Remember how “Goldilocks” rejected Papa Bear’s bed because it was too hard, Mama Bear’s bed because it was too soft and chose Baby Bear’s bed because it was just right?
That was a simple decision, but when it comes to figuring out the connection between the number of hours we need to sleep each night and the risk of developing Alzheimer’s disease, how much is just right?
Getting too little sleep in later life is associated with an increased risk for Alzheimer’s disease. But paradoxically, so is getting too much sleep.
Dr. Judith Seme, a faculty member at Keiser University who teaches nursing courses, says that 9 hours of sleep nightly on a regular basis are too many – and could be a sign of underlying health issues, like depression.
But she adds, “if you sleep less than 6 to 7 hours a night regularly, it can impair your overall brain function and possibly lead to dementia, including Alzheimer’s.”
Johns Hopkins Medicine explains that if you’ve ever felt foggy after a poor night’s sleep, it won’t surprise you to learn that sleep significantly impacts brain function. A healthy amount of sleep is vital for the brain’s ability to adapt to input.
A lack of good quality sleep may also lead to a build-up of a protein that can contribute to Alzheimer’s, according to Dr. Seme.
“Amylase is an enzyme, a type of protein that helps your body break down carbohydrates,” she says. “The pancreas and salivary glands in your mouth make amylase.
“During the night, if you’re enjoying a deep relaxing sleep, the lymphatic system helps clean out waste – including amylase – that has accumulated in the brain.
“If that sleep is disturbed, or there’s not enough of it, some of the amylase can remain. If it’s allowed to build up over years, the result may increase the risk of dementia, including Alzheimer’s disease.”
Medical News Today outlines the four stages of sleep and explains what happens to our bodies as we cycle through them several times each night. The first three form non-REM sleep and the fourth one is REM or Rapid Eye Movement sleep, where dreams occur.
In the first non-REM stage, the brain changes its electrical oscillations from the active, wakefulness pattern of brainwaves into a slower rhythm. Muscle tone throughout the body relaxes.
In the second non-REM stage, the body’s temperature drops, heartbeat and breathing become slower, and brainwaves slow down further.
The third stage of non-REM sleep is the deep sleep stage, which our bodies need to wake up feeling refreshed and restored. In this stage, heart rate, breathing and brain activity all drop to their lowest point.
The REM, dream-filled light-sleep stage is the fourth and last one. REM typically starts about 90 minutes after falling asleep. During REM sleep, breathing becomes more rapid and irregular, and heart rate and blood pressure increase to near waking levels.
REM sleep, which tends to decline with age, has important benefits for mental and physical health.
“During this 90- to 110-minute stretch of dozing, emotional experiences are processed, and memories are consolidated, recent research has shown. The brain also rests and repairs itself. If you’ve had enough REM sleep, you’ll wake up feeling refreshed and alert. It is also associated with better mental health and a stronger immune system,” according to the University of California health system.
A report by Mayo Clinic released in 2024 noted that Alzheimer’s disease is the most common cause of dementia. Alzheimer’s disease is the biological process that begins with the appearance of a buildup of proteins in the form of amyloid plaques (amylase) and neurofibrillary tangles in the brain. This causes brain cells to die over time and the brain to shrink.
About 6.9 million people in the United States age 65 and older live with Alzheimer’s disease.
Dr. Seme adds, “There’s normally a small amount of amylase in your blood and urine. But levels that are too high can indicate a health problem.”
The Mount Sinai Health Network explains that sleep problems are common in older adults. Among the causes are:
- Alcohol use.
- Changes in the body’s natural internal clock, causing some people to fall asleep earlier in the evening.
- Chronic disease, such as heart failure.
- Certain medicines, herbs, supplements and recreational drugs.
- Depression.
- Not being active.
- Pain caused by diseases such as arthritis.
Dr. Seme has some additions to that list. “Sleep apnea, which is often undiagnosed, and restless leg syndrome both cause sleep interruption that can affect the memory and lead to cognitive decline.”
At the same time, the Fisher Center for Alzheimer’s Research Foundation explains that those who sleep nine or more hours a night tended to score lower on tests of memory and thinking skills, though they did not have higher levels of amylase in the brain than healthy sleepers.
Excess sleep had a particularly detrimental effect on executive function, which allows us to plan, organize and remember instructions. Those who slept a lot also scored higher on assessments of depression, which has been linked to an increased risk of developing Alzheimer’s disease.
Joe Winer, a postdoctoral fellow of neurology and neurological sciences in the Center for Sleep and Circadian Sciences at Stanford University, says that some of the first areas in the brain affected by Alzheimer’s are those that help regulate sleep and circadian rhythms. As a result, people who develop the condition may experience sleep problems that contribute to the affliction even before they show signs of memory loss or other symptoms.
Sleep aids aren’t the answer, says Dr. Seme. “They may provide short-term relief but they’re not a long-term solution. Cognitive behavioral therapy and good sleep hygiene are better choices.”
Good sleep hygiene includes a combination of healthy habits and environmental factors that can help people fall asleep faster and stay asleep. It includes keeping the bedroom cool, not engaging in stimulating activities near bedtime, such as vigorous exercise or video games, using an eye mask to block out light, and going to bed at the same time each day.
“Other things you can do to get better sleep include prioritizing sleep, eating a healthy diet rich in antioxidants and omega 3 oils, and avoiding heavy sugars and trans-fatty acids,” Dr. Seme says.
“Get medical care from your primary care doctor, sleep specialist, geriatrician, or neurologist as soon as you suspect there may be a problem.
Dr. Judith Seme earned her Ph.D. in Nursing from Barry University in Miami. She has been a faculty member at Keiser University’s Port St. Lucie campus since August 2022 and has been in nursing academia since 2018. Dr. Seme currently teaches Care Management I, Professional Nursing III and Leadership in Nursing.
