Time to wake the giant of obstructive sleep apnoea

Abstract

Earlier this year, The Lancet Respiratory Medicine reported staggering global estimates for the number of people aged 30–69 years who are affected by obstructive sleep apnoea (OSA). The figure of nearly a billion adults with mild to severe OSA suggests that the condition is both underdiagnosed and under-recognised. The paper also highlighted the paucity of quality evidence available to derive estimates of the prevalence and burden of OSA. To provide such global data is important because the condition, especially severe OSA, is associated with neurocognitive impairment, reduced quality of life, and an increased risk of hypertension, cancer, and metabolic, cardiovascular, and cerebrovascular diseases. According to the UK National Institute for Health and Care Excellence (NICE), OSA is defined by repeated episodes of apnoea (temporary cessation of breathing) and hypopnoea (slow or shallow breathing), loud snoring, and excessive daytime sleepiness. The degree of OSA is classified by the number of apnoea and hypopnoea events, recorded by respiratory polygraphy or polysomnography, in an apnoea–hypopnoea index (AHI). Most classifications denote mild cases as 5–15 events per h, moderate as 15–30 per h, and severe as over 30 events per h. Many studies have suggested a male predominance of OSA, and US researchers using data from the multi-ethnic study of atherosclerosis (MESA) have investigated why that might be. Their findings suggest that AHI varies in men and women according to the definition of events, and that significant sex differences exist for AHI recorded during non-REM sleep (relatively low AHI in women) but not during REM (so-called dream) sleep. The study raises the possibility that combining events across sleep states could lead to the underdiagnosis of OSA in women. There is a pressing need for further studies to refine approaches to diagnosis and to lay the groundwork for precision medicine. OSA can be treated using continuous positive airway pressure (CPAP) therapy. However, deciding which patients to treat and how to measure effectiveness can be difficult. Two randomised clinical trials using CPAP, recently published in the journal, had differing findings. The first trial, by Alison Wimms and colleagues, assessed the use of 3 months of CPAP treatment plus standard care versus standard care alone in mild cases of OSA, and found positive effects on quality of life, as measured by the Short Form-36 questionnaire vitality scale. By contrast, Ferran Barbé and colleagues assessed CPAP use plus usual care versus usual care alone in OSA patients with acute coronary syndrome, and found no effects on the primary endpoint of a composite of cardiovascular events or on quality of life. These studies highlight difficulties in assessing the usefulness of such treatments in terms of endpoints used, masking, selection of populations that might benefit, and differences in the diagnostic criteria used to define OSA and its severity across studies. CPAP can be difficult to tolerate for some patients, which can result in poor compliance rates, and new treatments and technologies are needed to tackle the high prevalence and morbidity of OSA. Weight loss has been suggested as an alternative treatment option, as high body-mass index is a major risk factor for OSA. Other potentially modifiable risk factors include alcohol consumption. With the increasing obesity crisis and increased life expectancy in many populations across the globe, the number of OSA cases looks set to rise further. Around 8 million people aged 30–69 years might be affected by OSA in the UK alone. Interestingly, a recent position statement from the American Academy of Sleep Medicine highlights that chronic opioid use could be another contributing factor, which is especially worrying given the need for such medication in many chronic and end-stage respiratory conditions. In Maslow's hierarchy of need, a good night's sleep is quite rightly listed at the base of the pyramid as one of life's essentials. Despite this, there is still a lack of awareness of OSA and its consequences among the general public. Education about the signs and symptoms of OSA is becoming increasingly important as we anticipate an increase in global prevalence. We welcome efforts to strengthen the evidence base to guide the diagnosis and treatment of OSA, with a view to minimising the substantial short-term and longer-term consequences of the condition. NICE are due to release updated guidelines within the next year, the first update in 10 years, and hopefully through their dissemination, an increase in awareness of OSA, and improved care for those affected, will be seen, both in the UK and globally.