In the U.S., older people with dementia are usually told they have Alzheimer's disease.
But a range of other brain diseases can also impair thinking, and memory and judgment, according to scientists attending a summit on dementias held Thursday and Friday at the National Institutes of Health.
These include strokes, a form of Parkinson's disease, and a disease that damages brain areas that regulate emotion and behavior.
"There's a host of things that can cause loss of cognitive function," says Dr. Julie Schneider, a professor at the Rush Alzheimer's Disease Center in Chicago and scientific chair of the NIH summit. And many patients have more than one disease affecting the brain, she says.
Most of these diseases can't be stopped, Schneider says. But it's important that families get the right diagnosis in order to get the best care and plan for the future.
The emphasis on non-Alzheimer's dementias reflects a change in doctors' understanding of what happens to aging brains.
When Schneider was training to be a doctor in the 1980s and '90s, dementia was simple. "We were taught that almost all dementia is Alzheimer's disease," she says.
But since then, studies have shown that 20 percent to 40 percent of the nation's 5.8 million dementia patients have some other disease.
Statistics from the Alzheimer's Association show that some of the most common are:
- Vascular disease, which is caused by a stroke or blood vessel damage and accounts for up to 10 percent of all dementia cases.
- Lewy body disease, which is related to Parkinson's disease, also accounts for up to 10 percent of dementia patients.
- Frontotemporal lobar degeneration, which affects areas of the brain involved in personality, language and behavior. It accounts for less than 10 percent of dementia cases.
"We still believe that Alzheimer's is important," Schneider says. "But these other pathologies are also important."
Alzheimer's is associated with plaques and tangles in the brain. But a different culprit causes Lewy body dementia, Schneider says.
"It's these little aggregates called Lewy bodies, which were first identified in the brains of people with Parkinson's disease," she says.
And people with Lewy body disease can expect different challenges than people with Alzheimer's.
"You're going to be more rapidly declining," Schneider says. "You might have more motor problems, more falls, gate changes, sleep problems, hallucinations."
Many of those symptoms can be treated, even though the underlying disease can't be.
Frontotemporal degeneration is a group of disorders that also have a distinctive appearance, says Dr. Walter Koroshetz, director of the National Institute of Neurological Disorders and Stroke, which organized the dementia summit.
"Those folks can oftentimes be seen as peculiar but not demented," Koroshetz says. "But they can be severely impaired."
For example, people with frontotemporal dementia may begin to behave inappropriately or make poor decisions or become insensitive to others. That can lead to tragic misunderstandings if family members don't know the cause, Koroshetz says.
"Not infrequently, the spouse thinks that their spouse is just not worth being married to anymore, and they believe it's a psychological thing, and they get divorced," He says. "And later there's a lot of guilt."
One preventable cause of dementia is stroke, says Roderick Corriveau, a program director at the National Institutes of Neurological Disorders and Stroke.
"One-third of the people who have strokes go on to have dementia," he says. "Preventing strokes is about preventing damage to your brain."
And people who've had one stroke can often avoid a second by taking blood thinners and controlling their blood pressure, he says.