How Much Sleep Do I Need?
Men need about eight hours of sleep each night. Women cycle through the phases of sleep slightly faster and on average need about seven to seven and a-half hours. But these numbers vary from individual to individual. I do best at seven hours and fifty minutes, which is pretty typical for men. My wife (whom I believe to be part cat) does best with just shy of nine hours.
Do We Need Less Sleep As We Age?
There is a myth that as people get older they need less sleep. In fact, while it is true that people tend to get less sleep as they age, is is not true that they need less sleep. There is a tiny structure, about the size of a small pea, which lies in the center of the brain, just behind the eyes. It is called the pineal gland and it produces a serotonin-based hormone called melatonin which helps to induce and maintain the sleep state. The pineal gland is the only endocrine gland that has communication with the outside world. It senses light through activation of receptors behind the eyes. In the absence of light, these receptors are quiet, and the pineal gland secretes melatonin which makes us sleepy and helps us to cycle down into deeper sleep. In the presence of light, the receptors become stimulated (even when the eyes are closed) causing them to signal the pineal gland to stop producing melatonin and initiating a reflex to induce wakefulness. The production of sleep-inducing melatonin in the dark and the shutting off of melatonin production in the presence of light, ties us to the cycles of day and night. The pineal gland is the control center of our circadian rhythm.
The pineal glands of babies produce a lot of melatonin. A little less gets produced during childhood, but it is still a lot compared to the precipitous decline which takes place during adulthood. By the time we reach the age of 50, our pineal glands are able to produce only about 25% the amount of melatonin that we produced in our teen years. By age 70 we produce only 5-10%. High levels of melatonin production in infancy and childhood help to explain why children are able to drop suddenly into such deep sleep and to maintain sleep for nine, ten, or more hours. Similarly, progressively lower levels of melatonin helps account for the difficulty many people experience getting adequate sleep as they get older. But this does not mean that our bodies need less sleep as we age. It is more accurate to say that the aging process–the breakdown of healthy body tissues due to increased inflammation and diminished circulation–is exacerbated by lack of sleep, a problem which tends to accelerate as we age due in part to diminishing levels of melatonin.
I Get Enough Sleep, So Why Do I Still Feel Tired?
The right quantity of sleep is important for necessary restoration and recuperation. But equally important is the quality of the sleep that we get. Many of my patients report sleeping 7-8 hours per night, but they still wake up feeling tired and unrefreshed a clinically significant amount of the time (more than twice per month). Do you need coffee to get you going most mornings? Is it the rare morning when you wake up full of energy, feeling as though you’d slept just the right amount in order to feel great? If you are waking up feeling tired despite getting plenty of sleep, then you are probably experiencing poor quality sleep.
REM, the deepest phase of sleep, is also the most fragile phase and is very susceptible to disruption. Noise, light, difficulty breathing due to excess fat in the throat area (sleep apnea), back pain, neck pain, shoulder pain, even the pressure of a full bladder can be enough to nudge us out of this most important phase, either waking us up, or almost waking us and causing the cycle to restart at pre-sleep or phase I without having spent any or enough time in REM restoring our bodies and brains. This is how we are able to get eight or more hours of sleep yet still wake up feeling tired and unrefreshed. We are simply not spending enough time during those eight hours in the deep restorative phases of sleep, especially REM.