Sleep is an important factor in health. It is recommended to sleep eight hours a night (“sleep awareness”). Sleeping less than seven hours can increase the risk of diseases like obesity, diabetes, high blood pressure, heart disease and depression (“sleep consciousness”). Some of the consequences of insufficient sleep are memory problems, depression, decreased immune response, fatigue, and increased pain (“sleep stages”). There are four stages of sleep plus REM sleep. Stages one through four are non-REM sleep and last five to fifteen minutes (Figure 1) (“stages of sleep”). During REM sleep, muscle tone is lost and rapid eye movements occur (“stages of sleep”). During a night's sleep, four to six sleep cycles are carried out ("sleep awareness"). Not only is sleep important for health, it is also important for safety. 20% of serious car accidents are linked to drowsy driving (“sleep awareness”). A blood alcohol level of 0.10 over the legal limit is equivalent to not sleeping for 24 hours (“sleep awareness”). Insomnia is the most common sleep disorder, affecting approximately 30% of adults (“sleep awareness”). Lack of sleep causes alcohol to have more powerful effects on the body. Many aspects of life can affect sleep. The SCN is the primary circadian pacemaker that coordinates the body's metabolic and physiological rhythms (Maywood, 2014). Caffeine works by blocking adenosine and keeping a person awake (Andrew, 2014). Caffeine also acts on the skin and causes changes in body temperature and alertness (Andrew, 2014). Human behavior is affected by sleep deprivation due to a functional ADA polymorphism (Carolin, 2014). Sleep duration, sleep quality and jet la...... middle of paper ...... phase disorder (DSPD) were treated with bright light and melatonin to positively affect the patients' sleep habits (Ane, 2013). Circadian rhythms are also disrupted in patients with bipolar disorder (Geoffroy, 2014). Sleep is extremely important for health. Not getting enough sleep each night can increase your risk of obesity, diabetes, high blood pressure, heart disease and depression. Illnesses also impact sleep and can cause delayed sleep, advanced sleep, or irregular sleep-wake cycles that can affect daily life. Waking up earlier means you're tired earlier and waking up later may mean you're tired for work in the morning. In conclusion, many factors can alter the body clock and using melatonin and light treatments could resolve some sleep disorders and help regulate sleep-wake cycles in people with other types. of diseases..