Studies have shown that a lack of sleep causes the following problems:

• Thinking processes slow down. It becomes harder to focus and pay attention.
• People are more easily confused.
• People become angry or upset more easily.
• It leads to faulty decision-making and more risk taking.
• It slows down reaction times.

Students who have trouble grasping new information or learning new skills are often advised to "sleep on it," and that advice seems well-founded. Studies reveal that people can learn a task better if they are well rested. They can also remember better if they get a good night's sleep after learning the task than if they are sleep-deprived. Volunteers had to sleep at least six hours to show improvement in learning, and the amount of improvement was directly linked to how much time they slept. In other words, volunteers who slept eight hours outperformed those who slept only six or seven hours. Other studies suggest that all the benefits of training for mentally challenging tasks are maximized after a good night's sleep, rather than immediately following the training or after sleeping for a short period overnight.

Exactly what happens during sleep to improve our learning, memory, and insight is not known. Experts suspect, however, that while people sleep, they form or reinforce the pathways of brain cells needed to perform these tasks. This process may explain why sleep is needed for proper brain development in infants. And not only is a good night's sleep required to form new learning and memory pathways in the brain, but sleep also speeds up the activity on existing pathways.

Most people report being irritable, if not downright unhappy, when they lack sleep. People who chronically suffer from a lack of sleep, either because they do not spend enough time in bed or because they have an untreated sleep disorder, are at greater risk of developing depression. One group of people who usually do not get enough sleep is mothers of newborns. Some experts think depression after childbirth (postpartum blues) is caused, in part, by a lack of sleep.

Sleep gives the heart and vascular system a much-needed rest. During non-REM sleep, the heart rate and blood pressure progressively slow as people enter deeper sleep. During REM sleep, heart rates and blood pressure have boosted spikes of activity. Overall, however, sleep reduces heart rates and blood pressure by about 10 percent.

If people do not get enough sleep, this nightly dip in blood pressure, which appears to be important for good cardiovascular health, may not occur. According to several studies, if blood pressure does not dip during sleep, people are more likely to experience strokes, chest pain known as angina, an irregular heartbeat, and heart attacks. People are also more likely to develop congestive heart failure, a condition in which fluid builds up in the body because the heart is not pumping sufficiently.

A lack of sleep also puts the body under stress and may trigger the release of more adrenaline, cortisol, and other stress hormones during the day. These hormones contribute to blood pressure levels not dipping during sleep, thereby increasing the risk for heart disease. Inadequate sleep may also negatively affect the heart and vascular system by the increased production of certain proteins thought to play a role in heart disease. For example, some studies find that people who chronically do not get enough sleep have higher blood levels of C-reactive protein. Higher levels of this protein may suggest a greater risk of developing hardening of the arteries (atherosclerosis).

Deep sleep triggers more release of growth hormone, which fuels growth in children and boosts muscle mass and the repair of cells and tissues in children and adults. Sleep's effect on the release of sex hormones also encourages puberty and fertility. Consequently, women who work at night and tend to lack sleep are, therefore, more likely to have trouble conceiving or to miscarry.

There is also evidence that a good night's sleep can help keep people from getting sick, and help them heal faster if they do. During sleep, the body creates more cytokines (cellular hormones that help the immune system fight various infections). Lack of sleep can reduce the ability to fight off common infections. Research also reveals that a lack of sleep can reduce the body's response to the flu vaccine. For example, sleep-deprived volunteers given the flu vaccine produced less than half as many flu antibodies as those who were well rested and given the same vaccine.

Evidence is growing that sleep is a powerful regulator of appetite, energy use, and weight control. During sleep, the body's production of the appetite suppressor leptin increases, and the appetite stimulant grehlin decreases. Studies find that the less people sleep, the more likely they are to be overweight or obese and prefer eating foods that are higher in calories and carbohydrates. People who report an average total sleep time of five hours a night, for example, are much more likely to become obese compared to people who sleep seven to eight hours a night.

A number of hormones released during sleep also control the body's use of energy. A distinct rise and fall of blood sugar levels during sleep appears to be linked to sleep stage. Not getting enough sleep overall (or enough of each stage of sleep) disrupts this pattern. One study found that when healthy young men slept only four hours a night for six nights in a row, their insulin and blood sugar levels mimicked those seen in people who were developing diabetes. Another study found that women who slept less than seven hours a night were more likely to develop diabetes over time than those who slept between seven and eight hours a night.

When you are sleep deprived your brain reacts slower, meaning your feet and hands react slower. S

Sleep Improves Driving Safety
Sleep deprivation while driving causes one third of all motor accidents. Even minor amounts of sleep deprivation, over a short amount of time, can put you and others on the road at risk.

• Nutrition
• Fitness
• Stress and anxiety