Table 2.

Age-adjusted associations of risk factors with ER+ invasive breast cancer in the whole cohort

Variable (comparison)Relative risk (95 % CI)
No. cases*196
Education > 16 y (≤16 y)1.7 (1.1-2.5)
Weight (per 10 kg)1.2 (1.1-1.3)
Distal radius BMD1.3 (1.1-1.5)
Family history of breast cancer1.2 (0.8-1.8)
Current smoker (noncurrent)1.1 (0.7-1.7)
Surgical menopause (natural)1.2 (0.8-1.9)
Takes walks for exercise (none)0.8 (0.6-1.1)
Alcoholic drinks/wk (per four drinks)1.1 (1.0-1.3)
Exercise (kcal/wk; per 1,631 kcal)1.0 (0.9-1.2)
Age at last natural menses (per 6.3 y)1.1 (0.9-1.3)
Age at menarche (per 1.5 y)0.9 (0.8-1.1)
Years of reproductive life (per 6.5 y)1.1 (0.9-1.3)
Age at first child born (per 5 y)1.0 (0.9-1.2)
Births (per 1.6 live births)1.0 (0.8-1.1)
Children breast-fed (per 1.6 children)1.0 (0.9-1.2)
  • Abbreviation: BMD, bone mineral density.

  • * The number of cases in the whole cohort (208) is greater than in the case-cohort analyses because 12 participants did not have sufficient blood for analyses of sex hormone levels in the case-cohort study.

  • Per SD increase in BMD.

  • At least one sister or mother with breast cancer.