The following is an excerpt from a book on aging I’m now writing. The working title is “Fast After 50.” Even though the book’s market is 50+ aged athletes I’m sure much of what I’ve written here on sleep is applicable across the board regardless of age. Far too many athletes, both young and old, get too little sleep. That shows up as lackluster training and poor performance. Sometimes the athlete doesn’t have a clue that he or she is simply not getting enough sleep. Sleep is critical to adaptation and fitness. Too little sleep can greatly reduce the benefits of androgenic hormones such as growth hormone and testosterone. Many could improve by simply getting more snooze time. Since this is a rather long piece I’m going to post it in two parts. Here is Part 1. The book, by the way, is due to be on the shelves around the end of the year.
The purpose of sleep is the growth and rejuvenation of the body’s many systems such as the muscular, skeletal, immune, nervous and other systems. This is your primary means of recovery from training stress. There is nothing you can do that will help you recover faster or more completely. Sleep is not something to mess around with and yet some do by shortening their sleep time in order to pack more stuff into their lives. It’s quite common for athletes to stay up late watching their favorite TV shows and then set an alarm so they get up early the next morning in order to fit in a workout before heading off to work. If you depend on an alarm clock to wake you then you probably aren’t getting enough sleep—or enough recovery. Going to bed earlier would more than likely improve your performance. That single lifestyle change may even improve your life in other ways.
Several studies have found that the amount of sleep you get is closely associated with not only your health, but also your longevity. Short sleep durations have been shown to increase the risk of obesity, heart disease and type 2 diabetes.7,8,9 (Patel, Ferrie, Reynolds) Conversely, those who report regularly sleeping six to seven hours per night appear to have long lifespans.10 (Kripke) Interestingly, sleeping more than seven hours nightly has been associated in one study with a shorter life.8 (Ferrie) Note that “association” doesn’t mean “cause,” but rather that the two were found to occur together. There could be a cause effect, but this isn’t known with any degree of certainty. Even if long sleep was causal this shouldn’t be taken to mean that setting an alarm to wake you up after seven hours in bed is the key to a long life. An innate sleep duration is probably best for longevity as well as health. Your normal nightly sleep duration is probably determined by genetics11 (He) and shouldn’t be artificially shortened. It is probably most beneficial when you wake up naturally rather than to the buzzing of a clock.
To appreciate the benefits of sleep for recovery it’s necessary to understand sleep. What happens during slumber that produces renewal so that you can do another hard workout? Let’s start by finding out what goes on in your body when you’re asleep.
Sleep researchers divide your snooze time into two broad periods: rapid eye movement (REM) and non-rapid eye movement (NREM).12 (Dement) Non-REM is further divided into three stages called N1, N2 and N3. The last of these is referred to as slow wave sleep because the amplitude of the brain’s electrical activity becomes quite low. In a full night of normal sleep your body progresses through the N1, N2, N3 and REM stages several times. Slow wave sleep makes up much of the early stages of a full night of sleep with most of the REM time occurring in the latter half of the night. These two stages have a lot to do with how well you recover so we’ll take a closer look.
Your body operates on a built-in clock called the “circadian rhythm.” This “clock” is set by how much light enters your eyes. In the evening, around sunset, your clock initiates the release of a hormone called melatonin from the pineal gland in the brain as your body temperature is also lowered. This produces the drowsiness and yawning that is the start of the N1 stage. As with most hormones, as you get older melatonin production decreases.13,14 (Sack, Goldenberg) That means sleepiness for some oldsters may not be as compelling as it is for younger athletes. Then again, many older athletes find that they become drowsy much earlier in the evening than they did when young and often fall asleep in a chair long before making it to the bedroom. These older athletes also tend to wake up earlier in the morning.14,15 (Duffy, Goldenberg) Generally, the circadian clock for seniors is not as rhythmic as it was when younger.
A specific type of light, called “blue light,” which is produced by the sun, interferes with the production of melatonin. The light bulbs in your home also give off some blue light, not nearly as much as the sun, but possibly enough to hinder melatonin release thus keeping you awake longer in the evening. To stimulate a melatonin discharge in order to start feeling drowsy you can turn off most of the lights before bedtime. There are also special blue-blocking glasses that look like sunglasses and can be worn in the evening if you must be in a bright, artificially lit room.16 (Burkhart) You can search the web to find such products.
7. Patel SR, Ayas NT, Malhotra MR, et al. 2004. A prospective study of sleep duration and mortality risk in women. Sleep 27(3):440-4.
8. Ferrie JE, Shipley MJ, Cappuccio FP, et al. 2007. A prospective study of change in sleep duration: associations with mortality in the Whitehall II cohort. Sleep 30(12):1659-66.
9. Reynolds AC, Dorrian J, Liu PY, et al. 2012. Impact of five nights of sleep restriction on glucose metabolism, leptin and testosterone in young adult men. PLoS One 7(7):e41218.
10. Kripke DF, Garfinkel L, Wingard DL, et al. 2002. Mortality associated with sleep duration and insomnia. Arch Gen Psychiatry 59(2):131-6.
11. He Y, Jones CR, Fujiki N, et al. 2009. The transcriptional repressor DEC2 regulates sleep length in mammals. Science 325(5942):866-70.
12. Dement W, Kleitman N. 1957. Cyclic variations in EEG during sleep and their relation to eye movements, body motility and dreaming. Electroencephalogr Clin Neurophysiol 9(4):673–90.
13. Sack RL, Lewy AJ, Erb DL, et al. 1986. Human melatonin production decreases with age. J. Pineal Res. 3(4):379–88.
14. Goldenberg F. 1991. Sleep in normal aging. Neurophysiol Clin 21(4):267-79.
15. Duffy JF, Dijk DJ, Hall EF, Czeisler CA. 1999. Relationship of endogenous circadian melatonin and temperature rhythms to self-reported preference for morning or evening activity in young and older people. J Investig Med 47(3):141-50.
16. Burkhart K, Phelps JR. 2009. Amber lenses to block blue light and improve sleep: a randomized trial. Chronobiol Int 26(8):1602-12.