Introduction: Siesta is a relevant aspect of sleep due to its possible relation to important aspects of human life, such as health or cognitive functioning. However, unlike nighttime sleep, studies about daytime sleep... [ view full abstract ]
Introduction: Siesta is a relevant aspect of sleep due to its possible relation to important aspects of human life, such as health or cognitive functioning. However, unlike nighttime sleep, studies about daytime sleep determinants and characteristics are scarce, and the genetic and environmental structure of siesta is still unknown. Our main objective was to explore the relative contribution of genetic and environmental factors to variation in the sleep-wake rhythm as measured by a continuous assessment of temperature, activity, and position (TAP), which allows for analysis of diurnal sleep.
Methods: The sample comprised 53 pairs (28 MZ and 25 DZ) of female twins selected from the Murcia-Twin Register (MTR). Mean age of participants was 52 (SD: 6) years. Zygosity was determined by DNA. We conducted separate univariate analyses to study the sources of variance of daytime and nighttime sleep parameters.
Results: About 60% of the sample reported to take siesta at least once a week. Daytime sleep duration was positively associated to anthropometric measures (BMI, total body fat and visceral fat). Heritability of self-reported siesta taking was .65 (95% CI: 0.19, 0.92). Sleep parameters assessed through continuous monitoring of TAP, including daytime and nighttime sleep duration, showed heritability estimates between .36 (95% CI: 0, 0.68) and .69 (95% CI: .38, .85), suggesting a relevant impact of genetic factors on the sleep rhythm.
Conclusions: This is the first study to investigate the relative contribution of genetic factors to siesta. By using an integrative measure (TAP) we have been able to introduce a novel approach to the study of diurnal sleep characteristics. Results represent a significant step in the understanding of siesta and daytime sleep nature that are relevant to assess the chronobiological system condition and its possible association with pathologies such as obesity.
