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Table 3 Frequency distribution of low-dose aspirin among CRC cases and controls, and RR (95% CI) for their association with risk of CRC

From: New use of low-dose aspirin and risk of colorectal cancer by stage at diagnosis: a nested case–control study in UK general practice

Low-dose aspirin use Controls
N = 10,000
n (%)
Cases
N = 3033
n (%)
RR (95% CI)a RR (95% CI)b
Recency
 Non-use 3557 (35.6) 1247 (41.1) 1.00 (−) 1.00 (−)
 Current use 4562 (45.6) 1255 (41.4) 0.80 (0.73–0.88) 0.66 (0.60–0.73)
 Recent/past usec 475 (4.8) 158 (5.2) 0.73 (0.64–0.84) 0.78 (0.64–0.95)
Daily dosed
 75 mg 4128 (41.3) 1137 (37.5) 0.78 (0.71–0.86) 0.66 (0.60–0.73)
 150 mg 402 (4.0) 107 (3.5) 0.75 (0.60–0.94) 0.62 (0.50–0.78)
 300 mg 32 (0.3) 11 (0.4) 0.97 (0.49–1.94) 0.82 (0.41–1.64)
Formulation
 Plain 3716 (37.2) 1008 (33.2) 0.77 (0.70–0.85) 0.65 (0.59–0.72)
 Enteric coated 846 (8.5) 247 (8.1) 0.83 (0.71–0.97) 0.70 (0.59–0.82)
Duration of use
 < 1 year 1430 (14.3) 433 (14.3) 0.86 (0.76–0.97) 0.72 (0.63–0.82)
 1–5 years 2370 (23.7) 632 (20.8) 0.76 (0.68–0.84) 0.64 (0.57–0.72)
 ≥ 5 years 762 (7.6) 190 (6.3) 0.70 (0.59–0.84) 0.61 (0.51–0.73)
  1. All estimates are among current users of low-dose aspirin (reference group = non-use) unless otherwise specified
  2. BMI body mass index, CI confidence interval, NSAIDS non-steroidal anti-inflammatory drugs, PCP primary care practitioner, RR rate ratio
  3. aAdjusted by the matching factors (age, sex and year of index date)
  4. bAdjusted by the matching factors (age, sex and year of index date) and number of PCP visits, smoking (any time before index date), insulin, NSAIDs, BMI (any time before index date) and oral steroids
  5. cFor patients with a duration of use of at least 1 year (25% of all recent/past users)
  6. dRefers to the estimated average quantity dose. No appreciable difference in the results were observed when dose of the first prescription during follow-up was used or when the dose of last prescription before the index date was used
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