More research needed into effect of sleep apnoea on elderly, scientists say
1 July 2008
The call comes as the team at Imperial College London publish a study showing that older people have a delayed cardiovascular response to arousal from sleep that may offer protection from developing high blood pressure and heart disease.
Audio: Long pauses in breathing or snoring can be an indication of sleep apnoea.
Obstructive sleep apnoea (OSA) occurs when the muscles of the throat relax, leading to a blockage of the airway and causing frequent arousal from sleep - in severe cases as often as once a minute. It causes an acute cardiovascular response as the person wakes: their blood pressure rises and their heart races as they gasp for breath. Over the long term, this cardiovascular response can lead to high blood pressure and an increased risk of heart attack and stroke. However, many people will be unaware that they suffer from the condition, which can cause extreme tiredness through lack of sleep.
Doctors are increasingly aware of the condition amongst younger and middle-aged people, who are more likely to be diagnosed with the condition. Following a report by the National Institute for Clinical Excellence (NICE), Continuous Positive Airway Pressure (CPAP) machines, which keep the airway open during sleep, were recently made available across the UK on the NHS to treat the condition.
"Waking up through sleep apnoea is like being woken up by your mobile phone ringing," explains Dr Mary Morrell from the Clinical and Academic Unit of Sleep and Ventilation at the Royal Brompton Hospital, and Imperial College, London. "Imagine your mobile ringing every minute throughout the night - that's how severe the condition can be."
In older people, the condition is less well understood and rarely diagnosed, despite as many as one in five older people suffering from the condition - ten times the number of younger people. The symptoms, which may include high blood pressure and poor memory, are easily confused with other diseases common in old age. In a recent study of elderly people in US nursing homes, less than one per cent of people were diagnosed as having sleep apnoea.
In research published today in the journal ‘Sleep’, Dr Morrell and colleagues have shown that the cardiovascular system responds differently between younger and older people in both timing and severity.
"We found that the increase in heart rate and blood pressure was significantly reduced in older people and that the response was delayed when compared to younger people," says Elizabeth Goff, first author on the study.
25 healthy adults under the age of 40 and 20 over the age of 60 took part in the study. Their brain activity, heart rate, blood pressure and breathing patterns were monitored. Once they had reached a stage of steady sleep, they were played a short tone, long enough to disturb them from their sleep but not to fully rouse them. This caused an average increase in blood pressure of 18mmHg in the younger volunteers compared to a 13mmHg change in the older volunteers. In the younger volunteers, it caused their heart rate to increase by around 12 beats per second, compared to an increase of only six beats per second for the older people. These changes tended to occur just over a second later in older people.
"We believe that this response may be caused by the changes in the structure and function of the cardiovascular system in older people," says Miss Goff. "It might even offer protection to older people, who commonly wake more often during the night."
As people age, their blood vessels become less flexible, slowing blood flow, meaning that blood pressure rises more slowly in response to these brief awakenings. Similarly, the autonomic system, which controls heart rate, becomes less responsive. While sleep apnoea leads to hypertension in younger people, researchers do not yet know how it affects older people: whether the delayed and smaller response to waking from sleep in older people does indeed protect them or whether some other factor is present.
"The big question is 'how does sleep apnoea affect the elderly?'," says Dr Morrell. "Our population is getting older and we have large numbers of people aged over 65. If the mechanisms that cause sleep apnoea differ in older people, then so might the symptoms, which may require different treatment strategies. This could have significant cost implications at a societal level. The important question is: 'can we improve the health-related quality of life in older people?'"
Image: Libby Welch, Wellcome Images
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Notes for editors
1. Resnick HE, Phillips B. Documentation of sleep apnea in nursing homes: United States 2004. J Am Med Dir Assoc. 2008 May;9(4):260-4. Epub 2008 Apr 8.
2. Goff, E et al. The Cardiovascular Response to Arousal from Sleep Decreases with Age in Healthy Adults. Sleep, published 1 July 2008.
3. The Wellcome Trust is the largest charity in the UK. It funds innovative biomedical research, in the UK and internationally, spending over £600 million each year to support the brightest scientists with the best ideas. The Wellcome Trust supports public debate about biomedical research and its impact on health and wellbeing.
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