Do you have difficulty falling asleep at night? Once you get to sleep, do you wake up frequently? Do you feel lethargic in the morning? Are you drowsy by mid afternoon and unable to stay alert as you go about your day? If you answered yes to one of these questions, you may be one of the millions of people who are chronically sleep deprived and not even aware of it!
Most of these people are also unaware of the extent to which their lack of sleep contributes to feelings of irritability, impatience, anxiety and depression. Sleep deprivation can also affect memory, thinking, reaction time and productivity. It may adversely affect job performance and cause unwanted accidents. Over time, lack of sufficient sleep can have serious health consequences. In fact, more and more studies are showing that getting enough ZZZs is as vital as diet and exercise if you want to live a long and healthy life.
To function properly, the human body needs to sleep a certain number of hours within a 24-hour cycle. The body of research has shown that 8 to 10 hours of sleep per day is optimal for sustaining maximal mental and physical function. Unfortunately, the average American gets only about 7 hours’ sleep per day--90 minutes less than a century ago (Kantrowitz 2002). It has been estimated that as many as 70 million Americans experience some kind of sleep disorder (Kantrowitz 2002).
Studies have shown that too little sleep can affect human beings in all kinds of ways, most notably in terms of cognitive functioning, weight management and athletic performance.
The Army Physical Fitness Research Institute has conducted studies to determine how lack of sleep can affect the productivity of soldiers during waking hours (Wesensten et al. 2002). During total sleep deprivation, the soldiers’ cognitive performance on a task requiring decision making, short-term memory and mathematical processing declined by about 25 percent for every 24 hours of wakefulness.
Countless studies have found a direct correspondence between lack of sleep and a decline in cognitive ability; the less sleep subjects got, the worse they fared in terms of performance, productivity and functionality.
Researchers have also found a link between obesity and sleep deprivation (Brink et al. 2000). One hormone that appears important in this equation is human growth hormone (HGH), which controls the body's proportions of fat and muscle. The majority of HGH secretion occurs shortly after sleep begins, especially during the deepest stages. If sleep is impaired, so is HGH secretion.
As we age, we spend less time in deep sleep, so HGH secretion decreases. With lower than normal levels of HGH, the body cannot properly control the proportion of fat to muscle. When this happens, we tend to store more fat in the stomach area. Some researchers have theorized that lack of sleep at a younger age can prematurely drive down HGH levels and accelerate the fat-building process (Spiegel et al. 1999; Brink et al. 2000).
Lack of sleep can also affect appetite in a negative way. Because many of the symptoms of fatigue and hunger are so similar, people tend to eat when they actually need sleep. Fatigue can also affect energy levels and, consequently, the ability to adhere to regular exercise.
For the endurance athlete looking for every edge, it appears that proper sleep during heavy training or competition is critical for optimal performance. In a sleep-deprived athlete, glycogen (energy) storage may be slowed. During endurance events exceeding 90 minutes (e.g., a marathon), this can lead to hypoglycemia and contribute to what athletes call “hitting the wall,” where they essentially run out of fuel (Ketchum 2003).
Other studies have shown that sleep deprivation causes elevated nighttime levels of the hormone cortisol, which can interfere with tissue repair and growth (Ketchum 2003). Over time, this can prevent an athlete from properly adapting to heavy training and may lead to overtraining injuries.
Adequate sleep is essential for health and peak performance. Above all, remember that good sleep hygiene is as important a daily lifestyle habit as regular exercise or proper nutrition.
Susan B. Johnson, EdD, is vice president and director of education and certification at the Cooper Institute in Dallas.
Crystal Quintana is a personal trainer based in New York City who holds fitness certifications from the Cooper Institute and the National Academy of Sports Medicine.