Sleep‐disordered breathing and risk of the breast cancer: A meta‐analysis of cohort studies

Abstract

Sleep-disordered breathing (SDB) is a common syndrome characterised by recurrent episodes of intermittent pauses or reductions of breathing and subsequent hypoxia during sleep. 1,2 The prevalence of SDB varies according to the characteristics of the population studied. 3 It has been reported that approximately half of the high-risk population may suffer from SDB, such as the elderly or obese people. 4 Pathophysiologically, SDB is related to intermittent hypoxia and continuously activated inflammation, which may partly explain the association between SDB and the pathogenesis of various chronic diseases. [5][6][7] Since intermittent hypoxia and low-grade inflammation has been involved in carcinogenesis, it has been suggested that SDB may be associated with a higher risk for cancer. 8-10 However, epidemiological studies evaluating the association between SDB and cancer risk showed inconsistent results. 11 An early meta-analysis including five retrospective cohort studies showed that SDB may increase the risk of cancer. 12 However, a subsequent meta-analysis including six studies failed to show that SDB is independently associated with a higher risk of overall cancer incidence or mortality. 13 Since both the studies reported overall cancer events rather than site-specific cancer, the inconsistency of the results may reflect that