The role of circadian rhythms in sleep onsetFuture research trends in sleep onset Sleep is essential for physical and psychological performance.1 Since millions of individuals worldwide deal with sleep-related problems, scientists have focused on understanding the mechanisms associated with sleep and wakefulness. This could help alleviate the issues linked to sleep disorders and improve overall quality of life.
Sleep is critical for waking cognition and is associated with one's ability to think efficiently, be alert, and sustain attention. It has been observed that vigilant attention declines considerably after more than sixteen hours of continuous wakefulness.5 Partial sleep deprivation accumulates over time and leads to a steady deterioration of alertness. Furthermore, sleep plays a vital role in emotional regulation, metabolic processes, and body healing.
The expression of clock genes inside a cell influences many signaling pathways that allow the cell to identify specific times of day and, accordingly, conduct essential functions. Phosphorylation of core clock proteins helps manage 24-hour sleep/wake cycles.9 A disruption of the circadian cycle has many health implications associated with immune, skeletal, renal, cardiac, gastrointestinal, and endocrinal functions.
Brain nuclei that control the sleep/wake states display heterogeneity and are composed of intermingled neuronal populations that support differentially activated states. Complex interactions of subcortical neuromodulatory neurons in the hypothalamus, brainstem, midbrain, thalamus, basal forebrain , and the cortex are responsible for the differential physiological behavioral, and electrocortical sleep/wake states.
GABAergic sleep-active neurons also inhibit cholinergic neurons in the basal forebrain. Since the cholinergic system is one of the key players in the wakefulness of the brain, its inhibition deactivates the cortex and promotes sleep. Both pharmacological and non-pharmacological strategies have been developed to alleviate sleeping disorders, such as insomnia.15 Epidemiologic research has shown that regular light to vigorous exercise improves sleep quality and reduces the risk of insomnia.