Table 1. Estimated age-adjusted incidence rate ratios (IRR) and corresponding 95% confidence intervals (CI) for developing CSCC, by different dose and duration of tobacco smoking.
| Exposure variable | No of cases (%) | Person-years accumulated | IRR (95% CI) |
|---|---|---|---|
| Reference (never tobacco user) | 209 (35) | 1 920 810 | 1 (ref) |
| Any tobacco smoker | |||
| Previous | 141 (24) | 710 190 | 0.95 (0.77–1.18) |
| Current | 245 (41) | 2 150 910 | 0.97 (0.80–1.17) |
| Total smoking tobacco dose (g day −1 ) | |||
| ⩽10 | 222 (39) | 1 410 290 | 0.99 (0.82–1.19) |
| 11–15 | 112 (20) | 1 119 380 | 0.88 (0.70–1.11) |
| >15 | 27 (5) | 230 650 | 0.95 (0.64–1.42) |
| Years of tobacco smoking | |||
| ⩽15 | 87 (15) | 1 534 570 | 1.08 (0.83–1.39) |
| 16–25 | 110 (19) | 725 130 | 1.11 (0.87–1.40) |
| >25 | 188 (32) | 563 890 | 0.87 (0.72–1.07) |
| Time since cessation of tobacco smoking (years) a | |||
| <10 | 74 (21) | 487 210 | 1.00 (0.76–1.30) |
| ⩾10 | 66 (19) | 197 480 | 0.89 (0.68–1.18) |
a
Stratified Cox proportional hazards model, by age.
CSCC=cutaneous squamous cell carcinoma.