Table 2.

Crude and adjusted rate ratios of colorectal cancer associated with the use of metformin

Exposure to metforminCases (n = 607)Controls (n = 5,837)Crude RRAdjusted RR (95% CI)a
Never use, n (%)163 (26.9)1,431 (24.5)1.001.00 (reference)
Ever use, n (%)444 (73.2)4,406 (75.5)0.900.94 (0.74–1.19)
Cumulative duration of use (d), n (%)b
 <449132 (21.8)1,100 (18.9)1.121.13 (0.85–1.49)
 449–84598 (16.1)1,099 (18.8)0.790.82 (0.60–1.12)
 845–144798 (16.1)1,105 (18.9)0.770.80 (0.58–1.10)
Ptrend = 0.69
  • aAdjusted for: obesity, smoking, statins, nonsteroidal anti-inflammatory drugs, aspirin, excessive alcohol use, HbA1c, diabetes duration, cholecystectomy, inflammatory bowel diseases, referrals to colonoscopy, referrals to sigmoidoscopy, history of polyps, previous cancer (other than nonmelanoma skin cancer), and use of sulfonylureas, thiazolidinediones, insulins, and other antidiabetic agents.

  • bQuartiles based on the distribution of use in the controls.