Disrupted sleep linked to higher risk of death, particularly in women, study shows

A study has shown a clear link between disrupted sleep and a higher risk of death, particularly in women.

The study, published in the European Heart Journal, monitored 8001 men and women and found that women who suffered from unconscious wakefulness had an increased risk of dying from cardiovascular disease which was nearly double that seen in the general female population.

The association was not so clear in men and it seemed that their risk of cardiovascular death due to interrupted sleep increased by just over a quarter, in comparison with risks seen the general male population.

Unconscious wakefulness is a normal part of sleep which happens spontaneously and plays a part in the body’s ability to respond to danger. Triggers can include noise, obstructed breathing, pain, trauma, temperature, light and limb movements.

Dominik Linz, associate professor in the cardiology department at Maastricht University Medical Centre in The Netherlands, pointed out that a common trigger for unconscious wakefulness is sleep apnoea.

Sleep apnoea is a sleep disorder where sufferer’s breathing repeatedly stops and starts during sleep. This causes people to wake slightly as the body changes position to reopen the airways.

Professor Linz said: “Typically, people will feel exhausted and tired in the morning because of their sleep fragmentation but will not be aware of the individual arousals.”

Previous research has illustrated that sleep duration is linked to increased risks of death from cardiovascular or other causes, both for individuals who sleep too much and those who sleep too little.

However, until now, it was not known if there was also a link between arousal burden (a combination of the number of arousals and how long they go on for) and risk of death.

The study was carried out by a team led by associate professor Mathias Baumert from the School of Electrical and Electronic Engineering at the University of Adelaide in Australia and Professor Linz from Maastricht University Medical Centre in The Netherlands.

Data from sleep monitors worn overnight by men and women in one of three studies was examined by researchers.

In total, data from 2782 men in the Osteoporotic Fractures in Men Sleep Study, 424 women in the Study of Osteoporotic Fractures, and 2221 men and 2574 women in the Sleep Heart Health Study was examined.

The average ages those taking part in the studies were 77, 83 or 64 years respectively.

Participants were followed up over a period of several years, ranging from an average of six to 11 years and data recorded accordingly.

Having adjusted results to take other influencing factors into account, researchers found that women’s arousal burden was lower than that of men.

Indeed, it appears that women who had an arousal burden, which made up more than 6.5 per cent of their night’s sleep, had a greater risk of dying from cardiovascular disease than women who had a lower arousal burden.

Overall, it appeared that women with an arousal burden of more than 6.5 per cent had a 12.8 per cent risk of dying from cardiovascular disease. This figure was almost double that of women of a similar age in the general population who were thought to have a risk of dying from cardiovasular disease of 6.7 per cent.

Generally speaking, the risk of dying from any cause was 21 per cent among women in the general population. However, this increased to 31.5 per cent among women in the two studies who had an arousal burden totalling more than 6.5 per cent.

On the other hand, men with an arousal burden which made up more than 8.5 per cent of their night’s sleep had a risk of 13.4 per cent and 33.7 per cent respectively of dying from cardiovascular disease or any cause.

In the general population, men of similar ages had a risk factor of 9.6 per cent and 28 per cent, respectively.

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.”

The professor went on to add that arousal burdens can be affected by age, BMI and severity of the sleep apnoea. He explained: “While age cannot be changed, BMI and sleep apnoea can be modified and may represent an interesting target to reduce arousal burdens. Whether this will translate into lower risks of dying from cardiovascular disease warrants further study.”

Meanwhile, Professor Baumert said: “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.”

He suggested that wearable devices for “measuring activity and changes in breathing patterns” could be key to this.

The study was limited in that it was conducted in older, mainly white people and so its findings cannot be extrapolated to other races or to younger men and women.

The possible effect of medications was also not taken into account and monitoring only took place over a single night.

The European Society of Cardiology also pointed out that results are only able to show an association between greater sleep arousal burden and increased risk of death. Therefore it cannot be concluded that that sleep arousals cause the increased death risk.