Associated Links Among Smoking, Chronic Obstructive Pulmonary Disease, and Small Cell Lung Cancer: A Pooled Analysis in the International Lung Cancer Consortium.

All the smoking variables showed a higher effect on SCLC risk in COPD subgroup than those in non-COPD subjects with significance or borderline significance except for time since quitting smoking which was probably due to insufficient sample size (Table S2).

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Further, stratified analyses by control type showed a trend of higher effects of smoking behaviors on SCLC risk in the studies with population-based controls than those in the studies with hospital-based controls (Table S5).

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