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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