Fig. 1.
The dose–response relationship between smoking behaviors and the risk of SCLC. Smoking pack-years were explored on the non-linear dose–response relationship on SCLC risk among all samples (a), or stratified by COPD status (b, c), by gender (d, e), or by study areas (f, g). Time since quitting smoking was also explored by cubic spline regressions for non-linearity among all samples (h), or stratified by COPD status (i, j), by gender (k, l), or among Caucasian-dominated areas (m). Due to insufficient sample size, there was no subgroup analysis done among non-Caucasian-dominated areas. The x-axis represents the quantitative smoking information while the y-axis represents the odds in loge scale.