Table 3.
The heritability of alertness and sleep
| Intra-pair correlation | Genetic models | |||||||
|---|---|---|---|---|---|---|---|---|
| MZ/DZ pairs | rMZ | rDZ |
(95% CI) |
A | C or D | E | p | |
| Daytime alertness | 121/38 | 0.43 | 0.30 |
0.25 (−0.34, 0.84) |
24.9% | 17.8% (C) | 57.3% | <0.001 |
| Morning alertness | 120/38 | 0.41 | 0.215 |
0.39 (−0.26, 1.03) |
38.6% | 2.2% (C) | 59.2% | <0.001 |
| Happiness | 88/28 | 0.32 | 0.08 |
0.32 (0.13, 0.51) |
0% | 32.0% (D) | 68.0% | 0.011 |
| Sleep duration | 121/38 | 0.51 | 0.22 |
0.51 (0.37, 0.64) |
38.2% | 12.5% (D) | 49.4% | <0.001 |
| Sleep efficiency | 121/38 | 0.68 | 0.17 |
0.68 (0.58, 0.77) |
0.6% | 67.1% (D) | 32.3% | <0.001 |
| Sleep onset | 121/38 | 0.60 | 0.305 |
0.595 (0.04, 1.15) |
59.5% | 0.7% (C) | 39.8% | <0.001 |
| Sleep offset | 121/38 | 0.72 | 0.63 |
0.18 (−0.16, 0.51) |
17.6% | 54.2% (C) | 28.2% | <0.001 |
rMZ = monozygotic intra-pair correlation coefficient, rDZ = dizygotic intra-pair correlation coefficient, = broad-sense heritability of the phenotype, defined as the percentage of total phenotypic variance explained by genetic factors (= A in ACE models and A + D in ADE models), A = additive genetic effect, D = non-additive genetic effect, C = shared environmental effect, E = non-shared environmental effect. All models are adjusted for age and sex. Two-tailed p-values were obtained using a likelihood-ratio test comparing the goodness of fit of the full model to a restricted model that only included individual-specific environmental factors (E). Source data are provided as a Source Data file.