A wake up call for sleep disordered breathingBMJ 1997; 314 doi: https://doi.org/10.1136/bmj.314.7084.839 (Published 22 March 1997) Cite this as: BMJ 1997;314:839
Evidence of ill effects is conflicting and inconclusive
- John A Fleetham, Professor of medicinea
Sleep disordered breathing is characterised by recurrent obstruction of the upper airway, which results in episodic asphyxia and interruption of the normal sleep pattern. Although manifestations of sleep disordered breathing have been described for many years, the condition has achieved wider recognition only in the past decade.1 2 3 It comprises a continuum–from chronic snoring to obstructive sleep hypopnoea to severe obstructive sleep apnoea–associated with progressively increasing clinical consequences.4
In this week's BMJ Ohayon and colleagues present data from questionnaires which confirm that sleep disordered breathing is common in Britain and is associated with increased use of medical care (p 860).5 The reported prevalence depends on the recognition threshold. A community based study by Young et al found that 2% of women and 4% of men had both daytime sleepiness and an apnoea and hypopnoea index greater than five episodes per hour.6 Thus, sleep disordered breathing is as prevalent as diseases such as asthma and diabetes, and some consider it to rival smoking as a major public health problem.7
Sleep disordered breathing remains undiagnosed in most patients, and doctors should routinely ask patients and their bed partners about snoring, interruption of breathing, and daytime sleepiness. Other symptoms include nocturnal choking, nocturnal awakenings, unrefreshing sleep, morning headache, and daytime fatigue. Most patients show no abnormality while awake, making it necessary to study sleeping patients. Increased awareness of the condition has increased demand for overnight sleep monitoring. Weight reduction, avoidance of alcohol, and relief of nasal obstruction should be addressed in every patient with sleep disordered breathing. For those who fail to improve on conservative treatment, a variety of treatments have been developed. Nasal continuous positive airway pressure (CPAP) is generally accepted as the first option, but oral appliances and corrective upper airway surgery are also widely used.
Increased demand for both diagnostic and therapeutic services prompted the systematic review published in this week's BMJ (p 851).8 9 This evaluated all studies published between 1966 and 1995 on the association between obstructive sleep apnoea and mortality and morbidity, and on the efficacy of nasal continuous positive airways pressure. The authors concluded that there was limited evidence of increased mortality or morbidity in patients with obstructive sleep apnoea, and that the evidence linking the condition to cardiac arrhythmias, ischaemic heart disease, left and right ventricular dysfunction, systemic and pulmonary hypertension, stroke, and automobile accidents was conflicting and inconclusive. They thought that most of the studies failed to adequately take into account the confounding factors of obesity, smoking, age, and alcohol consumption and that few were of sufficient quality to be able to determine the effectiveness of treatment. They concluded that, although nasal continuous positive airways pressure had been shown to improve objective daytime sleepiness, there were insufficient data to determine its effect on quality of life, morbidity, or mortality.
In our understanding of the natural history of sleep disordered breathing and the impact of treatment, we are at a similar stage as we were with systemic hypertension and hypercholesterolaemia several decades ago. There is clearly enough observational evidence of the ill effects of sleep disordered breathing and the benefits of treatment to justify further research. We now need long term population based prospective cohort studies, with stratification by severity of sleep disordered breathing and risk factors, to examine the association with morbidity and mortality. More studies are needed on the link between sleep disordered breathing and road traffic accidents, taking into account the potential confounding factors of shift work, alcohol and drug use, and annual distance travelled. Well designed randomised controlled trials with adequate sample sizes are needed to further determine the indications, benefits, and risks of each of the currently proposed treatments. These studies should include quality of life measurements, objective assessment of daytime performance, covert monitoring of compliance, and long term follow up.
The quality of research into sleep disordered breathing is becoming more rigorous as it moves up the hierarchy of study design.10 A short term randomised placebo controlled crossover study of nasal continuous positive airways pressure has shown improvement in daytime sleepiness.11 A short term randomised crossover study has demonstrated that oral appliances are an effective treatment in some patients with mild to moderate obstructive sleep apnoea.12 The United States National Institute of Health has recently funded a long term multicentre prospective study to examine the cardiovascular and cerebrovascular mortality and morbidity associated with sleep disordered breathing.
Sleep disordered breathing is common and has important implications for the population's health. Wright and Dye's recent systematic review has highlighted the limitations of current data about its associations and the effectiveness of treatment.8 9 Agencies funding health services, in collaboration with the manufacturers of the different treatments, need to fund well designed studies of the effects of sleep disordered breathing and the benefits of treatment.