Scottish researchers report that a gene variant linked to Alzheimer's disease may also be a factor in normal memory loss and mental decline that comes with age.

The researchers, reporting in the journal Nature, said that people who carry a variant of the gene apolipoprotein E, known as APOE-e4, did worse on a general intelligence test even though they had not been diagnosed with Alzheimer's.

The APOE-e4 gene variant is found in about 25 percent of the population, and has been shown by studies to be associated with Alzheimer's.

The researchers gave a Moray House Test to 466 men and women aged 80 who had not been diagnosed with dementia, and then tested participants to see which carried the APOE-e4 gene variant.

Those carrying the gene fared worse on the test than those who did not, the researchers reported.

Other sources: Nature