If counting sheep is not working for you, here are some facts you may want to sleep on-chronic sleep deprivation can do more than make you tired. It can significantly affect your health, safety, performance, and lifestyle.

Most people are surprised to learn that sleeping less than six or seven hours a night can increase their mortality risk more than smoking, high blood pressure or heart disease.

Losing as little as one and a half hours of sleep for just one night could result in a reduction of daytime alertness by as much as 32 percent. This loss can impair memory and the ability to think and process information effectively.

Decreased alertness can also affect your life by limiting your participation in activities that require sustained attention, such as reading a book or watching your favorite TV show. And the risk of receiving an occupational injury more than doubles when a person is sleepy.

Car accidents are another problem. The National Highway Traffic Safety Administration (NHTSA) estimates conservatively that each year drowsy driving is responsible for at least 100,000 automobiles crashed, 71,000 injuries and 1,550 fatalities.

As many as 70 million Americans have sleep disturbances-which include taking a long time to get to sleep, sleeping less and waking up frequently.

Sleep disturbances may in fact be a symptom of a much larger problem, especially if they are associated with irritability and mood swings. Emotional stress, racing thoughts and restlessness can be signs of something more serious, such as bipolar disorder.

"If someone is experiencing restlessness and irritability, along with sadness or emotional ups and downs for more than two weeks," said Dr. Ellen Frank, professor of psychiatry and psychology, University of Pittsburgh Medical Center and the Western Psychiatric Institute and Clinic, "they should seek medical attention from a specialist who is trained to diagnose or perhaps just rule out depression or bipolar disorder."

The Depression and Bipolar Support Alliance (DBSA) has launched a new Web site, www. sleeplessinamerica.org, which offers educational resources that provide screening for sleeplessness, information on when to see a doctor and a questionnaire to determine when sleeplessness might be symptomatic of a more serious illness. The Web site is also available in Spanish.