Sleep is a state of reversible unconsciousness in which the brain is less responsive to external stimuli . Throughout the period of sleep, the body will cycle periodically between non-rapid eye movement (NREM) sleep and rapid-eye-movement (REM) sleep. NREM sleep is further divided into four stages, which is a continuum of relative depth Sleep episode in adults starts with a brief period of NREM stage 1, the lightest sleep stage. It progresses through NREM stage 2, stage 3 and stage 4, the deepest sleep stage. NREM sleep is then followed by REM sleep, which is known for the most vivid dreams and bodily movements. The cycle is repeated three to six times, and as sleep episode progresses, the duration of stages of NREM sleep shorten while the duration of REM sleep lengthens Healthy sleep is essential for neural development, learning, memory, cardiovascular and metabolic regulation. Sufficient sleep is needed to provide recovery after preceding waking activities and ensure optimal functioning during subsequent wakefulness younger adults is seven to nine hours, and for older adults is seven to eight hours In general, sleep duration decreases with increasing age. In a meta-analysis that involved 5273 healthy adults, total sleep time decreased by approximately 10 minutes for each decade of age wake time after sleep onset of 20 minutes and less, and occur at a minimum of three nights per week for three months, and associated with one or more daytime symptom such as fatigue, cognitive impairment or mood disturbance. In comparison to the DSM-IV, the distinction into primary and secondary insomnia, whether the insomnia is comorbid with or caused by other disorders, was replaced by the term “insomnia disorder” in DSM-5. This shift reflects that insomnia is now recognized as an independent disorder Ashwagandha extract is generally well tolerated. A study has shown the hematological and biochemical organ function safety of Ashwagandha even in higher doses ranging from 6–10 gm of crude pulverized roots administered in aqueous extract form . The exact mechanism is unknown. In an earlier study, Ashwagandha was thought to induce sleep through GABAergic activity, as seen in sleep-deprived rats. Withanolides, the major biologically active constituents of Ashwagandha roots and leaves, are believed to be responsible for the majority of biological functions of Ashwagandha. However, Kaushik and colleagues noted ethanol extract that contains a high ratio of Withanolides has failed to induce sleep in mice, indicating that Withanolides might not be involved in sleep promotion. A more recent study found that the diethylene glycol (TEG) in water extract is responsible for sleep in mice. TEG induces sleep by increasing the number of NREM episodes and decreasing the duration of the wake episode. However, studies on the effect of Ashwagandha related to insomnia in human are limited. Methods The protocol was registered under the PROSPERO with the registration number CRD42021229064. This meta-analysis was conducted according to the PRISMA statement (Preferred reporting items for systematic reviews and meta-analyses) The keywords applied were (Ashwagandha OR Withania OR “Withania somniferous” OR “WS” OR “somniferous, Withania” OR “Indian ginseng” OR “winter cherry”) AND (sleep OR insomnia OR “difficulty sleeping” OR “disorder of sleep initiation and maintenance” OR “sleep initiation and maintenance disorder” OR “DIMS” OR “sleep wake disorder” OR “SWD” OR “sleep quality” OR “quality of sleep” OR “sleep index” OR “sleep scale” OR “sleep time” OR “actigraphy”). Ashwagandha extract in any form, any dose, or any duration, and evaluated at least one outcome on sleep. Data extraction Two authors (CKL and RAR) independently screened titles and abstracts and assessed the full text of potentially eligible studies. Studies were selected if they met the inclusion criteria. At each stage of screening and assessing the eligibility of studies, we excluded trials which were non-clinical trials, animal studies, and examining the effect of Ashwagandha extract along with other interventions. Review papers, abstracts in conferences, book chapters, and duplicate studies were also excluded.
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