New Delhi, May 7 (PTI) The brains of nearly all individuals aged over 65 years and having two copies of the Alzheimer's risk gene - APOE4 - displayed biological signs of the disease in their cerebrospinal fluid and brain scans, according to new research.

Cerebrospinal fluid is a clear liquid produced in the brain, which fills and protects cavities in the brain and spinal cord.

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The study, led by Sant Pau Research Institute, Spain, analysed data from close to 3,300 brain donors, and over 10,000 individuals, 519 of whom had two copies of the APOE4 gene (called homozygotes).

Researchers evaluated clinical, pathological, and biomarker changes to determine the individuals' risk of developing Alzheimer's disease, a neurodegenerative disease impairing memory and cognition.

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It is known that APOE is one of the genes considered the strongest genetic risk factor for late-onset Alzheimer's disease.

The results from the latest study, published in the journal Nature Medicine, suggested that virtually all APOE4 homozygotes showed Alzheimer's pathology and had higher levels of disease-associated biomarkers at age 55.

At age 65, over 95 per cent of APOE4 homozygotes showed abnormal levels of amyloid protein in cerebrospinal fluid - a key early pathological feature in Alzheimer's disease - and 75 per cent had positive amyloid PET scans, the researchers said.

Based on these results, the authors suggested that the genetic variant of the APOE4 gene is not only a risk factor for Alzheimer's disease, as previously thought, but could also represent a distinct genetic form of Alzheimer's disease.

"These data represent a reconceptualisation of the disease or what it means to be homozygous for the APOE4 gene. This gene has been known for over 30 years and it was known to be associated with a higher risk of developing Alzheimer's disease," explained lead researcher Juan Fortea, Director of the Memory Unit of the Neurology Service at Sant Pau Research Institute.

"But now we know that virtually all individuals with this duplicated gene develop Alzheimer's biology. This is important because they represent between 2 and 3 per cent of the population," said Fortea.

The authors said that these findings could be useful for the development of individualised prevention strategies, clinical trials, and targeted treatment approaches for this specific population having two copies of the APOE4 gene, which "not only increases the risk but also anticipates the onset of Alzheimer's."

(The above story is verified and authored by Press Trust of India (PTI) staff. PTI, India’s premier news agency, employs more than 400 journalists and 500 stringers to cover almost every district and small town in India.. The views appearing in the above post do not reflect the opinions of LatestLY)