Table 3.
Selected Baseline Characteristics of the Family Sample, According to Sibling Type, National Longitudinal Study of Adolescent Health, 1994–1995a
| Characteristic | Full Siblings (473 Pairs, 946 Individuals) | Dizygotic Twins (179 Pairs, 358 Individuals) | Monozygotic Twins (188 Pairs, 376 Individuals) |
| Birth weight measure | |||
| Mean birth weight, kg | 3.4 (0.6)b | 2.6 (0.6) | 2.4 (0.6) |
| Low birth weight (<2.5 kg), % | 5.4 | 41.3 | 53.3 |
| High birth weight (>4 kg), % | 14.0 | 0.0 | 0.5 |
| Mean birth weight difference, kg | 0.5 (0.4) | 0.3 (0.3) | 0.2 (0.2) |
| BMIc measure | |||
| Mean BMI | 22.3 (4.4) | 22.2 (4.1) | 22.0 (4.1) |
| Obesity (BMI ≥30), % | 8.8 | 8.9 | 9.8 |
| Mean BMI difference | 3.4 (3.4) | 3.2 (3.2) | 1.5 (1.7) |
| Mean age, years | 15.6 (1.7) | 15.5 (1.6) | 15.6 (1.5) |
| Female sex, % | 49.3 | 44.1 | 47.9 |
| Total no. of females | 466 | 158 | 180 |
| Race/ethnicity, % | |||
| White | 64.6 | 63.3 | 59.5 |
| Black | 15.0 | 23.0 | 18.4 |
| Hispanic | 15.2 | 11.5 | 16.2 |
| Asian | 5.3 | 2.2 | 6.0 |
Abbreviation: BMI, body mass index.
a
The analytical sample used for this table included individuals/pairs with complete data at baseline. Individuals/pairs who were missing a BMI value at baseline (40 pairs) were excluded from these descriptive analyses.
b
Numbers in parentheses, standard deviation.
c
Weight (kg)/height (m)2.