Build-up of 'tangles' in the brain increases risk of dementia more than having the Alzheimer's gene
Those with greatest number of 'plaques' or 'tangles' saw memory decrease by a fifth over 18 monthsPlaques can appear years before obvious symptoms such as forgetfulness
19:19 GMT, 15 October 2012
A build up of plaque in the brain may be more harmful than having the Alzheimer’s gene, a study has found.
It has implications for dementia care as while genetic tests are cheaper than brain imaging for beta amyloid or 'plaques', the latter is likely to be the most effective way to spot the condition.
Researchers from the University of Melbourne in Victoria, Australia, looked at 141 people with an average age of 76 who were free of any problems in memory and thinking.
In most people with Alzheimer's, symptoms first appear after age 60
They found those with a greater number of the “plaques” see their memory decrease by a fifth over a year and a half, far more than those carrying the APOE genotype or 'Alzheimer's gene.'
Study author Yen Ying Lim said: 'Our results show that plaques may be a more important factor in determining which people are at greater risk for cognitive impairment or other memory diseases such as Alzheimer’s disease.
'Unfortunately, testing for the APOE genotype is easier and much less costly than conducting amyloid imaging.'
The study participants underwent PET brain scans and were tested for the APOE gene.
Their memory and thinking was then tracked over the following year and a half, using a set of computer-based cognitive assessments that were based on playing card games and remembering word lists.
The study found that after a year and a half, people who had more brain plaques at the start of the study had up to 20 percent greater decline on the computer based assessments of memory than did those who had fewer brain plaques.
The study also found that while carriers of the APOE allele also showed greater decline on the memory assessments than those who did not have the allele, carrying the gene did not change the decline in memory related to the plaques.
The author added: 'Our finding that brain plaque-related memory decline can occur while people still have normal memory and thinking shows that these plaque-related brain changes can be detected and measured while older people are still healthy.
'This provides an enormous opportunity for understanding the development of early Alzheimer’s disease and even a sound basis for the assessment of plaque-targeting therapies.'
Dr Simon Ridley, Head of Research at Alzheimer’s Research UK, the UK’s leading dementia research charity, said: 'We know that people with the APOE4 gene can be at higher risk of Alzheimer’s, but it doesn’t mean they will definitely develop the disease.
'This study shows that the amount of the hallmark Alzheimer’s protein amyloid in the brain is a stronger indicator of memory decline than whether someone has the APOE4 gene.
'There is a lot of research currently underway to develop ways of stopping amyloid from building up in the brain. These findings suggest that drugs which prevent amyloid build-up could have real potential for slowing the disease.
'We know that amyloid can start to appear years before symptoms, so testing potential new drugs at an early stage of the disease will be vital. With over half a million people in the UK living with Alzheimer’s, we must invest in research to defeat this devastating disease.'
The findings are published in Neurology, the medical journal of the American Academy of Neurology.