Sleep apnea and the subsequent risk of breast cancer in women: a nationwide population-based cohort study.

BACKGROUND:Hypoxia plays an important role in the development of solid tumors. Intermittent hypoxia is the hallmark of sleep apnea (SA). We tested the hypothesis that SA may increase the risk of breast cancer in Taiwan by using a population-based data set. METHODS:Our study cohort consisted of women diagnosed with SA between January 2003 and December 2005 (n = 846). For each SA patient, five age-matched control women were randomly selected as the comparison cohort (n = 4230). All participant cases were followed for 5 years from the index date to identify the development of breast cancer. Cox proportional-hazards regression was performed to evaluate the 5-year breast-cancer-free survival rates. RESULTS:Forty-four women developed breast cancer during the 5-year follow-up period, among whom 12 were SA patients and 32 were in the comparison cohort. The adjusted hazard ratio (HR) of breast cancer in patients with SA was higher [HR, 2.09; 95% confidence interval (CI), 1.06-4.12; P < 0.05] than that of the controls during the 5-year follow-up. Despite not meeting statistical significance, we found increases in the risk of breast cancer in women aged 30-59 years (HR, 2.06; 95% CI, 0.90-4.70) and ≥60 years (HR, 3.05; 95% CI, 0.90-10.32) compared with those aged 0-29 years. CONCLUSION:The findings of our population-based study suggest an association between SA and an increased risk of breast cancer in women.