“To sleep, perchance to dream…”
– William Shakespeare, Hamlet
While Prince Hamlet was contemplating a more permanent form of sleep, sleeping and sleep-related dreaming are very much a part of our daily existence. But why? And just what IS sleep anyway?
We spend about one third of our lives sleeping. No one really knows why we and most other organisms need to sleep. Scientists have a developed a number of theories of why sleep is needed, e.g.:
- Restoration theory holds that sleep occurs so our bodies can repair and restore themselves through muscle and tissue repair, processing of waste materials, and hormone release.
- Energy conservation theory holds that sleep helps us conserve our energy resources by our becoming inactive during those times of the day when our ancestors found it was inefficient or dangerous to search for food (old habits die hard)
- Brain plasticity theory holds that sleep is necessary for the brain to reorganize neural pathways based on new experiences. As we acquire new knowledge and skills through instruction or experience, there must be changes in the brain to reflect and retain that new knowledge or skills.
Perhaps we sleep for some combination of these reasons or for some other reason(s). Point is: no one knows.
We know a bit more about what sleep IS. In sleep, we enter a state of reduced consciousness. Physical activity is reduced and we become less responsive to external stimuli. Since physiological requirements are reduced, our body temperature and blood pressure drop somewhat. Our brain activity, breathing and heart rate may be quite steady during some stages of our sleep experience and quite variable during other stages.
Scientists define two main stages or types of sleep: Rapid Eye Movement (REM) sleep and Nonrapid Eye Movement (NREM) sleep.
NREM sleep is where we normally begin our sleep commencing with a light sleep that gradually becomes deeper and deeper. Breathing, heart rate, and brain activity are generally reduced and steady during NREM sleep. Without deep NREM sleep it becomes difficult to wake up feeling rested.
REM sleep is still a deep sleep but is characterized by rapid eye movement and changes in breathing, heart rate and brain activity. Our most intense dreaming occurs during REM sleep. During REM sleep we do not move our arms and legs which is a good thing since if our bodies acted out our most intense dreams we might hurt ourselves or our bed partner.
Babies spend a lot of time in REM sleep. In younger adults, REM sleep usually follows deep NREM sleep and then alternates with NREM sleep until waking. In older adults, it appears to take longer to reach the deepest levels of NREM sleep and less time is spent in REM sleep. So if senior sleepers observe that they just don’t seem to sleep as well (deeply, soundly, restfully) as they used to, it may well be due to normally occurring changes in their sleep patterns.
OK, so what is dreaming all about? Again, nobody knows. Some scientists suggest dreams are part of the brain’s process of sorting out life’s events and helping to create memories; others say dreams are simply the result of random brain activities. We do know that the most vivid dreams seem to occur during REM sleep, however night terrors (waking up screaming) are usually not the result of dreams and usually occur in NREM sleep. Your author tends to think of dreams as free movies – some good, some not so much.
So what happens with sleep as we get older?
Generally speaking, our quality of sleep tends to decline with age. It tends to take longer to get to sleep in the first place; we spend more time in light sleep and less time in deep sleep, both NREM and REM; we wake up more easily and frequently.
So what can we do to increase the likelihood of getting a good night’s rest? Experts suggest:
- Get regular exercise but not right before bed
- Avoid alcohol, caffeinated drinks and chocolate late in the day
- Keep your bedroom cool, dark and quiet
- Go to bed at the same time each night and get up at the same time each morning
What about napping?
In some cultures an afternoon nap or siesta after a substantial midday meal is part of the daily routine for people of all ages. Sleep experts say that short napping (30-60 minutes) can be a good thing if it is used to compensate for inadequate nighttime sleep. But if napping during the day makes it harder for you to sleep at night, then it should be avoided.
Even though there is much we don’t know about sleep, we do know it is necessary to maintain physical, mental and emotional health. Tired Nature’s sweet restorer, balmy sleep – Edward Young.
R. Kevin Price
© 2008-2009 R.K. Price