LOS ANGELES, CA (Catholic Online) - The discovery may lead to an even greater understanding of the causes of the disease and may lead to new treatments.

Researchers studied data from more than 25,000 people to link a rare variant of the TREM2 gene to a higher risk of Alzheimer's. The gene is known to play a role in the immune system.

Headed by the Institute of Neurology, University College London or UCL, the findings have been published in the New England Journal of Medicine.

"These findings are particularly exciting because they give us a clear signal about what could be going wrong in Alzheimer's disease," study leader Dr. Rita Guerreiro says.

"While the genetic mutation we found is extremely rare, its effect on the immune system is a strong indicator that this system may be a key player in the disease.

"The more we can understand about the causes of Alzheimer's, the better our chances of developing treatments that could stop the disease developing."

Genes that increase the risk of Alzheimer's have been made previously, but they didn't explain entirely all of the genetic risk.

The researchers set out to uncover some of the rarer genetic variants involved in Alzheimer's, in a bid to get a clearer picture of the causes of the disease.

After sequencing the genes of 1,092 people with Alzheimer's and a control group of 1,107 healthy people they found several mutations in the TREM2 gene occurred more frequently in people who had Alzheimer's.

The R47H mutation had a particularly strong association with the disease. R47H appeared in two percent of people with Alzheimer's compared to 0.5 per cent of people without the disease.

The scientists confirmed their findings in two larger independent groups, analyzing data from a total of 6,675 people with Alzheimer's and 16,242 people without.

The mutation was found to be extremely rare, affecting just 0.3 per cent of the population, but increases the likelihood of developing Alzheimer's roughly three-fold. This is far more than any of the genes that have been linked to Alzheimer's in the last 20 years.

"Thanks to new advances in technology it's now possible to get a much more detailed look at the genetic risk for Alzheimer's, picking up rare variants like this one that were previously impossible to identify."

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