Table 3.

Estimates of colorectal cancer risk associated with metformin use, by gender

MaleFemale
Metformin useNo. of eventsPerson-yearsAdjusteda HR (95% CI)No. of eventsPerson-yearsAdjusteda HR (95% CI)
 Never288138,490.831.00 (reference)199119,040.101.00 (reference)
 Ever16687,405.380.81 (0.65–1.03)15983,515.621.01 (0.78–1.31)
Total duration, years
 <2.05430,979.850.80 (0.59–1.08)5030,049.970.98 (0.71–1.37)
 2.0–4.96729,269.830.95 (0.71–1.28)5527,123.401.10 (0.79–1.55)
 ≥5.04527,155.700.65 (0.45–0.94)5426,342.250.95 (0.65–1.38)
Ptrend = 0.05Ptrend = 0.98
  • aAdjusted for gender, race/ethnicity, birth year, diabetes duration, BMI, alcohol use, smoking status, Charlson comorbidity index, education, income level, creatinine, HbA1c, history of lower endoscopy (all fixed at baseline); first lower endoscopy after baseline (time-varying) and use of other types of diabetes medications (time-varying).