Scientists have identified a rare genetic mutation that protects people from developing Alzheimer's disease and age-related cognitive declines in a discovery that may potentially pave the way to a cure for the mind-robbing disease.

The latest findings, published in the science journal Nature, show a gene for amyloid-beta precursor protein (APP) may play an essential role in forming amyloid protein plaques in the brains of Alzheimer patients, and Icelandic scientists say that the study results suggest that a mutation in this gene may help protect against Alzheimer's disease and other mental declines experienced in aging.

These amyloid protein plaques accumulate in the brains of people affected by the degenerative disease and stick together and prevent neurons from communicating with each other, eventually leading to severe memory loss and speech problems.

"We found a coding mutation in the APP gene that protects against Alzheimer's disease and cognitive decline in the elderly without Alzheimer's disease," researchers wrote in the study.

Neurologists said that a drug that mimics this rare variant could stop the mind-robbing disease in its tracks.

Study lead author Kari Stefansson, chief executive of Icelandic company deCODE Genetics in Reykjavik, and his team found that the mutation results in a 40 percent reduction in the formation of these harmful plaques, according to the study.

Furthermore, researchers found that study participants between the ages of 80 and 100 year old who do not have Alzheimer's disease and who carry this mutation possess significantly better mental function compared to those without the mutation.

While mutations in the APP gene have already been linked to early-onset Alzheimer's that runs in families, researchers said that it had not been linked to the more prevalent form of the neurodegenerative disease that occurs in later life.

Stefansson said that the latest results are supported by previous studies showing that manipulating the gene, which can be achieved with some existing drugs currently being tested in clinical trials.

Despite almost four decades of Alzheimer research, scientists have made little headway in creating drugs that effectively inhibit interactions between proteins, in part because drug molecules are infinitely smaller than the proteins so even if drug molecules can attach themselves to the larger protein molecules, they are still too tiny to prevent other proteins from linking together in a different brain region.

"The prevalence of dementia in the Western world in people over the age of 60 has been estimated to be greater than five per cent, about two thirds of which are due to Alzheimer's disease," researchers wrote in the study.

"The age-specific prevalence of Alzheimer's disease nearly doubles every five years after age 65, leading to a prevalence of greater than 25 per cent in those over the age of 90," he added.

"The implication of these data is that general cognitive decline and late-onset Alzheimer‘s disease share biological pathways,” Stefansson said in a company news release. “It also suggests that approaches to treating Alzheimer’s may have benefit to those elderly who do not carry the protective mutation, and do not suffer from AD.”