Table 1.

Select population characteristics of breast cancer cases and controls from the Nurses' Health Study

VariableCases, n = 1,122Controls, n = 1,147P
Age at blood draw*, mean (SD)58.4 (6.5)58.4 (6.4)0.98
Age at diagnosis*, mean (SD)65.7 (6.7)65.6 (6.7)0.78
RTL, mean (SD)17.8 (6.6)17.9 (7.0)0.90
RTL, median16.716.90.64
Pack-years of smoking at blood draw, mean (SD)24.0 (20.9)21.9 (18.1)0.07
BMI at blood draw, mean (SD)25.5 (4.6)25.4 (4.6)0.58
Family history of breast cancer§ (%)24.217.7<0.01
  • * Age was a matching factor.

  • P value obtained using the Wilcoxon signed-rank test on 1,105 case-control pairs.

  • Among cigarette smokers only.

  • § P value obtained by χ2 test.