Table 1.

Demographic characteristics of study participants

NCI-MD studyMayo Clinic study
Cases (n = 624)Controls (n = 348)P*Cases (n = 172)Controls (n = 289)P*
Age (y)0.990.64
    Mean ± SD66.6 ± 10.366.6 ± 9.561.3 ± 12.761.9 ± 14.6
Gender (%)0.700.50
    Male320 (51)183 (53)49 (28)91 (31)
    Female304 (49)165 (47)123 (72)198 (69)
Highest levels of education (%)<0.0010.06
    Less than high school139 (24)27 (9)12 (7)10 (4)
    High school degree340 (58)180 (58)80 (48)140 (49)
    College degree87 (15)76 (25)39 (23)49 (17)
    Graduate degree20 (3)26 (8)37 (22)85 (30)
Smoking history (%)§<0.001
    Never smoker45 (7)134 (39)172 (100)289 (100)
    Ex-smoker305 (49)176 (51)0 (0)0 (0)
    Current smoker274 (44)38 (11)0 (0)0 (0)
  • *P values are calculated from a Pearson χ2 test, except for age, which is calculated using Student's t-test.

  • P value is based on an overall comparison, rather than individual strata, of the characteristic in cases versus controls.

  • Education data missing from 38 cases and 39 controls from the NCI-MD study and 4 cases and 5 controls from the Mayo Clinic study.

  • §The Mayo Clinic study consisted only of never smokers.