Deep Sleep: The Defense Against Dementia
What is deep sleep?
We can all describe how we feel after having slept soundly, but this is subjective. Sleep specialists use an objective way to measure so-called deep sleep.
Sleep architecture basics
If you undergo a sleep study (also known as polysomnography) at a sleep clinic, you’ll be fitted with electrodes across your scalp. These measure brain signals that occur across the night as you sleep (and no, they don’t deliver electricity of any kind to the brain).
The types of signals your brain produces as you sleep, and where they occur across your scalp, are used to define your sleep stages at night.
Stage 1: This describes very light sleep, such as right when you are falling asleep, or the kind of transitional sleep between other stages.
Stage 2: You spend about half of the night in this stage. This “garden variety” nonREM sleep happens throughout the entire night.
Stage 3: Hello, deep sleep! Also called slow-wave sleep or delta sleep, it happens mostly in the early part of the night. You’ll spend 20 percent of your time in this stage. This stage is also known as the slow-wave sleep, or delta sleep—that constitutes the time when your brain does repair work, “rinses your brain” of toxins, and releases an important substance called human growth hormone (HGH).1
Stage REM: The previous stages represent nonREM sleep. REM (rapid eye movement) sleep takes place when you enter the dream phase. REM mostly takes place in the second half of the night.
Deep sleep and aging
It’s thought that the older we get, the less deep sleep we get, simply because we’re no longer growing and need far less HGH. However, we should still experience some deep sleep. Aging does provide added challenges to sleep, however. We may toss and turn because of aging-related illnesses, like arthritis, GERD (gastroesophageal reflux disease), or overactive bladder. These disruptions can cut into our opportunities to get adequate deep sleep.
Medications we take for other health conditions can also fragment sleep. Retirement removes a certain structure to our days and nights, which can make sleep troublesome. Circadian rhythms can also be disrupted if we struggle to sleep at night and end up napping too much during the day.
Another common concern for some older people? A circadian rhythm disorder known as advanced sleep phase disorder, in which people begin to naturally fall asleep earlier in the evening and awaken earlier in the morning.2 If you’ve noticed a loved one in a senior residence dining at 4:30p—sometimes called the “earlybird special”—that’s because the staff caters to its residents’ sleep-wake cycles. Many will go to bed before 7 pm.
Deep sleep and dementia
A loss of deep sleep doesn’t mean you’re bound to develop dementia. However, recent research suggests that inadequate deep sleep in our later years can increase the risk for memory impairment and changes in levels of certain brain proteins associated with dementia (tau and beta amyloid). 3 Elevated levels of tau are linked to brain damage and cognitive decline, signaling the presence of Alzheimer’s disease.4
Researchers now believe that sleep monitoring could become a standard screening tool for uncovering early signs of the cognitive decline associated with dementia.5 The study lead author, Dr. Brendan P. Lucey, told Science Daily that, “measuring how people sleep may be a noninvasive way to screen for Alzheimer's disease before or just as people begin to develop problems with memory and thinking.”
Tips for sleep if you or a loved one are already diagnosed with cognitive decline, dementia, or Alzheimer’s?
- Stick to a regular bedtime and rise time. Try it; it’s one of the easiest ways to support your circadian rhythms.
- Actively treat any health problems that may make it hard to fall asleep.
- Another sleep disorder, restless legs disorder (RLS) can make falling asleep difficult. Consult your doctor to find relief.
- Set aside handheld electronics at night; this will also make it easier to fall asleep at bedtime.
- Avoid caffeine after lunch and alcohol at bedtime. These create withdrawal effects occurring right in the middle of your deep sleep stage.
- Review your medications to ensure they aren’t intruding upon your sleep architecture.
- Talk to your doctor if these solutions don’t improve your sleep, especially in the first half of the night. Doctors may offer other options to help you fall and stay asleep.
As for people entering their golden years who aren’t experiencing poor sleep and who haven’t been diagnosed with dementia, take note: protecting your deep sleep cycles with good sleep hygiene can help reduce your risk for cognitive decline.6
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