Table 1.
Characteristics of the study population by levels of serum estradiol
| Low estradiol | Normal estradiol | Total | P-value b | |
|---|---|---|---|---|
| (n = 104) | (n = 166) | (n = 270) | ||
| BMD (g/cm2) a | 1.16 (0.09) | 1.19 (0.09) | 1.18 (0.09) | 0.03 |
| LSBMD (g/cm2) | 1.18 (0.14) | 1.23 (0.15) | 1.21 (0.15) | 0.005 |
| FNBMD (g/cm2) | 1.02 (0.12) | 1.07 (0.13) | 1.05 (0.13) | 0.001 |
| Age (years) | 44.2 (2.7) | 43.5 (2.6) | 43.8 (2.6) | 0.05 |
| Age at menarche (years) | 12.7 (1.5) | 12.5 (1.6) | 12.6 (1.5) | 0.2 |
| Number of pregnancies | 3.0 (1.5) | 2.6 (1.2) | 2.8 (1.3) | 0.05 |
| Breastfeeding (months) | 9.6 (10.1) | 9.3 (10.1) | 9.4 (10.4) | 0.8 |
| Use of contraceptives (months) | 4.7 (14.7) | 6.9 (19.8) | 6.1 (18.0) | 0.3 |
| Days after menstruation | 7.5 (1.7) | 7.7 (1.8) | 7.6 (1.7) | 0.9 |
| BMI (k/m2) | 26.7 (4.2) | 26.9 (4.2) | 26.8 (4.2) | 0.6 |
| Physical Activity (METS/day) | 2.4 (2.7) | 2.5 (2.1) | 2.5 (2.5) | 0.7 |
| Tobacco smoking (%) | 19.1 | 16.8 | 18.2 | 0.7 |
| Family history of osteoporosis (%) | 21.3 | 17.6 | 19.3 | 0.7 |
| Dietary factors | ||||
| Energy intake (kcal/day) | 2153 (1008) | 2072 (836) | 2104 (905) | 0.4 |
| Dietary calcium (mg/day) | 1012 (537) | 1162 (560) | 1031 (546) | 0.4 |
| Dietary vitamin D (IU/day) | 211 (133) | 235 (154) | 226 (146) | 0.2 |
| Caffeine (mg/day) | 81 (95) | 121 (159) | 106 (139) | 0.02 |
| Alcohol (g/day) | 3.1 (6.1) | 1.6 (2.8) | 2.2 (4.4) | 0.01 |
BMD (g/cm 2 ) total bone mineral density, LSBMD (g/cm 2 ) lumbar spine bone mineral density, FNBMD (g/cm 2 ) femoral neck bone mineral density
a Mean value (SD). Only smoking and family history of osteoporosis are values expressed as percentage
b t-test for quantitative variables and chi2-test for qualitative variables