Table 2.

Multivariate-adjusteda geometric means of estrogen metabolism measures by quartiles of caffeine intake

Geometric mean by caffeine intake
<49 mg/d49–163 mg/d164–366 mg/d≥367 mg/dPtrend
Individual and grouped EM (pmol/mg creatinine)
Total EM199.0183.4203.5211.00.10
Parent estrogens40.839.440.541.30.67
Methylated catechols11.410.910.110.50.28
 Methylated 2-catechols11.110.69.710.10.25
  2-Hydroxyestrone-3-methyl ether1.
 Methylated 4-catechols0.
2-Hydroxylation pathway70.164.864.076.70.25
4-Hydroxylation pathway8.
16-Hydroxylation pathway62.361.067.365.30.33
Ratios (pmol/pmol)
2-Catechols/methylated 2-catechols5.
4-Catechols/methylated 4-catechols31.725.927.226.80.53
Catechols/methylated catechols5.
Parent estrogens/2-, 4-, 16-pathways0.
2-Pathway/parent estrogens1.
4-Pathway/parent estrogens0.
16-Pathway/parent estrogens1.
  • aAdjusted for age at urine collection (continuous), BMI at collection (kg/m2, continuous), height (continuous), ovulatory cycle (yes/no), first-morning urine (yes/no), quartiles of alcohol intake (nondrinker, ≤1.49, 1.50–4.85, >4.85 g/day), total physical activity (<3, 3–8.9, 9–17.9, 18–26.9, 27–41.9, ≥42 MET h/wk), current tobacco use (yes/no), luteal day (≤5, 6–7, 8–9, ≥10 days to next period), usual menstrual cycle length (<26, 26–31, ≥32 days), menstrual cycle regularity (extremely regular, very regular, regular, usually/always irregular), and age at first birth and parity (nulliparous, age at first birth <25 years/1–2 children, age at first birth 25–29 years/1–2 children, age at first birth ≥30 years/1–2 children, age at first birth <25 years/≥3 children, age at first birth ≥25 years/≥3 children). Numbers do not sum to 603 due to missing values for exposure. Significant Ptrend shown in bold.