Purpose: We aimed to study the effect of obstructive sleep apnea (OSA) on cancer risk.

Methods: We searched PubMed, Embase, and Cochrane databases for relevant studies. The qualities of included studies were assessed using Newcastle-Ottawa Scale (NOS). Unadjusted and adjusted analyses were performed. We also conducted subgroup analyses stratified by gender, severity of OSA, study design, and cancer type.

Results: After literatures search, 18 studies were included in the present study. In the unadjusted analysis, we discovered an increased cancer risk in patients with OSA with a pooled relative risk (RR) in the OSA group of 1.49 (95% confidence interval (CI): 1.32-1.69, I² = 32%, P = 0.15). In adjusted analysis, OSA correlated with cancer risk (RR: 1.36, 95% CI: 1.18-1.56, I² = 54%, P < 0.01). In subgroup stratified by gender and OSA severity, OSA statistically with cancer risk in females (RR: 1.27, 95% CI: 1.06-1.51) and moderate to severe OSA groups (RR: 2.62, 95% CI: 1.64; 4.19). In subgroup stratified by study design, a trend toward statistically significant differences was observed in prospective studies (RR: 1.21, 95% CI: 0.99-1.48) and cross-sectional studies (RR: 1.81, 95% CI: 0.96-3.41). Patients with OSA in the retrospective study group had a statistically higher chance of developing cancer (RR: 1.41, 95% CI: 1.11-1.79). When stratified by cancer group, statistically significant differences was observed in many types of cancer (breast cancer: RR: 1.32, 95% CI: 1.03-1.70; central nervous system cancer: RR: 1.71, 95% CI: 1.06-2.75; kidney cancer: RR: 1.81, 95% CI: 1.20-2.74; liver cancer: RR: 1.19, 95% CI: 1.10-1.29; and pancreatic cancer: RR: 1.23, 95% CI: 1.14-1.33).

Conclusions: This systematic review and meta-analysis suggests that obstructive sleep apnea may increase risk of cancer.