title: Sleep apnea and the subsequent risk of breast cancer in women: a nationwide population-based cohort study.
abstract: 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.
  
  
  CONCLUSIONS
  The findings of our population-based study suggest an association between SA and an increased risk of breast cancer in women.
authors.affiliation: Department of Healthcare Management, Yuanpei University, HsinChu, Taiwan.
authors.forename: Wei-Pin
authors.initials: WP
authors.lastname: Chang
authors.affiliation: Department of Psychiatry, Taipei Veterans General Hospital, Taipei, Taiwan; Division of Psychiatry, School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Mu-En
authors.initials: ME
authors.lastname: Liu
authors.affiliation: Department of Clinical Pharmacy, School of Pharmacy, Taipei Medical University, Taipei, Taiwan.
authors.forename: Wei-Chiao
authors.initials: WC
authors.lastname: Chang
authors.affiliation: Department of Psychiatry, Taipei Veterans General Hospital, Taipei, Taiwan; Division of Psychiatry, School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors.forename: Albert C
authors.initials: AC
authors.lastname: Yang
authors.affiliation: Nursing Department, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan.
authors.forename: Yan-Chiou
authors.initials: YC
authors.lastname: Ku
authors.affiliation: Department of Healthcare Management, Yuanpei University, HsinChu, Taiwan.
authors.forename: Jei-Tsung
authors.initials: JT
authors.lastname: Pai
authors.affiliation: Department of Healthcare Management, Yuanpei University, HsinChu, Taiwan.
authors.forename: Yea-Wen
authors.initials: YW
authors.lastname: Lin
authors.affiliation: Department of Psychiatry, Taipei Veterans General Hospital, Taipei, Taiwan; Division of Psychiatry, School of Medicine, National Yang-Ming University, Taipei, Taiwan. Electronic address: tsai610913@gmail.com.
authors.forename: Shih-Jen
authors.initials: SJ
authors.lastname: Tsai
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000209:etiology / Q000401:mortality; D015331:Cohort Studies; D018572:Disease-Free Survival; D005260:Female; D005500:Follow-Up Studies; D006306:Health Surveys; D006801:Humans; D000860:Hypoxia / Q000150:complications / Q000453:epidemiology; D008875:Middle Aged; D016016:Proportional Hazards Models; D012306:Risk; D020181:Sleep Apnea, Obstructive / Q000150:complications / Q000453:epidemiology* / Q000401:mortality; D013624:Taiwan
keywords: Breast cancer; Population-based study; Sleep apnea; Taiwan population; Women