TABLE 2.
RR (95% CI) of CHD associated with plasma markers of body iron stores among U.S. women1
| Quartile of body iron store biomarker |
|||||
|---|---|---|---|---|---|
| Biomarker2 | 1 (lowest) | 2 | 3 | 4 (highest) | P-trend3 |
| sTfR:ferritin ratio | |||||
| Cases/control, n/n | 48/120 | 75/121 | 57/121 | 62/121 | |
| Mean (range) | 0.01 (0.001–0.02) | 0.02 (0.01–0.04) | 0.04 (0.02–0.08) | 0.17 (0.04–2.48) | |
| Model 1 (matching factors) | 1.0 | 1.54 (0.99, 2.41) | 1.19 (0.75, 1.90) | 1.27 (0.80, 2.02) | 0.95 |
| Model 2 (multivariate) | 1.0 | 1.42 (0.89, 2.28) | 1.14 (0.70, 1.86) | 1.15 (0.70, 1.90) | 0.72 |
| Model 3 (multivariate) | 1.0 | 1.39 (0.82, 2.36) | 1.12 (0.66, 1.91) | 1.13 (0.65, 1.97) | 0.61 |
| Ferritin, μg/L | |||||
| Cases/control, n/n | 57/120 | 53/119 | 70/123 | 62/121 | |
| Mean (range) | 21.1 (3.0–41.3) | 49.8 (34.4–68.1) | 90.5 (64.3–120.2) | 189.4 (118.4–683.0) | |
| Model 1 (matching factors) | 1.0 | 0.94 (0.60, 1.47) | 1.19 (0.77, 1.84) | 1.09 (0.69, 1.73) | 0.58 |
| Model 2 (multivariate) | 1.0 | 1.01 (0.63, 1.63) | 1.21 (0.75, 1.94) | 1.14 (0.69, 1.88) | 0.55 |
| Model 3 (multivariate) | 1.0 | 1.05 (0.62, 1.77) | 1.19 (0.69, 2.03) | 1.05 (0.60, 1.85) | 0.90 |
| sTfR, mg/L | |||||
| Cases/control, n/n | 33/121 | 61/120 | 59/122 | 89/120 | |
| Mean (range) | 1.41 (0.53–2.37) | 1.76 (1.21–2.86) | 2.11 (1.44–3.39) | 2.80 (1.73–7.45) | |
| Model 1 (matching factors) | 1.0 | 1.94 (1.17, 3.21) | 1.81 (1.10, 2.97) | 2.79 (1.70, 4.59) | 0.0004 |
| Model 2 (multivariate) | 1.0 | 1.91 (1.11, 3.26) | 1.56 (0.92, 2.63) | 2.39 (1.40, 4.07) | 0.01 |
| Model 3 (multivariate) | 1.0 | 1.74 (0.98, 3.10) | 1.40 (0.79, 2.47) | 1.54 (0.85, 2.77) | 0.36 |
The lowest quartile is the reference group. Mean (range) of each quartile is based on the distributions among controls.
Model 1 is controlled for matching factors, i.e. age at blood draw (y), smoking status (never, past, current), and fasting status (yes, no). Multivariate model 2 is further controlled for postmenopausal status (yes, no), postmenopausal hormone use (never, past, current), physical activity (in tertiles), alcohol intake (0, 0–4, 5–14, ≥15 g/d), intake of red meat (g/d), parental history of MI before age 65 y (yes, no), and BMI (<25, 25–29, ≥30 kg/m2). Based on model 2, model 3 is further adjusted for history of hypertension (presence, absence), history of hypercholesterolemia (presence, absence), and history of diabetes (presence, absence).
Linear scores derived from the medians of quartiles of biomarker levels among controls were used to estimate P-values for trend. Estimates of P-value for linear trend are all based on t tests.