Reproductive and hormonal factors and the risk of nonsmall cell lung cancer

Although exposure to estrogen may directly influence or modify the association between cigarette smoking and lung cancer risk, results from epidemiologic studies examining the association between reproductive and hormonal factors and risk of lung cancer among women have been inconsistent. Between 1998 and 2008, 430 women diagnosed with nonsmall cell lung cancer, 316 hospital controls and 295 population controls were recruited into the multi-center Maryland Lung Cancer Study. Conditional logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) according to reproductive and hormonal exposures adjusting for age, smoking, passive smoking, education and household income. Results were similar for hospital and population based controls, so the control groups were combined. Reduced risks of lung cancer were observed among women with greater parity (≥ 5 vs. 1-2 births: OR = 0.50, 95% CI = 0.32, 0.78, p-trend = 0.002) and later ages at last birth (≥ 30 vs.