Sleep Needs: Cross-Cultural Comparisons and Problems with Sleep Deprivation

Abstract

AbstractThis manuscript provides an overview of sleep need, starting by introducing previous reports on sleep duration. Sleep amounts decrease from the newborn infant to older individuals. Sleep duration of children has been found to have decreased over the last 100 years. Cross-culturally, declines in sleep duration can be clearly seen in Europe, the USA, Canada and Asia. Consistently, current sleep durations are longest in Australia and New Zealand. Not only extrinsic factors (screen time, extracurricular after-school activities, family lifestyle, late and irregular dinner time, delayed bedtime, school schedule, etc.) but also intrinsic ones (reduced accumulation of sleep needs summated during the day, melatonin secretion, etc.) affect sleep duration. Sleep deficit produces unfavourable effects on cognitive functioning, academic performance, emotional regulation, occurrence of injuries, body weight, and cardiovascular, immune and various metabolic systems. However, individual sleep need is difficult to be determined. According to International Classification of Sleep Disorders (third edition), insufficient sleep syndrome, which is a condition with abundant sleep need, was described by sleep duration and sleepiness. Then, a novel index of a function of both sleep duration and sleepiness, called the sleep need index, was designed. Higher grades, female gender, poor self-reported academic performance, breakfast skipping, longer after-school activity and longer physical activity were independently associated with pupils whose sleep need index was the average value or more. To support pupils with sleep need, we should instruct them to avoid excessive after-school and physical activities to improve their daytime functioning. This promotion is expected to contribute to the physical and mental health of youngsters.KeywordsSleep durationInsufficient sleep syndromeSleepinessAfter-school activityPhysical activitySkipping breakfastAcademic performance