An alteration in a gene may speed up the loss of memory and thinking skills in people who are already at the risk of Alzheimer's disease according to a study. According to researchers people with Alzheimer's risk who have the gene mutation called the BDNF Val66Met allele or the Met allele may have a more rapid decline of memory and thinking skills. Further people with the gene mutation who also had more beta-amyloid -- a sticky protein that can build up into plaques found in the brains of people with Alzheimer's disease -- had an even steeper rate of decline.