Table 2.

Risk of lung cancer in relation to reproductive characteristics and body mass index (Singapore Chinese Health Study 1993-2005, women only)

Person-yearsAll lung cancers
Adenocarcinomas only
Other histologic types
No. of casesRR* (95% CI)No. of casesRR* (95% CI)No. of casesRR* (95% CI)
No. of livebirths
    All women
        023,290361.00231.00131.00
        1-295,025550.52 (0.34-0.79)260.35 (0.20-0.62)290.81 (0.42-1.56)
        3-4128,103900.59 (0.40-0.87)450.42 (0.25-0.70)450.90 (0.48-1.67)
        5+94,1041170.49 (0.33-0.72)440.32 (0.19-0.55)730.77 (0.42-1.41)
        P for trend<0.01<0.010.48
    Ever smokers
        02,070151.0071.0081.00
        1-25,259140.40 (0.19-0.84)30.18 (0.05-0.71)110.59 (0.23-1.46)
        3-48,041280.65 (0.34-1.23)90.41 (0.15-1.12)190.85 (0.37-1.97)
        5+12,902520.45 (0.25-0.82)110.21 (0.08-0.57)410.65 (0.30-1.42)
        P for trend0.0890.0270.53
    Lifetime nonsmokers
        021,220211.00161.0051.00
        1-289,767410.58 (0.34-0.99)230.42 (0.22-0.79)181.11 (0.41-3.00)
        3-4120,062620.58 (0.35-0.96)360.44 (0.24-0.81)261.03 (0.39-2.68)
        5+81,202650.51 (0.30-0.86)330.37 (0.19-0.70)320.95 (0.36-2.50)
        P for trend0.0450.0200.71
Age at menarche
    All
        <15 y178,4631191.00531.00661.00
        15+ y161,9901791.22 (0.96-1.55)851.44 (1.01-2.05)941.07 (0.78-1.48)
0.100.0460.67
    Ever smokers
        <15 y13,041421.00121.00301.00
        15+ y15,207671.16 (0.78-1.72)181.14 (0.54-2.40)491.18 (0.74-1.87)
0.450.740.49
    Lifetime nonsmokers
        <15 y165,423771.00411.00361.00
        15+y146,7821121.27 (0.94-1.72)671.54 (1.03-2.31)450.99 (0.63-1.56)
0.120.0370.98
Age at menopause (y)
    All
        <5088,4041251.00481.00771.00
        50+137,3031430.83 (0.65-1.06)690.97 (0.67-1.41)740.73 (0.53-1.01)
        P value0.130.880.06
    Ever smokers
        <5011,438561.00161.00401.00
        50+13,637490.81 (0.55-1.18)120.69 (0.32-1.45)370.85 (0.54-1.33)
        P value0.270.320.47
    Lifetime nonsmokers
        <5076,965691.00321.00371.00
        50+123,666940.85 (0.62-1.16)571.11 (0.72-1.70)370.62 (0.40-0.99)
        P value0.300.650.04
Use of hormonal contraceptives
    All
        Never250,6742551.001201.001351.00
        <10 y79,083330.73 (0.50-1.07)130.49 (0.27-0.88)201.07 (0.65-1.76)
        10+ y10,696101.33 (0.70-2.52)51.23 (0.5-3.03)51.47 (0.60-3.63)
        P for trend0.560.150.45
Use of hormone replacement therapy
    All
        No322,7972861.001321.001541.00
        Yes17,656121.38 (0.76-2.49)61.11 (0.48-2.56)61.75 (0.75-4.06)
        P value0.290.810.19
  • * Adjusted for age at interview, year of interview (1993-1995, 1996-1998), dialect group (Cantonese, Hokkien), educational level (none, primary, secondary, or higher), body mass index, total vegetable intake, total fruit/juice intake, β-cryptoxanthin, total isothiocyanates, and (except for nonsmokers) duration of smoking (years), cigarettes per day, and number of years since quitting. Adjustment for number of livebirths did not alter results for menarche/menopause materially.

  • Women aged 50+ only.

  • The number of cases was too small for meaningful analysis by smoking status.