title: Sleep duration and breast cancer risk in the Breast Cancer Detection Demonstration Project follow-up cohort.
abstract: BACKGROUND
  Short sleep has been hypothesised to increase the risk of breast cancer. However, little is known about the association between sleep and different subtypes of breast cancer defined by hormone receptor status.
  
  
  METHODS
  Among 40 013 women in the Breast Cancer Detection Demonstration Project, including 1846 incident breast cancer cases, we prospectively examined self-reported weekday and weekend sleep duration in relation to breast cancer risk. We used multivariate Cox proportional hazards regression models to estimate relative risks (RRs) and 95% confidence intervals (CIs).
  
  
  RESULTS
  We found no association between sleep and overall breast cancer. However, we observed a decreased risk of ER+PR+ breast cancer (RR <6 vs 8 - 9 h (95% CI): 0.54 (0.31, 0.93), P for trend, 0.003) with shorter sleep duration.
  
  
  CONCLUSIONS
  Our finding does not support an association between sleep duration and overall breast cancer risk. However, the effect of sleep on different subtypes of breast cancer deserves further investigation.
authors.affiliation: Nutritional Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Rockville, MD, USA.
authors.forename: X
authors.initials: X
authors.lastname: Qian
authors.affiliation: Hormonal and Reproductive Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Rockville, MD, USA.
authors.forename: L A
authors.initials: LA
authors.lastname: Brinton
authors.affiliation: Biostatistics Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Rockville, MD, USA.
authors.forename: C
authors.initials: C
authors.lastname: Schairer
authors.affiliation: Nutritional Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Rockville, MD, USA.
authors.forename: C E
authors.initials: CE
authors.lastname: Matthews
mesh_terms: D000367:Age Factors; D000368:Aged; D015992:Body Mass Index; D001943:Breast Neoplasms / Q000175:diagnosis / Q000453:epidemiology*; D055088:Early Detection of Cancer; D015914:Estrogen Replacement Therapy / Q000706:statistics & numerical data; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008875:Middle Aged; D012307:Risk Factors; D012890:Sleep / Q000502:physiology*; D012959:Socioeconomic Factors; D013997:Time Factors