TABLE 1.
Serum ferritin concentrations according to categories of sociodemographic and lifestyle factors1
| Men | Women | |||||
| n | Mean, ng/mL | Multivariable-adjusted mean (95% CI), ng/mL | n | Mean, ng/mL | Multivariable-adjusted mean (95% CI), ng/mL | |
| Age, y | ||||||
| 18–44 | 1457 | 132.8 | 137.4 (129.5, 145.9) | 2196 | 29.1 | 28.5 (26.9, 30.1) |
| 45–54 | 960 | 132.0 | 128.7 (119.7, 138.3) | 1114 | 39.3 | 40.1 (37.3, 43.1) |
| 55–65 | 901 | 117.4 | 118.7 (110.6, 127.4) | 1044 | 81.7 | 75.2 (69.8, 81.1) |
| P-trend | 0.009 | <0.001 | <0.001 | <0.001 | ||
| Place of residence | ||||||
| Urban | 918 | 122.4 | 120.7 (113.0, 128.9) | 1093 | 44.7 | 41.5 (39.0, 44.3) |
| Rural | 2400 | 131.1 | 133.4 (126.5, 140.7) | 3261 | 37.9 | 39.8 (37.7, 42.0) |
| P value | 0.06 | 0.008 | <0.001 | 0.24 | ||
| Annual income, RMB | ||||||
| <9000 | 1472 | 117.9 | 121.6 (113.3, 130.5) | 2660 | 39.7 | 39.2 (36.7, 41.8) |
| 9000–15,000 | 538 | 133.1 | 136.5 (125.3, 148.7) | 707 | 39.8 | 40.4 (37.3, 43.7) |
| >15,000–25,000 | 642 | 130.9 | 131.3 (121.6, 141.7) | 581 | 38.4 | 40.3 (37.3, 43.5) |
| >25,000 | 666 | 134.4 | 131.0 (122.5, 140.1) | 406 | 43.3 | 43.2 (40.2, 46.4) |
| P-trend | 0.01 | 0.28 | 0.07 | 0.03 | ||
| BMI, kg/m2 | ||||||
| <18.5 | 173 | 89.7 | 89.8 (77.3, 104.2) | 210 | 27.8 | 36.6 (31.8, 42.1) |
| 18.5–24 | 1712 | 113.4 | 114.2 (107.9, 120.9) | 2031 | 34.4 | 38.8 (36.7, 41.0) |
| >24–28 | 1063 | 152.0 | 153.4 (143.7, 163.8) | 1101 | 44.2 | 42.3 (39.4, 45.3) |
| >28 | 294 | 171.4 | 174.9 (155.8, 196.5) | 379 | 49.5 | 46.5 (41.7, 51.8) |
| P-trend | <0.001 | <0.001 | <0.001 | <0.001 | ||
| Moderate-to-vigorous physical activity time, h/wk | ||||||
| <1 | 856 | 132.9 | 130.5 (121.7, 139.9) | 1152 | 35.1 | 40.5 (37.9, 43.2) |
| 1–3 | 688 | 134.6 | 137.0 (126.7, 148.2) | 890 | 39.7 | 40.6 (37.6, 43.7) |
| >3–6 | 793 | 124.9 | 127.1 (117.7, 137.3) | 930 | 40.7 | 40.4 (37.4, 43.5) |
| >6 | 905 | 121.4 | 124.1 (115.3, 133.6) | 749 | 37.5 | 39.9 (36.8, 43.4) |
| P-trend | 0.02 | 0.12 | 0.19 | 0.76 | ||
| Education | ||||||
| Illiterate | 349 | 121.7 | 131.6 (118.2, 146.4) | 1416 | 57.8 | 40.4 (37.6, 43.4) |
| Primary school | 582 | 119.1 | 124.1 (114.4, 134.7) | 792 | 39.8 | 36.4 (33.9, 39.2) |
| High school | 1906 | 130.9 | 128.6 (123.0, 134.4) | 1713 | 30.9 | 34.7 (33.0, 36.5) |
| Some college | 264 | 129.2 | 128.4 (113.9, 144.7) | 271 | 37.4 | 44.6 (39.4, 50.5) |
| ≥College | 217 | 140.4 | 133.7 (116.6, 153.2) | 162 | 33.9 | 47.0 (39.8, 55.5) |
| P-trend | 0.03 | 0.75 | <0.001 | 0.94 | ||
| Geographic region | ||||||
| South | 1040 | 124.9 | 119.4 (111.8, 127.6) | 1223 | 36.5 | 37.1 (34.8, 39.6) |
| Middle | 770 | 138.9 | 137.7 (127.7, 148.5) | 935 | 35.8 | 39.3 (36.5, 42.3) |
| North | 1508 | 125.3 | 131.2 (123.7, 139.2) | 2196 | 44.7 | 45.0 (42.3, 47.9) |
| P value | 0.04 | 0.01 | <0.001 | <0.001 | ||
| Tea consumption, times/wk | ||||||
| ≤1 | 1908 | 123.0 | 126.1 (119.5, 133.1) | 2891 | 37.4 | 40.7 (38.7, 42.8) |
| >1–6 | 302 | 134.7 | 133.2 (119.0, 149.1) | 236 | 40.2 | 41.2 (36.1, 47.0) |
| >6 | 1032 | 135.8 | 134.2 (125.3, 143.8) | 594 | 39.8 | 38.3 (35.0, 41.8) |
| P-trend | 0.009 | 0.11 | 0.19 | 0.19 | ||
| Smoking | ||||||
| No | 1308 | 124.3 | 124.3 (116.9, 132.2) | 4233 | 39.8 | 40.0 (38.2, 42.0) |
| Current or ever | 2010 | 130.8 | 132.3 (125.4, 139.7) | 121 | 62.5 | 51.2 (42.5, 61.7) |
| P value | 0.14 | 0.08 | <0.001 | 0.01 | ||
| Alcohol intake, g/d | ||||||
| 0 | 1339 | 121.1 | 124.8 (117.3, 132.7) | 3444 | 37.8 | 40.2 (38.3, 42.1) |
| >0–15 | 990 | 120.3 | 120.2 (112.4, 128.7) | 219 | 40.1 | 42.3 (37.0, 48.5) |
| >15 | 913 | 148.4 | 147.1 (137.0, 158.0) | 58 | 44.3 | 42.6 (32.8, 55.2) |
| P-trend | 0.87 | 0.41 | 0.45 | 0.46 | ||
| Iron intake | ||||||
| Quartile 1 | 795 | 134.2 | 133.4 (122.7, 145.1) | 906 | 36.6 | 38.1 (35.1, 41.4) |
| Quartile 2 | 818 | 125.3 | 126.2 (117.2, 136.0) | 1001 | 39.0 | 40.3 (37.4, 43.3) |
| Quartile 3 | 817 | 129.7 | 131.9 (122.5, 142.0) | 959 | 39.1 | 41.5 (38.6, 44.7) |
| Quartile 4 | 812 | 121.9 | 125.8 (115.7, 136.9) | 855 | 37.6 | 42.4 (39.0, 46.1) |
| P-trend | 0.09 | 0.50 | 0.85 | 0.11 | ||
| Phytate intake | ||||||
| Quartile 1 | 793 | 141.6 | 143.0 (132.1, 154.8) | 925 | 39.2 | 42.3 (39.1, 45.7) |
| Quartile 2 | 809 | 128.2 | 130.0 (120.6, 140.1) | 979 | 37.3 | 40.2 (37.4, 43.2) |
| Quartile 3 | 823 | 125.2 | 125.8 (116.9, 135.4) | 947 | 38.7 | 40.2 (37.4, 43.2) |
| Quartile 4 | 817 | 118.4 | 119.9 (110.7, 129.9) | 870 | 36.7 | 38.5 (35.4, 41.8) |
| P-trend | <0.001 | 0.002 | 0.30 | 0.11 | ||
| Vitamin C intake | ||||||
| Quartile 1 | 807 | 132.3 | 130.7 (121.4, 140.8) | 915 | 37.1 | 40.5 (37.6, 43.6) |
| Quartile 2 | 818 | 135.8 | 134.5 (125.1, 144.6) | 988 | 35.8 | 39.4 (36.7, 42.3) |
| Quartile 3 | 812 | 129.0 | 130.7 (121.3, 140.7) | 947 | 38.3 | 40.6 (37.8, 43.7) |
| Quartile 4 | 805 | 115.7 | 121.0 (112.0, 130.7) | 871 | 41.3 | 41.2 (38.1, 44.6) |
| P-trend | 0.002 | 0.07 | 0.01 | 0.57 | ||
| Calcium intake | ||||||
| Quartile 1 | 810 | 133.7 | 134.3 (124.2, 145.2) | 930 | 38.4 | 41.3 (38.1, 44.6) |
| Quartile 2 | 811 | 126.7 | 128.1 (119.0, 138.0) | 930 | 35.4 | 37.4 (34.8, 40.3) |
| Quartile 3 | 811 | 129.2 | 129.4 (120.1, 139.3) | 931 | 37.1 | 40.0 (37.2, 43.0) |
| Quartile 4 | 810 | 122.7 | 125.6 (116.2, 135.9) | 930 | 41.4 | 43.1 (39.8, 46.5) |
| P-trend | 0.12 | 0.30 | 0.03 | 0.13 | ||
All the mean values are the geometric mean of ferritin concentration. The medians for quartiles of nutrient intake (men/women) were as follows—iron: 15.0/13.0, 19.8/17.3, 24.9/21.8, and 35.8/31.7 mg/d; vitamin C: 37.3/33.6, 64.0/61.4, 90.6/88.6, and 137.4/137.0 mg/d; calcium: 230.4/198.8, 322.5/285.6, 431.2/381.8, and 640.7/578.6 mg/d; and phytates: 3.8/3.3, 9.7/8.4, 14.3/12.5, and 21.8/18.9 g/d. For categories of age, annual income, place of residence, geographic region, educational status, and smoking status, the general linear model (model 1) was simultaneously adjusted for age, annual income level, moderate-to-vigorous physical activity time, BMI, alcohol intake, tea consumption, and serum high-sensitivity C-reactive protein concentration as continuous variables and educational status, place of residence, geographic region, and smoking status as categorical variables except the stratification variable. For categories of moderate-to-vigorous physical activity time, BMI, alcohol intake, tea consumption, and dietary intakes of vitamin C, iron, phytates, and calcium, the general linear model was adjusted for total energy intake as continuous variables in addition to model 1 except the stratification variable. RMB, renminbi.