For years the terms “Alzheimer’s disease” and “dementia” have been used interchangeably, often as a catch-all term to describe cognitive decline and memory loss.
But new research published today suggests the two conditions don’t share the same meaning, and that the understanding of dementia may be incorrect.
“A lot of what we thought about dementia was wrong,” Dr. Peter Nelson, the study’s lead author and a professor at the Sanders-Brown Center on Aging at the University of Kentucky, told Healthline.
“We previously thought it was OK to use the terms ‘Alzheimer’s’ and ‘dementia’ interchangeably. Yet we now know that Alzheimer’s disease is just one of many paths to dementia,” he explained.
According to researchers, recent clinical trials have shown that not all people believed to have Alzheimer’s disease actually have the condition.
In fact, many people who’ve enrolled in clinical trials for Alzheimer’s disease drugs were found not to have amyloid in their brain. Amyloid is a sticky substance that interferes with cognitive processes.
In recent years, the scientific community has also noted that a significant number of people with advanced symptoms of dementia didn’t have signs of either amyloid or tau proteins in their brain when autopsies were performed after their death.
It’s believed that a protein known as TPD-43 was a factor instead.
Nelson is part of a group of international researchers who set out to define diagnostic criteria for this protein, a newly named dementia called LATE, which stands for limbic-predominant age-related TDP-43 encephalopathy.
The particular disease appears in the elderly and looks different inside the brain than Alzheimer’s disease does, even though it’s similar to the deadly disease.
“LATE is a newly described cause of dementia, but there’s been ongoing research on it for about 15 years,” Keith Fargo, PhD, director of Scientific Programs & Outreach at the Alzheimer’s Association, told Healthline. “Many people have LATE, especially people over age 80. And it presents itself in ways that are very similar to Alzheimer’s disease symptoms. According to the study authors, about 1 in 4 people over age 85 have enough of the TPD-43 protein that causes LATE to have problems with their memory and thinking. Today many people with LATE may be diagnosed with Alzheimer’s disease.”
The idea that TPD-43 could be contributing to cognitive decline or memory loss isn’t new. Researchers have been exploring the idea for the past decade.
The research from Nelson and colleagues is the first to give a name to the finding as well as to gather data to look at how common it is.
Fargo says the work will assist in providing better prevention and treatment programs for people with dementia.
“Research like this may bring us closer to precision medicine in the future, where individuals receive personalized prevention and treatments based on their unique health status,” he said. “Accurate identification of the biological changes in LATE — and other forms of dementia — supports a better understanding of the brain, which will eventually lead researchers to develop new therapeutics that more selectively target these hallmarks that cause disease.”
Experts say this research emphasizes that it’s no longer appropriate to use the terms Alzheimer’s disease and dementia as if they’re the same thing.
“They should not be used interchangeably,” Dr. Michael Greicius, an associate professor of neurology at Stanford University in California, told Healthline. “Dementia is the umbrella term meaning that someone has had a change in their cognitive capacity which renders them unable to live safely and independently. Under that umbrella term, there are many different causes of dementia. Alzheimer’s disease is the most common cause of dementia, followed by vascular dementia, Lewy body dementia, frontotemporal dementia, and now somewhere in that lineup probably LATE.”
Brittany Dugger, PhD, is an assistant professor at the University of California Davis School of Medicine’s department of pathology. She says having distinct definitions for complex conditions isn’t only helpful for clinicians, but also for patients.
“Definitions are important. One patient once said to me that they were relieved when they got their diagnosis since it gave a name to what they were experiencing,” Dugger told Healthline. “However, a lot of our definitions in the field of dementia, like that of LATE, are pathological, meaning only after a person dies can the diagnosis be given.”
“The true test is if these definitions can be meaningful in terms of prevention, diagnosis, treatment, and prognosis,” she explained. “Further work examining diverse cohorts and populations if possible is warranted.”
Nelson likens the work of the research group into LATE akin to Benjamin Franklin’s discovery of electricity. Franklin was able to formalize an idea that supported others to study electricity.
In a similar way, Nelson says, by providing a scientific focus and a name for the idea behind TPD-43, researchers around the world will be able to advance their understanding of dementia and in turn provide new opportunities for treatment.
“It ultimately comes down to making people better and improving public health. Everything else is just window dressing,” he said. “We hope this report will help get these people with LATE, who have the dementia syndrome, out of Alzheimer’s clinical trials… the fact that non-Alzheimer’s people are in those trials has been one reason they’ve failed probably. And of course, secondly, we’ll need new clinical trials for LATE.”