Table 2.

Lung cancer risk of study participants exposed to childhood secondhand smoke

NCI-MD studyMayo 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-smoker250 (82)140 (80)1.32 (0.79-2.19)
    Current smoker236 (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 home33 (6)33 (10)1.02 (0.56-1.87)27 (16)34 (12)1.78 (0.99-3.19)
Moderate exposure in childhood home31 (6)17 (5)2.19 (1.08-4.42)30 (17)33 (11)1.84 (1.04-3.26)
Heavy exposure in childhood home339 (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 home109 (23)118 (41)1.00 (reference)74 (45)153 (57)1.00 (reference)
    Light exposure from father145 (31)79 (27)1.85 (1.21-2.83)30 (17)41 (14)1.51 (0.88-2.61)
    Moderate exposure from father153 (33)66 (23)2.04 (1.31-3.17)27 (16)37 (13)1.51 (0.85-2.66)
    Heavy exposure from father58 (12)25 (9)2.89 (1.59-5.26)34 (20)39 (14)1.80 (1.05-3.08)
    P trend0.0010.02
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 home109 (34)118 (56)1.00 (reference)74 (74)153 (78)1.00 (reference)
    Light exposure from mother27 (8)17 (8)1.83 (0.87-3.84)9 (5)12 (4)1.55 (0.63-3.84)
    Moderate exposure from mother108 (34)53 (25)1.93 (1.17-3.16)6 (4)8 (3)1.55 (0.52-4.63)
    Heavy exposure from mother74 (23)23 (11)2.92 (1.55-5.48)11 (6)24 (8)0.95 (0.44-2.04)
    P trend<0.0010.47
  • *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.