Table 1. Baseline characteristics of premenopausal and postmenopausal women.
| Premenopause (n = 4229) | Postmenopause (n = 3071) | p-value | |
| Age (years) | 36.45±8.50 | 63.63±9.22 | <0.001 |
| Height (cm) | 159.35±5.57 | 153.02±5.84 | <0.001 |
| Weight (kg) | 57.40±9.19 | 56.68±8.58 | 0.001 |
| BMI (kg/m2) | 22.61±3.44 | 24.17±3.20 | <0.001 |
| Hb (g/dL) | 12.83±1.18 | 13.11±0.97 | <0.001 |
| Serum Ferritin (ng/mL) | 32.22±27.64 | 68.22±47.70 | <0.001 |
| Serum Vitamin D (ng/mL) | 16.44±5.80 | 19.10±7.27 | <0.001 |
| Serum ALP (IU/L) | 183.24±52.85 | 253.36±74.48 | <0.001 |
| Serum PTH (pg/mL) | 66.67±23.49 | 68.13±29.87 | 0.446 |
| Ca intake/day (mg) | 467.06±300.56 | 419.17±392.40 | <0.001 |
| P intake/day (mg) | 1042.90±435.36 | 945.38±430.67 | <0.001 |
| Total femur BMD (g/cm2) | 0.90±0.11 | 0.77±0.12 | <0.001 |
| Femur neck BMD (g/cm2) | 0.76±0.10 | 0.62±0.11 | <0.001 |
| Lumbar spine BMD (g/cm2) | 0.99±0.12 | 0.80±0.14 | <0.001 |
| Resident district | <0.001 | ||
| Urban | 2968 (70.2) | 179 (58.4) | |
| Rural | 1261 (29.8) | 1279 (41.6) | |
| Education | <0.001 | ||
| Elementary | 186 (4.4) | 2039 (67.0) | |
| Middle, High school | 2301 (54.6) | 880 (28.9) | |
| University, College | 1729 (41.0) | 126 (4.1) | |
| Occupation | <0.001 | ||
| Office type | 3851 (91.5) | 2178 (71.6) | |
| Outfield type | 360 (8.5) | 866 (28.4) | |
| Alcohol | <0.001 | ||
| Never | 2163 (51.3) | 2523 (82.4) | |
| ≤Once/month | 1578 (37.4) | 418 (13.7) | |
| >Once/month, ≤Once/week, | 395 (9.4) | 85 (2.8) | |
| >Once/week, ≤Everyday | 84 (2.0) | 35 (1.1) | |
| Smoking | <0.001 | ||
| Never | 3638 (88.5) | 2790 (92.4) | |
| Ever | 193 (4.7) | 95 (3.1) | |
| Current | 280 (6.8) | 136 (4.5) | |
| Physical activity | 0.001 | ||
| Low | 2684 (63.7) | 2071 (67.9) | |
| Moderate | 890 (21.1) | 600 (19.7) | |
| High | 640 (15.2) | 381 (12.5) | |
| Dietary intake | <0.001 | ||
| Frequently difficult | 14 (0.4) | 57 (2.0) | |
| Occasionally difficult | 107 (2.8) | 239 (8.5) | |
| Enough, but not diverse | 1932 (50.3) | 1569 (55.5) | |
| Diverse, Enough | 1790 (46.6) | 960 (34.0) | |
| Personal history of fracture | <0.001 | ||
| Yes | 101 (2.4) | 637 (20.7) | |
| Family history of fracture | 0.797 | ||
| Yes | 723 (17.1) | 518 (16.9) | |
| HT | <0.001 | ||
| No | 4138 (97.8) | 2637 (85.9) | |
| Yes | 91 (2.2) | 434 (14.1) |
BMI: Body mass index, Hb: Hemoglobin, ALP: Alkaline phosphatase, PTH: Parathyroid hormone, Ca: Calcium, P: Phosphate, BMD: Bone mineral density, HT: Hormonal therapy.
Reference range: Hb 12.0–16.0 g/dL; Ferritin 10.0–130.0 ng/mL; Vitamin D 30.0–100.0 ng/mL; ALP 39.0–117.0 IU/L; PTH 10.0–57.0 pg/mL.