Every 67 seconds someone develops Alzheimer’s, and it remains an elusive, incurable disease for now. However, a new breakthrough in Alzheimer’s research may make the path clearer for diagnosing and even preventing the disease one day.
Amyloid – a sticky, toxic protein found in the brains of Alzheimer’s patients — has been the focus of research and diagnosis for decades. But a new Mayo Clinic study published in the journal Brain shows that another toxic protein, called tau, may be a bigger culprit in cognitive decline and Alzheimer’s over the lifetime of the disease.
Researchers say the discovery could lead to better diagnosis, treatments, and prevention tools.
The study was conducted in two parts. Researchers studied 3,016 brains donated to the Mayo Clinic over the course of more than a year; 1,375 of these brains were from patients who had been diagnosed with Alzheimer’s. These patients had died at different stages of dementia and at different ages. Therefore, researchers were able to evaluate Alzheimer’s progression on a timeline versus in a snapshot in time. This study was unique because researchers looked simultaneously at the impacts of tau and amyloid, which allowed them to evaluate the progressive, wide-ranging impacts of both proteins. The researchers used recommended scoring systems to examine the evolution of amyloid and tau in dissected brain tissue. The findings showed that the severity of tau, but not of amyloid, predicted age onset of cognitive decline, disease duration, and mental deterioration.
The second part of the study examined amyloid brain scans taken of patients prior to death and compared the scans with measures of tau and amyloid brain pathology. It showed that amyloid can be found in the brains of older people who have not experienced cognitive decline.
The findings indicated that it is actually tau that is driving the cognitive decline and memory loss seen in Alzheimer’s disease, explains Melissa Murray, PhD, an assistant professor in neuroscience at the Mayo Clinic and lead study author. “The thought behind this is that tau is leading to the death of the neurons whereas amyloid may be causing a miscommunication between neurons. But it’s that death of the neuron that is really the extreme aspect of the disease,” Murray tells Yahoo Health. Ultimately, she says, tau may have the stronger impact on cognitive decline than amyloid.
Murray emphasizes that amyloid brain scanning is still important, but says there needs to be a shift to focus more on the impact of tau specifically for Alzheimer’s treatments.
While amyloid imaging has been available for 10 years, the use of tau imaging is still in research stages. Murray predicts that both imaging types will be useful for improving diagnosis of Alzheimer’s in the future, especially for people with early-onset Alzheimer’s, which is harder to confirm.