CALCULATING YOUR ALZHEIMER’S RISK

THE biggest Alzheimer’s study of its kind has more than doubled the number of genetic variations known to be implicated in the disease.

The research points to a future in which people could be given a genetic risk score for their potential to develop the condition and personalised strategies for prevention and treatment.

Alzheimer’s is the most common cause of dementia, affecting more than 850,000 people in the UK. About 60 to 80 per cent of the risk for the condition is thought to be due to genetics.

To find more of the genetic factors responsible, Rebecca Sims at Cardiff University in the UK and her colleagues looked at the genomes of more than 100,000 people who had Alzheimer’s or had a parent with the condition, and compared them with about 600,000 people with no family history of the disease.

This is much more than the number of people with Alzheimer’s analysed by any previous genome-wide association study (GWAS).

“The last major GWAS in Alzheimer’s had about 22,000 people with Alzheimer’s in its initial set-up,” says Sims.

The analysis confirmed the role of 33 gene variations that had previously been linked to the disease and added a further 42 specific variations to that list (Nature Genetics, doi.org/hpdw).

Sims says no variation seems more significant than any other. “Part of what this study shows is how complex this disease actually is and how multifactorial it is,” she says.

But it does highlight the role that microglia – immune cells in the brain – can play in the disease, says Sims. “Years ago, we were only looking at neurons and how they might be involved in Alzheimer’s, but now we know that these cells are really important too.”

This research will make it easier to ensure people are given the best treatment for them, she says. For example, Alzheimer’s in one person may be caused by variations involving microglia, whereas in another it could be due to dysfunctions in fat metabolism.

“A lot of drugs may be more useful in certain people than others depending on what type of pathways are involved,” says Sims. “Potentially, the drugs will have a bigger effect if we target the right pathways.”

The team found that including these newly discovered gene variations improved the accuracy of genetic risk scores, which could be used to inform people about their potential to develop the disease. “If someone’s got a really high risk of developing Alzheimer’s, potentially they can start taking drugs earlier in life to help either delay it or even prevent it,” says Sims.

“I am incredibly excited by the implications of this study,” says Catherine Kaczorowski at the Jackson Laboratory in Bar Harbor, Maine.

One limitation of the study is that nearly all the participants in it were white – in common with many other GWAS. This is by design, because different populations of people will have different genetic variations and so it is harder to compare people with and without a specific disease in a more diverse study group.

Sims says it is unclear to what extent the findings will be applicable to people of colour. “We need this research funded for other populations,” she says. 

What Alzheimer's does to a person?

As Alzheimer's worsens, people experience greater memory loss and other cognitive difficulties. Problems can include wandering and getting lost, trouble handling money and paying bills, repeating questions, taking longer to complete normal daily tasks, and personality and behavior changes.

Can Alzheimer be cured?

There's currently no cure for Alzheimer's disease. But there is medicine available that can temporarily reduce the symptoms. Support is also available to help someone with the condition, and their family, cope with everyday life.

Can Alzheimer cause death?

Alzheimer's disease is ultimately a fatal form of dementia. It is the sixth leading cause of death in the United States, accounting for almost 4% of all deaths in 2014.2,3 The number of Alzheimer's deaths has increased, in part, because of a growing population of older adults.

How long can you live with Alzheimer's?

People live for an average of 8 years after their symptoms appear. But the disease can progress quickly in some people and slowly in others. Some people live as long as 20 years with the disease. No one knows what causes Alzheimer disease.