Table 3.
Longitudinal analysis of LTL in relation to age, sex and twin sex composition [opposite sex (OS) vs same sex (SS)]
| A. DZ and MZ twins combined, n=1535 samples, R2=0.98 | ||||
|---|---|---|---|---|
| Parameter | Estimate (SE) | F | DF denominator | P |
| Intercept | 7.900 (0.128) | 403.3 | <0.0001 | |
| Average age | −0.0221 (0.0028) | 61.400 | 403.2 | <0.0001 |
| Delta (Δ) age | −0.01955 (0.0006) | 1209.000 | 735.2 | <0.0001 |
| Sex | −0.1597 (0.0616) | 6.728 | 400.8 | 0.0098 |
| Opposite sex (OS) | −0.2286 (0.0820) | 7.764 | 490.5 | 0.0055 |
| Sex * OS | 0.1917 (0.0808) | 5.624 | 773.7 | 0.0180 |
| Δ Age * OS | 0.0067 (0.0014) | 22.260 | 734.1 | <0.0001 |
| Rejected terms | ||||
| OS * Sex * Δ Age | −0.0004 (0.00285) | 0.020 | 733.9 | 0.8880 |
| Sex * Δ Age | 0.0002 (0.00104) | 0.041 | 734.6 | 0.8400 |
| B. DZ twins only, n=845 samples, R2=0.98. | ||||
|---|---|---|---|---|
| Parameter | Estimate (SE) | F | DF denominator | P |
| Intercept | 7.84 (0.1646) | |||
| Average age | −0.0209 (0.0035) | 35.08 | 242.2 | <0.0001 |
| Delta (Δ) age | −0.0192 (0.0008) | 517.00 | 399.5 | <0.0001 |
| Sex | −0.1857 (0.0878) | 4.47 | 220.9 | 0.0356 |
| Opposite sex (OS) | −0.2173 (0.0912) | 5.67 | 281.0 | 0.0179 |
| Sex * OS | 0.2174 (0.1084) | 4.02 | 399.6 | 0.0456 |
| Δ Age * OS | 0.0063 (0.0016) | 16.61 | 399.5 | <0.0001 |
| Rejected terms | ||||
| OS * Sex * Δ Age | 0.0010 (0.0031) | 0.11 | 397.5 | 0.7400 |
| Sex * Δ Age | −0.0012 (0.0014) | 0.75 | 398.5 | 0.3800 |
Sex was coded 0 (females) and 1 (males). Opposite sex was also coded 0 (SS) and 1 (OS). Twin identity, and individual identity nested in twin identity were included as random effects. Model was obtained after backward deletion of least significant terms starting with the initial model that included the rejected terms shown in A. Numerator DF=1.