Formula Predicts Alzheimer's Longevity

LEXINGTON, Ky. (April 23, 2010) – The answer to life expectancy of Alzheimer's patients has largely been a guessing game. "'Tell me, doctor, how long do I have?' This is the first question patients ask after receiving a diagnosis of Alzheimer's disease," said Dr. Gregory A. Jicha, a University of Kentucky College of Medicine assistant professor of neurology and faculty member in the UK Sanders-Brown Center on Aging and UK Alzheimer's Disease Research Center.

Jicha, who recently presented his findings at the annual meeting of the American Academy of Neurology in Toronto, Canada, along with his colleagues have developed a simple formula based on a patient's sex, age, and cognitive skills at the time of diagnosis to more accurately predict life expectancy.

"Having a better of idea of how long they will live will allow patients and families to better plan for the future," Jicha said.

He decided to develop the formula after treating a patient who lived 22 years from the time she was diagnosed with Alzheimer's disease.

When Jicha and colleagues scrutinized the records of nearly 1,300 men and women who had been diagnosed with Alzheimer's at the UK Sanders-Brown Center on Aging, they found patients lived anywhere from one to 26 years from when they first started losing their memory.

The researchers started using standard statistical methods to weed out which risk factors best predicted patients' life expectancies.

"We looked at everything from age and education to family history and genetics to medical risk factors such as high blood pressure and heart disease," said Jicha.

Only three factors seemed to matter:  age at first symptoms (older people die more quickly), sex (men fare worse), and level of impairment at diagnosis. Adding in any of the other risk factors didn't change the bottom line, he said.

Using the three factors, the researchers derived a simple formula to predict patients' risks of dying. Then, based on these so-called risk scores, the patients were divided into four categories of life expectancy.

"People in the top fourth lived from four and one-half to nine years, or an average of about seven years, from diagnosis," said Jicha. "Those in the bottom fourth lived from about one year and nine months to five years, or an average of about three years."

"A two- to four-year difference in survival can be incredibly important for budgeting resources. If a patient is going to live longer, you may want to care for them at home longer. Whereas, if we know there will be a rapid progression of disease, you may want to make plans for a nursing home or other care facility."

Other neurologists at the conference said that the fact that the model is science-based gives it some validity.

According to Dr. Stephen Salloway, professor of neurology, Brown University, "We’re not at the point where we can be that specific. You have to couch it a little; tell a patient that 'the majority of people with your stage of disease and your age might be expected to live five to seven years,' for example. But I would not give an exact number."

Jicha agrees. "You always need the caveat. This is a best guess estimate."

For more information about the UK Sanders-Brown Center on Aging, go to www.mc.uky.edu/coa.