The study looked at 726 middle-aged people with a family history of Alzheimer's disease, genotyped them for the TOMM40 and APOE gene variants and then conducted a range of cognitive tests.
The TOMM40 and APOE gene variants have already been linked to Alzheimer's disease in previous studies. Researchers at Duke University in North Carolina led by Professor Allen Roses discovered the TOMM40 gene and its association with Alzheimer's disease, which is also close to APOE in the genome.
The researchers found that those individuals with a 'high risk' variant of the TOMM40 gene (129 people) performed significantly worse than individuals with a 'low risk' variant (229 people) in a series of memory tests.
Professor Clive Ballard from the Alzheimer's Society in the UK said 'These interesting preliminary studies have shown a gene linked to Alzheimer's also alters cognitive function in mid-life'.
'A better understanding of how genetic and other risk factors lead to cognitive impairment in mid-life will help researchers target prevention of dementia more effectively'.
The findings were announced at the Alzheimer's Association International Conference on Alzheimer's (AAICAD) in Hawaii on the 14 July by researchers at the University of Wisconsin Medical School.