Genetic variants have been identified that are associated with lacking a good memory in middle and later life and Alzheimer’s disease.

Scientists analysed international data from 30,000 people aged 45 and over who took memory tests including recalling set words and stories.

Each individual’s performance was compared with his or her genetic code.

People with lower scores were found to have DNA variants near a gene called Apolipoprotein E, which is known to have links with Alzheimer’s disease, and another involved in the immune response.

A study of post-mortem brain tissue samples confirmed that individuals with the same genetic variants were more likely to display very early signs of Alzheimer’s.

Ian Deary, from the University of Edinburgh, who co-led the research, said: “These international collaborations help us to find the small individual genetic variants that contribute to memory and other important skills. Once we find them, the hope is that they will lead us to the mechanisms that underpin healthy cognitive ageing.”

Co-author Stephanie Debette, from Boston University School of Medicine in the US, said: “Interestingly, genetic variants associated with memory performance also predicted altered levels of expression of certain genes in the hippocampus, a key region of the brain for the consolidation of information.”