According to the Centers for Disease Control and Prevention, Alzheimer's disease is the sixth leading cause of death in the US, trailing the top two killers, heart disease and cancer. But a new study suggests Alzheimer's actually contributes to nearly as many deaths as the top two, pointing to incorrect identification of the disease as the real reason for death.
The researchers, led by Bryan D. James of Rush University Medical Center in Chicago, published the results of their study in Neurology, the journal of the American Academy of Neurology.
To conduct their study, they followed 2,566 people over the age of 65 who received annual testing for dementia. After an average of 8 years, 1,090 of the participants died.
Of the participants who did not have dementia at the start of the study, a total of 559 developed the neurological condition, and the average time from diagnosis to when they died was about 4 years.
After the participants died, an autopsy was performed, and it confirmed Alzheimer's disease for about 90% of the patients who were clinically diagnosed, the researchers say.
James explains that Alzheimer's and other dementias are commonly under-reported. "Death certificates often list the immediate cause of death, such as pneumonia, rather than listing dementia as an underlying cause," he says.
The authors note that the rankings from the Centers for Disease Control and Prevention (CDC) for causes of death are based on what is reported on death certificates.
Deaths from Alzheimer's 'six times higher than reported'
After analyzing their data, the team found that the death rate was over four times higher for participants between the ages of 75 and 84 after an Alzheimer's diagnosis, and it was nearly three times higher for people over the age of 85.
The researchers note that more than one third of deaths in those age groups were due to Alzheimer's disease.
James says this means an estimated 503,400 deaths were attributable to Alzheimer's in the US population over the age of 75 in 2010. However, the number reported by the CDC is 83,494, which means the study's estimate is nearly six times higher.
He notes that attempts to pinpoint a single cause of death is not always accurate for most elderly people, since multiple health issues can be responsible. James adds:
"The estimates generated by our analysis suggest that deaths from Alzheimer's disease far exceed the numbers reported by the CDC and those listed on death certificates."
Quite a bit of research has recently gone into identifying key causes of dementia. Medical News Today recently reported on a study that suggested eating grilled meat increases risk of Alzheimer's.
Another study recently suggested infections impair the brain's ability to make memories, while another claimed a byproduct of dichlorodiphenyltrichloroethane (DDT) in the blood is linked to increased risk of Alzheimer's.
Given that Alzheimer's affects so many people in the US, the researchers say understanding the disease is vital.
"Determining the true effects of dementia in this country is important for raising public awareness and identifying research priorities regarding this epidemic," James says.