Image credit: iStock.com/giocalde
A time may come when biomarkers will make it possible to easily identify and treat Alzheimer’s disease before patients exhibit symptoms of dementia. That’s the assessment of a new report by the Alzheimer’s Association, “Alzheimer’s Disease: The Next Frontier.” The report pegged development and validation of Alzheimer’s-related biomarkers as a “top research priority” because doing so could “markedly change” how the disease is diagnosed.
Indeed, with development and implementation of early markers of disease, the Alzheimer’s Association envisions a time when Alzheimer’s “is placed in the same category as other chronic diseases, such as cardiovascular disease or diabetes, which can be readily identified with biomarkers and treated before irrevocable disability occurs.”
The association embedded this special report in its 2017 Alzheimer’s Disease Facts and Figures report, which estimates that 5.5 million individuals—most of whom are aged 65 and older—currently have Alzheimer’s in the United States. In 2017, 480,000 senior citizens are expected to develop the disease.
The report highlights the growing importance of biomarkers in Alzheimer’s disease. “By the time cognitive symptoms appear in an individual with Alzheimer’s disease, years of irreversible brain damage have likely occurred,” said Maria Carrillo, PhD, the Alzheimer’s Association’s chief scientific officer, in a statement.
Numerous studies have highlighted the use of biomarkers in identifying and diagnosing Alzheimer’s disease at earlier stages, even before symptoms are evident, Carrillo told CLN Stat.
The special report references more than two dozen studies, and even more are on the horizon, she said. Several biomarkers show potential in identifying early stage Alzheimer’s disease, including fluctuations in brain size and activity, and beta-amyloid and tau accumulations in the brain, which clinicians can measure either through cerebrospinal fluid and blood, or through brain imaging.
“Studies have validated that biomarkers are indeed reliable measures of the relevant disease-related changes in the living brain,” according to the authors of the report. While much of the current research has focused on these biomarkers, other tools are being explored as well, including measures in blood and saliva, which are less expensive and invasive. Although they’re not ready for clinical use, advances are being made, Carrillo said.
The expectation is biomarkers may be used to detect and treat Alzheimer’s when an individual is either asymptomatic or showing signs of mild cognitive impairment (MCI). It’s estimated that Alzheimer’s may account for symptoms in up to 56% of individuals with MCI.
Experts have proposed that biomarkers could help determine whether Alzheimer’s is the source of dementia—thus excluding individuals who have another type of dementia. “Although we have known for years about the occurrence of dementia due to Alzheimer’s, as a result of the recent use of biomarkers in studies, we have learned that a proportion of people previously thought to have cognitive impairment caused by Alzheimer’s disease lack those biomarkers,” the authors noted.
Biomarkers thus have the ability to alter how researchers track incidence and prevalence of this disease, if diagnoses are based on brain changes rather than functional or cognitive changes.
MCI for example may or may not be attributed to brain changes in Alzheimer's disease, Carrillo explained. “If it’s not due to Alzheimer’s disease, then it is important to understand what is driving the memory condition, perhaps another type of dementia or even a potentially reversible condition. If the memory changes are due to Alzheimer’ disease, the goal is to stop the progression before it becomes Alzheimer’s dementia.”
Validating current biomarkers for Alzheimer’s and identifying new ones, calls for additional research and the development of therapies, Carrillo said. “Validated biomarkers will allow researchers to identify which individuals to enroll in clinical trials to test new therapies, and to enroll individuals with the disease-related brain changes that potential treatments are targeting,” she said.
Researchers will be able to leverage biomarkers to monitor the potential benefits of these therapies, she added. “Consideration should also be given to how we use validated biomarkers in future epidemiological studies to better understand the true number of people living with Alzheimer’s dementia and the full extent of the disease burden,” Carrillo indicated.
With newly recalculated estimates on incidence and disease, the hope is experts such as epidemiologists, demographers, and biostatisticians will be able to develop updated information on the costs of care, estimates on the number of caregivers taking care of Alzheimer’s patients, and mortality estimates on the disease.