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BMJ No 7104 Volume 315 Letters Saturday 9 August 1997 Obstructive sleep apnoeaAuthors' replyEditor,These letters show the uncertainty about sleep apnoea. The common claim of significant associations of sleep apnoea with premature death and vascular morbidity(1-2) is reiterated by John Shneerson and Ian Smith, and Allan I Pack and Terry Young; however, J R Stradling and R J O Davies, and G J Gibson and K Prowse, agree with us that the evidence is weak. Patients will be reassured that assertions about associations between sleep apnoea and disability and death are unfounded or premature. Uncertainty also exists over the role of weight reduction. Shneerson and Smith suggest that weight loss is the first line of treatment, yet Gibson and Prowse believe that patients should begin treatment with continuous positive airways pressure immediately. The strong statistical association suggests that sleep apnoea is frequently a symptom of obesity. Surely it is logical to tackle the cause rather than the symptom, particularly in view of the other health benefits derived from weight loss. A review has shown that weight loss can be maintained.(3) Our systematic approach ensures a rigorous and scientific review of the evidence. All data from relevant studies are shown in the tables so readers can derive their own conclusions. This is an advance on the more ad hoc surveys such as that by the Royal College of Physicians referred to by S J G Semple and D R London(2) or those reviews by enthusiasts who often selectively quote research which supports their view and ignore methodological quality. Pack and Young show this lack of rigour by their failure to appreciate not only the importance of adjusting for confounding but also the fact that brief rises in blood pressure have not been shown to be a significant risk factor for vascular morbidity. Hopefully, the longitudinal studies in progress are better designed than the relatively poor research available. We did not say that treatment with continuous positive airways pressure is unjustified. We stated that there can be large benefits but that these predominantly seem to occur in patients with severe sleep apnoea. This is echoed in the Australian report, which supports our conclusions about the paucity of good epidemiological research and finds that there is `very little evidence of effectiveness' of continuous positive airways pressure for patients with sleep apnoea of mild to moderate severity.(4) We acknowledge the support from Pack and Young for our call for further trials on treatment with continuous positive airways pressure. Clinicians, and their professional organisations, have a responsibility to determine in which patients treatment is beneficial and cost effective. To suggest, as some of these authors do, that the NHS should invest extensively in services for 2-4% of the middle aged population on the basis of a case report or a new trial of 16 patients is irresponsible.(5) John Wright
Bradford Royal Infirmary, Trevor Sheldon
Centre for Reviews and Dissemination, References 1 Phillipson E A. Sleep apnoea - a major public health problem. N Engl J Med 1993;328;1271-3. 2 Royal College of Physicians. Sleep apnoea and related conditions. A report of a working party. London: RCP, 1993. 3 The prevention and treatment of obesity. Effective Health Care 1997; No 3. 4 Australian Health Technology Advisory Committee. The effectiveness and cost effectiveness of nasal continuous positive airways pressure (nCPAP) in the treatment of obstructive sleep apnoea. Canberra: Government Public Service, 1996. 5 Engleman H M, Martin S E, Dreary I J, Douglas N J. Effect of CPAP therapy on daytime function in patients with mild sleep apnoea/hypopnoea syndrome. Thorax 1997;52:114-9.
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