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In 1997 we published a systematic review on the health effects of obstructive sleep apnoea and the effectiveness of treatment with CPAP.1 This generated much controversy and considerable correspondence. About half the letters received by the authors suggested that the paper was just stating the obvious, the other half that the paper was completely inaccurate. To help clarify our findings this paper will discuss the public health impact of sleep apnoea and the rationale behind systematic reviews.
In recent years several traditional style reviews in leading medical journals have suggested the importance of sleep apnoea.2-4 These have claimed that sleep apnoea causes premature death, hypertension, heart disease, stroke, pulmonary hypertension, and road traffic accidents. The high prevalence of 2–4% of the middle aged population5 led an editorial writer in the New England Journal of Medicine to claim that the “staggering” impact of sleep apnoea was as big a public health hazard as smoking.2 If so, sleep apnoea would clearly be of major public concern.
The problem with traditional reviews is that they can be haphazard, biased and reflect the personal prior beliefs or interests of individual reviewers.6 Systematic reviews apply strict scientific criteria in an attempt to reduce this bias. They provide a more objective approach to summarising the large number of biomedical research papers and allow us to identify gaps in the research. In addition, systematic reviews can help increase understanding about the generalisability, consistency, and precision of results of individual trials. This is not the same as “evidence based medicine” but they can inform individual clinical decisions as well as health policy.
Like all good science, systematic reviews are based on rigorous methodology. This includes: (1) construction of a clearly focused question; (2) explicit and thorough search of the literature including non-English language …