February 20, 2008
People with Alzheimer's disease and other forms of dementia live, on average, about four and a half years after their condition is diagnosed. This is based mainly on people in their 80s and 90s who have recently developed Alzheimer's. In general, people with Alzheimer's have about one-half the life expectancy, after diagnosis, than people who do not have Alzheimer's. The present findings are from a large collaborative study group in the United Kingdom. The findings appeared in the British Medical Journal.
The findings may help those who care for a loved one with Alzheimer's disease to better plan for the future. The results highlight that dementia is a chronic condition, and that people with Alzheimer's will likely need care for a number of years after their diagnosis. At the same time, the average survival time is under five years, with wide variations depending on age and physical condition at the time of diagnosis.
Researchers at the University of Cambridge followed more than 13,000 men and women, aged 65 and up, for 14 years. During that time, 438 of the study participants developed Alzheimer's disease or another form of dementia, and more than 80 percent of those with dementia died.
Overall, men with dementia did not live as long as women with the disease: 4.1 years for men, versus 4.6 years for women. And men or women in frail physical shape did not tend to live as long as their more physically robust peers. It's important to note that these numbers mainly reflect people in their 80s and 90s. Younger people who get Alzheimer's generally live longer. The rule of thumb is to assume half the life expectancy of a normal person of the same age.
How far advanced the cognitive decline was, on the other hand, did not sharply influence how long someone tended to live after being diagnosed with Alzheimer's disease, according to the present study. Nor did being married, which some studies have linked with improved survival. People who lived at home tended to live slightly longer than those living in a nursing home, though the differences were not statistically significant.
The median age at death was 90 for women and 87 for men. Average survival times varied widely, however, depending on the age at diagnosis. Those who were diagnosed at a younger age, from 65 to 69, lived an average of 10.7 years after diagnsosis. Those diagnosed in their 90s, on the other hand, lived an average of 3.8 years.
People with more education tended to live slightly less long than those who were less educated. However, the difference was not significant.
A Growing Problem
While life expectancies are increasing around the globe, one side effect of the aging population is a growing incidence of Alzheimer's disease. Worldwide, more than 80 million people may suffer from dementia by the year 2040.
Knowing how long a person with dementia might survive is important for caregivers and health policymakers. People with Alzheimer's and other forms of dementia have markedly decreased life expectancies. They are two to four times more likely to die than someone of the same age who does not have dementia.
Various earlier reports have shown wide variation in expected survival after a diagnosis of dementia. President Ronald Reagan, for example, lived more than a decade with the disease. Some cases may progress very rapidly. Others may linger for decades.
Many factors come into play when estimating how long someone with Alzheimer's might survive. This study adds additional data about what caregivers might expect when preparing for a future of Alzheimer's.
Jing Xie, Carol Brayne, Fiona E. Matthews and the Medical Research Council Cognitive Function and Ageing Study Collaborators: "Survival Times in People With Dementia: Analysis from Population Based Cohort Study With 14 Year Follow-Up." British Medical Journal, online edition, January 11, 2008