Engineering, examined data from sleep monitors worn overnight by men and women taking part in one of three studies: 2,782 men in the Osteoporotic Fractures in Men Sleep Study (MrOS); 424 women in the Study of Osteoporotic Fractures (SOF); and 2,221 men and 2,574 women in the Sleep Heart Health Study (SHHS).
The participants were followed up over several years, which ranged from an average of six years (SOF) to 11 years (MrOS).
After adjusting for factors that could affect the results such as total sleep duration, the researchers found women had an arousal burden that was lower than men.
However, those whose arousal burden accounted for more than 6.5% of their night’s sleep had a greater risk of dying from cardiovascular disease than women with a lower arousal burden: double the risk in SOF and 1.6 times the risk in SHHS. Their risk of dying from all causes was also increased by 1.6 times in SOF and 1.2 times in SHHS.
When the researchers examined the data from women in both studies, they found those with an arousal burden of more than 6.5% had a 12.8% risk of dying from cardiovascular disease, nearly double that of women of a similar age in the general population who had a risk of 6.7%.
The risk of dying from any cause was 21% among women in the general population, which increased to 31.5% among women in the two studies with an arousal burden of more than 6.5%
Men with an arousal burden accounting for more than 8.5% of their night’s sleep had 1.3 times greater risk of dying from cardiovascular disease (MrOS) or any cause (SHHS), compared to men with lower arousal burdens, but findings for increased risk of death from any cause in MrOS or cardiovascular disease in SHHS were not statistically significant.
Professor Linz said: “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. This may explain the relatively higher risk of cardiovascular death in women. 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.”
Professor Baumert added: “In order to include assessment of arousal burdens into routine strategies for reducing the risk of cardiovascular disease, we need easily scalable, widely accessible and affordable techniques to estimate the duration and fragmentation of sleep and to detect arousals. Wearable devices for measuring activity and changes in breathing patterns may provide important information.”
Study limitations include that it was conducted in older, mainly white people and the possible effect of medications was not considered. Monitoring of the participants’ sleep was conducted on a single night and so does not take account of night-to-night variations.
Shahrbabaki SS, Linz D, Hartman S et al. Sleep arousal burden is associated with long-term all-cause and cardiovascular mortality in 8,001 community-dwelling older men and women. European Heart Journal. 19 April 2021; doi:10.1093/eurheartj/ehab151
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