SAN DIEGO – said a presenter at the annual meeting of the American College of Physicians.
Dementia prevalence is increasing as the proportion of the U.S. population older than 65 rises, said Zaldy Tan, MD, professor of neurology at Cedars-Sinai Medical Center, Los Angeles. AD deaths more than doubled between 2000 and 2018, he noted, while deaths from HIV infection, stroke, and heart disease decreased.
Most people in the United States who have AD are White, but studies suggest that, compared with Whites, the risk of AD is two times higher in Blacks and 1.5 times higher in Hispanics . “These data suggest that both genes and social determinants of health are at play,” Dr. Tan said.
Diagnosis of Alzheimer’s disease
The different types of dementia make it challenging for primary care physicians to identify the cause of cognitive impairment. “Even though AD is the most common type, clinicians should keep in mind that another type of dementia may be the cause of cognitive impairment,” Dr. Tan cautioned. Other dementia diagnoses include vascular, Lewy body, and frontotemporal.
Diagnostic criteria for AD include evidence of significant cognitive decline in at least one cognitive domain that interferes with independence in everyday activities, as well as the absence of another mental disorder or delirium that would explain the cognitive deficits.
“We see many patients with depressive symptoms and mild cognitive impairment, and it is not always easy to tell which of them have dementia because of the overlap in the symptoms of depression and AD,” said internist Roderick Kim, MD, of Grand Rapids, Mich., who attended the session.
It can be challenging to convince patients to undergo the appropriate diagnostic workup, Dr. Kim said. “This can delay treatment, so it is important to explain to patients that cognitive decline can progress quickly and that there are treatment options to slow it down.”
Why do we need biomarkers for Alzheimer’s disease?
AD is characterized by a long preclinical phase with no specific symptoms other than the typical signs and symptoms of aging, Dr. Tan said. That means cognitive impairment progresses rapidly after diagnosis in most patients with AD.
“In most cases, an accurate history, physical and neurologic examinations, basic labs, and neuroimaging are sufficient for memory loss evaluation. However, as more disease-modifying therapies come to market, biomarkers will rise in importance in primary care,” he said.
This long asymptomatic phase of AD creates the need for diagnostic biomarkers for an earlier diagnosis, he said. Amyloid-beta and tau deposits in PET images and the levels of amyloid-beta seeds, phosphorylated tau, and neurofilament light chain in the cerebrospinal fluid can be used as diagnostic biomarkers in patients with suspected AD. Emerging blood biomarkers for earlier detection include the levels of amyloid-beta1–42, phosphorylated tau, and neurofilament light chain.
With biomarkers and other new tools for the diagnosis of dementia in primary care, Dr. Tan said: “The greatest challenge is cost, as blood-based biomarkers are not currently covered by insurance and still rather costly. In addition, blood-based biomarkers will need to receive [Food and Drug Administration] approval in order to have more widespread availability.”