BACKGROUND: The magnitude of the link between cigarette smoking and lung cancer 
may vary by histological type.
METHODS: We used polytomous logistic regression to evaluate whether aspects of 
smoking have different effects across four histological types in the Nurses' 
Health Study.
RESULTS: From 1976 to 2002, we identified 1062 cases of lung cancer: squamous 
cell (n = 201), small cell (n = 236), adenocarcinoma (n = 543) and large cell 
carcinoma (n = 82), among 65 560 current or former smokers. Risk reduction after 
quitting ranged from an 8% reduction (relative risk (RR): 0.92, 95% CI 0.91 to 
0.94) to a 17% reduction (RR: 0.83, 95% CI 0.80 to 0.86) per year for 
adenocarcinoma and small cell carcinoma, respectively, with a 9% reduction 
observed for large cell carcinoma and an 11% reduction observed for squamous 
cell carcinoma. The association of age at smoking initiation and former 
cigarette smoking was similar across types, while the association of smoking 
duration differed. The risk of adenocarcinoma increased by 6% per year of 
smoking, compared to 7% for large cell, 10% for squamous cell and 12% for small 
cell. The 6% difference between adenocarcinoma and small cell carcinoma is 
equivalent to a 3.2 to 9.7-fold increase in risk for 20 years of smoking.
CONCLUSIONS: The effects of the number of cigarettes smoked per day and years 
since quitting smoking are different across the major types of lung cancer, 
which are fully appreciated at long durations of smoking and smoking cessation. 
Smoking prevention and cessation should continue to be the focus of public 
health efforts to reduce lung cancer incidence and mortality.