Table 3.
Frequency distribution of low-dose aspirin among CRC cases and controls, and RR (95% CI) for their association with risk of CRC
| 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) |
All estimates are among current users of low-dose aspirin (reference group = non-use) unless otherwise specified
BMI body mass index, CI confidence interval, NSAIDS non-steroidal anti-inflammatory drugs, PCP primary care practitioner, RR rate ratio
aAdjusted by the matching factors (age, sex and year of index date)
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
cFor patients with a duration of use of at least 1 year (25% of all recent/past users)
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