Table 3 Relative risks (RR; 95 CI) for former smoking for four main histological types of lung cancer, comparing former with never smokers, Nurses’ Health Study, 1976–2002*
Years since quitting
1 to <55 to <1010 to <1515 to <2020+
Squamous cell carcinoma:
    Cases282613811
    RR9.86 (3.87 to 25.0)8.42 (3.29 to 21.6)4.39 (1.58 to 12.19)2.74 (0.89 to 8.40)0.87 (0.30 to 2.53)
Small cell carcinoma:
    Cases2424642
    RR36.9 (7.95 to 171.2)33.9 (7.29 to 157.2)8.42 (1.56 to 45.6)5.69 (0.95 to 34.1)0.66 (0.09 to 5.13)
Adenocarcinoma:
    Cases7053472860
    RR3.10 (2.10 to 4.58)2.28 (1.57 to 3.44)2.15 (1.40 to 3.28)1.37 (0.84 to 2.24)0.76 (0.50 to 1.14)
Large cell carcinoma:
    Cases613644
    RR2.30 (0.71 to 7.42)5.08 (1.84 to 13.99)2.50 (0.76 to 8.16)1.69 (0.45 to 6.37)0.48 (0.13 to 1.79)
All histological types:
    Cases128116724477
    RR4.18 (3.05 to 5.73)3.64 (2.65 to 5.01)2.37 (1.67 to 3.37)1.53 (1.02 to 2.28)0.67 (0.47 to 0.96)
  • *Separate regression models for each histological type, adjusted for age, cigarettes smoked per day before quitting and follow-up period. Reference category consists of never smokers. See table 2.