Global scientists, including experts from the UK, carried out the biggest research project of its kind looking at the genome (genetic material) of more than 100,000 people with Alzheimer’s.
Their findings suggest the disease is caused by a multitude of different factors and provide new evidence for the role of a specific protein involved in inflammation.
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.
The team hopes that, in future, they will be able to determine which factors put people at risk and to develop therapies that better treat the condition.
Another possibility is that genetic testing will identify those people most at risk of developing Alzheimer’s before their symptoms 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 to look for differences in their genetic make-up.
The findings showed for the first time 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) contribute 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."
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 provides exciting new targets for therapeutic intervention and advances our ability to develop algorithms to predict who will develop Alzheimer’s in later life.”