It is known that inheriting two copies of a specific genetic variant, called apolipoprotein E4 ( APOE4 ) , greatly increases the risk of developing Alzheimer’s disease.
This study found that people with two copies of the APOE4 are almost certain that they will develop Alzheimer’s disease. The findings suggest that the two copies are not just a risk factor but an underlying cause of the disease, meaning it could be considered a distinct genetic form of dementia.
In an analysis of more than 13,000 people, researchers from Spain and the USA found that 95% of people over 65 with two copies of APOE4 had biological markers in the cerebrospinal fluid that are typical of a genetic form of Alzheimer’s disease.
“The data clearly shows that having two copies of the gene APOE4 not only increases the risk, but also anticipates the onset of Alzheimer’s disease, reinforcing the need for specific preventive strategies”, says neurologist Alberto Lleó, from the Sant Pau Research Institute, in Barcelona, co-author of the study.
But these early-onset hereditary cases are rare. Most cases of Alzheimer’s occur sporadically later in life, without a known genetic cause. The gene APOE particularly the variant APOE4 is a known risk factor for late-onset Alzheimer’s disease.
The consistent way early-onset forms of Alzheimer’s disease are inherited has shed some light on how late-onset versions of the disease may develop. Lleó and his colleagues wanted to compare these changes to people with copies of the APOE4 .
“The findings emphasize the importance of monitoring homozygotes APOE4 from an early age for preventive interventions», says molecular biologist Víctor Montal, co-author who worked at the Sant Pau Research Institute at the time of the study.
Researchers now look at Alzheimer’s disease as a biological condition which can be diagnosed by looking for biomarkers, even if there are no clinical symptoms. Although there are no treatments for the pre-symptomatic phase of the disease, this new information could help scientists develop some.
The research was published in Nature Medicine .
Tags: Alzheimers scientists identify genetic form dementia people common risk factor
