Struggling to get a good night’s sleep might be more than just an annoying inconvenience; it could be an indication of more serious underlying issues, such as dementia.

Experts in neurology suggest that the connection between sleep and the aging brain is complex and reciprocal. On one side, persistently inadequate sleep can heighten the risk of developing dementia. Conversely, the onset of dementia can interfere with the brain’s natural sleep-wake cycles, making sleep disturbances one of the earliest possible indicators of cognitive decline.

When our sleep patterns begin to falter, so does the brain’s ability to safeguard itself. This is largely due to the glymphatic system, the brain’s own cleaning mechanism, which is active primarily during sleep. Its essential role is to eliminate harmful proteins, including amyloid beta. These proteins can accumulate and form plaques, a hallmark of Alzheimer’s disease, a condition affecting nearly six million people in the United States.

When sleep hygiene breaks down, the brain’s ability to protect itself breaks down with it. A network called the glymphatic system, the brain’s cleanup system, only cleans during sleep.

Its primary job is to flush out toxic proteins, including amyloid beta. These clump together to form the plaques characteristic of Alzheimer’s disease, which affects roughly six million Americans. 

Consistently poor deep sleep blocks the glymphatic system’s ability to function as designed, and over time, that buildup of waste actively fuels dementia’s progression. 

One of the most alarming red flags is a sudden, unexplained onset of insomnia, not just the occasional restless night. In Alzheimer’s disease specifically, the circuits that regulate the brain’s sleep-wake cycle gradually degrade.

Neurologists point to extreme difficulty falling asleep, frequent nighttime awakenings and intense daytime fatigue as potential indicators of deteriorating brain networks. 

Aging slows the glymphatic system, reducing nightly toxin clearance. Chronic sleep loss worsens this deficit, potentially accelerating dementia-related plaque buildup (stock)

Nighttime insomnia and daytime sleepiness 

When neurodegeneration attacks the brain’s internal clock, the body loses sync with day and night. The same toxic protein that erodes memory—amyloid beta—also affects this internal timekeeper.

As these proteins accumulate in regions that regulate arousal and sleep stability, the brain literally forgets how to transition properly into deep, restorative sleep. The result is a scrambled, random sleep-wake cycle rather than a rhythmic one.

This disruption presents as sudden, severe insomnia, characterized by extreme difficulty falling asleep, frequent nighttime awakenings and profound daytime fatigue. Some people feel wide awake at 2 am.

It also plays out as excessive sleepiness during normal waking hours—losing the ability to stay awake during alert hours, falling asleep during meals or even mid-conversation.

The brain tries to clear waste and consolidate memories at the wrong times, leaving a person drowsy when they should be alert.

These two problems often go hand in hand. Nighttime insomnia and daytime sleepiness are opposite sides of the same circadian breakdown.

This pattern is frequently accompanied by confusion, agitation or disorientation in the late afternoon and evening, a common dementia symptom known as sundowning.

Experts urge a neurological evaluation rather than assuming these issues are simply stress or a bad bout of insomnia. 

Dr Chelsie Rohrscheib, a Michigan-based neuroscientist and sleep researcher advised people to see a sleep specialist for worsening insomnia, daytime sleepiness or unusual nighttime behaviors. See a neurologist for memory loss, confusion at nighttime, acting out in one’s sleep or personality changes

CDC data shows that at least 14 percent of American adults struggle with insomnia. The problem is most acute in younger adults

Acting out dreams

Acting out dreams, including punching, kicking, swearing or jumping out of bed, is known as REM Sleep Behavior Disorder. This symptom can appear years before memory problems surface, particularly in Lewy body dementia and Parkinson’s disease.

A sudden onset in mid-to-late life, especially when accompanied by no obvious stressor or psychological cause, should raise clinical suspicion. 

Normally, during REM (rapid eye movement) sleep, the brain paralyzes the body, a protective mechanism that keeps someone from physically responding to their vivid dreams.

In REM Sleep Behavior Disorder (RBD), that paralysis mechanism fails. People punch, kick, shout, swear or even leap out of bed, often reenacting action-filled or terrifying dreams. This represents a fundamental breakdown of brainstem circuitry.

RBD often precedes memory symptoms by years or even decades. 

Researchers have found that the vast majority of people diagnosed with isolated RBD will eventually develop a synucleinopathy, or a family of neurodegenerative diseases that includes Lewy body dementia and Parkinson’s disease.

‘There are certain neurodegenerative diseases that are either Parkinson’s or Parkinson’s-plus syndromes that often start with sleep disturbances,’ Dr Jeremy M Liff, a neurologist who specializes in blood flow to the brain at NYU Langone Health in New York City, told the Daily Mail.

‘Because the brain is degenerating, especially in the brainstem area or some of the basal nuclei, this leads to REM sleep behavioral disorder. This can be a very strong predictor, if it starts in adulthood, that a neurodegenerative disease is taking place.’

Alpha-synuclein protein clumps first accumulate in the brainstem, precisely in the region that normally inhibits muscle activity during REM sleep. By the time memory loss or movement problems appear, the disease has already been quietly spreading for years.

That means what a person does when they sleep can forecast dementia long before any cognitive test would catch it.

If a previously calm sleeper suddenly begins thrashing, kicking or screaming in response to nightmares, a neurological evaluation is warranted even in the absence of any other symptoms.

Nighttime wandering 

Nighttime wandering is a sign that the brain’s master clock has gone out of sync. 

People in the early stages of dementia might roam through the house, sometimes rearranging objects or attempting to go outside, often in a confused or agitated state.

Dr Jeremy M Liff, a neurologist who specializes in blood flow to the brain, said that Sleep disturbances are often the first sign of certain neurodegenerative diseases, such as Parkinson’s and Parkinson’s-plus syndromes such as Progressive Supranuclear Palsy (PSP)

When a person wanders at night, they are not getting the deep, restorative slow-wave sleep that the glymphatic system requires to clear toxic proteins like amyloid beta.

Over time, this chronic deprivation creates a vicious cycle in which poor sleep allows more waste to accumulate, and more waste further degrades the brain regions that regulate sleep.

Additionally, nighttime wandering poses serious safety risks, including falls, injuries and leaving the home unattended. 

If a loved one is regularly getting up and moving aimlessly through the house at night, especially when paired with confusion or agitation, it is time to consult a neurologist.

Dr Chelsie Rohrscheib, a Michigan-based neuroscientist, said: ‘You should see a sleep specialist when sleep-related symptoms are prominent or worsening, such as insomnia, excessive daytime sleepiness, disrupted sleep–wake cycles, snoring or pauses in breathing, or unusual nighttime behaviors.

‘A neurologist is more appropriate when there are clear signs of neurodegeneration, such as progressive memory loss, confusion, changes in behavior or personality, difficulty with language or movement, or concern for conditions like Alzheimer’s disease or Parkinson’s disease.’