From Baylor College of Medicine:

Persistent use of anti-dementia drugs during the course of Alzheimer's disease appears to increase life expectancy, said researchers at Baylor College of Medicine in Houston at a presentation at the Alzheimer's Association International Conference on Alzheimer's Disease 2008 in Chicago today.

"The life span of those with Alzheimer's is known to be shorter than that of cognitively healthy people," said Dr. Susan Rountree, assistant professor of neurology at BCM and lead author of the study. "Our findings suggest that those who took anti-dementia drugs more persistently, or longer time intervals, lived longer than those who took the medications for shorter time periods."

Additional 3.12 years
The study followed 641 people suffering from Alzheimer's disease between 1989 and 2005. All were on one or more commercially available anti-dementia drugs for varying amounts of time during the course of their illness. The drugs included donepezil, galantamine, rivastigmine, tacrine or memantine.

Researchers gave each subject a "persistency" score derived by dividing the total years that they took the medication by the total years that they had symptoms of the disease. They used these results to divide the patients into four quartiles, lowest to highest.

"We did take into account a variety of factors that influence life expectancy such as age and other diseases," Rountree said.

Those in the first quartile, the lowest persistency group, were 2.4 times more likely to die than those in the fourth quartile, or highest persistency group. Those within the second and third quartiles had an increased risk of death of 2.2 times and 1.5 times respectively, compared to those with the highest score. Those who had the higher scores lived, on average, 3.12 years longer than those with the lower scores.