1.model: expr ~ CS + FS + covariates, in which CS was compared with
FS+NS and FS was used as an indenpendent variable.
2.covariates includes: age, sex, bmi, alcohol consumption and diabetes
3.the results are stored in the files:
F3 smoking associated genes_lm.csv
S4 smoking associated genes_lm.csv
F4 smoking associated genes_lm.csv