Table 4.

Doubling of circulating endogenous hormones and breast cancer risk, by age at first birth and age at diagnosis: FMC (n = 3,480)

Age at diagnosis <40 yearsAge at diagnosis ≥40 years
Cases/controlsOR (95% CI)PhetaCases/controlsOR (95% CI)Pheta
Age at first birth <30 years
Estradiol
 Overall384/7381.20 (1.00–1.45)181/3410.96 (0.73–1.26)
 ER+/PR+108/2060.92 (0.65–1.31)0.0367/1271.12 (0.72–1.75)0.75
 ER/PR77/1501.72 (1.11–2.67)23/430.95 (0.38–2.41)
Estrone
 Overall384/7381.17 (1.01–1.35)181/3410.91 (0.75–1.12)
 ER+/PR+108/2060.97 (0.74–1.27)0.0867/1270.98 (0.71–1.35)0.46
 ER/PR77/1501.44 (1.02–2.05)23/430.71 (0.33–1.56)
Progesterone
 Overall384/7391.16 (0.89–1.51)181/3411.33 (0.90–1.95)
 ER+/PR+108/2060.84 (0.52–1.38)0.0467/1271.18 (0.61–2.29)0.92
 ER/PR77/1501.99 (1.04–3.82)23/431.10 (0.31–3.89)
Testosterone
 Overall383/7371.17 (0.96–1.41)181/3411.11 (0.84–1.49)
 ER+/PR+108/2061.03 (0.72–1.49)0.0867/1271.16 (0.71–1.88)0.24
 ER/PR77/1501.67 (1.13–2.47)23/430.55 (0.17–1.74)
Age at first birth ≥30 years
Estradiol
 Overall126/2411.31 (0.93–1.84)b501/9410.84 (0.71–0.99)b
 ER+/PR+41/781.11 (0.63–1.97)0.33218/4020.87 (0.68–1.13)0.71
 ER/PR20/380.61 (0.21–1.78)42/800.77 (0.43–1.40)
Estrone
 Overall126/2411.09 (0.86–1.39)501/9420.93 (0.82–1.05)
 ER+/PR+41/781.03 (0.66–1.61)0.60218/4030.98 (0.81–1.19)0.76
 ER/PR20/380.84 (0.45–1.55)42/800.92 (0.61–1.37)
Progesterone
 Overall126/2410.97 (0.62–1.53)501/9411.03 (0.84–1.26)
 ER+/PR+41/780.64 (0.26–1.56)0.10218/4020.94 (0.67–1.31)0.32
 ER/PR20/382.62 (0.61–11.20)42/800.59 (0.25–1.38)
Testosterone
 Overall126/2411.14 (0.83–1.58)500/9411.02 (0.87–1.20)
 ER+/PR+41/781.19 (0.67–2.09)0.90217/4021.06 (0.83–1.35)0.10
 ER/PR20/381.28 (0.47–3.46)42/800.61 (0.33–1.13)

NOTE: Conditional logistic regression models adjusted for gestational age at blood donation and family history of breast cancer.

  • aHeterogeneity between ER+/PR+ and ER/PR.

  • bPdifference < 0.05 comparing age at diagnosis <40 to ≥40 years; no significant heterogeneity by age at first birth.