EVERY THREE SECONDS, SOMEONE DEVELOPS DEMENTIA. Today, I explore the link between deep sleep and dementia: Snooze or lose.
I believe inadequate sleep is a potentially modifiable dementia risk factor.
A new study reports the results of studying sleep among individuals over 60. The researchers offer this provocative finding:
As little as a one percent reduction in deep sleep annually translates to a more than one-quarter increase in dementia risk.
First, some dementia numbers. Then, I’ll share the new research suggesting a link between deep sleep and dementia. I will end with some potential dementia risk-reducing strategies.
Dementia Numbers
I think the projected rise in dementia numbers is quite disturbing. Alzheimer’s Disease International offers these estimates:
Today, there are over 10 million new cases of dementia each year worldwide, implying one new case every 3.2 seconds.
Part of the rise is due to improving health care over the last century. Folks are living longer and healthier lives. This demographic change creates a greater proportion of older people.
Dementia primarily affects older people, although there is a growing awareness of individuals with the disease before age 65.
Sleep, Aging, and Slow Wave Sleep
Monash University (Melbourne, Australia) researchers wanted to clarify the relationship between sleep, aging, and dementia risk.
They examined data from 346 study participants over 60 enrolled in the Framingham Heart Study.
All the chosen participants had completed two overnight sleep studies, with about five years between each sleep study.
On average, the amount of deep sleep each study subject declined between the two studies, indicating slow-wave sleep loss due to aging.
For me, this is the case, according to my wearable sleep-tracking device.
Sleep, Aging, and Dementia
The study authors followed the participants from their second sleep study until 2018, looking for dementia diagnoses.
The authors recognize that there are currently no cures for dementia. In this context, they wanted to understand better how we might prevent the illness.
The research team identified 62 people who developed dementia. The findings are startling to me. After adjusting the results by age, sex, and sleep medicine use, the researchers discovered this:
Each percentage decrease in deep sleep each year was associated with a one-quarter (27 percent) increase in the risk of dementia.
Deep Sleep: What You Should Know
The United States Centers for Disease Control suggests that most adults aim for seven to nine hours of sleep.
A lot is going on when you sleep. For instance, you cycle between REM and non-REM sleep.
REM stands for rapid eye movement. During REM sleep, your eyes rapidly move in many directions but don’t send any visual information to your brain. That doesn’t happen during non-REM sleep.
Non-REM sleep comes first, followed by a shorter period of REM sleep, and then the cycle starts over again. Our dreams typically occur during REM sleep.
What Happens During Non-REM Sleep?
Non-REM sleep has three phases. Each stage can last from five to 15 minutes. You complete all three phases before reaching REM sleep.
Once you fall asleep, your body cycles through three non-rapid eye movement (NREM) sleep stages, followed by one rapid eye movement (REM) stage.
It usually takes between 90 and 120 minutes to cycle through all four stages, after which the cycle starts again. Adults typically have four to six cycles per night.
Breaking Down the Sleep Cycle
In the first half of the night, you spend more time in NREM sleep. However, as the night goes on, we spend progressively more time in REM sleep.
- Stage 1: This brief, drowsy stage marks the transition to sleep when your breathing and heartbeat slow.
- Stage 2: In this stage of light sleep, your breathing and heart rate slows even more. Your temperature drops, and your muscles relax. Stage 2 sleep lasts longer in each cycle throughout the night. About half of your total sleep every night is spent in this stage.
- Stage 3: Stage 3 sleep represents the deepest sleep of the sleep cycle when brain waves are at their slowest in frequency and highest in amplitude.
Deep Sleep, The Immune System, and More
Deep sleep helps strengthen the body’s immune system.
It also plays an important role in keeping the brain healthy by helping develop and store efficient learning, memories, and cognitive functions.
I am discovering this truth: With age, we sleep more lightly and get less deep sleep.
Aging is also linked to shorter periods of sleep, although studies show you still need as much sleep as when you were younger.
Other Studies
I hope I have made the point that deep sleep is vital in optimizing your brain health.
Insufficient sleep is associated with brain-related diseases such as dementia, including Alzheimer’s disease.
Other studies have had similar findings:
- A 2021 study showed that people in their 50s and 60s who slept six hours or less each night had a higher risk of developing dementia later in life.
- A 2023 study suggested that deep sleep may help protect against memory loss in older people with a high amount of beta-amyloid in the brain. This substance is thought by many to be a main driving factor for developing Alzheimer’s disease.
Actionable Advice — Snooze or Lose: The Link Between Deep Sleep and Dementia
Most of us spend about one-quarter of our night in deep sleep. Deep sleep strengthens our tissue (including bones and muscles) and immune function.
We experience deep sleep several times during our sleep time, but stress, insomnia, and aging influence our deep sleep duration.
If we are not getting enough sleep, our bodies prioritize deep sleep. I try to facilitate more deep sleep with these tactics:
- I take a warm shower (or bath) two hours before sleep.
- I optimize my diet.
- I sometimes listen to binaural beats before bedtime.
- I avoid screen time later in the afternoon and into the evening; I try to filter out blue light.
Deep sleep serves restorative functions necessary to feel your best each day. I prioritize sleep.
Thank you for reading “Deep Sleep and Dementia.”
