title: Population-wide Impact of Long-term Use of Aspirin and the Risk for Cancer.
abstract: OBJECTIVE
  The US Preventive Services Task Force recently recommended the use of aspirin to prevent colorectal cancer and cardiovascular disease among many US adults. However, the association of aspirin use with the risk for other cancer types and the potential population-wide effect of aspirin use on cancer, particularly within the context of screening, remain uncertain.
  
  
  OBJECTIVE
  To examine the potential benefits of aspirin use for overall and subtype-specific cancer prevention at a range of doses and durations of use and to estimate the absolute benefit of aspirin in the context of screening.
  
  
  METHODS
  Two large US prospective cohort studies, the Nurses' Health Study (1980-2010) and Health Professionals Follow-up Study (1986-2012), followed up 135 965 health care professionals (88 084 women and 47 881 men, respectively) who reported on aspirin use biennially. The women were aged 30 to 55 years at enrollment in 1976; the men, aged 40 to 75 years in 1986. Final follow-up was completed on June 30, 2012, for the Nurses' Health Study cohort and January 31, 2010, for the Health Professionals Follow-up Study cohort, and data were accessed from September 15, 2014, to December 17, 2015.
  
  
  METHODS
  Relative risks (RRs) for incident cancers and population-attributable risk (PAR).
  
  
  RESULTS
  Among the 88 084 women and 47 881 men who underwent follow-up for as long as 32 years, 20 414 cancers among women and 7571 cancers among men were documented. Compared with nonregular use, regular aspirin use was associated with a lower risk for overall cancer (RR, 0.97; 95% CI, 0.94-0.99), which was primarily owing to a lower incidence of gastrointestinal tract cancers (RR, 0.85; 95% CI, 0.80-0.91), especially colorectal cancers (RR, 0.81; 95% CI, 0.75-0.88). The benefit of aspirin on gastrointestinal tract cancers appeared evident with the use of at least 0.5 to 1.5 standard aspirin tablets per week; the minimum duration of regular use associated with a lower risk was 6 years. Among individuals older than 50 years, regular aspirin use could prevent 33 colorectal cancers per 100 000 person-years (PAR, 17.0%) among those who had not undergone a lower endoscopy and 18 colorectal cancers per 100 000 person-years (PAR, 8.5%) among those who had. Regular aspirin use was not associated with the risk for breast, advanced prostate, or lung cancer.
  
  
  CONCLUSIONS
  Long-term aspirin use was associated with a modest but significantly reduced risk for overall cancer, especially gastrointestinal tract tumors. Regular aspirin use may prevent a substantial proportion of colorectal cancers and complement the benefits of screening.
authors.affiliation: Department of Nutrition, Harvard T. H. Chan School of Public Health, Boston, Massachusetts2Clinical and Translational Epidemiology Unit, Massachusetts General Hospital and Harvard Medical School, Boston3Division of Gastroenterology, Massachusetts General.
authors.forename: Yin
authors.initials: Y
authors.lastname: Cao
authors.affiliation: Department of Nutrition, Harvard T. H. Chan School of Public Health, Boston, Massachusetts4Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, Massachusetts 5Department of Biostatistics, Harvard T. H. Chan School of Public Heal.
authors.forename: Reiko
authors.initials: R
authors.lastname: Nishihara
authors.affiliation: Department of Nutrition, Harvard T. H. Chan School of Public Health, Boston, Massachusetts.
authors.forename: Kana
authors.initials: K
authors.lastname: Wu
authors.affiliation: Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, Massachusetts 5Department of Biostatistics, Harvard T. H. Chan School of Public Health, Boston, Massachusetts.
authors.forename: Molin
authors.initials: M
authors.lastname: Wang
authors.affiliation: Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, Massachusetts 6Department of Medical Oncology, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts7Department of Pathology, Brigham and Women's Hosp.
authors.forename: Shuji
authors.initials: S
authors.lastname: Ogino
authors.affiliation: Department of Nutrition, Harvard T. H. Chan School of Public Health, Boston, Massachusetts4Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, Massachusetts 8Channing Division of Network Medicine, Brigham and Women's Hospital a.
authors.forename: Walter C
authors.initials: WC
authors.lastname: Willett
authors.affiliation: Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, Massachusetts.
authors.forename: Donna
authors.initials: D
authors.lastname: Spiegelman
authors.affiliation: Department of Medical Oncology, Dana-Farber Cancer Institute and Harvard Medical School, Boston, Massachusetts8Channing Division of Network Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts.
authors.forename: Charles S
authors.initials: CS
authors.lastname: Fuchs
authors.affiliation: Department of Nutrition, Harvard T. H. Chan School of Public Health, Boston, Massachusetts4Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, Massachusetts 8Channing Division of Network Medicine, Brigham and Women's Hospital a.
authors.forename: Edward L
authors.initials: EL
authors.lastname: Giovannucci
authors.affiliation: Clinical and Translational Epidemiology Unit, Massachusetts General Hospital and Harvard Medical School, Boston3Division of Gastroenterology, Massachusetts General Hospital and Harvard Medical School, Boston8Channing Division of Network Medicine, Brigham.
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Chan
mesh_terms: D000328:Adult; D000368:Aged; D001241:Aspirin / Q000009:adverse effects / Q000627:therapeutic use*; D015179:Colorectal Neoplasms / Q000453:epidemiology / Q000473:pathology / Q000517:prevention & control*; D005260:Female; D005500:Follow-Up Studies; D005770:Gastrointestinal Neoplasms / Q000453:epidemiology / Q000473:pathology / Q000517:prevention & control*; D006801:Humans; D008297:Male; D008875:Middle Aged; D018570:Risk Assessment
chemical_list: D001241:Aspirin