How much sleep is enough? How much is too much?
Questions like this have dogged sleep researchers for many years. And they often befuddle the public.
Several years ago I was questioned on MSNBC on “reports” that people sleeping more than eight hours a night died at a higher rate than people sleeping less. Should the reporter try sleeping less in order to preserve his life?
I tried to explain that correlation is not causation. Just because 85% of Americans die in bed doesn’t mean that beds kill people. Lots of people will sleep long because they’re ill. Others will sleep long because they’re sleep is disrupted. Some will sleep long because they’re ill with something not yet diagnosed.
Now a recent study from Boston University argues you can use sleep times to predict dementia. In their study, from the formidable Framingham data, twice the people who slept nine hours or longer were demented ten years on compared to those who slept less. For those without high school diplomas who slept more than nine hours, the rates of dementia were six times higher.
Is it the total amount of sleep that’s predictive? Or is it the change in sleep?
How Much Sleep Do You Need?
Sleep researchers are well aware that sleep need is a very fungible topic. In the eighteenth century, people routinely slept in three phases – first sleep, with an interruption of perhaps an hour, followed by second sleep, with waking usually around dawn, followed by afternoon naps. The total amount of sleep between these phases was often 9.5-10 hours through the 24 hour day.
Enter the post-industrial America “lie down and die” model, where people sleep in only one episode. That itself has changed a lot in the last 50 years, and continues to shift with changes in culture and technology. Perhaps 90 minutes have been shaved off American sleep times since the 1960s. This fact influenced the American Sleep Disorders Association when they recently argued “seven hours or more” sleep in 24 hours might be a standard for the nation.
Yet some people sleep very effectively with just three hours. Some require 10 hours, and have throughout adulthood. Many lifetime “long sleepers” have illnesses like narcolepsy or conditions like depression or ADD that “explain” their long sleep times. Yet there are many folks who just are genetically built to sleep long. The interesting stuff happens when people’s sleep patterns change.
How We Get Ill
Much of present day medicine operates with an implicit model of illness – the body breaks down. With age, our heart “wears out,” or our joints “ fall apart.” This extraordinary misconception fuels some of the confusion regarding total sleep times.
Bodies don’t wear out – they fail to rebuild and regenerate. Most of the heart gets replaced in three days. Most of your body gets replaced, internally, in a few weeks. The information systems powering the whole lot are continuously rebuilt. But we don’t see our immune system “learn” anymore than we witness our brains making different connections. Out of sight, not in mind. Except that learning and intelligence, though frequently not conscious, is critical to the function of all organs.
When someone gets sick, whether it’s a cold or cancer, sleep is often disrupted. This will often lead to longer periods in bed and therefore “longer” sleep times. But sleep is itself a specific and highly required part of the body's natural remaking process. For example, the brain reorganizes itself in sleep very differently than when awake. In conventional cognitive terms, sleep deprive people and they stop learning effectively.
So there are two major reasons why illness will cause long sleep times – direct effects of the illness, followed by the need for more rest and sleep to reverse the damage and failed rebuilding that illnesses may produce. When you get rheumatoid arthritis, the pain will wake you up. The damage to joints, connective tissue and arteries produces more inflammation. More inflammation means more work clearing out dead and dying tissues and regrowing and rebuilding what’s been lost. That demands more rest time – and more sleep. And as we know with Alzheimer’s, or even the chronic snoring that eventually leads to sleep apnea, illnesses can take many years to develop.
Looking Underneath the Hood
The body always changes. Otherwise we don’t survive. Sleep clinicians rightly are most concerned with changes in sleep, rather than overall sleep times.
Ever watch someone who’s sleeping seven hours a night for years suddenly starting sleep 2-4 hours one night and 12-16 the next, cycling back and forth? If you do, please start thinking about possible bipolar disorder. If someone who sleeps normally goes on a business trip and develops insomnia which then continues so forcibly their worries about sleep drive them nuts, think psychophysiologic insomnia. If someone who always wakes at 6:30 a.m. finds their energy, interest and concentration declining just as their wake time changes to 4 a.m., you may want to think about depression.
Long sleep demands explanation. It may be the natural state of an individual, just as it was in their parents or grandparents. But if it’s a new state, it signifies something else – that the body is changing its sleep pattern to take respond to a new derangement. And that derangement in the body’s regeneration system may be very subtle, like the originally tiny changes that can produce congestive heart failure or dementia. Look less to the time, and more to the change.