Table 2. Lung cancer risk of study participants exposed to childhood secondhand smoke.
| NCI-MD study | Mayo Clinic study | |||||
|---|---|---|---|---|---|---|
| Cases (n = 624) |
Controls (n = 348) |
Adjusted OR (95% CI) |
Cases (n = 172) |
Controls (n = 289) |
Adjusted OR (95% CI) |
|
| Subjects exposed during childhood to secondhand smoke (%) | ||||||
| Never smoker* | 28 (62) | 61 (46) | 2.25 (1.04-4.90) | 98 (57) | 135 (47) | 1.47 (1.00-2.15) |
| Ex-smoker† | 250 (82) | 140 (80) | 1.32 (0.79-2.19) | |||
| Current smoker‡ | 236 (86) | 29 (76) | 1.91 (0.77-4.73) | |||
| No exposure in childhood home§,‖,¶ | 109 (21) | 118 (37) | 1.00 (reference) | 76 (44) | 163 (56) | 1.00 (reference) |
| Light exposure in childhood home | 33 (6) | 33 (10) | 1.02 (0.56-1.87) | 27 (16) | 34 (12) | 1.78 (0.99-3.19) |
| Moderate exposure in childhood home | 31 (6) | 17 (5) | 2.19 (1.08-4.42) | 30 (17) | 33 (11) | 1.84 (1.04-3.26) |
| Heavy exposure in childhood home | 339 (66) | 147 (47) | 2.23 (1.55-3.20) | 39 (23) | 59 (20) | 2.37 (1.83-4.28) |
| P trend | <0.001 | <0.001 | ||||
| Exposed to father's smoke § | 437 (80) | 192 (62) | 2.30 (1.62-3.25) | 91 (53) | 117 (41) | 1.22 (1.04-1.45) |
| No exposure in childhood home | 109 (23) | 118 (41) | 1.00 (reference) | 74 (45) | 153 (57) | 1.00 (reference) |
| Light exposure from father | 145 (31) | 79 (27) | 1.85 (1.21-2.83) | 30 (17) | 41 (14) | 1.51 (0.88-2.61) |
| Moderate exposure from father | 153 (33) | 66 (23) | 2.04 (1.31-3.17) | 27 (16) | 37 (13) | 1.51 (0.85-2.66) |
| Heavy exposure from father | 58 (12) | 25 (9) | 2.89 (1.59-5.26) | 34 (20) | 39 (14) | 1.80 (1.05-3.08) |
| P trend | 0.001 | 0.02 | ||||
| Exposed to mother's smoke § | 253 (70) | 107 (48) | 2.46 (1.63-3.73) | 26 (15) | 44 (15) | 0.92 (0.72-1.16) |
| No exposure in childhood home | 109 (34) | 118 (56) | 1.00 (reference) | 74 (74) | 153 (78) | 1.00 (reference) |
| Light exposure from mother | 27 (8) | 17 (8) | 1.83 (0.87-3.84) | 9 (5) | 12 (4) | 1.55 (0.63-3.84) |
| Moderate exposure from mother | 108 (34) | 53 (25) | 1.93 (1.17-3.16) | 6 (4) | 8 (3) | 1.55 (0.52-4.63) |
| Heavy exposure from mother | 74 (23) | 23 (11) | 2.92 (1.55-5.48) | 11 (6) | 24 (8) | 0.95 (0.44-2.04) |
| P trend | <0.001 | 0.47 | ||||
OR is adjusted for age, gender, exposure to secondhand smoke during adulthood, education, and first-degree relative with lung cancer.
OR is adjusted for same as never smokers along with number of cigarettes/day, number of years smoked, age at initiation, and time since quitting.
OR is adjusted for same as never smokers along with number of cigarettes/day, number of years smoked, and age at initiation.
OR is adjusted for age, gender, smoking status, exposure to secondhand smoke during adulthood, education level, first-degree relative with lung cancer, number of cigarettes/day, number of years smoked, age at initiation, and time since quitting.
Light exposure during childhood was <0.5 half pack per day smoked by members of the household, moderate exposure was 0.5 to 1 pack of exposure per day, and heavy exposure was >1 pack per day.
One hundred twelve cases (18%) and 33 controls in the NCI-MD study (9%) were missing data on number of cigarettes smoked by their mother or father so exposure level could not be calculated.