Study author Bryan D. James, a researcher with the Rush Alzheimer's Disease Center in Chicago, said the Centers for Disease Control and Prevention in Atlanta list Alzheimer's disease as the sixth leading cause of death in the United States, according to data reported on death certificates.
However, Alzheimer's disease might actually be responsible for as many deaths each year as heart disease or cancer -- the two leading causes of death in the United States.
James said this translates into an estimated 503,400 deaths from Alzheimer's in the U.S. population age 75 and older in 2010, which is five to six times higher than the 83,494 number reported by the CDC based on death certificates.
James said attempting to identify a single cause of death does not always capture the reality of the process of dying for most elderly people, as multiple health issues often contribute.
"Alzheimer's disease and other dementias are under-reported on death certificates and medical records," James said in a statement. "Death certificates often list the immediate cause of death, such as pneumonia, rather than listing dementia as an underlying cause."
The study, published in the journal Neurology, found the death rate was more than four times higher after a diagnosis of Alzheimer's in people age 75 to 84 and nearly three times higher in people age 85 and older. More than one-third of all deaths in those age groups were attributable to Alzheimer's disease, the study said.