Genetic risk for Alzheimer’s disease could depend on how well you sleep

New research published in Alzheimer’s & Dementia provides evidence that genetic variations related to brain fluid movement interact with sleep quality to influence memory and brain structure in older adults. The findings suggest that the effects of certain genetic profiles on Alzheimer’s disease risk might depend heavily on how well a person sleeps. This points toward sleep as a potential focal point for helping individuals with specific genetic vulnerabilities protect their brain health over time.

Alzheimer’s disease is a progressive neurological condition characterized by the gradual accumulation of a toxic protein called amyloid beta in the brain. Over time, this protein clumps together to form solid plaques between nerve cells. These events tend to drive neurotoxicity and trigger the accumulation of another protein called tau. This biological cascade leads to severe damage to brain cells, physical tissue shrinkage, progressive cognitive decline, and eventual dementia.

In a healthy brain, biological mechanisms continuously work to wash out these toxic waste products before they can cause damage. One major waste removal network in the human brain is known as the glymphatic system. You can think of the glymphatic system as a biological plumbing network that washes away cellular waste using the brain’s internal fluids. This system relies heavily on a water channel protein known as aquaporin-4, or AQP4.

This specific protein sits on tiny projections of specialized support cells in the brain called astrocytes. From this position, the AQP4 protein acts as a microscopic gatekeeper, regulating the movement of fluids and flushing out waste products. Research suggests that this essential brain washing process operates mostly while we are resting in deep sleep. Poor sleep habits tend to limit the brain’s ability to efficiently remove amyloid beta.

Because the AQP4 protein is a main component of this waste removal system, scientists are very interested in the specific gene that holds the biological instructions for building it. Humans naturally carry different versions of this gene, which feature tiny alterations in their DNA sequence. These tiny genetic differences are called single-nucleotide polymorphisms, and they are passed down through families. Small changes in the DNA sequence can alter how much of the AQP4 protein a person makes or how well that protein functions.

Free daily newsletter

A research team from Edith Cowan University, the Commonwealth Scientific and Industrial Research Organisation, and other institutions organized a project to explore this biological dynamic. They wanted to know if different AQP4 genetic variations affect markers like brain shrinkage and cognitive decline. They also aimed to see if a person’s sleep habits modified the impact of these genetic differences on physical brain health.

The researchers looked at data from 351 older adults with an average age of about 75. These participants were part of an ongoing research project called the Australian Imaging, Biomarkers and Lifestyle study. At the start of the observation period, all participants had normal memory and thinking skills. However, they were considered at high risk for Alzheimer’s disease because brain scans showed they already had a significant buildup of amyloid beta.

To measure sleep habits, the scientists used a standard questionnaire asking participants to rate their sleep quality over the past month. This survey captured details like how many hours they slept, how long it took them to fall asleep, and how often their sleep was disrupted. The research team used specialized medical scans to evaluate the physical state of each participant’s brain. Positron emission tomography, or PET scans, allowed the team to measure amyloid beta levels.

The authors also used magnetic resonance imaging, or MRI scans, to measure the exact volume of different brain regions. To assess mental performance, the participants took a comprehensive battery of tests measuring multiple areas of thought. These mental tests evaluated executive function, episodic memory, recognition, language skills, and processing speed. Finally, the team analyzed blood samples to determine which versions of 13 different AQP4 genetic variants each person carried.

The scientists tracked many of these individuals over several years to monitor gradual changes in their physical brain health and cognitive abilities. During their statistical analysis, the team accounted for variables like age, sex, body weight, depression, and cardiovascular disease history. The scientists found one direct link between an AQP4 genetic variant and mental performance, regardless of sleep habits. People carrying a less common version of a specific genetic variant called rs162007 demonstrated better overall scores on memory and thinking tests at the beginning of the study.

Other direct links between the genetic variations alone and brain volume or amyloid beta levels were not statistically significant. However, the study revealed several ways that genetics and sleep habits interacted to affect physical brain health. For instance, gray matter is the outer layer of brain tissue that contains the main bodies of nerve cells. The researchers noted that for people with specific genetic variations known as rs151245 and rs2339214, shorter sleep duration was associated with a faster rate of gray matter loss over time.

“Our study shows that individuals carrying certain AQP4 variants showed faster gray matter loss when they reported shorter sleep,” said Ayeisha Milligan Armstrong, a researcher at Edith Cowan University. For individuals without these specific genetic profiles, sleeping fewer hours did not show this same accelerated shrinkage. “It’s not just which genes you carry, it’s how those genes interact with the world around you,” Armstrong said. “The same variant can look protective or detrimental depending on how someone is sleeping.”

Armstrong noted that these interactions highlight a tangible path for intervention. “That’s important, because sleep is one of the few modifiable factors people can actually act on,” she said. The team also looked at the brain’s ventricles, which are internal fluid-filled cavities. These spaces naturally expand as the surrounding brain tissue shrinks from aging or disease.

The authors found that a longer time spent trying to fall asleep was linked to larger ventricles, but only in people carrying a genetic variant called rs7240333. Worse overall sleep quality predicted faster expansion of these ventricles over time for people with the rs2339214 variant. White matter consists of the insulated nerve fibers connecting different parts of the brain. The scientists reported that longer sleep duration was tied to smaller white matter volumes for people with another variant, rs68006382.

Interestingly, the researchers also found that some genetic variants seemed to offer a protective effect in the face of poor sleep. For participants carrying two copies of the rarer versions of variants rs12968026 or rs3875089, an increase in sleep disturbances actually corresponded with a slower rate of cognitive decline.

“We’ve known for a while that poor sleep and Alzheimer’s risk are linked,” said Tenielle Porter, a researcher at Edith Cowan University. “What this shows is that rather than assuming everyone at risk follows the same pathway, a more targeted and personalized approach to Alzheimer’s prevention may be needed.”

The lack of an association between these genes and changes in amyloid beta levels was slightly unexpected. Because the AQP4 protein is thought to help remove this exact protein, scientists anticipated a measurable link. The authors suggest that because amyloid beta buildup happens very slowly over decades, the relevant genetic effects might have occurred much earlier in the participants’ lives. By the time this study took place, the downstream consequences of that buildup, like brain tissue shrinkage, were simply more visible.

Readers should remember that this type of observational research cannot prove that poor sleep directly causes brain shrinkage in people with these genes. The study provides evidence of a relationship, but it does not definitively establish cause and effect. It is also important to note that the observed differences in brain volume and memory scores were relatively small. Having one of these genetic variants does not guarantee that someone will develop Alzheimer’s disease.

The researchers pointed out a few specific limitations in their methodology. The sleep data relied entirely on self-reported questionnaires, which are notoriously subjective. Human memory is often imperfect, and participants might not have accurately recalled their exact sleep habits over the prior month. In addition, the sample size for the long-term tracking portion of the study was somewhat small, which can make it harder to detect subtle biological changes.

The study group also consisted mostly of Caucasian and highly educated individuals. This lack of diversity means that the results might not apply evenly across different populations. The researchers also specifically selected participants who already had significant amyloid beta buildup in their brains. This specific selection criteria means the findings might not translate to the broader, healthy public.

“But we’re not at the point of recommending genetic testing; our findings need replication in larger and more diverse cohorts,” Porter said. Understanding the exact biological functions of these genetic variants in a laboratory setting could also help explain how they physically affect the brain. Until then, these findings highlight the potential of personalized medicine in neurological care. Tracking genetic vulnerabilities could eventually help doctors provide targeted lifestyle recommendations for older adults.

“This moves us closer to understanding why some people decline faster than others, even when they have similar risk on paper,” said Simon Laws, director of the Center for Precision Health at Edith Cowan University. “Identifying who is most vulnerable, and who is most likely to benefit from a particular lifestyle intervention, is where precision health needs to go rather than treating everyone at risk of Alzheimer’s the same way.” Taking proactive steps to improve sleep hygiene could serve as a practical defense against age-related cognitive decline.

The study, “Evidence for direct and sleep-moderated relationships between aquaporin-4 genetic variants and Alzheimer’s disease phenotypes,” was authored by Tenielle Porter, Ayeisha Milligan Armstrong, Eleanor K. O’Brien, Vincent Doré, Pierrick Bourgeat, Mitchell Turner, Paul Maruff, Christopher C. Rowe, Belinda M. Brown, Victor L. Villemagne, Stephanie R. Rainey-Smith, Simon M. Laws, and the AIBL Research Group.