Table 1.
Association between covariables and time to first cigarette in the Environment and Genetics in Lung Cancer Etiology study control subjects (n = 1437)*
| Characteristics | No.† | TTFC, min (increasing dependency with shorter minutes) | ||||
|---|---|---|---|---|---|---|
| >60 | 31–60 | 6–30 | ≤5 | P‡ | ||
| Total | 1437 | 51.0 | 18.2 | 20.5 | 10.3 | |
| Age, y | 1437 | 65.9 (8.8) | 65.4 (7.9) | 64.6 (8.2) | 65.6 (8.6) | .20 |
| Smoking status | <.0001 | |||||
| Former | 909 | 58.9 | 15.7 | 16.0 | 9.5 | |
| Current | 527 | 37.4 | 22.4 | 28.5 | 11.8 | |
| Pack-year, packs per day × y | 1435 | 16.4 (15.7) | 32.7 (20.2) | 38.1 (18.6) | 50.3 (27.2) | <.0001 |
| Cigarettes per day | 1435 | 10.9 (7.9) | 18.6 (9.6) | 20.4 (7.7) | 27.3 (12.1) | <.0001 |
| Smoke duration, y | 1435 | 27.5 (15.7) | 35.3 (13.7) | 37.5 (12.1) | 37.4 (12.5) | <.0001 |
| Years since quitting, y | 909 | 23.5 (13.5) | 19 (11.0) | 16.4 (10.7) | 17.7 (10.4) | <.0001 |
| Age at smoking initiation, y | 1437 | 20.1 (6.8) | 18.7 (5.0) | 17.8 (3.8) | 17.5 (4.8) | <.0001 |
| Depth of inhale | <.0001 | |||||
| Not inhale | 111 | 85.6 | 7.2 | 2.7 | 4.5 | |
| Slightly | 183 | 63.9 | 15.9 | 15.9 | 4.4 | |
| Moderately | 571 | 57.6 | 17.2 | 19.3 | 6.0 | |
| Deeply | 568 | 33.5 | 22.0 | 26.8 | 17.8 | |
| Body mass index, kg/m2 | 1437 | 25.9 (3.8) | 26 (3.6) | 26.2 (3.9) | 27.1 (5.9) | <.01 |
| Sex | <.01 | |||||
| Male | 1220 | 49.3 | 18.9 | 21.1 | 10.8 | |
| Female | 217 | 60.8 | 14.3 | 17.5 | 7.4 | |
| Study area | <.01 | |||||
| Brescia | 168 | 52.4 | 10.7 | 22.6 | 14.3 | |
| Milan | 977 | 51.2 | 20.7 | 18.2 | 9.9 | |
| Monza | 80 | 43.8 | 13.8 | 31.3 | 11.3 | |
| Pavia | 92 | 50.0 | 13.0 | 27.2 | 9.8 | |
| Varese | 120 | 53.3 | 15.0 | 24.2 | 7.5 | |
| Occupations with higher lung cancer risk | <.01 | |||||
| No | 1063 | 53.4 | 17.1 | 20.2 | 9.2 | |
| Yes | 374 | 44.1 | 21.1 | 21.4 | 13.4 | |
| Lung cancer family history | .03 | |||||
| No | 1142 | 52.9 | 17.6 | 19.9 | 9.6 | |
| Yes | 132 | 43.2 | 19.7 | 23.5 | 13.6 | |
| COPD | <.0001 | |||||
| No | 1265 | 52.5 | 18.2 | 20.2 | 9.2 | |
| Yes | 148 | 40.5 | 16.2 | 21.6 | 21.6 | |
| Education | <.0001 | |||||
| None | 58 | 43.1 | 15.5 | 20.7 | 20.7 | |
| Elementary | 389 | 45.0 | 21.6 | 22.4 | 11.1 | |
| Middle | 424 | 47.9 | 18.4 | 21.0 | 12.7 | |
| High | 389 | 57.6 | 15.7 | 19.8 | 6.9 | |
| University | 177 | 59.9 | 16.4 | 16.9 | 6.8 | |
| ETS exposure | 0.32 | |||||
| No | 87 | 59.8 | 17.2 | 13.8 | 9.2 | |
| Yes | 1341 | 50.5 | 18.3 | 20.9 | 10.3 | |
| ETS exposure at home in childhood | 0.001 | |||||
| No | 455 | 57.1 | 17.1 | 17.6 | 8.1 | |
| Yes | 973 | 48.1 | 18.8 | 21.9 | 11.2 | |
| ETS exposure at home in adulthood | 0.31 | |||||
| No | 765 | 52.4 | 18.0 | 18.8 | 10.7 | |
| Yes | 612 | 48.9 | 18.6 | 22.5 | 10.0 | |
| ETS exposure in the work place | 0.16 | |||||
| No | 404 | 52.5 | 15.8 | 22.3 | 9.4 | |
| Yes | 1024 | 50.5 | 19.2 | 19.8 | 10.4 | |
* For continuous variables we present mean and standard deviation; otherwise we present row percentages. COPD = chronic obstructive pulmonary disease; ETS = environmental tobacco smoke; TTFC = time to first cigarette.
† Sample size may not sum up to 1437 because of missing values or restricting to former smokers (years since quitting).
‡ P values were calculated by χ2 test (categorical/dichotomized variables) or analyses of variance (continuous variables). All statistical tests were two-sided.