The Association of Sleep Apnea and Cancer in Veterans

Objective To test the association between preexisting obstructive sleep apnea (OSA) and subsequent cancer in a large long-term cohort of veteran patients. Study Design Retrospective matched cohort study. Setting The Veterans Affairs Health Care System. Subjects and Methods All veteran patients diagnosed with OSA between 1993 and 2013 by International Classification of Diseases, Ninth Revision (ICD-9) codes in any Veterans Affairs facility and veteran patients without an OSA diagnosis, matched to patients with OSA by age and index year. Cancer diagnoses were identified by ICD-9 codes for the time period at least 2 years after OSA diagnosis or index date. We tested the association between OSA and cancer using multivariate Cox regression with time since cohort entry as the time axis, adjusting for potential confounders. Results The cohort included 1,377,285 patients (726,008 with and 651,277 without an OSA diagnosis) with mean age of 55 years, predominantly male (94%), a minority obese (32%), and median follow-up of 7.4 years (range, 2.0-25.2). The proportion of patients diagnosed with cancer was higher in those with vs without an OSA diagnosis (8.3% vs 3.6%; mean difference 4.8%; 95% confidence interval [CI], 4.7%-4.8%; P < .001). After adjusting for age, sex, year of cohort entry, smoking status, alcohol use, obesity, and comorbidity, the hazard of incident cancer was nearly double in patients with vs without an OSA diagnosis (hazard ratio, 1.97; 95% CI, 1.94-2.00; P < .001). Conclusion Preexisting OSA was strongly associated with subsequent cancer in this veteran cohort, independent of several known cancer risk factors. These findings suggest that OSA may be a strong, independent risk factor for subsequent cancer development.