Table 2. Incidences of oral cancer by metformin exposure in the original sample and the hazard ratios comparing metformin exposed to unexposed patients in the original sample and the matched sample.
| Original sample | Matched sample | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Metformin use | n/N | Person-years | Incidence rate(per 100,000 person-years) | PS-adjusted model | IPTW model | n/N | PS-adjusted model | IPTW model | ||||
| HR (95% CI) | P | HR (95% CI) | P | HR (95% CI) | P | HR (95% CI) | P | |||||
| Never users | 119/16263 | 72760.7 | 163.6 | 1.000 | 1.000 | 119/16263 | 1.000 | 1.000 | ||||
| Ever users | 1273/288198 | 1373325.0 | 92.7 | 0.584 (0.483-0.707) | <0.0001 | 0.562 (0.465-0.678) | <0.0001 | 77/16263 | 0.592 (0.444-0.789) | 0.0003 | 0.602 (0.452-0.802) | 0.0005 |
| Tertiles of cumulative duration of metformin therapy (months) | ||||||||||||
| Never users | 119/16263 | 72760.7 | 163.6 | 1.000 | 1.000 | 119/16263 | 1.000 | 1.000 | ||||
| <21.5 | 715/95463 | 344951.9 | 207.3 | 1.403 (1.152-1.708) | 0.0008 | 1.244 (1.024-1.511) | 0.0281 | 35/5287 | 1.176 (0.806-1.717) | 0.4000 | 1.127 (0.772-1.645) | 0.5359 |
| 21.5-45.9 | 418/94666 | 471050.1 | 88.7 | 0.557 (0.453-0.684) | <0.0001 | 0.526 (0.429-0.645) | <0.0001 | 31/5307 | 0.693 (0.466-1.029) | 0.0689 | 0.703 (0.473-1.043) | 0.0802 |
| >45.9 | 140/98069 | 557322.9 | 25.1 | 0.152 (0.119-0.194) | <0.0001 | 0.138 (0.108-0.176) | <0.0001 | 11/5669 | 0.197 (0.106-0.366) | <0.0001 | 0.205 (0.110-0.380) | <0.0001 |
n: incident cases of oral cancer, N: cases followed, HR: hazard ratio, CI: confidence intervals
PS: propensity score created from variables in Table 1
IPTW: Cox regression model incorporated with the inverse probability of treatment weighting (IPTW) using PS
The models shown in the table were created with covariates defined at the start of follow-up. Additional models created with covariates defined at censor were not much different from the respective models shown in the table.