Obstructive Sleep Apnea and Colorectal Cancer: A Systematic Review and Meta-Analysis.

Background: Obstructive sleep apnea (OSA), characterised by recurrent episodes of upper airway collapse, intermittent hypoxia (IH) and sleep fragmentation (SF), has been associated with carcinogenesis in pre-clinical models. The relationship between OSA and colorectal cancer (CRC) in clinical studies is controversial.

Aim: The objective of this meta-analysis was to assess the association between OSA and CRC.

Methods: Two independent investigators searched studies indexed in CINAHL, MEDLINE, EMBASE, the Cochrane Database and clinicaltrials.gov that were randomised controlled trials (RCT) or observational studies evaluating the relationship between OSA and CRC. Studies were included if they had available odds ratios (OR) and relative risks (RR) or if hazard ratios (HR) with 95% confidence intervals (CI) were available and a reference group composed of participants who did not have OSA. OR and 95% CI were calculated using a random-effect, generic inverse variance method.

Results: We included four observational studies out of 85 records, comprising a combined cohort of 5,651,662 identified patients in the data analysis. Three studies used polysomnography to identify OSA. The pooled OR of CRC in patients with OSA was 1.49 (95% CI, 0.75 to 2.97). The statistical heterogeneity was high with I of 95%.

Conclusions: Our study is unable to conclusively point towards OSA being a risk factor in the development of CRC, despite the plausible biological mechanisms for this. Further well-designed prospective RCT assessing the risk of CRC in patients with OSA and the impact of OSA treatments on the incidence and prognosis of CRC are needed.