Sleep is like plugging your body into its own built-in charger. It replenishes your depleted energy levels and gives you enough charge or energy to do what you need to do in your waking hours.^{1Zisapel N. Sleep and sleep disturbances: biological basis and clinical implications. Cell Mol Life Sci 2007;64(10):1174-86.}

Much like a cell phone that hasn’t fully recharged and cuts off mid-call, if you don’t sleep enough, you can run out of energy far too soon.^{1Zisapel N. Sleep and sleep disturbances: biological basis and clinical implications. Cell Mol Life Sci 2007;64(10):1174-86.} How much you sleep affects your energy levels and performance, which is why a lack of sleep can even affect your outward appearance.^{1Zisapel N. Sleep and sleep disturbances: biological basis and clinical implications. Cell Mol Life Sci 2007;64(10):1174-86. 2Robotham D, Chakkalackal L, Cyhlarova E. Sleep matters: The impact of sleep on health and wellbeing. London, UK: Mental Health Foundation. 2011.} So, your nightly sessions on “charge” shouldn’t be taken lightly, and since we spend roughly a third of our lives “recharging,” we should try to get the best out of it.^{1Zisapel N. Sleep and sleep disturbances: biological basis and clinical implications. Cell Mol Life Sci 2007;64(10):1174-86. 2Robotham D, Chakkalackal L, Cyhlarova E. Sleep matters: The impact of sleep on health and wellbeing. London, UK: Mental Health Foundation. 2011. 3Suni E. What Happens When You Sleep? online 2022. cited Apr 2022. URL: Available: https://www.sleepfoundation.org/how-sleep-works/what-happens-when-you-sleep#:~:text=When%20you%20sleep%2C%20your%20body,and%20over%20the%20long%2Dterm}

We all need to ensure we get the right amount of sleep and enough good quality sleep.^{2Robotham D, Chakkalackal L, Cyhlarova E. Sleep matters: The impact of sleep on health and wellbeing. London, UK: Mental Health Foundation. 2011.} There is no set amount of sleep that is appropriate for everyone; some people need more sleep than others.^{2Robotham D, Chakkalackal L, Cyhlarova E. Sleep matters: The impact of sleep on health and wellbeing. London, UK: Mental Health Foundation. 2011.} So, it’s not just about how much you sleep; it’s also about how well you sleep.^{1Zisapel N. Sleep and sleep disturbances: biological basis and clinical implications. Cell Mol Life Sci 2007;64(10):1174-86. 2Robotham D, Chakkalackal L, Cyhlarova E. Sleep matters: The impact of sleep on health and wellbeing. London, UK: Mental Health Foundation. 2011.} Sleep is necessary to maintain your physical and mental health, as it is required for the brain to recover and regenerate.^{1Zisapel N. Sleep and sleep disturbances: biological basis and clinical implications. Cell Mol Life Sci 2007;64(10):1174-86. 2Robotham D, Chakkalackal L, Cyhlarova E. Sleep matters: The impact of sleep on health and wellbeing. London, UK: Mental Health Foundation. 2011.} During sleep, the brain processes information and strengthens memory – that is why it is better to get a good night’s sleep before an exam or an important day at work.^{2Robotham D, Chakkalackal L, Cyhlarova E. Sleep matters: The impact of sleep on health and wellbeing. London, UK: Mental Health Foundation. 2011.}

Melatonin is a hormone synthesised and secreted by the pineal gland in the brain.^{3Suni E. What Happens When You Sleep? online 2022. cited Apr 2022. URL: Available: https://www.sleepfoundation.org/how-sleep-works/what-happens-when-you-sleep#:~:text=When%20you%20sleep%2C%20your%20body,and%20over%20the%20long%2Dterm} It has been linked scientifically to regulating sleep, which boosts the immune system and helps maintain a better mood and quality of life.^{3Suni E. What Happens When You Sleep? online 2022. cited Apr 2022. URL: Available: https://www.sleepfoundation.org/how-sleep-works/what-happens-when-you-sleep#:~:text=When%20you%20sleep%2C%20your%20body,and%20over%20the%20long%2Dterm}

Our bodies have a built-in clock – or circadian rhythm – that regulates our sleep cycles, which controls how much melatonin your body secretes.^{1Zisapel N. Sleep and sleep disturbances: biological basis and clinical implications. Cell Mol Life Sci 2007;64(10):1174-86. 4Reiter RJ, Tan DX, Galano A. Melatonin: exceeding expectations. Physiology 2014;39:325-333. 5Wilson SJ, Nutt DJ, Alford C, Argyropoulos SV, Baldwin DS, Bateson AN, et al. British Association for Psychopharmacology consensus statement on evidence-based treatment of insomnia, parasomnias and circadian rhythm disorders. J Psychopharmacol 2010;24(11):1577-601.} Under normal circumstances, melatonin levels go up in the mid to late evening and stay up most of the night.^{6Pandi-Perumal SR, Trakht I, Spence DW, Srinivasan V, Dagan Y, Cardinali DP. The roles of melatonin and light in the pathophysiology and treatment of circadian rhythm sleep disorders. Nat Clin Pract Neurol 2008;4(8):436-47.} They then drop again in the early morning.^{6Pandi-Perumal SR, Trakht I, Spence DW, Srinivasan V, Dagan Y, Cardinali DP. The roles of melatonin and light in the pathophysiology and treatment of circadian rhythm sleep disorders. Nat Clin Pract Neurol 2008;4(8):436-47.}

Our natural melatonin levels slowly decrease as we get older, so a supplement may sometimes be needed to get a good night’s rest – especially if you are an older adult suffering from insomnia.^{5Wilson SJ, Nutt DJ, Alford C, Argyropoulos SV, Baldwin DS, Bateson AN, et al. British Association for Psychopharmacology consensus statement on evidence-based treatment of insomnia, parasomnias and circadian rhythm disorders. J Psychopharmacol 2010;24(11):1577-601.} See Ageing and Sleep for more.

The 24-hour sleep/wake cycle, also known as the 24-hour circadian rhythm, is regulated by a clock in the brain’s suprachiasmatic nuclei (SCN).^{6Pandi-Perumal SR, Trakht I, Spence DW, Srinivasan V, Dagan Y, Cardinali DP. The roles of melatonin and light in the pathophysiology and treatment of circadian rhythm sleep disorders. Nat Clin Pract Neurol 2008;4(8):436-47.} The SCN is responsible for regulating melatonin secretion by the pineal gland.^{5Wilson SJ, Nutt DJ, Alford C, Argyropoulos SV, Baldwin DS, Bateson AN, et al. British Association for Psychopharmacology consensus statement on evidence-based treatment of insomnia, parasomnias and circadian rhythm disorders. J Psychopharmacol 2010;24(11):1577-601.}

Melatonin modifies circadian rhythms and signals day-night transitions.^{5Wilson SJ, Nutt DJ, Alford C, Argyropoulos SV, Baldwin DS, Bateson AN, et al. British Association for Psychopharmacology consensus statement on evidence-based treatment of insomnia, parasomnias and circadian rhythm disorders. J Psychopharmacol 2010;24(11):1577-601.} Melatonin levels are low during the day and increase at night.^{6Pandi-Perumal SR, Trakht I, Spence DW, Srinivasan V, Dagan Y, Cardinali DP. The roles of melatonin and light in the pathophysiology and treatment of circadian rhythm sleep disorders. Nat Clin Pract Neurol 2008;4(8):436-47.} In most people, melatonin levels usually begin to increase steadily between 7-11 pm and reach their peak value between 2-4 am. The levels then decline and reach their lowest values during daytime hours.^{6Pandi-Perumal SR, Trakht I, Spence DW, Srinivasan V, Dagan Y, Cardinali DP. The roles of melatonin and light in the pathophysiology and treatment of circadian rhythm sleep disorders. Nat Clin Pract Neurol 2008;4(8):436-47.}

Sleep disturbances affect our sleep quality, which can make it difficult to function psychosocially, physically, and occupationally.^{1Zisapel N. Sleep and sleep disturbances: biological basis and clinical implications. Cell Mol Life Sci 2007;64(10):1174-86.}

Circadian rhythm sleep disorders are a group of conditions tied to dysfunctions or misalignments with the body’s internal clock.^{7Pacheco D. Circadian Rhythm Sleep Disorders. online 2022. cited Apr 2022. URL: Available: https://www.sleepfoundation.org/circadian-rhythm-sleep-disorders} Since melatonin modifies circadian rhythms and signals day-night transition, abnormal melatonin profiles can cause circadian rhythm sleep disorders.^{5Wilson SJ, Nutt DJ, Alford C, Argyropoulos SV, Baldwin DS, Bateson AN, et al. British Association for Psychopharmacology consensus statement on evidence-based treatment of insomnia, parasomnias and circadian rhythm disorders. J Psychopharmacol 2010;24(11):1577-601.}