title: A short-term effect of low-dose aspirin on major hemorrhagic risks in primary prevention: a case-crossover design.
abstract: BACKGROUND
  Very few studies have examined the risk of short-term adverse hemorrhage of low-dose aspirin use in primary prevention. This case-crossover study examined the transient effect of low-dose aspirin use on major hemorrhagic risks.
  
  
  METHODS
  A representative database of 1,000,000 patients randomly sampled from the Taiwan's National Health Insurance Research Database in 2000 was analyzed. The study cohort consisted of a total of 501,946 individuals, aged 30-95 years old, at risk of a major bleeding event in 2000. A case-crossover study was used to retrieve data on 10,905 incident patients with major hemorrhagic complications (3,781 cerebral and 7,124 gastrointestinal) and prescribed low-dose aspirin (≤300 mg/day) from 2000-2008. A 56-day time window (∼2 months) was used as the case period for which the odds ratio (OR) was estimated using the ratio of patients exposed during the 56-day case period only (1-56 days before the index date) compared to its corresponding 56-day control period only (57-112 days before the index date).
  
  
  RESULTS
  Four hundred eighty-nine (4.5%) of the 10,905 hemorrhagic patients had used low-dose aspirin during the 56-day case only period; 294 (2.7%) of the same patients had used low-dose aspirin during control only period. Low-dose aspirin use increase the risk of developing a major hemorrhage 1.33-fold (95% CI = 1.13-1.55, P<0.0001). Significance was found prominent in 4,453 non-hypertensive and non-diabetic subjects (Adjusted odds ratio = 1.88, 95% CI = 1.21-2.91).
  
  
  CONCLUSIONS
  Transient low-dose aspirin use increases risk for major hemorrhagic events in Han Chinese.
authors.affiliation: Kaohsiung Medical University, Kaohsiung, Taiwan; Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
authors.forename: I-Chen
authors.initials: IC
authors.lastname: Wu
authors.affiliation: Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Ming-Yen
authors.initials: MY
authors.lastname: Lin
authors.affiliation: Kaohsiung Medical University, Kaohsiung, Taiwan; Kaohsiung Medical University Hospital, Kaohsiung, Taiwan.
authors.forename: Fang-Jung
authors.initials: FJ
authors.lastname: Yu
authors.affiliation: Kaohsiung Medical University, Kaohsiung, Taiwan.
authors.forename: Hui-Min
authors.initials: HM
authors.lastname: Hsieh
authors.affiliation: Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung, Taiwan.
authors.forename: Kuei-Fen
authors.initials: KF
authors.lastname: Chiu
authors.affiliation: Kaohsiung Medical University, Kaohsiung, Taiwan; Kaohsiung Medical University Hospital, Kaohsiung, Taiwan; Kaohsiung Municipal Hsiao-Kang Hospital, Kaohsiung, Taiwan.
authors.forename: Ming-Tsang
authors.initials: MT
authors.lastname: Wu
mesh_terms: D000328:Adult; D001241:Aspirin / Q000009:adverse effects* / Q000494:pharmacology; D018592:Cross-Over Studies; D006470:Hemorrhage / Q000139:chemically induced*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011322:Primary Prevention / Q000379:methods*; D012306:Risk; D013997:Time Factors
chemical_list: D001241:Aspirin