Could Treating Sleep Apnea Help Prevent Alzheimer’s?
Article Summary
- Researchers from the University of Miami Miller School of Medicine found evidence linking sleep apnea with neurological changes likely indicative of Alzheimer’s disease and related forms of dementia.
- Dr. Alberto Ramos and Dr. Christian Agudelo studied data from the Hispanic Community Health Study/Study of Latinos project that involved sleep apnea tests and, years later, MRIs to assess changes in the brain.
- The researchers found participants who had lower levels of blood oxygen at night tended to have more white matter hyperintensities, but those with lower oxygen levels and more sleep disruptions had larger, not smaller, hippocampi.
New research hints at the potential harm one sleep disorder — sleep apnea — can cause to the brain over time.
In a study published in Neurology on December 18, researchers from the University of Miami Miller School of Medicine and their colleagues found evidence linking sleep apnea with neurological changes likely indicative of Alzheimer’s disease and related forms of dementia.
“We have come to understand that sleep is really intertwined with the neurological processes driving Alzheimer’s and similar dementias,” said Alberto Ramos, M.D., M.S.P.H., a professor of neurology and research director of the Sleep Disorders Program at the Miller School and the study’s senior and co-first author. “The idea is that maybe we can identify those at high risk for sleep-related dementia and develop treatment strategies that can help us prevent it based on what we are observing in studies like this.”
Their analysis relied on data previously collected as part of a larger, ongoing project, the Hispanic Community Health Study/Study of Latinos (HCHS/SOL), which tracks the health of Latinos. While sleep affects brain health regardless of race or ethnicity, studies have found higher rates of dementia, including that due to Alzheimer’s, and age-related cognitive impairment among members of this population as compared to their white counterparts.
Researchers don’t understand the reasons for Latinos’ elevated risk, but sleep apnea may contribute to it, according to Dr. Ramos.
Stressful Sleep
Sleep apnea occurs when the upper section of the throat collapses repeatedly, blocking the breath and forcing the person to awaken briefly. These temporary obstructions reduce the oxygen available to the brain and activate the body’s panic response via the sympathetic nervous system, increasing heart rate and blood pressure.
“This is an accumulative process that happens many times each night, sometimes for decades without a diagnosis or a treatment,” Dr. Ramos said.
To examine the implications for brain health, he and co-first author, Christian Agudelo, M.D., an assistant professor of clinical neurology and co-director of education for the Evelyn F. McKnight Brain Institute, drew on data previously collected through the HCHS/SOL for 2,667 of its participants.
Between 2008 and 2011, participants took a sleep apnea test for one night at home. About 10 years later, when they were 50 years old or older, they received magnetic resonance imaging (MRIs) that looked for problematic changes in their brains, including signs of Alzheimer’s and dementia.
Signs of Cognitive Decline
In Alzheimer’s disease — the most prominent form of dementia, which affects an estimated 6.7 million Americans age 65 and older — the brain atrophies. This shrinkage is particularly notable in the hippocampus. Using MRI data, the researchers examined hippocampal volume. They also looked at the presence of white matter intensities, which indicate damage to small blood vessels, itself a contributor to the risk for Alzheimer’s.
“Does the way you sleep influence your risk for dementia or your risk of any sort of brain disease? I’m betting on yes,” Dr. Agudelo said. “Now, what the mechanisms are, we don’t know.”
Their analysis, however, offers some clues. The researchers found, as expected, that participants who had lower levels of blood oxygen at night tended to have more white matter hyperintensities. But, in a counterintuitive result, those with lower oxygen levels and more sleep disruptions had larger, not smaller, hippocampi.
“Even though it appears paradoxical, we think the brain is swelling as a result of damage caused by the low oxygen levels and possibly inflammation,” said Dr. Ramos.
Over time, he and Dr. Agudelo expect this swelling to cause the hippocampus to atrophy.
Treating Sleep to Treat the Brain
Study data is too limited to indicate sleep apnea causes harmful neurological changes. However, follow-up research may uncover more evidence of the disorder’s role.
Dr. Ramos is leading the Sleep in Neurocognitive Aging and Alzheimer’s Research initiative, following up on 3,000 participants who took the overnight sleep test more than a decade ago. These people are taking a second sleep apnea test and will receive blood pressure monitoring for 24 hours, as well as MRI scans that detect clumps of beta-amyloid, the toxic deposits that accompany Alzheimer’s disease.
“The idea is that we’ll see their trajectories over time. For those that develop dementia, we’ll be able to reconstruct, hopefully, the process of how they got there,” Dr. Ramos said.
Does the way you sleep influence your risk for dementia or your risk of any sort of brain disease? I’m betting on yes.
—Dr. Alberto Ramos
Meanwhile, Dr. Agudelo has been awarded a five-year career development grant from the National Institutes of Health for a related project studying sleep patterns, the microstructure of the brain’s gray matter and Alzheimer’s disease risk.
Unlike with Alzheimer’s disease, physicians currently have the means to fully treat sleep apnea. If used regularly at night, continuous positive airway pressure (CPAP) machines can reduce breathing disruptions to normal levels, even in severe cases, according to Dr. Agudelo, who treats patients with this condition at the Miami Veterans Administration Healthcare System.
This study points to a simple take-home message.
“It gives credence to the idea that if you treat your sleep apnea, you’re probably helping your brain,” Dr. Agudelo said.
Tags: Alzheimer's disease, amyloid-beta protein, cognitive decline, dementia, Department of Neurology, Dr. Alberto Ramos, neurology, obstructive sleep apnea, sleep apnea