Baseline characteristics of the study population by case status
| Characteristic | Median (IQR)* | p value† | |
|---|---|---|---|
| Cases n = 630 | Controls n = 730 | ||
| Age at blood draw, yr, mean ± SD | 56.1 ± 6.5 | 56.1 ± 6.6 | matching |
| White, % | 98 | 98 | matching |
| Body mass index, kg/m2 | 29.9 (26.3–33.7) | 25.6 (22.9–30.9) | < 0.01 |
| Smoking status, % | 0.2 | ||
| Never smoked | 46 | 48 | |
| Past smoker | 42 | 42 | |
| Current smoker | 12 | 10 | |
| Activity, METs/wk‡ | 8.6 (3.8–18.7) | 12.2 (5.2–23.0) | < 0.01 |
| Alcohol intake, g/d | 1.0 (0–3.7) | 2.5 (0.4–8.0) | < 0.01 |
| Animal protein intake, g/d | 57.8 (50.9–64.8) | 56.4 (49.2–63.1) | < 0.01 |
| Potassium intake, mg/d | 2863 (2577–3171) | 2868 (2570–3205) | 0.6 |
| Total calcium intake, mg/d | 859 (676–1062) | 865 (685–1109) | 0.3 |
| Magnesium intake, mg/d | 286 (252–322) | 290 (257–332) | 0.08 |
| Cereal fibre intake, g/d | 3.6 (2.8–4.6) | 3.7 (2.9–4.8) | 0.04 |
| Trans fat intake, g/d | 3.2 (2.8–3.8) | 3.2 (2.7–3.8) | 0.2 |
| Glycemic index | 52.7 (50.8–54.5) | 52.2 (50.3–54.3) | 0.02 |
| Diabetes diet score§ | 11.0 (9.0–14.0) | 12.0 (10.0–14.0) | 0.01 |
| COPD, % | 14 | 12 | 0.2 |
| Hypertension, % | 52 | 31 | < 0.01 |
| Hypercholesterolemia, % | 49 | 39 | < 0.01 |
| Thiazide use, % | 24 | 16 | <0.01 |
| Family history of diabetes, % | 48 | 23 | < 0.01 |
| Use of postmenopausal hormones, % | 0.09 | ||
| Premenopausal | 21 | 23 | |
| Past use | 12 | 11 | |
| Current use | 30 | 35 | |
| Never used | 37 | 31 | |
| Fasting at blood draw, % | 67 | 65 | matching |
| Creatinine, mg/dL | 0.67 (0.60–0.76) | 0.69 (0.62–0.77) | < 0.01 |
| Estimated GFR, mL/min/1.73m2 | 97.4 (88.3–104.6) | 96.4 (86.2–102.6) | 0.02 |
| C-reactive protein, mg/dL | 0.37 (0.20–0.62) | 0.15 (0.07–0.34) | < 0.01 |
| Hemoglobin A1C, % | 6.1 (5.8–6.5) | 5.6 (5.4–5.8) | < 0.01 |
| Insulin, μU/mL | 11.3 (7.1–16.9) | 9.0 (5.0–12.7) | < 0.01 |
| Plasma bicarbonate, mmol/L | 22.0 (20.2–23.7) | 22.4 (20.5–23.9) | 0.02 |
Note: COPD = chronic obstructive pulmonary disease, GFR = glomerular filtration rate, IQR = interquartile range, METs = metabolic equivalents, SD = standard deviation.
↵* Unless otherwise stated.
↵† p values are from the Student t test for characteristics reported as means, Wilcoxon rank sum test for those reported as medians, and χ2 test for those reported as percentages.
↵‡ Physical activity reported on questionnaires was converted into METs using an established coding system. (15)
↵§ Diabetes scores ranged from 4 to 20, with higher scores associated with a reduced risk of type 2 diabetes mellitus.