The fact that more than 35 million people around the world are currently living with Alzheimer’s disease has led some experts to refer to this condition as a “global epidemic.” According to estimates, the prevalence of Alzheimer’s will double almost every two decades.
Early detection of the disease makes it easier to plan appropriate care and begin therapeutic interventions as early as possible, which can relieve symptoms.
Researchers are convinced that Alzheimer’s begins many years before symptoms begin. In fact, emerging research has suggested that some Alzheimer’s-related brain mechanisms begin at least 10 years before diagnosis.
However, it is not yet defined exactly when these changes occur. In a new study, researchers set out to detect more precise “turning points” in the evolution of Alzheimer’s biomarkers, identifying changes in brain neurochemistry and anatomy that occur decades before individuals experience any symptoms of Alzheimer’s disease. Alzheimer’s.
Laurent Younes, professor and chair of the Department of Applied Mathematics and Statistics at Johns Hopkins University in Baltimore (USA) explains his findings in the article that appears in the journal Frontiers in Aging Neuroscience.
Change points
To find out when biochemical and anatomical changes occur, experts reviewed the medical records of 290 people who were at least 40 years old. The scientists accessed the data from the BIOCARD project, which aims to discover predictors of cognitive decline. Most of the study participants had at least one first-degree relative with Alzheimer’s, which greatly increased the risk of developing this condition.
The researchers had access to the participants’ cerebrospinal fluid samples and MRI brain scans, which they had collected every 2 years between 1995 and 2013 as part of the BIOCARD study.
During the same period, the BIOCARD scientists conducted five standard tests each year, examining the participants’ memory, learning, reading and attention.
At the start of the new study, the team considered all the participants to be “cognitively normal,” but by the end of the study period, 81 participants had developed Alzheimer’s disease.
The key: tau levels
In the participants who developed Alzheimer’s disease, the researchers found signs of cognitive decline 11-15 years before the onset of any symptoms. These subtle signs were visible from small changes in cognitive test scores, but the participants did not show any symptoms at the time. They also found elevated levels of the protein Tau, a biomarker of Alzheimer’s disease, in these participants. In fact, they detected higher levels of this protein up to 34 years before the appearance of the first symptoms.
Additionally, levels of a modified version of the tau protein called “p-tau” increased 13 years before visible symptoms of cognitive decline appeared.
Finally, the team also used computer algorithms to track brain changes in the participants over time. The scientists assigned numbers to different parts of the brain and found that the rate at which the medial temporal lobe changed was slightly different in participants with Alzheimer’s.
The medial temporal lobe has an association with memory, and the scientists noticed changes in this region of the brain 3 to 9 years before the participants became symptomatic.
Michael I. Miller, co-author of the work, comments: “Several biochemical and anatomical measures can be observed that change up to a decade or more before the onset of clinical symptoms. The goal is to find the correct combination of markers that indicate an increased risk of cognitive decline and use that tool to guide future interventions to help prevent it. “
Experts caution that changes in the brain vary considerably from person to person and that the study sample was small. However, the results may lead to better diagnostic tests, which could, in turn, offer better treatment options.
“Our study suggests that brain imaging and cerebrospinal fluid analysis can be used to assess the risk of Alzheimer’s disease at least 10 years or more before the most common symptoms, such as mild cognitive impairment,” concludes Laurent Younes.
Referencia: Identifying Changepoints in Biomarkers During the Preclinical Phase of Alzheimer’s Disease. Laurent Younes, Marilyn Albert, Abhay Moghekar, Anja Soldan, Corinne Pettigrew and Michael I. Miller. Frontiers in Aging Neuroscience. 2019 DOI. 10.3389/fnagi.2019.00074
