What your sleep may reveal about Alzheimer’s years before memory problems

A new scientific review finds sleep disruption may contribute to processes associated with Alzheimer’s while also emerging as an early effect of changes in the brain, but experts stress that poor sleep has not been proven to cause the disease Poor sleep does more than leave you tired the next morning.

A new scientific review examining the relationship between sleep and Alzheimer’s disease describes a more complicated picture: sleep disturbances may contribute to biological processes associated with the disease, but they may also result from early changes in the brain, long before noticeable memory problems emerge.

The narrative review, published recently in the Journal of Dementia and Alzheimer’s Disease , was conducted by researchers from the Medical University of Varna and St. Marina University Hospital in Bulgaria. It brings together research on the biological mechanisms connecting sleep and Alzheimer’s, different types of sleep disorders and their potential effects on memory and cognition.

Gallery Sleep disturbances may emerge before noticeable memory decline ( Photo: Shutterstock ) “We know that good sleep is essential for brain function, memory and our ability to learn and process information,” said Prof. Michael Davidson, a psychiatrist and chairman of the Israeli Alzheimer’s Medical Center.

“Studies point to an association between long-term poor sleep and an increased risk of memory decline and developing Alzheimer’s.” But, he cautioned, the evidence does not mean that one necessarily causes the other. “We still cannot say that poor sleep inevitably causes Alzheimer’s, or that good sleep can prevent the disease.” Sleep plays an important role in consolidating memories, restoring the body and brain and clearing metabolic waste.

The review focuses in particular on slow-wave sleep, also known as N3 sleep, the deepest stage of non-REM sleep. This stage is associated with memory processes and with activity in the glymphatic system, a waste-clearance network in the brain. Among the substances it helps remove are amyloid-beta and tau proteins, whose abnormal accumulation is a hallmark of Alzheimer’s disease.

Prof. Michael Davidson Research discussed in the review suggests that sleep deprivation may increase the release of these proteins while interfering with their clearance. The relationship may also work in the opposite direction: as amyloid and tau accumulate, they may disrupt neural networks involved in regulating sleep and wakefulness, potentially worsening sleep problems.

Researchers have also proposed several other mechanisms that could connect disrupted sleep with Alzheimer’s, including neuroinflammation, oxidative stress, impaired cellular energy production, disruption of connections between neurons and problems with autophagy, the process cells use to remove damaged components.

Much of the evidence for these mechanisms, however, comes from animal studies. Even in human research, changes in amyloid or tau levels after a sleepless night do not prove that long-term accumulation or Alzheimer’s disease will follow. Evidence about the glymphatic system in humans also remains limited and largely indirect.

The review distinguishes between insomnia, obstructive sleep apnea, excessive daytime sleepiness, disruption of the body’s circadian clock and a decline in deep sleep. These are different conditions with different causes and treatments. Obstructive sleep apnea, for example, involves repeated blockage of the airway, drops in blood oxygen and repeated awakenings.

In addition to fragmenting sleep, it may affect the brain through damage to blood vessels. Insomnia generally involves difficulty falling asleep or staying asleep and may be accompanied by heightened physical or mental arousal. A disrupted circadian rhythm, meanwhile, can interfere with the timing of sleep even when a person appears to be sleeping for an adequate number of hours. ( Photo: Shutterstock ) Davidson said three factors matter: sleep duration, continuity and depth.

“Sleeping what is considered a normal number of hours is not enough if the sleep is fragmented, if you wake repeatedly during the night or if you regularly wake up feeling exhausted,” he said. “Deep sleep is also important because processes that support brain recovery and memory function take place during this stage.” Follow-up studies included in the review have linked greater loss of deep sleep with the later development of dementia, and such a decline can occur even when total sleep duration remains normal.

Lighter sleep and more frequent awakenings also become more common with age and do not necessarily indicate disease. People with vascular risk factors, genetic susceptibility or early Alzheimer’s-related changes in the brain, however, may be more vulnerable to their effects. Sleep deprivation can impair attention, working memory, information-processing speed and the ability to absorb and consolidate new information.

Some of those effects can resemble early cognitive decline. When sleep deprivation is temporary, the problems generally improve once normal sleep returns. Chronic sleep disorders, however, may be associated with more persistent difficulties.

So is disturbed sleep a contributing factor to Alzheimer’s or an early sign of the disease? “It is not always possible to distinguish between the two,” Davidson said. “The existence of a sleep disorder in itself does not necessarily indicate Alzheimer’s.” ( Photo: shutterstock ) He said new and persistent changes in sleep deserve particular attention in older adults.

Long-term difficulty falling asleep, repeated nighttime awakenings, unusual daytime fatigue, breathing problems during sleep or a major change in sleep habits can justify a medical evaluation. “If a person or their family also notices worsening forgetfulness, confusion or difficulty performing tasks that used to be simple, they should not limit the evaluation to sleep alone and should seek medical assessment,” Davidson said.

“There are many causes of sleep problems and memory difficulties, and some of them are treatable.” For chronic insomnia, the researchers point to cognitive behavioral therapy for insomnia, known as CBT-I, as a first-line treatment. One randomized trial cited in the review tested a seven-week app-based CBT-I program.

Insomnia went into remission in 48% of participants receiving the intervention, compared with 18% in the control group. The study, however, examined insomnia rather than whether treatment reduced the risk of Alzheimer’s. That distinction is important.

A separate 2026 randomized trial of cognitively healthy older adults with insomnia found that CBT-I improved insomnia but did not produce measurable improvements in cognition or amyloid-beta accumulation after one year. Researchers said longer follow-up would be needed to determine whether treating insomnia affects Alzheimer’s risk.

For people with obstructive sleep apnea, continuous positive airway pressure, or CPAP, delivers pressurized air through a mask during sleep and can improve oxygen levels, sleep continuity and daytime alertness. Using a CPAP machine to treat obstructive sleep apnea can improve sleep quality and continuity ( Photo: perthstagedtosell / shutterstock ) Some research suggests CPAP may also benefit certain aspects of cognition in people with mild cognitive impairment, but the evidence remains mixed and does not establish that the treatment prevents Alzheimer’s.

Recent reviews have similarly stressed that cognitive benefits have not yet been demonstrated conclusively in randomized trials. For circadian rhythm problems, approaches can include maintaining regular sleep and wake times, appropriate exposure to light and daytime physical activity.

The review also urges caution with sleeping medications in older adults because some can impair cognitive function and increase the risk of falls. People taking such drugs for extended periods should discuss any reduction with their doctor and should not abruptly stop treatment on their own.

Omega-3 supplements and other nutritional approaches have also been proposed, but there is currently no solid evidence that they treat insomnia or prevent Alzheimer’s disease. The review itself has important limitations. It is a narrative review rather than a systematic review, meaning the authors did not follow a formal protocol designed to identify all relevant studies.

They also did not conduct a pooled statistical analysis or formally grade the quality of the evidence. The underlying studies vary considerably in their methods, and factors including depression, diabetes, cardiovascular disease and medication use make it difficult to isolate the effect of sleep alone.

“It is important to distinguish between improving sleep and preventing Alzheimer’s,” Davidson said. “The important message is that sleep problems should not be ignored or simply accepted as an inevitable part of aging. Proper diagnosis and treatment can improve quality of life and are an important part of maintaining health, even though we still cannot promise that they will prevent Alzheimer’s.”