Children who sleep more may have longer telomeres: evidence from a longitudinal population study in Spain

Abstract

Sleep is a necessary physiological process and has a critical role in promoting balanced health.1 In children, adequate sleep is associated with normal growth, wellbeing and different development domains such as nutrition, hygiene, communication and physical contact.2,3 Inadequate sleep, instead—defined mainly as the number of hours a child sleeps—negatively impacts cognitive functions, socioemotional domains, early childhood development and physical health.2 The American Academy of Sleep Medicine recommends sleeping 10–13h per day for children between 3 and 5 years old to reach their full developmental potential.3 However, not all children meet this recommendation. For instance, 34.9% of American children and adolescents aged 4 months to 17 years reported sleeping less than the recommendations for their age.4 In Spain, Ruiter et al. estimated that sleep duration in children between 2 and 14 years had decreased by 20min in the last decades and that only 55% of children were sleeping enough hours per day.5 In addition to the aforementioned consequences of sleep disturbance, inadequate sleep duration has been suggested as a chronic stressor associated with changes in telomere length.6–8 Telomeres are nucleoprotein structures containing repeat sequences of tandem TTAGGG DNA stretches that protect chromosome ends from illicit DNA repair. Naturally, they shorten over time; however, they are susceptible to faster shortening under stressors. Previous studies have identified that shorter telomeres are associated with a higher risk of adverse health outcomes and have been identified as a useful ageing biomarker.9 Although studies evaluating telomere length in children are limited, previous works highlighted the association between childhood abuse, early life adversity, childhood socioeconomic status and maternal factors (such as depression, smoking and inheritance) with telomere length.10,11 Regarding sleep, studies conducted in adults have shown that poor sleep quality is associated with shorter telomere length.6–8 In children, two studies evaluated the potential association between sleep duration and telomere length. However, results from both studies are inconclusive since one evidenced a positive association and the other no association between these two variables.12,13 Considering that the literature has proposed that the environmental conditions during adulthood might have less impact over telomere length than those during childhood14,15—and the poorly investigated role of sleep in children—this study aimed to explore the association between sleep duration and telomere length using data from the INMA birth cohort study.