Table 2

. Associations between metformin use and risk of colorectal adenoma recurrence in patients with type 2 diabetes

Adjusted HR (95% CI)
Indication for repeat colonoscopyaLocation at baselinea,b
Exposure categoriesSample (n)Adenoma detected (n)Recurrent adenoma (all indications and locations)DiagnosticSurveillanceRight colonLeft colon/rectum
Separate categories for metformin-only and combination therapy
 No diabetes medication (reference)1,5787391.001.001.001.001.00
 Metformin-only4571960.76 (0.65–0.89)0.62 (0.50–0.79)0.89 (0.73–1.09)0.75 (0.62–0.90)0.66 (0.41–1.05)
 Metformin + other3771820.72 (0.62–0.85)0.66 (0.52–0.83)0.80 (0.64–1.02)0.73 (0.58–0.92)0.96 (0.63–1.47)
Any metformin
 No diabetes medication (reference)1,5787391.001.001.001.001.00
 Any metformin8343780.74 (0.66–0.84)0.64 (0.53–0.77)0.85 (0.71–1.02)0.74 (0.64–0.86)0.79 (0.54–1.15)
Total dose, quartilesc
 No diabetes medication (reference)1,5787391.001.001.001.001.00
 Quartile 1205880.90 (0.72–1.12)0.63 (0.46–0.86)1.32 (1.01–1.73)0.86 (0.66–1.13)1.17 (0.61–2.23)
 Quartile 2209950.98 (0.79–1.21)0.97 (0.69–1.37)1.02 (0.79–1.31)0.91 (0.73–1.15)0.62 (0.32–1.21)
 Quartile 3205950.80 (0.63–1.01)0.69 (0.48–0.97)0.91 (0.69–1.20)0.71 (0.51–0.98)1.14 (0.70–1.85)
 Quartile 42151000.50 (0.42–0.60)0.47 (0.35–0.62)0.55 (0.41–0.72)0.58 (0.46–0.72)0.49 (0.28–0.88)

NOTE: Models were run separately for each set of exposure categories. All models are adjusted for age category, sex, race/ethnicity, BMI, and indication for repeat examination, as appropriate.

  • aPinteraction = 0.02 for indication, but was 0.95 for tumor location.

  • bUnspecified adenoma location at baseline (n = 874).

  • cIncludes patients receiving metformin alone and metformin in combination with other medications Ptrend < 0.001.