Gene linked to Alzheimer's risk in African-Americans

Genetic variants linked to higher Alzheimer's disease risk in African-Americans have been found by a team at Columbia University, USA.

The study, published in the Journal of the American Medical Association, found that those with an alteration in the ABCA7 gene had a much higher risk of developing Alzheimer's disease.

The researchers found that a mutation in the ABCA7 gene corresponded with a 70 to 80 percent increase in the risk that an African-American individual would go on to develop Alzheimer's disease. In the white population, an ABCA7 alteration only increases the risk of developing Alzheimer's by 10 to 20 percent.

'Our findings strongly suggest that ABCA7 is a definitive genetic risk factor for Alzheimer's disease among African-Americans', said Richard Mayeux, professor of neurology at Columbia University and senior author of the study. 'Until now, data on the genetics of Alzheimer's in this patient population have been extremely limited'.

The team also found that that the gene apolipoprotein E (APOE), which is a known risk factor in the white population, also indicated higher risk in African-Americans. Those with a specific variant of the gene known as APOE-e4 had double the chance of developing Alzheimer's disease in both populations.

Alzheimer's disease is more common among African-Americans but until now, research only focused on those of European descent. The meta-analysis is the largest study to date into genes for Alzheimer's in African-Americans and looked at data from around 6,000 African-Americans, 2,000 of whom had Alzheimer's disease.

The research focused on late-onset Alzheimer's, the more common form of the condition, where symptoms begin to show after the age of 65. Around one percent of the population has Alzheimer's at age 65, but this figure rises to 30 percent in those over 80 years of age.

As ABCA7 is involved in the production of cholesterol and lipids, the scientists believe it may be possible that lipid metabolism is a more important pathway in Alzheimer's disease in African-Americans than in those of European descent. They hope that by confirming these results, they can develop more effective ways of diagnosing, treating, and preventing the disease.

'Our next step is to do more lab work and more genetic sequencing, to understand the biological reasons for the increased risk seen with ABCA7 and other genes implicated in late-onset Alzheimer's disease', said Dr Mayeux.

Robert Nussbaum, professor of medicine at the University of California, who was not involved in the study, noted that while genetic factors do appear to significantly affect a person's risk of developing the disease, there are many people who have those genetic risk factors that do not go on to develop the disease.