TABLE 2.
Mean difference in log serum concentrations of reproductive hormones, stratified by race of participants according to caffeine and coffee intakes (n = 433 ovulatory cycles)1
| Caffeine≥200 compared with <200 mg/d |
Coffee≥1 compared with <1 cup/d |
|||
| Log hormone | Model 12 | Model 23 | Model 12 | Model 23 |
| White (n = 277 cycles) | ||||
| E2 (pg/mL) | −0.09 (−0.19, 0.005) | −0.14 (−0.25, −0.03) | −0.04 (−0.14, 0.05) | −0.06 (−0.16, 0.03) |
| Free E2 (pg/mL) | −0.11 (−0.21, −0.01) | −0.15 (−0.26, −0.05) | −0.05 (−0.14, 0.04) | −0.03 (−0.07, 0.01) |
| Luteal progesterone (ng/mL) | −0.01 (−0.24, 0.23) | 0.00 (−0.27, 0.27) | −0.06 (−0.26, 0.15) | 0.04 (−0.17, 0.26) |
| FSH (mIU/mL) | −0.02 (−0.10, 0.05) | −0.04 (−0.12, 0.04) | 0.03 (−0.05, 0.10) | 0.02 (−0.05, 0.10) |
| LH (ng/mL) | −0.04 (−0.15, 0.06) | −0.12 (−0.23, −0.002) | −0.05 (−0.15, 0.05) | −0.06 (−0.16, 0.03) |
| Black (n = 92 cycles) | ||||
| E2 (pg/mL) | 0.14 (−0.16, 0.45) | 0.24 (−0.05, 0.53) | −0.03 (−0.28, 0.22) | −0.03 (−0.25, 0.20) |
| Free E2 (pg/mL) | 0.17 (−0.14, 0.47) | 0.27 (−0.01, 0.56) | 0.003 (−0.24, 0.25) | −0.01 (−0.23, 0.21) |
| Luteal progesterone (ng/mL) | 0.04 (−0.56, 0.65) | −0.10 (−0.74, 0.55) | −0.05 (−0.56, 0.47) | −0.05 (−0.56, 0.46) |
| FSH (mIU/mL) | −0.36 (−0.59, −0.14) | −0.36 (−0.57, −0.14) | −0.06 (−0.24, 0.13) | −0.08 (−0.25, 0.09) |
| LH (ng/mL) | −0.06 (−0.39, 0.28) | −0.08 (−0.39, 0.24) | 0.08 (−0.19, 0.35) | −0.003 (−0.25, 0.24) |
| Asian (n = 64 cycles) | ||||
| E2 (pg/mL) | 0.44 (0.15, 0.73) | 0.61 (0.31, 0.92) | 0.35 (0.16, 0.54) | 0.32 (0.13, 0.51) |
| Free E2 (pg/mL) | 0.27 (−0.02, 0.56) | 0.44 (0.13, 0.74) | 0.28 (0.09, 0.47) | 0.26 (0.07, 0.44) |
| Luteal progesterone (ng/mL) | 0.18 (−0.60, 0.96) | 0.28 (−0.60, 1.17) | −0.21 (−0.66, 0.25) | −0.11 (−0.56, 0.34) |
| FSH (mIU/mL) | 0.20 (−0.02, 0.42) | 0.17 (−0.06, 0.40) | 0.19 (0.04, 0.33) | 0.11 (−0.04, 0.25) |
| LH (ng/mL) | 0.43 (0.11, 0.74) | 0.52 (0.19, 0.85) | 0.27 (0.06, 0.47) | 0.14 (−0.06, 0.34) |
All values are mean differences (95% CIs). Coffee includes caffeinated (98%) and decaffeinated (2%) forms. Anovulation was defined as any cycle with a peak progesterone concentration ≤5 ng/mL and no observed serum LH peak at the mid– or late–luteal phase visits. There were 433 ovulatory cycles among whites, blacks, and Asians. The analyses were performed by using linear mixed-effects models on the log scale of hormones. Interactions between race and caffeine intake (≥200 compared with <200 mg/d) on total and free E2 and LH concentrations were significant (likelihood ratio test: P = 0.01, P = 0.02, and P = 0.01, respectively) and between race and coffee intake (≥1 compared with <1 cup/d) on total and free E2, LH, and FSH were significant (P = 0.06, P = 0.14, P = 0.01, and P = 0.03, respectively). E2, estradiol; FSH, follicle-stimulating hormone; LH, luteinizing hormone.
Adjusted for age, waist-to-hip ratio, perceived stress, daily exercise, and energy and alcohol intakes (all continuous).
Adjusted for age, waist-to-hip ratio, perceived stress, daily exercise, energy and alcohol intakes, and relevant phase-specific hormone concentrations by using inverse probability of exposure weights.