Table 1.

Demographic characteristics by case–control status

Case (N = 500)Control (N = 500)P value*
Age (mean ± SD)62.50 ± 1.1261.80 ± 1.120.310
Age group (%)
 Age ≤ 50 y80 (16.00)65 (13.00)0.209
 Age > 50 y420 (84.00)435 (87.00)
Gender (%)
 Male245 (49.00)246 (49.20)0.949
 Female255 (51.00)254 (50.80)
Smoking (%)
 Never smokers91 (18.20)171 (34.20)<0.001
 Ever smokers409 (84.00)329 (65.80)
  Smoking intensitya (%)
   Light (0 < pack-years ≤ 20)79 (15.80)109 (21.80)<0.001
   Moderate (20 < pack-years ≤ 40)117 (23.40)86 (17.20)
   Heavy (40 < pack-years)213 (42.60)134 (26.80)
Smoking pack-yearsb (mean ± SE)45.56 ± 1.4337.53 ± 1.58<0.001
Environmental exposurec (%)
 Without environmental exposure243 (48.60)269 (53.80)0.114
 With at least 1 environmental exposure257 (51.40)231 (46.20)
  • *P values were obtained from Pearson χ2 test (categorical variables) and the Student 2-sample t test (continuous variables).

  • aSmoking intensity, light smokers (0 < pack-years ≤ 20), moderate smokers (20 < pack-years ≤ 40), heavy smokers (40 < pack-years).

  • bSmoking pack-years, years smoked times the average number of cigarettes per day divided by 20.

  • cSelf-reported exposure to at least 1 of 7 environmental agents (i.e., asbestos, fiberglass, wood dust, solvents, paints, exhaust, and bleach).