By Matt McMillen
WebMD Health News
Reviewed by Arefa Cassoobhoy, MD, MPH
March 5, 2014 -- The number of people who die from Alzheimer's disease may be five times higher than previously thought, researchers at Rush University Medical Center in Chicago say.
The study's numbers would make Alzheimer's the third leading cause of death in the U.S., right behind heart disease and cancer. The CDC lists Alzheimer's as the sixth leading cause of death.
The CDC says 83,494 people died from the disease in 2010. That number is based on death certificates, which often fail to list Alzheimer's as a contributing cause. The true number of deaths may be more than half a million for Americans, according to the study, which appears today in the journal Neurology.
"Trying to identify a single cause of death may not reflect the reality of dying for many older people, where multiple health issues contribute and lead to a cascade of deterioration of health and function that leads to death," says lead researcher Bryan James, PhD. "And it's hard to say which of those conditions is the single cause of death."
Alzheimer's causes the brain to decline over time. At first, it affects those parts of the brain responsible for thinking and memory. Eventually, it can lead to problems with feeding and swallowing. This puts people at risk for poor nutrition, dehydration, and infection. At that stage, James says, it can lead to fatal conditions such as pneumonia and heart failure.
"I'm not sure that most people grasp that Alzheimer's is a fatal disease," he says. "And it's leading to a lot more death than we recognized before."
Death certificates, James says, require a single, immediate cause of death, such as pneumonia or heart failure. While there's room on the form to write underlying causes, several things often get in the way. For example, the doctor who signs the death certificate may not know the person's medical history. And, James says, some people with Alzheimer's never get diagnosed.
A key point James makes is that Alzheimer's can be at the root of a chain of health problems.
In 2013, Alzheimer's care cost $203 billion in the U.S. Costs are expected to climb past $1 trillion by 2050.
James and his colleagues looked at the health records of 2,566 volunteers between 1994 and 2013. The volunteers were 65 or older and dementia-free at the start of the study. Nearly three-quarters were women, and close to 90% of them were white. Their average age was 78. In general, they had a higher-than-average level of education and were likely in better-than-average health.
Each participant had yearly medical exams in which they were tested for Alzheimer's disease and other dementia. Their medical histories were reviewed, and chronic conditions such as heart disease, high blood pressure, and diabetes were noted. They also were asked questions to check on memory, thinking, and how they did tasks. They agreed to allow autopsies at the time of their deaths as well. The researchers followed them for an average of 8 years.
Over the course of the study, 559 participants were diagnosed with Alzheimer's disease. They lived an average of 4 years after the disease was found. Alzheimer's accounted for one-third of the 1,090 deaths that occurred during the study.
"This," the researchers write, "translates into more than 500,000 deaths attributable to AD dementia in the United States in 2010."
"We know that 5 million people have Alzheimer's disease, that there are no effective treatments for it, and that it's a fatal disease, so the numbers were not that surprising to us," James says.
"This study does make the case very strongly that AD accounts for a larger proportion of deaths in any given time period than had been thought," says Terry Goldberg, PhD. He's the director of research in neurocognition at the Litwin Zucker Alzheimer's Center at the Feinstein Institute for Medical Research. Goldberg was not involved in the study. "Alzheimer's may not be the proximal, or immediate, cause of death, but you can often trace it back to AD."
Neurologist Liana Apostolova, MD, was also impressed by the study. She's an Alzheimer's researcher at the Mary S. Easton Center at UCLA.
"This is a more realistic estimate of the death toll of AD relative to the one that we can get from the CDC, and knowing how prevalent AD is, the results of the study are not unexpected," she says.
"The high death rate underscores the lack of a cure," says Apolostova, who was not connected to the research team. "Many families are affected by this devastating disease, and it robs patients of what makes them uniquely human: their social and intellectual graces. This study will really help raise awareness about Alzheimer's."
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