Table 2 Twin intra-class correlations for sleep-related parameters.

From: Heritability of siesta and night-time sleep as continuously assessed by a circadian-related integrated measure

  Intra-class correlation
r MZ (CI 95%) r DZ (CI 95%)
Siesta (Self-report) 0.694 (0.196, 0.932) 0.156 (−0.443, 0.672)
Daytime sleep duration 0.671 (0.379, 0.839) −0.014 (−0.427, 0.408)
Night-time sleep duration 0.706 (0.419, 0.844) −0.116 (−0.495, 0.314)
Mesor 0.749 (0.478, 0.884) 0.100 (−0.331, 0.495)
Acrophase 0.700 (0.387, 0.861) 0.060 (−0.349, 0.451)
Total daily sleep duration 0.730 (0.444, 0.874) −0.124 (−0.513, 0.309)
Sleep depth (%) 0.648 (0.341, 0.827) 0.246 (−0.186, 0.594)
Percentage of rhythmicity (PR) 0.572 (0.029, 0.785) −0.057 (−0.440, 0.345)
Interdaily stability (IS) 0.644 (0.322, 0.828) 0.028 (−0.373, 0.422)
Intradaily variability (IV) 0.436 (0.029, 0.712) −0.117 (−0.503, 0.309)
Relative amplitude (RA) 0.655 (0.349, 0.831) 0.398 (−0.031, 0.698)
Circadian Function Index (CFI) 0.653 (0.335, 0.832) 0.040 (−0.365, 0.435)