Sleep is an essential physiologic process concerned with maintaining many bodily functions and systems. Lack of sleep can produce a number of serious side effects affecting every area of human health. These include errors of judgment, which may kill or maim many people. Other consequences include increased morbidity and mortality, poor performance, increased risk of accidents and injuries, reduced level of functioning, and poorer quality of life. Family life suffers, and many more healthcare visits become necessary.
Immediate consequences include driving accidents which cause over 2000 fatal crashes and 40,000 non-fatal injuries each year in the US. Delayed sequelae include the metabolic disorders, such as hypertension, diabetes, obesity, depression, cardiovascular disease, and even cancers.
Impairment of long- and short-term memory, poor concentration and difficulty in assimilating new things, poor judgment and decreased creativity, and labile emotions, are some serious effects brought about by sleep deprivation. Motor function is reduced, as is the attention span, while the reaction time actually goes up in proportion to the sleep deprivation, leading to poor hand-eye coordination similar to that of a person with a blood alcohol concentration of 0.1%.
In persons with bipolar disorder, mania is often precipitated by sleeplessness. Studies of people who were allowed only a little sleep every night found that their levels of stress, anger, sadness, and mental fatigue went up significantly. Hallucinations, depression, impulsive behavior, and suicidal thoughts may be prompted by lack of sleep. Microsleeps, lasting for a few seconds in most cases, which occur without the person knowing it, have been incriminated in many driving and other machinery-related accidents.
Lack of sleep can cause the immune system to produce less antibodies and T-lymphocytes, and thus the body becomes more prone to infection and has reduced capability to fight illness. Insomniacs are at higher risk of colds and influenza. One study on mice has also found that sleep disruption on a regular basis leads to faster tumor growth than when normal sleep is allowed. Rodents who were absolutely deprived of sleep died of fatal infections in a remarkably short time.
Chronic illnesses such as obesity, heart disease, and diabetes are more likely to occur in individuals with long-term insomnia. Sleep deprivation is associated with higher cortisol and ghrelin levels, and lowered leptin levels. Since ghrelin makes for increased hunger, and leptin has the opposite effects, lack of sleep on a frequent or long-term basis can produce weight gain and obesity.
Insulin levels increase following sleeplessness, which can cause type 2 diabetes. Again, lack of sleep elevates the blood pressure for more than 24 hours.
Since insomnia is associated with higher levels of pro-inflammatory chemicals, the odds of cardiovascular disease also go up.
The risk of depression and anxiety is increased when individuals sleep less than 6 hours a night.
Cancer risk is also higher in sleep-deprived individuals. Mortality rates are higher, and overall quality of life is reduced.
Sleep deprivation causes disruption of the reproductive hormones and hence prevents ovulation from occurring properly, which can result in infertility. In addition, libido is also lower in individuals with less sleep.
Loss of productivity is associated with not getting enough sleep, which may be below 10 hours a day for children, 9-10 hours for adolescents, and 7-8 hours for adults. However, a third of adults get 6 hours or less of sleep, while a third of adolescents get only 8 hours or less of sleep a night on average.
Children with sleep problems are more mischievous and less focused at school. Concentration is affected, the risk of attention-deficit hyperactivity disorder is increased, while impulsive and risk-taking behavior becomes more common.