Sleep times drop during workweek

Washington -- Long workdays are taking a toll on Americans' ability to get enough sleep, according to a new poll released on March 3 by the National Sleep Foundation. Sleep experts worry that the trend could hurt people's health.

A phone survey of 1,000 adults found that about 90% of respondents worked outside the home and arose, on the average weekday, at 5:35 a.m. after sleeping for about 6 hours and 40 minutes. This average worker reported spending 9½ hours at the workplace each day topped off by another 4½ hours per week working from home.

This combination of too much work and too little sleep has serious repercussions. Thirty-six percent of those surveyed reported they had nodded off or dozed while driving, and 32% said they drive while drowsy at least one to two times per month.

Many people, even when they try to sleep, have trouble dozing off, wake during the night and often feel unrefreshed when they get up. Forty-four percent of survey respondents reported that they experience such problems almost every night.

Many health problems also are associated with sleep loss. It is linked to the obesity epidemic and its accompanying chronic illnesses, including diabetes and hypertension.

Chronic sleep loss appears to interfere with the immune and endocrine systems. Evidence also is building that it is associated with a rise in blood pressure during the night that lasts through the following day. An association exists between too much or too little sleep and an increased risk of coronary heart disease in women, according to information from the sleep foundation.

A 2006 Institute of Medicine report on sleep disorders added cardiovascular disease, anxiety symptoms, moodiness, depression and alcohol use to the list of ills caused by sleep deficiency, which was defined as less than seven hours per night.

The new poll was released during the sleep foundation's conference, "The Role of Sleep in Memory and Learning," held March 3 and 4 in Washington, D.C. The foundation is an independent, nonprofit research group based in Washington.

Effects of the life cycle

Researchers presented findings that covered sleep quality from birth to old age. Age is the strongest factor influencing normal sleep and its distribution between REM, or active phases, and non-REM phases, said Phyllis Zee, MD, PhD, professor of neurology and physiology and associate director of the Center for Sleep and Circadian Biology at Northwestern University Medical School in Chicago.

A newborn will sleep for an average of 14½ hours per day, with about 50% being in the REM phase. Hours begin to drop during the toddler and preschool years, and the REM phase dips to about 35% of total sleep time.

A marked change in the timing of sleep and wakefulness occurs during adolescence. Nine hours of rest is recommended for this age group. Teens' biological clocks run longer and collide with the generally early start of the school day -- a phenomenon that has been noted in recent studies. Early school start times result in chronic sleep loss for many teens who often will recover this loss on weekends with marathon sleep-ins, Dr. Zee noted.

Needs during young adulthood and middle age remain fairly constant, with most people requiring seven to eight hours of sleep each night, she said. During this time, the REM phase remains relatively stable at 20% to 25% of total sleep time.

A change occurs at about age 60, she said, when the percentage of REM sleep begins to decline. The combination of normal age-related changes in circadian rhythms and the poorer health and disorders that can accompany aging can lead to chronic sleep loss in this age group, she said. This in turn, may contribute to cognitive decline.

As sleep deteriorates with advancing age, individuals may be less able to deal with more challenging tasks and may need more time or effort to perform such tasks, said Michael Vitiello, PhD, professor of psychiatry and behavioral sciences at the University of Washington in Seattle. But, Dr. Vitiello asked, "Are older adults chronically sleep deprived?" Additional research will be necessary to answer this question, he concluded.