For the first time, more than 40 genes have been linked to Alzheimer’s disease in a “landmark” new study that could pave the way for better diagnosis and treatment.
Scientists from across the globe, including the UK, have carried out the biggest research project of its kind looking at the genome of more than 100,000 people with Alzheimer’s.
The findings suggest that the disease is caused by a multitude of different factors and provide new evidence for the role of a specific protein that is involved in inflammation.
The team hopes that, in future, they will be able to determine which factors put people at risk of Alzheimer’s and to develop therapies that better treat the condition.
Genetic testing could help identify those at risk
Genetic testing could also identify those who are most at risk of developing Alzheimer’s before their symptoms begin to appear.
The study, published in Nature Genetics, identified 75 genes associated with an increased risk of developing Alzheimer’s disease, including 42 genes not previously implicated in the condition.
It also confirmed previous findings regarding the proteins amyloid-beta and tau, which build up in and around nerve cells as Alzheimer’s progresses and found that inflammation and the immune system play a role in the disease.
A group of 111,326 people with Alzheimer’s disease were compared with 677,663 healthy individuals in order to look for differences in their genetic make-up.
For the first time, the findings showed that a specific biological signalling pathway involving TNF-alpha (a protein with an important role in inflammation and the immune system) is implicated in Alzheimer’s.
The research also offered more evidence that the dysfunction of microglia (immune cells in the brain that are responsible for eliminating toxic substances) contributes to the way the disease progresses.
Ongoing and future studies will now look closer at the genes and how they are implicated in the death of brain cells, which could lead to new treatments.
A genetic risk score has also been created that could determine how likely it is that patients with cognitive impairment will develop Alzheimer’s disease within three years of symptoms appearing.
Professor Julie Williams, centre director at the UK Dementia Research Institute at Cardiff University and co-author of the study, said: “This is a landmark study in the field of Alzheimer’s research and is the culmination of 30 years’ work.
“Genetics has and will continue to help us identify specific disease mechanisms which we can target therapeutically.
“This piece of work is a major leap forward in our mission to understand Alzheimer’s, and ultimately produce several treatments needed to delay or prevent the disease.
“The results support our growing knowledge that Alzheimer’s disease is an extremely complex condition, with multiple triggers, biological pathways and cell types involved in its development.
“Components of our immune system have a big role to play in the development of the disease.
“For example, immune cells in the brain known as microglia are responsible for clearing out damaged tissue, but in some people that may be less efficient which could accelerate the disease.
“Lifestyle factors such as smoking, exercise and diet influence our development of Alzheimer’s, and acting to address these now is a positive way of reducing risk ourselves.
“However, 60-80% of disease risk is based on our genetics and therefore we must continue to seek out the biological causes and develop much-needed treatments for the millions of people affected worldwide.”
Dr Rebecca Sims, senior research fellow at Cardiff University and UK Dementia Research Institute co-investigator, and co-leader of the research, said: “This study more than doubles the number of identified genes influencing risk for the more common form of Alzheimer’s disease.
“It provides exciting new targets for therapeutic intervention and advances our ability to develop algorithms to predict who will develop Alzheimer’s in later life.”
Eight countries, including the UK, US and Australia, took part in the study.
Alzheimer’s disease is the most common cause of dementia and affects more than 850,000 people in the UK alone.
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