Table 4.
Relation between smoking cessation and cancer incidence
| Years since quitting among former smokers | ||||
|---|---|---|---|---|
| Cancer site | Current smoker | <10 years | ≥10 years | Never smoker |
| All cancers | ||||
| No. of cases, whole cohort (n=5253) | 1577 | 356 | 355 | 2965 |
| Multivariable RRa, whole cohort | 1 (Referent) | 0.84 (0.75–0.94) | 0.67 (0.59–0.75) | 0.61 (0.57–0.66) |
| Head and neck cancer | ||||
| No. of cases, whole cohort (n=345) | 148 | 31 | 17 | 149 |
| Multivariable RR a, whole cohort | 1 (Referent) | 0.81 (0.55–1.2) | 0.37 (0.22–0.61) | 0.47 (0.36–0.61) |
| Upper gastrointestinal tract cancer | ||||
| No. of cases, whole cohort (n=458) | 161 | 38 | 37 | 222 |
| Multivariable RR a, whole cohort | 1 (Referent) | 0.87 (0.61–1.3) | 0.69 (0.48–1.0) | 0.66 (0.52–0.84) |
| Hepatobiliary and pancreas cancer | ||||
| No. of cases, whole cohort (n=480) | 165 | 31 | 49 | 235 |
| Multivariable RR a, whole cohort | 1 (Referent) | 0.67 (0.46–0.99) | 0.85 (0.62–1.2) | 0.69 (0.54–0.86) |
| Lung cancer | ||||
| No. of cases, whole cohort (n=905) | 519 | 88 | 44 | 254 |
| Multivariable RR a, whole cohort | 1 (Referent) | 0.59 (0.47–0.74) | 0.23 (0.17–0.32) | 0.20 (0.16–0.23) |
| Bladder/renal pelvis cancer | ||||
| No. of cases, whole cohort (n=146) | 52 | 21 | 12 | 61 |
| Multivariable RR a, whole cohort | 1 (Referent) | 1.2 (0.75–2.1) | 0.52 (0.27–0.98) | 0.54 (0.36–0.82) |
a
Relative risk (95% confidence interval) estimated from a multivariable-adjusted proportional hazards model adjusted for age (years), gender (males, females), dialect group (Cantonese, Hokkien), year of recruitment, level of education (no formal education, primary school, secondary school or above), daily ethanol intake (g), and h/week of moderate physical activity (none, ½ to 3 h/week, 4 h/week or more).