11/14/2012 05:29 pm ET

R47H Gene Mutation Linked With Tripled Alzheimer's Risk

Scientists have identified a gene mutation that triples the risk of Alzheimer's disease.

The findings were published online Wednesday in the New England Journal of Medicine and involved collaboration by more than 44 research institutions.

The study included gene analysis of 1,092 people with Alzheimer's disease and 1,107 healthy people without the disease. The researchers then identified several variants in the gene TREM2, which is known to play a role in the body's immune system, that were more likely to occur in the people with Alzheimer's than those without.

A specific variant, called R47H, was the most common of all the variants. In a separate study, researchers then did an analysis of the R47H gene variant in 1,994 people with Alzheimer's and 4,062 people without the condition.

The researchers found that 1.9 percent of people with Alzheimer's had the R47H variant, while 0.37 percent of people without ALzheimer's had it.

"This strong effect rivals that of the well-established genetic variant known as APOE 4, and it was observed both in our study and in the independent study led by deCODE that was published with ours," study researcher Minerva Carrasquillo, Ph.D., a scientist at the Mayo Clinic, said in a statement.

"R47H isn't fully penetrant -- meaning that not all people who have the variant will develop Alzheimer's and in those who do, other genes and environmental factors will also play a role -- but like APOE 4 it does substantially increase risk," Carrasquillo added.

Researchers noted that R47H could be a good "goldilocks variant" -- meaning it's a "just right, not too rare and strong enough" variant to indicate risk that could be researched in future studies.

Earlier this year, researchers from deCODE Genetics in Reykjavik identified a gene mutation that makes people less likely to develop Alzheimer's disease -- a finding that could spur hope for new drugs, Reuters reported.

"It confers extraordinarily strong protection," study researcher Dr. Kari Stefansson told Reuters. "We found only five Alzheimer's cases (out of thousands of people) with it."



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