From Our 2010 Archives
Formula Predicts Alzheimer's Longevity
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Researchers Develop Method to Predict How Long Alzheimer's Patients Will Live
Reviewed By Louise Chang, MD
April 13, 2010 (Toronto) -- "Tell me, doctor, how long do I have?"
That, says Gregory A. Jicha, MD, is the first question patients ask after receiving a diagnosis of Alzheimer's disease.
Until now, the answer has largely been a guessing game. But Jicha and 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," says Jicha, an assistant professor of neurology at the University of Kentucky in Lexington.
He presented his findings at the annual meeting of the American Academy of Neurology.
Wide Range of Life Expectancies
Jicha tells WebMD he decided to develop the formula after treating a patient who lived 22 years from the time of her Alzheimer's diagnosis.
"We typically think of Alzheimer's disease as being rapidly progressing, telling new patients they may have six to eight years, but that really, it is in God's hands," he says.
When Jicha and colleagues scrutinized the records of nearly 1,300 men and women who had been diagnosed with Alzheimer's at their institution, they found patients lived anywhere from one to 26 years from when they first started losing their memory.
So the researchers used standard statistical methods to weed out which risk factors best predicted patients' life expectancies.
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, Jicha says.
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. Those in the bottom fourth lived from about one year and nine months to five years, or an average of about three years, Jicha says.
Jicha gave some examples. Based in the formula, an 82-year-old woman with mild to moderate dementia can be expected to live five years from diagnosis, he says. A 63-year-old man with mild dementia at diagnosis should survive seven years, he says.
Help for Alzheimer's Planning
"A two- to four-year difference in survival can be incredibly important for budgeting resources," Jicha says. "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."
Stephen Salloway, MD, a professor of neurology at Brown University, says that the fact that the model is science-based gives it some validity.
Still, he tells WebMD, "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."
SOURCES: American Academy of Neurology 62nd Annual Meeting, Toronto, April 10-17,