Obstructive sleep apnea severity and subsequent risk for cancer incidence

In vitro and animal models suggest that obstructive sleep apnea (OSA) increases cancer risk. However, the impact of OSA severity on cancer risk is poorly understood. We conducted a case-cohort study (a variant of the case-control study design), nested in a cohort of patients with a clinical diagnosis of OSA. OSA patients diagnosed between 2005 and 2013 were linked to a population-based cancer registry to identify cancers diagnosed subsequent to OSA between 2005 and 2015. Medical records were reviewed for a representative sample of 1162 OSA patients from this cohort (including 24 with subsequent cancer), and for an additional 304 OSA patients diagnosed with cancer; information regarding OSA severity indicators, including apnea-hypopnea index (AHI) was abstracted from these records. Adjusted Cox proportional hazards regression were used to calculate hazard ratios (HR) and 95% confidence intervals (CI) for associations of OSA severity indicators on cancer incidence. Compared with individuals in the lowest AHI category (5-14.9), indicating mild OSA, the adjusted HR (95% CI) for cancer incidence associated with having moderate (15-29.9) or severe (30+) OSA were 0.72 (0.40-1.29) and 0.87 (0.52-1.45) respectively. Associations with other severity indicators were not significantly associated with cancer. However, the proportion of patients with severe OSA (AHI ≥30) was consistently higher across numerous cancer sites relative to the subcohort, suggesting increased cancer risk relative to patients with less severe OSA. The absence of significant associations with OSA severity measures suggest that the underlying mechanisms deserve further investigation.