Table 2.
Association between time to first cigarette and lung cancer among smokers in the Environment and Genetics in Lung Cancer Etiology study*
| Group/Subgroup | Odds ratio (95% confidence interval) | ||||||
|---|---|---|---|---|---|---|---|
| Case subjects/ control subjects | TTFC >60 min | TTFC 31–60 min | TTFC 6–30 min | TTFC ≤5 min | P trend | P interaction | |
| All smokers | 1807/1434 | 1.00 | 2.57 (2.03 to 3.26) | 2.27 (1.79 to 2.88) | 3.50 (2.64 to 4.64) | <.001 | |
| Sex | |||||||
| Male | 1504/1217 | 1.00 | 2.71 (2.09 to 3.52) | 2.28 (1.75 to 2.96) | 3.68 (2.71 to 4.99) | <.001 | .78 |
| Female | 303/217 | 1.00 | 2.01 (1.06 to 3.82) | 2.48 (1.37 to 4.5) | 2.86 (1.28 to 6.43) | .002 | |
| Smoking status | |||||||
| Current | 971/525 | 1.00 | 3.13 (2.16 to 4.53) | 2.73 (1.9 to 3.92) | 4.20 (2.72 to 6.49) | <.001 | .03 |
| Former | 836/909 | 1.00 | 2.50 (1.81 to 3.46) | 2.15 (1.54 to 3) | 3.28 (2.24 to 4.81) | <.001 | |
| Cigarettes per day | |||||||
| ≤10 | 232/515 | 1.00 | 3.43 (2.00 to 5.87) | 3.03 (1.55 to 5.91) | 7.44 (2.04 to 27.20) | <.001 | .02 |
| 11–20 | 946/660 | 1.00 | 2.69 (1.96 to 3.68) | 2.06 (1.51 to 2.8) | 3.52 (2.38 to 5.19) | <.001 | |
| >20 | 629/259 | 1.00 | 1.56 (0.83 to 2.94) | 1.75 (0.98 to 3.11) | 2.29 (1.28 to 4.1) | .005 | |
* We used logistic regression, adjusting for age, area, sex, smoking intensity (in categories ≤5, >5–≤10, >10–≤20, >20–≤30, >30 cigarettes per day), smoking duration (≤20, >20–≤30, >30–≤40, >40–≤50, >50 years), pack-years (≤10, >10–≤20, >20–≤30, >30–≤40, >40–≤50, >50), current/former smoking status, years since quitting (≤2, >2–≤5, >5–≤10, >10–≤20, >20–≤30, >30 years), age at smoking initiation, body mass index (continuous), lung cancer family history (in categories yes, no, missing), chronic obstructive pulmonary disease (in categories: yes, no, missing), education, and occupations associated with increased lung cancer risk. P trend was obtained by treating time to first cigarette (TTFC) as an ordinal variable; Pinteraction was obtained by adding the interaction term of TTFC (ordinal) and sex, current/former, and cigarettes per day (ordinal). Sex was removed in the male and female models, smoking status was removed in the current and former smoker models, years since quitting was removed in the current smoker model. All statistical tests were two-sided. Sample sizes are slightly less than 1812/1437 due to missing data in some continuous covariates.