Typically, coroners list only the most immediate condition as a person's cause of death on an official death certificate. But a new study suggests that this practice can lead to a drastic under-reporting of the number of people who die each year due to complications from Alzheimer’s disease.

In a study published in the journal Neurology, researchers estimate that Alzheimer’s, the most common form of dementia, is responsible for some 500,000 deaths a year, more than six times the official estimate of 83,000 deaths in 2010.

Based on the new estimates, Alzheimer’s disease could cause as many deaths in the U.S. as heart disease or cancer, the two leading causes of death for adults.

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Getting an Accurate Alzheimer’s Estimate

Lead study author Bryan James of Rush University Medical Center in Chicago and his colleagues studied 2,566 people over the age of 65, with an average age of 78. Within eight years of the study, 1,090 participants had died and a total of 559 of them had developed Alzheimer’s disease.

On average, the participants lived for about four years after an Alzheimer's diagnosis. Autopsies confirmed the presence of Alzheimer’s in 90 percent of those diagnosed.

More than one third of the deaths in the study group were attributable to Alzheimer’s. People ages 75 to 84 were four times more likely to die after being diagnosed with Alzheimer’s, and three times more likely after the age of 85.

Researchers say expanding these findings to current death estimates from the U.S. Centers for Disease Control and Prevention (CDC) means that Alzheimer’s was responsible for 503,400 deaths 2010.

Attempting to identify a single cause of death in the elderly is difficult and doesn’t adequately capture the reality of the process of death, James said.

“Alzheimer's disease and other dementias are under-reported on death certificates and medical records,” he said in a statement. “Death certificates often list the immediate cause of death, such as pneumonia, rather than listing dementia as an underlying cause."

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A Disease With No Survivors

Maria Carrillo, vice president of medical and scientific relations at the Alzheimer's Association, said it’s well established that deaths due to Alzheimer’s have been historically under-reported.

She said that swallowing disorders and malnutrition can lead to pneumonia, a common cause of death among Alzheimer’s patients. While pneumonia would be listed as the cause of death, it wouldn’t have happened if the person had not had Alzheimer’s, Carrillo said.

The new research, she said, highlights the fatal nature of Alzheimer’s.

“Alzheimer's disease is much more than occasional memory loss. It is a progressive, fatal disease that causes brain cells to malfunction and die,” she said in a statement. “It eventually takes away the ability to think, eat, talk, walk, and care for oneself. Alzheimer's disease has no survivors.”

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