Table 2.

Characteristics of the study population

VariablesCase-control studyP
Cases (n = 720)Controls (n = 720)
Age (y)
    Mean ± SD61.3 ± 8.860.6 ± 9.30.12*
    Median (interquartile)62 (12)61 (12)0.06
Sex
    Male565 (78.5)565 (78.5)
    Female155 (21.5)155 (21.5)
Smoking status<0.001§
    Current463 (64.3)331 (46.0)
    Former116 (16.1)191 (26.5)
    Never141 (19.6)198 (27.5)
Pack-years
    Mean ± SD39.8 ± 18.132.8 ± 18.0<0.001*
    Median (interquartile)40 (20)31 (23)<0.001
Histologic types
    Squamous cell carcinoma320 (44.4)
    Adenocarcinoma273 (37.9)
    Large cell carcinoma12 (1.7)
    Small cell carcinoma115 (16.0)
  • *t test.

  • Wilcoxon rank-sum test.

  • Numbers in parenthesis, column percentage.

  • §χ2 test.

  • In current and former smokers.