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Sleep deprivation hurts body and mind

Studies find links to depression, diabetes

Jane E. Brody, Special to the Rocky

Published October 30, 2007 at midnight

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For decades, I assumed I needed to sleep just five to six hours a night. I nearly always awoke before the alarm in the morning. But I also nearly always fell asleep at concerts and plays, on the subway or while reading or riding in a car.

Last summer, when I was able to operate completely on my body's own time clock, I discovered that it preferred seven to 7 1/2 hours of sleep. I also discovered that when I slept at night for however long my body wanted to, my daytime dozes all but disappeared.

Surveys have shown that few of us past toddlerhood receive the amount of sleep our bodies and brains need to restore them to full function for the day ahead. And many of us - children, teenagers and adults of all ages - may pay a hefty price. Crucial brain functions occur in sleep that can't be reproduced when we're awake.

More than intellectual prowess can suffer. Though definitive data are still lacking, a chronic shortage of sleep has been linked to serious physical ills, including heart disease, diabetes and obesity.

From infancy to adulthood, there are marked changes in how much sleep people need every day, the amount of time spent in each stage of sleep and how easily they fall asleep and stay asleep, a factor scientists call sleep efficiency.

Sleep deprivation seems to start early. A 2004 survey by the National Sleep Foundation found that on average, children in all age groups from infancy through fifth grade failed to get even the low end of the recommended range of sleep.

The real agony emerges in adolescence. As children go through puberty, two things happen to make getting enough sleep problematic: They need more sleep than prepubescent children, not less - nine to 10 hours a night - and their body clocks shift to a later time to fall asleep and, consequently, a later awakening.

Amy R. Wolfson, a psychologist at the College of the Holy Cross, in Worcester, Mass., and Mary A. Carskadon, a sleep researcher at the Brown University School of Medicine in Providence, R.I., have found that few adolescents sleep the amount they need. The average eighth-grader sleeps less than eight hours, and more than a quarter of high school and college students are chronically sleep-deprived, they reported.

In a report last February in the journal Pediatrics, researchers from the Columbia University School of Nursing estimated that "15 million American children are affected by inadequate sleep." They based this on the findings of a 2003 national health survey of 68,418 children ages 6 to 17. In the study, by Arlene Smaldone and colleagues, the percentage of children who failed to sleep enough rose with age and increased markedly among children 12 and older.

Sleep deprivation has been linked to poorer grades, moodiness and depression.

Dr. Ronald E. Dahl, a sleep expert at the University of Pittsburgh, says sleep deprivation among teenagers creates a "negative spiral" of fatigue, emotional instability, poor decision-making and risky behavior. Dahl and others agree that long- term studies of the effects of sleep deprivation in the teenage years are desperately needed.

Harmful effects on adult health have been associated with sleeping too little and with sleeping too much, though what constitutes too little and too much varies from study to study.

Studies suggest that adults who sleep seven to eight hours a night are the healthiest. About a third fall into that range. More than a third sleep less than seven hours, and nearly a third sleep more than eight hours.

Sleep numbers

A six-year study by researchers at the University of California, San Diego, and the American Cancer Society found that:

• The highest mortality rate was among those who slept less than four hours or more than eight hours a night.

• The lowest death rates were among those who averaged six to seven hours of sleep.

Other studies have found that:

• People who sleep the least or the most are more likely to have high blood pressure, symptoms of depression or heart disease.

• Sleep deprivation can also inhibit the body's ability to produce insulin and increases the risk of diabetes.