According to the Centers for Disease Control and Prevention (CDC), Alzheimer’s disease is the sixth leading cause of death in the United States responsible for more that 83,000 lives in 2010. A new study from Rush University Medical Center in Chicago suggests that Alzheimer’s may actually claim half a million lives each year, nearly as many lives as the top two killers – heart disease (600,000) and cancer (575,000).

Published in the journal Neurology, Bryan D. James of Rush University Medical Center and colleagues monitored 2,566 individuals over the age of 65 who received annual testing for dementia – a decline in memory and other thinking skills. After an average of eight years, 1,090 of the individuals died. 

A total of 559 individuals developed Alzheimer’s after the start of the test. Also, the individuals died by an average of four years after their diagnoses.

After death, the individuals’ bodies were analyzed via autopsy to confirm that Alzheimer’s disease was the cause of death. Approximately 90 percent of the individuals died from the mental condition. James believes that Alzheimer’s and many other mental conditions go underreported.  

The CDC ranks the cause of death based on what is reported on death certificates. James explains, "Death certificates often list the immediate cause of death, such as pneumonia, rather than listing dementia as an underlying cause.”

The researchers found that the death rate was more than four times higher for participants between the ages of 75 and 84 after an Alzheimer’s diagnosis, and nearly three times higher for people over the age the age of 85. James says that though the CDC reported 83,494 individuals died from Alzheimer’s, the death toll can close to six times higher to approximately 503,400 deaths.

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.”