A new study has found that a simple blood test could predict Alzheimer's disease a decade before symptoms appear.

A single blood protein, MAPKAPK5, has been identified by British researchers, which acts as a warning for mild cognitive impairment. The levels of this protein tend to be lower in those people whose brains’ functioning declined.

For the study, the researchers analyzed levels of 1,129 proteins circulating in the blood of more than 200 twins. They tracked them and examined the levels of the protein over the next decade.

The findings revealed that MAPKAPK5 was, on average, lower in individuals whose cognitive ability declined over a ten-year period. Although the research is at an early stage, scientists hope it might be developed into a test that can detect those who are at risk of developing Alzheimer's.

Study author Dr. Steven Kiddle, of 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”.

Alzheimer's is diagnosed in patients only when they start to lose their memory. Thousands are thought to be living without a diagnosis. Although brain scans display visible signs of the disease before the onset of symptoms, they are expensive.

Currently there are no treatments to prevent Alzheimer's. However, doctors hope that identifying those most at risk might give patients and their families more time to prepare. It will speed the search for new drugs and also help or even prevent the devastating brain disease.

The findings were funded by the Medical Research Council and published in the journal Translational Psychiatry.