Adults require 8-8.5 hours of sleep per 24-hour period. Here again, American adults are seriously sleep deprived. According to the National Sleep Foundation's 1998 Omnibus Sleep in America Poll, the average adult obtains <7 hours of sleep a night across the workweek, and 32% of American adults sleep as little as 6 hours a night across the workweek.

Napping is common with 38% of the adults surveyed taking at least one nap of over an hour on a weekday or over the weekend. A full 23% of the adults surveyed acknowledged falling asleep at the wheel during the past year. Being a man (30%), between the ages of 18 and 29 (33%), and working a rotating work shift schedule (40%) made falling asleep at the wheel more probable. Sleepiness behind the wheel now kills more young adults in traffic accidents than does alcohol.

The National Highway Traffic and Safety Administration (NHTSA) estimates that at least 56,000 motor vehicle crashes are caused by drowsy drivers yearly, resulting in more than 40,000 injuries and 1,544 fatalities. The National Transportation Safety Board (NTSB) estimates that 31% of all commercial driver fatalities and 58% of single-truck crashes are fatigue-related.

The National Sleep Foundation's 1998 Omnibus Sleep in America Poll found that 44% of American workforce adults between the ages of 25 and 64 attempted to "make up" some of their lost sleep across the workweek with increased sleep on the weekends -- similar to what is seen in teenagers. Bad habits in adolescence carry right over into adulthood.

Getting to bed too late was the primary factor in reducing total nocturnal sleep time, given a fixed wake-up time dictated by an employer. Whereas 52% of shift workers report daytime sleepiness having to do with the conflict between their work schedules and internal biological clocks.

Anywhere from 40%-80% of shift workers have difficulty sleeping during their off hours. It is estimated that sleep-related accidents in the workplace cost industry $10.3 billion yearly with another $100 billion in costs for lost workplace productivity. Some 40 million Americans suffer from chronic sleep disorders - 95% of whom are undiagnosed -- with another 20 to 30 million Americans suffering from intermittent sleep-related problems.

In Seniors, the 24-hour sleep need continues to remain at 8-8.5 hours. Unfortunately, the ability to obtain this amount of sleep during a single period deteriorates linearly above the age of 65.

The sleep of Seniors is fragmented and "light." What is lost with the aging process is the consolidation of the sleep state and the "deepest" NREM delta stage 4 sleep. In addition, there is a tendency for the internal clock to advance in the elderly, so that Seniors typically go to sleep much earlier in the evening and wake up during the early morning hours.

The entire sleep period advances to an earlier set of clock hours. Thus, it is not unusual for a 70 year old to go to bed at 7pm or 8pm and awaken at 4am or 5am, unable to return to sleep. Some of this advance in the biological clock is socially driven, but there does appear to be a biological aspect with a shortening of the clock's period length in old age.

Sleep in the elderly is further fragmented secondary to an increase in medical problems -- such as hypertension, heart disease, diabetes, lung disease, various cancers, and chronic pain -- an interaction with the medications used to treat these medical problems, and an age-related increase in sleep-related breathing disorders, restless legs syndrome, and periodic leg movements during sleep.

Maintaining an active lifestyle during the senior years of life with exposure to outdoor light is important towards maximizing sleep consolidation and sleep depth at night. It is normal for the elderly to compensate for their poorer quality sleep at night with an afternoon nap of an hour or so.

Above the age of 65 years old, Seniors find it difficult to stay awake between 1pm and 4pm in the afternoon, and are at greatest risk for falling asleep at the wheel during this afternoon time interval.

Sources: National Sleep Foundation, 1998 Omnibus Sleep in America Poll - a nationally representative telephone survey of 1,027 adults above the age of 18 living in households in the continental U.S. Estimates based on this sample size have an error range of plus or minus 3 percentage points at a confidence level of 95%. NCSDR/NHTSA 1997 Report, "Drowsy driving and automobile crashes - expert panel on driver fatigue and sleepiness."

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