Alzheimer’s, the most common form of dementia that affects up to five million Americans, may be the cause of death for a far larger number of people than previously reported. The CDC estimates that about 83,494 people die from Alzheimer's every year in the U.S., but new research suggests the real number may be five times higher.

According to the research, which will be published in the print issue of Neurology, “Alzheimer’s disease and other dementias are under-reported on death certificates and medical records,” Bryan D. James, an author of the study and a researcher at Rush University Medical Center in Chicago, said in a press release. “Death certificates often list the immediate cause of death, such as pneumonia, rather than listing dementia as an underlying cause.”

Currently, Alzheimer’s is considered the 6th most likely disease to kill you in the U.S., according to the Centers for Disease Control and Prevention (CDC). Heart disease and cancer take the first two spots. The CDC bases its list on what is reported in death certificates, and states that for every 100,000 people in the U.S., 27 die from Alzheimer’s. However, death certificates usually only list one cause of death; Alzheimer's is often the underlying disease that can lead to pneumonia or other illnesses, which may explain why it's under-reported. Alzheimer’s is the most common form of dementia and causes impaired memory, language, and reasoning skills in adults typically over the age of 60. However, Alzheimer’s is difficult to diagnose: it’s only when the person dies and is autopsied that it can truly be confirmed.

There is no cure for the disease, but treatment and therapy are available. Maintaining a healthy lifestyle that involves physical activity and mental exercises can actually improve symptoms, though it doesn't stop the disease. The Alzheimer's Association states on its website that the disease is "the only cause of death among the top 10 in America without a way to prevent it, cure it or even slow its progression."

The authors of the study reviewed 2,566 people who were ages 65 or older, with an average age of 78, and who received annual dementia tests. After an average of eight years, 1,090 of the participants died. There were 559 people who didn’t have dementia at the beginning of the study who ultimately developed Alzheimer’s disease; on average, people with Alzheimer’s died about four years after they were diagnosed.

According to James, the study revealed that there were some 503,400 deaths from Alzheimer’s in the U.S. in 2010, among people over the age of 75. This number is five to six times higher than the one reported by the CDC: 83,494.

According to the Alzheimer's Association, the number of people living with the disease is going to increase significantly in the next several years. James believes that finding a better way to track the number of deaths that are caused inherently by Alzheimer’s or dementia — rather than a corresponding illness like pneumonia — is “important for raising public awareness and identifying research priorities regarding this epidemic.”