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Table 4 Sensitivity analyses for the association between aspirin use and overall survival in patients with colorectal cancer

From: Low-dose aspirin use and survival in colorectal cancer: results from a population-based cohort study

  Aspirin user Aspirin non-user  
Mortality Patients Person years Mortality Patients Person years Unadjusted HR
(95% CI)
P value Adjusted HR
(95% CI)
P value
Overall survival
 Post-diagnostic aspirin use (fixed time exposure in first year)a
  Aspirin user vs. non-user 554 2150 5692 1081 6241 16,442 1.48 (1.33, 1.64) < 0.001 1.17 (1.03, 1.32) 0.01
 Post-diagnostic aspirin use versus non-use stratified by pre-diagnostic use (excludes 2009 cases)b
  Pre-diagnostic users 290 1333 2983 70 257 614 0.84 (0.65,1.10) 0.21 0.88 (0.67,1.17) 0.39
  Pre-diagnostic non-users 84 435 744 638 4301 9930 1.79 (1.42,2.25) < 0.001 1.53 (1.19,1.95) 0.001
 Aspirin use vs. non-use in year before colorectal cancer diagnosis (excludes 2009 cases)c
  Aspirin user vs. non-user 1506 2853 6460 3117 7555 18,652 1.37 (1.29, 1.46) < 0.001 0.99 (0.92, 1.06) 0.77
  1. Abbreviations: CI confidence interval, HR hazard ratio
  2. aModel contains age, sex, year of diagnosis, deprivation, site (colon or rectum), stage, grade, cancer treatment within six months (radiotherapy, chemotherapy, surgery), comorbidities (prior to diagnosis, including acute myocardial infarction, congestive heart failure, peripheral vascular disease, cerebral vascular accident, pulmonary disease, peptic ulcer, liver disease, diabetes, renal disease) and statin use (in first year after diagnosis)
  3. bExcluding patients diagnosed in 2009 (who do not have complete prescription records for year before diagnosis). Based upon main time-varying covariate multivariable model containing age, sex, year of diagnosis, deprivation, site (colon or rectum), stage, grade, cancer treatment within 6 months (radiotherapy, chemotherapy, surgery), comorbidities (prior to diagnosis, including acute myocardial infarction, congestive heart failure, peripheral vascular disease, cerebral vascular accident, pulmonary disease, peptic ulcer, liver disease, diabetes, renal disease) and statin use (as time-varying covariate)
  4. cExcluding patients diagnosed in 2009 (who do not have complete prescription records for year before diagnosis) but not excluding patients who die within 1 year of diagnosis; adjusted model contains age, sex, year of diagnosis, deprivation, site (colon or rectum), comorbidities (prior to diagnosis, including acute myocardial infarction, congestive heart failure, peripheral vascular disease, cerebral vascular accident, pulmonary disease, peptic ulcer, liver disease, diabetes, renal disease) and statin use (in year prior to diagnosis)