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. Author manuscript; available in PMC: 2025 Jun 6.
Published in final edited form as: Clin Chem. 2013 Sep 18;60(1):174–185. doi: 10.1373/clinchem.2013.207217

Table 3.

Adjusted geometric mean plasma concentrations of SHBG by regular coffee, decaffeinated coffee, and tea intakes in the WHI, 1993–1998.

SHBG concentrations, nmol/L P for linear trenda P for quadratic trenda
(Lowest) 95% CI Geometric mean 95% CI Geometric mean 95% CI Geometric mean 95% CI (Highest) 95% CI
Geometric mean Geometric mean
Regular coffee, n 1646 2135 4175 1245 393
 Range, cups/day, n    0    1  2–3  4–5 ≥6
 Model 1b   47.7 43.3–52.6   46.2 41.9–50.9   47.2 43.7–51.0   50.4 46.3–54.8  52.8 47.7–58.5 <0.001 0.002
 Model 2c   47.4 43.0–52.3   45.9 41.5–50.8   47.3 43.6–51.3   50.9 46.6–55.5  53.1 47.8–58.9 <0.001 0.002
Decaffeinated coffee, n 2215  859  645  121  22
 Range, cups/day, n    0    1  2–3  4–5 ≥6
 Model 1b   51.5 44.3–60.0   50.9 43.2–60.1   52.0 45.2–59.9   49.4 43.4–56.3  51.6 41.4–64.3 0.62 0.82
 Model 2c   51.6 44.0–60.4   50.8 42.5–60.6   51.8 44.9–59.7   49.3 43.4–55.9  53.2 42.4–66.7 0.64 0.57
Tea, n 4444  706  581   98  28
 Range, cups/day, n    0    1  2–3  4–5 ≥6
 Model 1b   51.1 43.5–59.9   49.5 43.9–55.8   50.2 44.6–56.5   52.6 42.7–64.8  51.1 41.2–63.3 0.70 0.47
 Model 2c   50.9 43.2–60.0   49.9 43.5–57.2   50.2 44.2–56.9   54.6 42.6–70.1  51.5 41.8–63.3 0.46 0.44
a

For increasing categories, 0, 1, 2.5, 4.5, and 6 cups/day were assigned to compute P values for trend.

b

Model 1, geometric mean and CI of SHBG concentrations and P values for linear trend and quadratic trend were estimated using the random-effects model with adjustment for age (continuous), ethnicity (categorical), BMI (continuous), cigarette smoking (never, past, or current), alcohol consumption (none/past drinkers, <1 drink/week, or ≥1 drink/week), physical activity (MET-h/week) (continuous), and total energy intake (continuous).

c

Model 2, further adjusted for reproductive history: use of exogenous estrogen, use of oral contraceptives, age of menarche (<13 vs ≥13 years), age of first pregnancy (<20 vs ≥20 years), parity (<5 vs ≥5 live births), and marital status (currently married vs not married).