The research, published in Translational Psychiatry, looked at data from more than 100 sets of twins from TwinsUK, the biggest adult twin cohort in the UK.
The researchers used 55 identical twin pairs in the study, which allowed them to show that the association between the blood protein and a 10-year decline in cognitive ability was independent of age and genetics, both of which are known to affect the risk of developing Alzheimer’s disease.
The study, the largest of its kind to date, measured more than 1,000 proteins in the blood of some 200 healthy individuals using a laboratory test called SOMAscan, a protein biomarker discovery tool that measures a wide range of different proteins. Using a computerised test, the researchers then assessed each individual’s cognitive ability and compared the results with the measured levels of each different protein in the blood.
For the first time, they found that the blood level of a protein called MAPKAPK5 was, on average, lower in individuals whose cognitive ability declined over a 10-year period.
There are currently no treatments available proven to prevent Alzheimer’s disease, and prevention trials for the condition can be problematic because to be effective, they must involve individuals at risk of the disease, and these must first be identified.
Studies using MRI and PET brain scans have been shown to display visible signs of the disease before the onset of symptoms, but these types of scans are timely and costly.
To date, few other studies have looked at the blood of individuals with the very early stages of cognitive decline and therefore most appropriate for a prevention study.
Identifying blood markers such as MAPKAPK5, which may indicate a person’s future risk of Alzheimer’s disease, could contribute towards the better design of prevention trials.
Dr Steven Kiddle, lead author and Biostatistics Research Fellow at the Medical Research Council (MRC) Social, Genetic & Developmental Psychiatry Centre at King’s College London, said: “Although we are still searching for an effective treatment for Alzheimer’s disease, what we do know is that prevention of the disease is likely to be more effective than trying to reverse it.
“The next step will be to replicate our finding in an independent study, and to confirm whether or not it is specific for Alzheimer’s disease, as this could lead to the development of a reliable blood test which would help clinicians identify suitable people for prevention trials.”
Co-author, Dr Claire Steves, Geriatrician and Senior Lecturer in Twin Research at King’s College London, added: “We’re very optimistic that our research has the potential to benefit the lives of those who don’t currently have symptoms of Alzheimer’s, but are at risk of developing the disease.”
The research was funded by the MRC, the National Institute of Health Research Biomedical Research Centre for Mental Health and the Wellcome Trust.