(USA TODAY) -- Most people know when they don't get enough sleep: They're grumpier, have trouble concentrating and may even eat more. But too little shut-eye does more than affect your mood. It can wreak havoc on your health, research shows.
Sleep deprivation is associated with an increased risk of many serious health problems, including obesity, high blood pressure, type 2 diabetes, depression, heart attacks and strokes, as well as premature death and reduced quality of life and productivity, according to the Centers for Disease Control and Prevention. Add to those an increased risk of automobile crashes, industrial disasters and medical and other occupational errors. A recent mouse study found that chronic sleep loss can lead to the irreversible damage and loss of brain cells.
CDC data show that 28% of U.S. adults report sleeping six hours or less each night, and that's just not enough for most people, experts say. It's no wonder that the CDC calls insufficient sleep "a public health epidemic."
Sleep is so critical to good health that it should be thought of "as one of the components of a three-legged stool of wellness: nutrition, exercise and sleep," says Safwan Badr, a past president of the American Academy of Sleep Medicine and a sleep expert with Detroit Medical Center and Wayne State University.
"The three are synergistic," he says. "It's hard to lose weight if you are sleep deprived. It's hard to eat healthy if you are sleep deprived. It is hard to exercise if you're tired."
Although people's sleep needs vary, the sleep medicine group recommends that adults get about seven to nine hours a night for optimal health, productivity and daytime alertness.
But that's difficult for many people to do. An estimated 70 million Americans suffer from sleep problems, such as insomnia, sleep apnea, restless leg syndrome, shift-work sleep disorder or narcolepsy, as well as sleep disturbances associated with many diseases, mental illnesses and addictions, according to the National Center on Sleep Disorders Research, part of the National Heart, Lung and Blood Institute.
"That's a conservative estimate when it comes to the number of people with sleep disorders or those who have difficulty sleeping," says Michael Twery, director of the center. "There are more than 70 sleep disorders."
Sleep-deprived people may have schedules that don't fit well with the body's natural sleep cycle, such as shift workers or high school students who have to get up early but whose bodies are wired to get up late, Badr says.
They may have insomnia and not be able to fall or stay asleep at night. They may have sleep apnea, which is characterized by frequent pauses in breathing and brief interruptions in sleep.
Or people getting insufficient shut-eye simply may not value sleep. This is a culture where not sleeping very much or pulling an all-nighter is considered a "badge of honor," he says.
Anne Wheaton, a CDC epidemiologist, agrees that people just don't make it a priority. Many people think taking the time to get sufficient sleep is being lazy and a waste of time, but they could be performing so much better if they were well-rested, she says.
There are a lot of physiological changes that occur with sleep, says Timothy Morgenthaler, a consultant at the Mayo Clinic Center for Sleep Medicine in Rochester, Minn. "One of the main hypotheses is that one primary function of sleep is to help eliminate metabolic waste products of the mental processes in your brain. Sleep clears those waste products out and replenishes the energy inside brain cells."
There is a recent study that showed that "when we don't get enough sleep, we actually injure brain cells. The research was done in mice, but I think there is very little doubt that our cognition suffers, and our brain does not function as well when we don't get enough sleep."
New research shows that "another significant function of sleep is to prune out less important things we learn every day and solidify those signals that are more important to remember. This occurs every night," Morgenthaler says.
"When you miss out on sleep, you take out a loan from the sleep bank," he says. "You can never completely repay the debt — and decreased health is the interest on your loan."
Adds Twery: "Sleep is not only important for brain health, it's part of the biology of virtually every tissue and organ in our body. A lifestyle that doesn't provide for sleeping long enough on a regular schedule each night with good-quality sleep doesn't support the body's natural biological rhythm. Then the chemistry of these tissues and organs works inefficiently.
"The amount of sleep needed to support human biological rhythm is typically seven to eight hours during the night. Like naps, shorter periods of sleep at other times of day may reduce the feeling of sleepiness but do not help the biological rhythms associated with long-term health," he says.
Twery encourages individuals who frequently feel excessively sleepy during the day to discuss their symptoms with a physician.
New treatments for sleep disorders have been developed based on these research advances, and more are in the development pipeline, he says.
Badr says there are some steps you can take to get a better night's sleep: Go to bed at about the same time every night, get up at the same time in the morning, don't drink caffeine at all or in the afternoon, limit alcohol consumption, and exercise regularly.
"Sleep well, live well," he says.
Daily sleep needs vary by ages and individuals but here are some general guidelines:
Newborns (up to 2 months), 12-18 hours
Infants (3-11 months), 14-15 hours
Toddlers (1-3 years), 12-14 hours
Preschoolers (3-5 years), 11-13 hours
School-age children (5-10 years), 10-11 hours
Teens (11-17 years) 8.5-9.5 hours
Adults (18 and older), 7-9 hours