Recent study revealed that presence of a gene known as APOE4 gene type increase the risk of developing Alzheimer's later.

Study subjects having APOE4 gene had more moment in an area of the brain of known as hippocampus. Studies have shown that hippocampus is the first area to be affected in Alzheimer's disease.

The researchers, from Oxford University and Imperial College London analyzed the data collected from a type of real-time imaging called functional magnetic resonance imaging or fMRI of 36 study subjects aged 20 to 35. 18 study subjects had at least one copy of APOE4.

Data analysis revealed that one copy of the ApoE4 gene raises the risk of Alzheimer's by up to four times whereas two copies by up to 10 times.

Dr. Christian Beckmann of Imperial College London, researcher said: "We were surprised to see that even when the volunteers carrying APOE4 weren't being asked to do anything, you could see the memory part of the brain working harder than it was in the other volunteers."

"Not all APOE4 carriers go on to develop Alzheimer's, but it would make sense if in some people, the memory part of the brain effectively becomes exhausted from overwork and this contributes to the disease."