Table 7 Relative risks (95 CI) for lung cancer by histological type, from the polytomous logistic regression model 2 comparing risks associated with current and former smoking, Nurses’ Health Study, 1976–2002: relative risks corresponding with 5, 10 and 15 years of smoking duration*

Histological type	Years of smoking duration
Histological type	5 years	10 years	15 years
Squamous cell carcinoma	1.58 (1.43 to 1.75)	2.50 (2.04 to 3.06)	3.95 (2.91 to 5.36)
Small cell carcinoma	1.73 (1.54 to 1.94)	2.98 (2.37 to 3.74)	5.14 (3.64 to 7.25)
Adenocarcinoma	1.35 (1.28 to 1.42)	1.82 (1.64 to 2.02)	2.45 (2.10 to 2.87)
Large cell carcinoma	1.42 (1.23 to 1.65)	2.02 (1.51 to 2.72)	2.88 (1.85 to 4.49)

*Age and cigarettes smoked per day included in the model.