Researchers said they could predict when a person would begin to develop brain impairments such as Alzheimer's by measuring a protein in their blood.

This new test could allow for early detection of Alzheimer's, which would allow for early preventative treatment, a John Hopkins Medicine news release reported.

Drugs meant to prevent brain damage have all failed in clinical trials, but the researchers believe this is because they were administered to patients too late.

"When we see patients with high blood pressure and high cholesterol, we don't say we will wait to treat you until you get congestive heart failure. Early treatments keep heart disease patients from getting worse, and it's possible the same may be true for those with pre-symptomatic Alzheimer's," Marilyn Albert, Ph.D., a professor of neurology at the Johns Hopkins University School of Medicine and leader of the study, said. "But it has been hard to see Alzheimer's disease coming, even though we believe it begins developing in the brain a decade or more before the onset of symptoms."

The team looked at 265 healthy middle aged participants, two-thirds of the group had close relatives with Alzheimer's which put them at a higher risk for developing the disease.

Through neurological and physical tests and found that two spinal fluid proteins, phosphorylated tau and beta amyloid, were a "precursor" to Alzheimer's as far as five years in advance. The more of the protein found in the fluid, the more likely symptoms were to appear.

"We wondered if we could measure something in the cerebral spinal fluid when people are cognitively normal to give us some idea of when they will develop difficulty," Albert said. "The answer is yes."

Out of the high-risk participants, 53 developed the first symptoms of dementia, such as repetitive speech, forgetting what other people said, and missing appointments.

Detection before these symptoms set in could open up the door for new treatment option.