Table 1.
Baseline sample characteristics by quartiles of selenium intake (n = 17,150).
| Factors | Q1 | Q2 | Q3 | Q4 | P-value |
|---|---|---|---|---|---|
| N = 4,331 | N = 4,315 | N = 4,255 | N = 4,249 | ||
| Selenium intake (ug/d), mean (SD) | 20.0 (5.0) | 31.8 (2.9) | 42.5 (3.6) | 71.2 (44.9) | <0.001 |
| Energy intake (kcal/d), mean (SD) | 1,793.9 (558.2) | 2,059.1 (561.2) | 2,281.0 (601.0) | 2,540.4 (687.6) | <0.001 |
| Fat intake (g/d), mean (SD) | 51.4 (30.9) | 62.8 (31.2) | 72.0 (33.2) | 86.1 (40.7) | <0.001 |
| Protein intake (g/d), mean (SD) | 48.0 (14.4) | 61.6 (14.9) | 72.5 (16.8) | 88.8 (23.8) | <0.001 |
| Carbohydrate intake (g/d), mean (SD) | 283.1 (115.1) | 308.5 (116.3) | 331.3 (126.6) | 345.8 (131.7) | <0.001 |
| Traditional southern dietary pattern score, mean (SD) | 0.1 (0.7) | −0.0 (0.9) | −0.0 (1.0) | 0.1 (1.3) | <0.001 |
| Modern dietary pattern score, mean (SD) | −0.5 (0.6) | −0.3 (0.8) | 0.0 (0.9) | 0.6 (1.3) | <0.001 |
| Age (years), mean (SD) | 44.0 (16.3) | 42.7 (15.4) | 41.9 (14.8) | 41.1 (14.4) | <0.001 |
| BMI (kg/m2), mean (SD) | 22.4 (3.3) | 22.7 (3.3) | 22.9 (3.3) | 23.3 (3.4) | <0.001 |
| Overweight (%) | 19.1% | 23.3% | 24.9% | 29.2% | <0.001 |
| Sex (%) | <0.001 | ||||
| Men | 37.3% | 43.2% | 52.5% | 59.6% | |
| Women | 62.7% | 56.8% | 47.5% | 40.4% | |
| Income (%) | <0.001 | ||||
| Low | 38.7% | 28.7% | 24.4% | 20.0% | |
| Medium | 33.5% | 35.4% | 34.2% | 30.3% | |
| High | 27.8% | 35.8% | 41.4% | 49.7% | |
| Education (%) | <0.001 | ||||
| Low | 52.8% | 40.1% | 33.7% | 26.6% | |
| Medium | 29.2% | 33.6% | 34.9% | 35.1% | |
| High | 18.1% | 26.3% | 31.5% | 38.3% | |
| Diabetes (baseline in 2009 only, %) n = 1228; 214, 274, 409, 2038 |
7.5% | 8.4% | 8.2% | 9.5% | 0.83 |
| Self-reported diabetes (%) | 1.6% | 1.8% | 2.0% | 2.9% | <0.001 |
| Hypertension (%) | 15.9% | 16.3% | 16.7% | 17.5% | 0.25 |
| Urbanization (%) | <0.001 | ||||
| Low | 43.5% | 30.3% | 24.4% | 19.3% | |
| Medium | 27.6% | 29.9% | 27.8% | 25.7% | |
| High | 28.9% | 39.7% | 47.7% | 55.0% | |
| Smoking (%) | <0.001 | ||||
| Non-smoker | 73.6% | 70.6% | 66.2% | 63.2% | |
| Ex-smokers | 2.0% | 1.8% | 1.9% | 2.4% | |
| Current smokers | 24.4% | 27.6% | 32.0% | 34.4% | |
| 7–9 h | 76.1% | 79.8% | 81.7% | 79.7% | |
| < = 6 h | 11.5% | 10.1% | 8.8% | 9.7% | |
| > = 10 h | 12.4% | 10.1% | 9.5% | 10.6% | |
| Physical activity (MET-hrs/week), mean (SD) | 143.8 (118.2) | 135.7 (113.0) | 129.4 (108.0) | 128.5 (108.7) | <0.001 |
| Survey year (%) | <0.001 | ||||
| 1997 | 49.1% | 47.7% | 46.1% | 37.3% | |
| 2000 | 14.3% | 15.0% | 13.3% | 13.7% | |
| 2004 | 9.1% | 7.8% | 8.3% | 11.2% | |
| 2006 | 3.9% | 4.7% | 5.1% | 6.5% | |
| 2009 | 6.6% | 8.0% | 9.5% | 11.8% | |
| 2011 | 16.9% | 16.7% | 17.8% | 19.6% |
BMI, body mass index; MET, metabolic equivalent; h, hours.