Although researchers do not know the exact cause behind Alzheimer’s disease, most agree the formation of beta-amyloid plaque build-upTrusted Source and tau tanglesTrusted Source characterize it.

Dr. Betty Tijms, associate professor of neurology, brain imaging, and neurodegeneration at Amsterdam University Medical Centers and lead author of this study, told Medical News Today that she and her team decided to look for biological processes other than beta-amyloid and tau that may affect Alzheimer’s disease.

They did that because genetic and tissue proteomic studies previously pointed out that other biological processes beyond amyloid and tau seem to be involved in Alzheimer’s disease.

“But this was difficult to study in patients because the brain is not easily accessible,” Dr. Tijms continued. “New techniques made it possible to measure many proteins in the cerebrospinal fluidTrusted Source, and the levels of those proteins provide a detailed picture of the processes that are ongoing in the brain.“

”So we made use of these innovations to study if certain subgroups of Alzheimer’s disease patients could be identified that share distinct underlying biological processes,” she added.

For this study, Dr. Tijms and her team examined a little over 1,000 proteins in the cerebrospinal fluid of 419 people with Alzheimer’s disease. Through this examination, they discovered five biological variants within this group.

According to Dr. Tijms, the first subtype was characterized by abnormal outgrowth of nerve cells.

Both researchers found some of the discovered Alzheimer’s disease biological variants surprising.

“I was surprised by the subtype with dysregulated RNA metabolism because such processes have not been highlighted as a key factor in Alzheimer’s disease,” Dr. Pieter Jelle Visser, professor of molecular epidemiology of Alzheimer’s disease at Maastricht University in the Netherlands and senior author of this study, told MNT.

“It was surprising to see the new subtype with choroid plexus dysfunction,” Dr. Tijms also noted. “They had similar effects as [the] blood-brain barrier with low cerebrospinal fluid tau levels, for example, but no indication at all of leakage of blood proteins in the cerebrospinal fluid.“

“To me that indicates that these brain interfaces are really two different entities, with their own roles in Alzheimer’s disease,” she told us.

Both researchers believe these findings may change how Alzheimer’s medications are developed and prescribed in the future.

“The existence of these subtypes suggests that each subtype may need a different treatment,” Dr. Visser explained. “Future trials should take this into account and test their treatment in the subtypes that matched with the working mechanism of the drug.”

“Alternatively, each future Alzheimer’s disease trial should stratify on subtypes such that the subtypes that best respond to treatment can be identified,” he added. “Future trials may also take into account that side effects may differ between subtypes as well.”

After reviewing this study, Dr. Karen D. Sullivan, a board-certified neuropsychologist, owner of I CARE FOR YOUR BRAIN, and Reid Healthcare Transformation Fellow at FirstHealth of the Carolinas in Pinehurst, NC, told MNT she found this research to be extremely hopeful, as it has been known for a long time that Alzheimer’s disease is an extremely heterogeneous subtype of neurodegenerative diseaseTrusted Source.

“Some patients have a slow and steady decline while others progress quickly,” she continued. “Some have predominantly memory symptoms while others experience primarily visual and spatial impairments. Identifying these five specific disease processes in Alzheimer’s disease is a necessary starting point [for] personalizing brain healthcare interventions.”

Dr. Jennifer Bramen, a senior research scientist at the Pacific Neuroscience Institute in Santa Monica, CA, also not involved in the current study agreed, saying: “There are many known risk factors for Alzheimer’s disease, and each patient has a unique risk profile. Patients exhibit diverse symptoms, progression timelines, and neurodegeneration patterns.”