Table 2.
Association Between Smoking and Colon Cancer Risk, by Sex, Multiethnic Cohort Study, 1993–2013
| Smoking Exposure | Men (n = 84,948) | Women (n = 103,104) |
P for
Heterogeneity d |
||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
No. of
Cases |
HR a | 95% CI |
No. of
Cases b |
HR c | 95% CI |
No. of
Cases |
HR a | 95% CI |
No. of
Cases b |
HR c | 95% CI | ||
| None (never smokers) | 489 | 1.00 | Referent | 464 | 1.00 | Referent | 1,055 | 1.00 | Referent | 919 | 1.00 | Referent | |
| Smoking status | 0.43 | ||||||||||||
| Former smoker | 1,050 | 1.20 | 1.08, 1.34 | 974 | 1.14 | 1.02, 1.27 | 609 | 1.17 | 1.06, 1.30 | 534 | 1.16 | 1.04, 1.30 | |
| Current smoker | 307 | 1.28 | 1.11, 1.48 | 287 | 1.20 | 1.03, 1.39 | 241 | 1.15 | 1.00, 1.33 | 205 | 1.07 | 0.91, 1.25 | |
| Ever smoker | 1,357 | 1.22 | 1.10, 1.35 | 1,261 | 1.15 | 1.03, 1.28 | 850 | 1.17 | 1.06, 1.28 | 739 | 1.14 | 1.03, 1.26 | 0.80 |
| Ever smokers | |||||||||||||
| Duration of smoking, years | 0.55 | ||||||||||||
| ≤20 | 533 | 1.16 | 1.03, 1.32 | 499 | 1.12 | 0.99, 1.28 | 363 | 1.07 | 0.94, 1.20 | 313 | 1.05 | 0.92, 1.19 | |
| 21–30 | 312 | 1.25 | 1.08, 1.44 | 298 | 1.19 | 1.03, 1.38 | 201 | 1.31 | 1.12, 1.53 | 176 | 1.26 | 1.07, 1.49 | |
| ≥31 | 476 | 1.26 | 1.11, 1.43 | 434 | 1.14 | 1.00, 1.31 | 257 | 1.24 | 1.08, 1.42 | 230 | 1.21 | 1.04, 1.40 | |
| P for trend | <0.001 | 0.04 | <0.001 | 0.002 | |||||||||
| No. of cigarettes smoked per day | 0.44 | ||||||||||||
| ≤10 | 436 | 1.15 | 1.01, 1.31 | 398 | 1.12 | 0.98, 1.28 | 428 | 1.07 | 0.95, 1.19 | 362 | 1.04 | 0.92, 1.17 | |
| 11–20 | 482 | 1.18 | 1.04, 1.34 | 446 | 1.09 | 0.96, 1.24 | 280 | 1.31 | 1.14, 1.50 | 248 | 1.26 | 1.09, 1.46 | |
| ≥21 | 401 | 1.35 | 1.18, 1.54 | 385 | 1.25 | 1.09, 1.43 | 127 | 1.35 | 1.12, 1.64 | 117 | 1.31 | 1.07, 1.60 | |
| P for trend | <0.001 | 0.005 | <0.001 | <0.001 | |||||||||
| Pack-years of smoking | 0.48 | ||||||||||||
| ≤10 | 374 | 1.17 | 1.02, 1.34 | 345 | 1.14 | 0.99, 1.31 | 331 | 1.08 | 0.95, 1.23 | 284 | 1.06 | 0.93, 1.22 | |
| 11–20 | 414 | 1.15 | 1.01, 1.31 | 388 | 1.09 | 0.95, 1.25 | 263 | 1.16 | 1.01, 1.33 | 227 | 1.11 | 0.96, 1.29 | |
| ≥21 | 513 | 1.32 | 1.16, 1.49 | 480 | 1.20 | 1.05, 1.37 | 221 | 1.37 | 1.18, 1.59 | 203 | 1.33 | 1.14, 1.56 | |
| P for trend | <0.001 | 0.01 | <0.001 | <0.001 | |||||||||
Abbreviations: CI, confidence interval; HR, hazard ratio.
a Adjusted for race/ethnicity and age at cohort entry.
b Participants with missing information on covariates were excluded.
c Results were further adjusted for family history of colorectal cancer, history of colorectal polyps, body mass index, physical activity, multivitamin use, nonsteroidal antiinflammatory drug use, menopausal hormone therapy (for women only), and intakes of alcohol, total energy, red meat, dietary fiber, calcium, folate, and vitamin D.
d Tests for heterogeneity between men and women were performed on the basis of joint multivariate-adjusted models with adjustment for sex as a strata variable.