A study in the US has found that people are likely to show characteristics of Alzheimer's disease long before symptoms become apparent if both their parents had the condition.
Published in the journal Neurology, the study involved 52 people without dementia aged between 32 and 72.
They were split into four groups, one made up of people whose parents did not have dementia, one where both parents were affected and the remaining two where either their mother or father developed the condition.
Brain scans were taken to identify structural changes, while activities were also used to measure cognitive activity.
Those whose parents had both suffered with dementia were found to have smaller brain volumes on average as well as lower level of metabolism and high quantities of amyloid – the protein which builds up in the brain and is the main cause of Alzheimer's.
It suggests that family history could play a role in the development of the illness.
Dr Simon Ridley, head of research at Alzheimer's Research UK, said: "We know that Alzheimer's can cause changes in the brain many years before symptoms start and this very small study suggests that genetics could be linked to these changes.
"Research is showing that genes can play a role in the risk of late-onset Alzheimer's, but it is a complex disease with many risk factors and age is still the biggest."
He added that the research only provided a snap-shot of that time so it is impossible to saw how the features identified will change over time.
Around 820,000 people are currently living with some form of dementia in the UK and around half of that number have Alzheimer's disease.
Currently, there is no cure, but Alzheimer's Research UK is currently investing millions of pounds into studies which could potentially bring suitable treatments closer.