Occasional memory lapses such as forgetting the name of a friend may be symptoms of a shrinking brain, researchers have found.
Scans revealed that a brain area linked to memory is smaller in people whose ability to remember or concentrate fails them now and then.
Scientists studied 500 people aged 50 to 85 living in the Netherlands who were not suffering from dementia.
Volunteers were asked about sporadic memory problems like struggling to find the right word, or forgetting a friend's name or things that happened in the last day or two.
They were also asked if they had problems concentrating or thinking quickly.
A high proportion of 453 participants reported having occasional memory or thinking problems, which would not show up on regular tests of cognitive skills.
Brain scans showed that the hippocampus was smaller in people who had memory problems than in people who did not.
The average volume of the brain region in the two groups was 6.7 millilitres and 7.1 millilitres respectively.
The hippocampus is one of the first parts of the brain to be damaged by Alzheimer's disease.
Study leader Dr Frank-Erik de Leeuw, from Radboud University Nijmegen Medical Centre in the Netherlands, said: "These occasional, subjective memory complaints could be the earliest sign of problems with memory and thinking skills.
"We were able to discover that these subjective memory complaints were linked to smaller brain volumes.
"Because occasional memory lapses were so common, though, much more work needs to be done to use such complaints diagnostically.''
All the volunteers also had small areas of damage in their brains, but these were not associated with memory lapses.
Dr de Leeuw added: "To further strengthen the possible connection between the subjective memory complaints, size of hippocampus and the development of Alzheimer's disease in all of the participants will be investigated again within the coming years.''