Wisconsin Psychocutaneous Clinic, Middleton, WI, USA
Sleep plays a vital role in proper brain functioning; it is a decreased state of arousal. Sleeping is different from being unconscious because there is still some awareness of the environment and we can arouse from sleep. From an evolutionary standpoint, sleeping does not make much sense for survival. Being in a state of decreased arousal puts us in danger, yet sleep exists in all species studied thus far.
Humans spend about one‐third of the day sleeping. People need different amount of sleep in different stages of their lives; most adults need six to eight hours of sleep per day.
Multiple case reports and publications have documented various sleep problems in patients with dermatologic disorders. While these publications are important, the subject has not entered the daily dermatology practice, and many dermatologists do not routinely ask about sleep problems in their patients. In addition, many patients do not report sleep problems to their physicians.
This chapter will discuss the relationship between sleep and skin and its implication in the treatment of skin diseases and patients’ quality of life.
Sleep is a temporary suspension of awareness during which there is a decreased response to external stimuli. Research shows all species need sleep, from fruit flies to humans . Our internal circadian clock regulates sleep. Sleeping regulates brain functions, and helps the brain to improve memory and cognition. How exactly sleep accomplishes its functions, is not completely known. Tononi and Cirelli suggest we need sleep for plasticity of the brain. They hypothesize that the fundamental function of sleep is to restore synaptic homeostasis .
Many hormones and neurotransmitters such as growth hormones have their peak secretion during sleep . Lack of sleep causes irritability and trouble with cognition and memory. It also has negative effects on other organs in our body, including our skin. Prevalence of insomnia is different based on the criteria used in different studies. However, an international consensus exists that about 30% of adults questioned in different countries report one or more symptoms of insomnia .
The US National Institute of Neurological Disorders and Stroke suggests that infants need about 16 hours a day of sleep, teenagers about 9 hours, and most adults 7–8 hours of sleep .Not getting the necessary amount of sleep causes sleep debt and symptoms of sleep deprivation.
In addition to affecting daytime functioning, memory, focus, physical performance, and the ability for performing math calculations and driving, sleep deprivation affects mood and the immune system [5–7].
Sleep deprivation reduces the life span of rats from two to three years to five weeks in REM (rapid eye movement) sleep‐deprived rats, and three weeks in total sleep‐deprived rats. The sleep‐deprived rats also show abnormally low body temperature and develop sores on their tail, and paws .
Insomnia also causes death in humans as is evidenced by the fatal familial insomnia, that is a rare autosomal dominant prion disease. There is no cure, and worsening insomnia in the affected individuals leads to confusion, hallucinations, ataxia, dementia‐like symptoms, and eventual death .
Sleep and Skin
Many skin functions show circadian variation; examples are transepidermal water loss (TEWL), skin permeability, skin surface pH, blood flow, and skin temperature. Blood flow to the skin is lowest in the morning and highest in the afternoon and early evening, and there is a second peak in the late evening before sleep onset [10, 11]. The circadian pattern of core temperature peaks in the afternoon and falls in the early hours of the morning during sleep . The peripheral temperature rises in the evening and nighttime leading to release of heat, and a decrease in core body temperature that will promote sleep. In contrast, the peripheral temperature decreases in the daytime leading to increasing in core temperature .
There is also a circadian change in hormones and cytokines in the body, with some going up and some down during sleep. Cancer and other inflammatory processes could dysregulate these functions. Cortisol levels are at a minimum at night, and increase in the morning as one awakens.
Melatonin secretion picks up in the evening, is highest in the middle of the night, and decreases in the morning. Exposure to short‐wave light can interrupt the secretion, hence avoidance of light from TVs or computers is recommended for at least an hour before sleep [14–16].
Proinflammatory cytokines including IL‐1, IL‐2, TNF (Tumor Necrosis Factor)‐α, Interferon‐gamma (IFN γ), and IL‐6, are elevated at night and promote sleep. Anti‐inflammatory cytokines such as IL‐4 and IL‐10 are elevated after awakening and inhibit sleep [17, 18]. Chronic insomnia could shift the secretion of TNF‐α and IL‐6 to daytime and cause 24‐hour hypersecretion of the corticotrophin releasing hormone (CRH) and cortisol that would cause daytime fatigue and sleepiness [18, 19].
A Swedish study in 2010 showed that sleep deprivation causes people to appear tired, less healthy, and unattractive. The study design was by comparing photos of sleep‐deprived and well‐rested individuals. Untrained observers rated the photos. They concluded that humans are sensitive to facial cues related to sleep deprivation and this could have potential implications in social settings .
Skin Diseases and Sleep Problems
Sleep deprivation and sleep disorders increase inflammation in the body. Activation of the Hypothalamus Pituitary Adrenal (HPA) axis causes arousal and sleeplessness. Activation of the HPA axis could be due to different reasons, including stress or administration of glucocorticoids . Deep sleep inhibits the HPA axis activation.
Skin diseases could cause sleep problems due to inflammation. In addition, many treatments used in dermatology could affect sleep. This creates a situation where there is a fine balance between treating the inflammation and not causing more of it by sleep deprivation.
Cytokines and Neuropeptides That May Alter Sleep Physiology
TNF‐α induces slow wave sleep in animal models and peaks during sleep [21, 22]. IL‐1 induces slow wave sleep in animal models [21, 22]. IL‐6 peaks during sleep. Shorter sleep duration increases IL‐6 production , so sleep deprivation increases the tissue’s exposure to this inflammatory cytokine. Research shows that Substance P worsens the mood and increases REM latency and time awake. It also increases stage I sleep as well as cortisol and TSH (thyroid‐stimulating hormone