Table 2.
Cox proportional hazards models for time to lung cancer incidence in the WHI-OS cohort: current/former and never smokers
| Models for time to development of lung cancer | Cases/ non-cases | Annualized incidence rates (cases per 100 000 person-years) | Age-adjusted model hazard ratio (95% CI) | Multivariable- adjusted model hazard ratio (95% CI) |
|---|---|---|---|---|
| Current/former smokers | ||||
| Smoking status for the entire cohort (N = 76 304) | 901/75 403 | 112.3 | P < 0.001 | P < 0.001 |
| Never smoker | 152/39 619 | 36.2 | Ref | Ref |
| Former smoker | 531/31 273 | 158.1 | 4.48 (3.75, 5.38) | 4.20 (3.48, 5.08) |
| Current smoker | 218/4511 | 472.9 | 15.26 (12.39, 18.79) | 13.44 (10.80, 16.74) |
| Pack-years smoked among current and former smokers (N = 36 484) | ||||
| Pack-years | P < 0.0001 | P < 0.0001 | ||
| 0–<5 (reference) | 52/11 286 | 42.9 | Ref | Ref |
| 5–<10 | 37/4132 | 83.0 | 1.81 (1.19, 2.75) | 1.80 (1.18, 2.75) |
| 10–<15 | 53/4887 | 100.6 | 2.26 (1.54, 3.32) | 2.26 (1.54, 3.31) |
| 15–<25 | 143/6231 | 216.0 | 3.86 (2.79, 5.32) | 3.86 (2.80, 5.35) |
| 25–<35 | 82/2792 | 273.3 | 5.59 (3.94, 7.94) | 5.68 (3.98, 8.06) |
| ≥35 | 382/6456 | 567.6 | 9.62 (7.14, 12.99) | 9.80 (7.25, 13.33) |
| Interaction of pack-years with smoking status (former or current) | P = 0.4282 | P = 0.4910 | ||
| Pack-years trend | P < 0.0001 | P < 0.0001 | ||
| Increase in pack-year category | 1.57 (1.49, 1.64) | 1.58 (1.50, 1.65) | ||
| Never smokers | ||||
| Any passive smoking exposure among never smokers only (N = 39 771) | P = 0.6044a | P = 0.8449a | ||
| No passive exposure | 16/3620 | 42.0 | Refb | Refb |
| Passive exposure | 136/35 999 | 35.6 | 0.87 (0.52, 1.45) | 0.88 (0.52, 1.49) |
| Passive exposure categories among never smokers only (N = 39 771) | ||||
| Live with smoker as a child | P = 0.8830 | P = 0.8240 | ||
| No | 65/16 766 | 36.9 | Refc | Refc |
| Yes | 87/22 853 | 35.7 | 1.03 (0.73, 1.43) | 1.04 (0.74, 1.46) |
| Live with smoker as adult (adult home) | P = 0.3785 | P = 0.3012 | ||
| No | 51/15 170 | 31.4 | Refd | Refd |
| Yes | 101/24 449 | 39.2 | 1.17 (0.83, 1.66) | 1.21 (0.85, 1.72) |
| Work with a smoker (work)e | P = 0.9544 | P = 0.8437 | ||
| No | 48/12 749 | 35.6 | Reff | Reff |
| Yes | 104/26 870 | 36.5 | 1.01 (0.72, 1.43) | 1.04 (0.73, 1.47) |
| Interaction of childhood and adult home exposure | P = 0.6445 | P = 0.5868 | ||
| Interaction of childhood and work exposure | P = 0.9870 | P = 0.9906 | ||
| Interaction of adult home and work exposure | P = 0.0792 | P = 0.0643 | ||
| Interaction of childhood, adult home, and work exposure | P = 0.7872 | P = 0.7843 | ||
| Passive exposure durations/categories among never smokers only (N = 39 771) | ||||
| Childhood exposure category | P = 0.9928 | P = 0.9783 | ||
| No childhood exposure | 65/16 766 | 36.9 | Refc | Refc |
| <10 years | 13/3552 | 34.6 | 1.02 (0.56, 1.85) | 1.03 (0.57, 1.88) |
| 10–18 years | 74/19 301 | 35.9 | 1.02 (0.72, 1.45) | 1.04 (0.73, 1.47) |
| Adult home exposure category | P = 0.3406 | P = 0.2448 | ||
| No adult home exposure | 51/15 170 | 31.4 | Refd | Refd |
| <20 years | 52/14 211 | 34.1 | 1.09 (0.74, 1.63) | 1.11 (0.74, 1.65) |
| 20–<30 years | 17/4560 | 35.8 | 1.07 (0.61, 1.88) | 1.11 (0.63, 1.96) |
| ≥30 years | 32/5678 | 55.0 | 1.52 (0.95, 2.42) | 1.61 (1.00, 2.58) |
| Work exposure category | P = 0.4017 | P = 0.4349 | ||
| No work exposure | 48/12 749 | 35.6 | Reff | Reff |
| <10 years | 59/14 281 | 38.5 | 1.14 (0.78, 1.67) | 1.16 (0.79, 1.70) |
| 10–<20 years | 18/6385 | 26.5 | 0.72 (0.42, 1.24) | 0.74 (0.43, 1.29) |
| ≥20 years | 27/6204 | 42.0 | 1.02 (0.63, 1.64) | 1.05 (0.64, 1.72) |
| Passive exposure combinations among never smokers only (N = 39 771) | ||||
| Category of exposure | P = 0.4438 | P = 0.2938 | ||
| No passive exposure (childhood, adult home, work) | 16/3620 | 42.0 | Refb | Refb |
| Adult home + work + no childhood | 49/13 146 | 35.5 | 0.81 (0.46, 1.43) | 0.83 (0.47, 1.46) |
| Any childhood + no adult home or work | 9/2338 | 35.4 | 0.97 (0.43, 2.20) | 0.96 (0.42, 2.17) |
| Childhood <10 + any adult (work or home) | 13/3043 | 40.5 | 1.01 (0.49, 2.11) | 1.04 (0.50, 2.18) |
| Childhood ≥ 10 + adult <20 + work <10 years | 21/7467 | 25.8 | 0.70 (0.36, 1.34) | 0.70 (0.36, 1.36) |
| Childhood ≥ 10 + adult <20 + work ≥ 10 years | 5/2186 | 21.1 | 0.56 (0.20, 1.53) | 0.57 (0.21, 1.58) |
| Childhood ≥ 10 + adult ≥ 20 + work <10 years | 5/1425 | 33.6 | 0.83 (0.30, 2.25) | 0.81 (0.30, 2.24) |
| Childhood ≥ 10 + adult ≥ 20 + work ≥ 10 years | 2/535 | 35.7 | 0.87 (0.20, 3.79) | 0.96 (0.22, 4.22) |
| Childhood ≥ 10 + adult < 30 + work ≥ 20 years | 8/2381 | 32.0 | 0.76 (0.33, 1.78) | 0.80 (0.34, 1.89) |
| Childhood ≥ 10 + adult ≥ 30 + work < 20 years | 15/2390 | 60.7 | 1.35 (0.67, 2.73) | 1.48 (0.72, 3.04) |
| Childhood ≥ 10 + adult ≥ 30 + work ≥ 20 years | 9/1088 | 81.1 | 1.76 (0.78, 3.98) | 1.96 (0.85, 4.55) |
Multivariable-adjusted model is adjusted for age group, BMI category, ethnicity, prior history of lung cancer, family history of cancer in female and male relatives, education, vitamin D category, main occupation, hormone therapy use, oral contraceptive use, fruit servings per day, vegetable servings per day, red meat servings per day, alcohol use and physical activity.
Models of pack-years among current and former smokers further adjust for age started smoking.
All passive exposure categories defined a priori.
aAll P-values in this table represent Global Wald t-tests.
bNo passive smoking exposure during childhood, adult home, or work. Note: Reference groups in this table differ depending on category of passive smoking tested.
cNo passive smoking exposure during childhood only.
dNo passive smoking exposure during adult home only.
eWork passive smoking exposure is likely to be during adulthood, but not explicitly defined as such.
fNo passive smoking exposure during work only.