Table 2.

The associations of incident postmenopausal breast cancer risk with metabolic health defined by HOMA-IR or insulin levels, stratified by BMI category

BMI categoryN (cases/subcohort)Age-adjusted HR (95% CI)PMultivariate HRa (95% CI)P
HOMA-IR–based definition of metabolic health
 Normal weight (<25 kg/m2)
  Metabolically healthyb113/3561.00 (Referent)1.00 (Referent)
  Metabolically unhealthyc18/1821.68 (0.85–3.33)0.131.80 (0.88–3.70)0.11
 Overweight (≥25 kg/m2)
  Metabolically healthyb87/3390.93 (0.64–1.34)0.680.96 (0.64–1.42)0.83
  Metabolically unhealthyc169/12381.60 (1.12–2.28)0.011.76 (1.19–2.60)0.005
Insulin-based definition of metabolic health
 Normal weight (<25 kg/m2)
  Metabolically healthyd108/3521.00 (Referent)1.00 (Referent)
  Metabolically unhealthye19/1801.86 (0.95–3.65)0.072.06 (1.01–4.22)0.048
 Overweight (≥25 kg/m2)
  Metabolically healthyd86/3290.93 (0.64–1.35)0.710.96 (0.64–1.42)0.82
  Metabolically unhealthye175/12501.86 (1.30–2.66)0.0012.01 (1.35–2.99)0.001
  • aVariables that are included in the multivariate model.

  • bHOMA-IR (quartile 1);

  • cHOMA-IR (quartiles 3+4);

  • dInsulin (quartile 1); and

  • eInsulin (quartiles 3+4); adjusted for age, ethnicity, age at menarche and menopause, parity, first-degree relative with breast cancer, education, alcohol consumption, physical activity, which of the two WHI studies each subject was enrolled in and, among those who participated in the clinical trials, which specific clinical trial arm they were assigned to and whether they were a member of the placebo or treatment group.