TABLE 2.
Hazard ratios for liver cancer by smoking characteristics and long‐term cooking fuel use
| N (rates/100 000 PYs) | HRs (95% CIs) a | |||
|---|---|---|---|---|
| Model 1: basic adjustment | Model 2: basic + lifestyle factors | Model 3: basic + lifestyle + medical factors | ||
| Smoking status | ||||
| Never (common reference) | 1374 (36.6) | 1.00 | 1.00 | 1.00 |
| Ex‐smoker | 153 (95.8) | 1.15 (0.96‐1.39) | 1.12 (0.93‐1.35) | 1.13 (0.94‐1.36) |
| Current smoker | 1470 (92.8) | 1.33 (1.20‐1.48) | 1.26 (1.13‐1.40) | 1.28 (1.15‐1.42) |
| No. of cigarettes/day | ||||
| ≤10 | 532 (91.4) | 1.24 (1.10‐1.40) | 1.19 (1.05‐1.35) | 1.19 (1.05‐1.35) |
| 11‐20 | 761 (91.8) | 1.35 (1.20‐1.52) | 1.28 (1.14‐1.44) | 1.30 (1.15‐1.47) |
| >20 | 330 (99.4) | 1.38 (1.19‐1.59) | 1.27 (1.10‐1.48) | 1.32 (1.14‐1.54) |
| P trend | <.001 | <.001 | <.001 | |
| Age started smoking (years) | ||||
| >25 | 372 (98.0) | 1.20 (1.05‐1.37) | 1.16 (1.01‐1.33) | 1.18 (1.03‐1.36) |
| 19‐25 | 775 (90.2) | 1.31 (1.17‐1.47) | 1.24 (1.10‐1.40) | 1.26 (1.12‐1.42) |
| ≤18 | 476 (94.3) | 1.43 (1.25‐1.62) | 1.33 (1.16‐1.52) | 1.34 (1.17‐1.53) |
| P trend | <.001 | .003 | .001 | |
| Long‐term fuel type | ||||
| Always clean (common reference) | 363 (38.5) | 1.00 | 1.00 | 1.00 |
| Solid to clean | 513 (45.2) | 1.09 (0.94‐1.27) | 1.12 (0.96‐1.30) | 1.10 (0.94‐1.28) |
| Always solid | 1009 (50.7) | 1.29 (1.07‐1.55) | 1.23 (1.01‐1.49) | 1.25 (1.03‐1.52) |
| Types of solid fuels b | ||||
| Always coal | 356 (45.2) | 1.17 (0.91‐1.50) | 1.15 (0.89‐1.48) | 1.14 (0.88‐1.47) |
| Always wood | 480 (56.7) | 1.31 (1.08‐1.58) | 1.24 (1.01‐1.51) | 1.27 (1.04‐1.56) |
| Always solid (mixed) | 173 (48.7) | 1.39 (1.08‐1.79) | 1.33 (1.03‐1.72) | 1.34 (1.04‐1.73) |
| Duration exposed (years) | ||||
| 1‐14 | 322 (42.6) | 1.05 (0.89‐1.24) | 1.06 (0.90‐1.26) | 1.06 (0.89‐1.25) |
| 15‐29 | 498 (41.6) | 1.17 (1.00‐1.37) | 1.18 (1.00‐1.38) | 1.16 (0.99‐1.37) |
| ≥30 | 702 (60.0) | 1.23 (1.04‐1.45) | 1.22 (1.03‐1.44) | 1.21 (1.03‐1.44) |
| P trend | .008 | .018 | .018 | |
HRs were stratified by sex, baseline age groups and study regions, model 1 were adjusted for education, household income, occupation and marital status; model 2 were additionally adjusted for alcohol consumption, environmental tobacco smoke, months of storing pesticides at home, long‐term heating fuel exposure, stoves with chimney/extractor, physical activity, BMI, having a refrigerator at home, consumption frequency of fresh fruit, preserved vegetables, red meat, fish and grains at baseline and mutually adjusted for long‐term cooking fuel exposure and smoking habits; model 3 were additionally adjusted for hepatitis B test result, family history cancer, medical history of hepatic cirrhosis and diabetes.
Analysis was restricted to individuals who always solid fuels in the last 3 residences before the baseline survey (N = 182 285).