A recent study published in Neurology has discovered a correlation between severe sleep apnea and decreased brain volumes in the medial temporal lobe region, including the hippocampus, in individuals displaying amyloid plaques—an early indicator of Alzheimer’s disease. Interestingly, this correlation, which suggests potential brain cell loss, was not observed in individuals without plaques. However, it is important to note that the study does not establish a causal relationship between sleep apnea and reduced brain volume.
The study underscores the necessity for further investigation into treatments for sleep-disordered breathing, as they may have the potential to enhance cognition and delay neurodegeneration. Previous studies have already established a link between sleep apnea and an elevated risk of dementia. This new study specifically examines the connection between sleep apnea and brain volume, and it was published in the online edition of Neurology on May 31, 2023, the medical journal of the American Academy of Neurology.
To conduct the study, researchers compared individuals with amyloid plaques in their brains—without any memory problems—to individuals without amyloid plaques. Geraldine Rauchs, PhD, from Inserm in Caen, France, and the study’s author, explains, “We found that people with amyloid plaques who had more severe sleep apneas also were more likely to have lower volumes in the medial temporal lobe area of the brain, including the hippocampus, which plays a role in memory and Alzheimer’s disease. The people who did not have amyloid plaques did not have this lower brain volume, even if they had severe sleep apneas.” It is crucial to highlight that the study only reveals an association and does not prove that sleep apnea directly causes reduced brain volume.
The study involved 122 participants, with an average age of 69, who did not experience any memory issues. Out of these participants, 26 had amyloid plaques in their brains. The individuals underwent brain scans, memory tests, and overnight sleep studies conducted at their homes. The memory tests were repeated after an average of 21 months.
Among those with amyloid plaques, individuals with more severe sleep apneas displayed lower brain volume in the medial temporal lobe region, suggesting a potential loss of brain cells. This relationship was not observed in participants without amyloid plaques. Rauchs states, “Our results suggest that some people may be more vulnerable to the adverse effects of sleep apnea. People who are in the very early stages of the Alzheimer’s continuum showed a specific vulnerability to sleep apneas. Further studies should look at whether treating sleep-disordered breathing could potentially improve cognition and prevent or delay neurodegeneration.”
Across the entire group, lower volumes in the hippocampus at the beginning of the study correlated with lower scores on an episodic memory test at the end of the study. However, no associations were found between sleep apneas at the beginning of the study and memory scores at the end of the study. One limitation of the research is that the same version of the verbal learning test was administered both at the start and end of the study, which could have potentially minimized any memory decline due to familiarity with the test.
Reference: “Association of Sleep-Disordered Breathing and Medial Temporal Lobe Atrophy in Cognitively Unimpaired Amyloid-Positive Older Adults” by Claire André, Elizabeth Kuhn, Stéphane Rehel, Valentin Ourry, Solène Demeilliez-Servouin, Cassandre Palix, Francesca Felisatti, Pierre Champetier, Sophie Dautricourt, Paul Yushkevich, Denis Vivien, Vincent de La Sayette, Gaël Chételat, Robin de Flores, and Géraldine Rauchs, for the Medit-Ageing Research Group, May 31, 2023, Neurology. DOI: 10.1212/WNL.0000000000207421
The study received support from the European Union’s Horizon 2020 Research and Innovation Program, Inserm, Region Normandy, and the MMA Corporate Foundation of Entrepreneurs of the Future (Fondation d’Entreprise MMA des Entrepreneurs du Futur).
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FAQ about sleep apnea brain volume
What does the study reveal about the relationship between sleep apnea and brain volume?
The study shows a correlation between severe sleep apnea and lower brain volumes in the medial temporal lobe area, including the hippocampus, in individuals with amyloid plaques—an early sign of Alzheimer’s disease. However, the study does not establish causality between sleep apnea and reduced brain volume.
Are individuals without amyloid plaques affected by sleep apnea in terms of brain volume?
No, the study found that the correlation between severe sleep apnea and lower brain volume was observed specifically in individuals with amyloid plaques. Participants without amyloid plaques did not exhibit this association, even if they had severe sleep apnea.
Can treating sleep-disordered breathing potentially improve cognition and delay neurodegeneration?
The study suggests a potential benefit. Individuals in the early stages of the Alzheimer’s continuum who had more severe sleep apneas showed a specific vulnerability. Further research is necessary to determine whether treating sleep-disordered breathing could enhance cognition and prevent or delay neurodegeneration.
Is there a connection between sleep apnea and memory decline?
The study observed that lower volumes in the hippocampus at the beginning of the study were associated with lower scores on a test of episodic memory at the end of the study. However, no direct associations were found between sleep apneas at the study’s start and memory scores at its conclusion. It’s worth noting that the memory test used was the same at both time points, potentially reducing the possibility of detecting memory decline due to familiarity with the test.
What support did the study receive?
The study received support from the European Union’s Horizon 2020 Research and Innovation Program, Inserm, Region Normandy, and the MMA Corporate Foundation of Entrepreneurs of the Future (Fondation d’Entreprise MMA des Entrepreneurs du Futur).
More about sleep apnea brain volume
- Neurology Study: Association of Sleep-Disordered Breathing and Medial Temporal Lobe Atrophy in Cognitively Unimpaired Amyloid-Positive Older Adults
- American Academy of Neurology: Sleep Apnea Linked to Smaller Brain Volume in Alzheimer’s Patients
