often be treated, and symptoms should be discussed with a physician. Daytime sleepiness can be dangerous and puts a person at risk for drowsy driving, injury, and illness and can impair mental abilities, emotions, and performance.
Studies have found a relationship between the quantity and quality of one's sleep and many health problems. For example, insufficient sleep affects growth hormone secretion that is linked to obesity; as the amount of hormone secretion decreases, the chance for weight gain increases. Blood pressure usually falls during the sleep cycle, however, interrupted sleep can adversely affect this normal decline, leading to hypertension and cardiovascular problems. Research has also shown that insufficient sleep impairs the body's ability to use insulin, which can lead to the onset of diabetes. More and more scientific studies are showing correlations between poor and insufficient sleep and disease.
Sleep experts recommend a range of seven to nine hours of sleep for the average adult. While sleep patterns change as we age, the amount of sleep we need generally does not. Older people may wake more frequently through the night and may actually get less nighttime sleep, but their sleep need is no less than younger adults. Because they may sleep less during the night, older people tend to sleep more during the day. Naps planned as part of a regular daily routine can be useful in promoting wakefulness after the person awakens.
The body rests during sleep, however, the brain remains active, gets "recharged," and still controls many body functions including breathing. When we sleep, we typically drift between two sleep states, REM (rapid eye movement) and non-REM, in 90-minute cycles. Non-REM sleep has four stages with distinct features, ranging from stage one drowsiness, when one can be easily awakened, to "deep sleep" stages three and four, when awakenings are more difficult and where the most positive and restorative