The critical role of sleep in optimising health
Bradley McEwen | PhD, MHSc( Hum Nutr), MPH, BHSc, AdvDipNat, DBM, DNutr, DSM, Fellow ATMS, Naturopath Nutritionist, and Mentor. Adjunct Senior Lecturer, Faculty of Health, Southern Cross University.
Abstract
Sleep is essential for optimum physical and mental health and wellbeing, supporting critical biological processes such as energy restoration, metabolism regulation, thermoregulation, immune function, and memory formation. Deficient sleep has been linked to an increased risk of mortality and is associated with a range of adverse health outcomes, including cardiovascular disease and metabolic syndrome, along with adverse effects on mental health, cognitive decline, weight gain and obesity, reproductive and hormonal health, muscle health, and immune function. This article provides an overview of the physiological mechanisms underlying sleep and explores the profound impact of sleep deprivation on various body systems. It highlights the intricate relationship between sleep and overall health.
Introduction
Sleep is fundamental for maintaining optimal physical and mental health. 1, 2 Both sleep quantity and sleep quality are essential for nearly every body system. 1 Sleep is described as a natural and reversible state characterised by decreased responsiveness to external stimuli 3, 4 and a period of relative inactivity, 3 which is accompanied by a loss of consciousness. 3, 4 Sleep occurs at regular intervals and is regulated through homeostatic mechanisms. 3 The sleepwake cycle is often considered the most significant expression of the circadian rhythm. 4, 5 Sleep and the circadian system are closely connected. 5 Sleep undergoes significant changes throughout human development. 6 Infants typically need between 14 and 20 hours of sleep each day, 6, 7 a duration that is reduced by half by the time they reach adolescence, 6 to about 8-10 hours of sleep each day. 7 Furthermore, whereas infants experience sleep in several segments( e. g., 6-8 naps per day), 6, 7 by the age of 5 to 7 years, sleep becomes consolidated into a single continuous period. 6, 7
Sleep is regarded as a powerful restorative for overall health. 1, 3 Sleep performs several fundamental biological functions in the body, such as serving an energysaving function, 1, 3 restoring energy resources, 1, 3 regulating metabolism, 1, 3 thermoregulation, 1, 3 adaptive immune functions, 1, 3 learning and the formation of memories, 8 and allowing for maintenance, repair, and building of the body. 1 Sleep also plays a key role in modulating neuroendocrine function and glucose regulation. 9, 10 Changes in sleep physiology affect cognition( e. g., memory consolidation). 3, 11
Many people are not getting enough sleep in terms of both the quantity and quality of sleep 1 and problems with sleep are common worldwide. 12 Lack of sleep has become standard behaviour in modern society. 13 The cumulative sleep loss per working week of a substantial portion of the adult population can be equivalent to missing a whole night of sleep. 14 Sleeping as little as possible is often seen as an admirable behaviour in contemporary society 9 and people often mock the time spent sleeping as“ lost” time. 11
Suboptimal sleep adversely affects cardiovascular health, 1, 4 type 2 diabetes, 4 mental health, 1 cognition, 1 memory consolidation, 1 reproductive health, 1 hormone regulation, 1 immunity, 1 and pain. 4 Poor sleep quality and irregular timing of sleep( for example, shift work) have been linked to mortality, 2 metabolic syndrome, 2 impaired glucose metabolism, 2 type 2 diabetes, 2, 4 coronary heart disease, 2 obesity, 4 and accidents. 2 Sleep deprivation is closely associated with health and performance, particularly among individuals employed in various fields, including multi-shift workers, nurses, doctors, students in professional schools, and members of the armed forces, significantly impairing their performance. 15
Sleep is essential for the development and growth of children’ s brains, as well as for their learning, memory functions, academic performance, and overall health. 7 Disruptions in sleep can cause various negative outcomes, such as excessive daytime drowsiness, impairments in neurocognitive function and performance, poor academic
138 | vol31 | no3 | JATMS