MUNICH, GERMANY -- September 6, 2006 -- Sleep apnoea is known to be associated with a number of cardiovascular risk factors. It had also been found that adequate treatment made it possible to relieve the main symptoms, whether daytime sleepiness or cognitive impairment.
The results that have just been revealed at the annual congress of the European Respiratory Society (ERS) now prove for the first time that correct treatment of apnoea also considerably reduces cardiac mortality among sufferers from the syndrome.
It has been recognised for some time that obstructive sleep apnoea syndrome, which involved interruptions to breathing for at least ten seconds five times an hour or more, has important repercussions for the sufferer's overall health. In addition to causing snoring, largely as a result of the sudden resumption of breathing, apnoea results in serious disruption of sleep, debilitating fatigue and dangerous daytime sleepiness, as well as a range of other physiological problems.
For example, increasing numbers of studies in recent years have shown the degree to which sleep apnoea affects the cardiovascular system. An article in September's European Respiratory Journal proves for the first time that sleep apnoea even increases the risk of dying of a myocardial infarction.
The question arose as to whether treating the apnoea could save lives, in addition to providing the immediate benefits of better sleep, reduced snoring and improved concentration.
Indeed it can, according to three studies presented at the ERS Congress, conducted by teams working respectively in Basel (Switzerland), Bochum (Germany) and Burgos (Spain).
This is an extremely important discovery, given the increasing frequency of sleep apnoea syndrome in our ageing societies and the human and economic costs of cardiovascular disease.
The three studies were based on the treatment that has become standard for sleep apnoea, namely continuous positive airway pressure (CPAP). This involves the subject wearing a type of mask, though which air is delivered continuously into the airway, over the mouth and nose at night to reduce the interruptions to breathing.
Seven times more deaths in the untreated group
Werner Strobel, of the Department of Respiratory Medicine at Basel University Hospital (Switzerland) approached the question from the opposite angle. The study he presented in Munich demonstrates that not using this treatment represents an independent risk factor for cardiovascular mortality and stroke.
The prospective study conducted by his team from 2001 to 2003 covered 739 patients with an average age of 52 and an average apnoea/hypopnoea index of 38.7 interruptions to breathing per hour. Three-quarters of the subjects were male.
The researchers compared the 523 patients regularly treated by CPAP (CPAP group) to the 216 patients who had either chosen to stop the treatment or used it for less than two hours a night (non-CPAP group).
And the results presented by the team in Munich leave no room for any doubt: there were, proportionately, seven times as many deaths or disabling cardiovascular events in the non-CPAP group than in the CPAP group (6.4% against 0.9%).
If one looks only at deaths of cardiovascular origin, there were ten in the non-CPAP group and two in the CPAP group, which makes the difference, when adjusted for group size, even larger.
"So it is clear", Strobel told the Congress, "that we could achieve a significant reduction in cardiovascular mortality and/or disabling strokes in less than three years using CPAP."
Over seven years, cardiovascular risk reduced by 64%
A second team, working under Nikolaus Buchner, of the Department of Internal Medicine at Ruhr University in Bochum (Germany), monitored 638 apnoea sufferers over an average seven-year period. Of those patients, 499 were under treatment (essentially CPAP) and 139 had declined all treatment.
The results are equally eloquent. There were far fewer cardiovascular events (heart attack, stroke or acute coronary syndrome requiring revascularisation) recorded in the treated group than among the untreated subjects. Over a ten-year period, the proportion of patients who remained free of cardiovascular events was 78.5% and 54.2% respectively.
"Multivariate analysis of our results shows that treating sleep apnoea reduces the cardiovascular risk by 64%", Buchner concluded. "And that's regardless of the degree of apnoea, the subject's age (under or over 55) or any history of cardiovascular problems."
The importance of early diagnosis
Similar results were reported to the Congress by José Cordero Guevara and his team, of the Sleep Respiratory Problems Unit at Yagüe General Hospital in Burgos (Spain). Their study set out to monitor, from 1997 to 2002, a group of 939 patients, mainly male (over 90%), suffering either from obstructive sleep apnoea or from upper airway resistance syndrome.
While the CPAP-treated patients had a much higher apnoea/hypopnoea index than their untreated counterparts (an average of 44.3 hourly interruptions to breathing compared to 24.7) and a larger body mass index (BMI), they suffered fewer cardiovascular events among the subjects receiving treatment.
"Our study shows that there were only 1.9 cardiovascular events per 100 person-years in the CPAP group, compared to 2.96 in the untreated group", explained Cordero Guevara.
Hence, the results of these three studies demonstrate the importance to cardiovascular health of adequately treating sleep apnoea. Indirectly, they emphasise the need for early diagnosis of the condition.
"CPAP treatment of sleep apnoea should even be part of primary and secondary cardiovascular prevention, even in cases of relatively mild apnoea", Buchner told the Munich audience.
SOURCE: European Respiratory Society
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