Formula Predicts Alzheimer's Longevity
Researchers Develop Method to Predict How Long Alzheimer's Patients Will Live
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.
"We looked at everything from age and education to family history and genetics to medical risk factors like high blood pressure and heart disease," Jicha says.
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.