Associations of Self-reported Obstructive Sleep Apnea with Total and Site-specific Cancer Risk in Older Women: A Prospective Study.

BACKGROUND Chronic intermittent hypoxia resulting from obstructive sleep apnea (OSA) may activate multiple carcinogenic pathways and lead to cancer development. METHODS We prospectively examined the association between OSA and cancer risk among 65,330 women in the Nurses' Health Study who were free of cancer in 2008 (mean age: 73.3 years). Incident cancer diagnoses were collected until 2016 and confirmed by pathology reports. Clinically-diagnosed OSA was self-reported in 2008 and updated in 2012. We used time-dependent Cox regression to estimate hazard ratios (HR) for the associations of OSA with total and site-specific cancer risk. RESULTS We documented 5,257 incident cancer diagnoses during follow-up. In the age-adjusted model, OSA was associated with a 15% (95% CI: 1.03, 1.29) increase in total cancer risk. The association became non-significant after adjustment for multiple cancer risk factors (HR: 1.08; 95% CI: 0.96, 1.21). When examining cancer risk by site, OSA was associated with significantly increased risk for lung (fully-adjusted HR: 1.52; 95% CI: 1.07, 2.17), bladder (fully-adjusted HR: 1.94; 95% CI: 1.12, 3.35) and thyroid cancer (fully-adjusted HR: 2.06; 95% CI: 1.01, 4.22) and possibly increased risk for kidney cancer (fully-adjusted HR: 1.59; 95% CI: 0.84, 3.01). When grouping cancer sites by risk factor profiles, OSA was positively associated with smoking-related cancers (fully-adjusted HR: 1.37; 95% CI: 1.11, 1.67), and this association was stronger in never smokers than ever smokers. CONCLUSION While OSA was not independently associated with overall cancer risk in older women, significant associations were observed for smoking-related cancers, especially in non-smokers.