A genetic variant found only on the X chromosome is linked to a significantly greater risk for late-onset Alzheimer's, a new study has found.
Researchers found that women who had a variant of the PCDH11X gene on both X chromosomes had a 75 per cent greater risk of developing Alzheimer's disease.
Women who had only one copy of the gene had a 26 per cent increase in their Alzheimer's risk.
Men can also have the PCDH11X variant, but only one version, as they only have one X chromosome.
Males in the study who did have one copy of the variant had an 18 per cent increase in their Alzheimer's risk.
According to the researchers, the study's findings need to be replicated before they can say for sure how great the risk of developing Alzheimer's really is for those who carry the genetic variant.
"This is a very common genetic variant, and many women who had two copies of it did not have disease," Dr. Steven Younkin, senior study investigator and a consultant-researcher at the Mayo Clinic's Florida campus, said in a statement. "But, overall, the odds were substantially greater that female patients with the disease did have two copies."
The research was conducted by scientists from the Mayo Clinic in Jacksonville, Fla., and published in the journal Nature Genetics.
The mutation in the PCDH11X gene is only the second to be linked to late-onset Alzheimer's. Previous research has identified a mutation in the APOE 4 gene as a risk factor, while other research has found genetic links for early onset Alzheimer's.
The PCDH11X gene is involved in maintaining the structure of the body's cells, as well as keeping central nervous system signals working well.
The team from the Mayo Clinic first detected the gene by scanning the genomes of more than 800 patients with Alzheimer's and more than 1,200 control subjects who did not have the disease.
They confirmed the link between the gene and Alzheimer's by scanning another 1,547 patients with the disease, and 1,209 who did not have the disease.
The scientists will next study how exactly the variant in the gene influences the risk of Alzheimer's and if the findings can lead to improved diagnostic tests and treatments.
According to recent statistics released by the Alzheimer Society of Canada, about 500,000 Canadians suffer from Alzheimer's disease and other forms of dementia, which are characterized by symptoms such as memory loss, impaired judgment or reasoning, as well as changes in mood and behaviour.
There is no cure, and experts say that within 25 years, between 1 million and 1.3 million Canadians may develop the disease.
