Alzheimer's disease linked to disrupted brain oxygenation and neuronal function

Research led by Lancaster University has revealed clear evidence that changes in the orchestration of brain oxygenation dynamics and neuronal function in Alzheimer's disease contribute to the neurodegeneration.

The study "Neurovascular phase coherence is altered in Alzheimer's Disease" is published in Brain Communications. The lead author is Aneta Stefanovska with Juliane Bjerkan, Gemma Lancaster, Peter McClintock and Trevor Crawford from Lancaster University and Bernard Meglič and Jan Kobal from the University of Ljubljana Medical Centre in Slovenia.

Professor Stefanovska said: "Alzheimer's can be hypothesized as being a result of the brain not being appropriately nourished via the blood vessels (vascular system)."

The vascular system and the brain work together to ensure that the brain receives sufficient energy. In fact, the brain needs as much as 20% of the body's overall energy consumption despite contributing only about 2% of the body's weight."

Dr. Bernard Meglič, clinical coordinator of the study

The "neurovascular unit" (NVU) consists of vasculature connected via brain cells called astrocytes to neurons and ensures that this cooperation is successful.

To assess the function of the NVU, researchers combined non-invasive measurements of brain blood flow and electrical activity with novel analysis methods developed by Lancaster's Nonlinear and Biomedical Physics group. They measured the brain's electrical activity and oxygenation using electrical and optical probes on the scalp while an electrocardiogram (ECG) measured heart rate, and a belt wrapped around the participant's chest measured breathing.

Simultaneously measuring blood oxygenation, brain electrical activity, respiration and electric activity of the heart let the researchers capture physiological rhythms and their imperfect timings. Efficient functioning of the brain depends on how well all these rhythms are orchestrated. To assess the efficiency of the NVU, both the strength and the coordination of these rhythms were assessed by computing their "power" and "phase coherence" using mathematical algorithms.

Researchers found that the median respiration rate was approximately 13 breaths per minute for the control group, and approximately 17 breaths per minute for the Alzheimer's group.

Professor Stefanovska said: "Quite unexpectedly, we also detected that the respiratory frequency at rest is significantly higher in subjects with Alzheimer's disease. This is an interesting discovery - in my opinion a revolutionary one - that may open a whole new world in the study of the Alzheimer's disease. It most likely reflects an inflammation, maybe in the brain, that once detected can probably be treated and severe states of Alzheimer's might be prevented in the future." 

Dr Meglič said: With disappointing results from protein-focused drug trials, the vasculature and neurovascular unit are promising targets for future treatments of Alzheimer's disease."

Professor Stefanovska said: "We show clear results of our approach and how Alzheimer's can be detected simply, noninvasively, and inexpensively. The method has a great potential, and we are discussing possibilities to create a spin-out or start-up company to proceed with it. Of course, more research is needed."