Persistent use of anti-dementia drugs during Alzheimer's disease appears to increase life expectancy, said Baylor College of Medicine researchers during a July 30 presentation at the Alzheimer's Association's International Conference in Chicago.

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

The study followed 641 Alzheimer's patients 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 they took the medication by the total years they had symptoms of the disease. Patients were divided into four quartiles from lowest to highest, based on their persistency scores.

"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.

Rountree said the study's findings will help create a model of what a patient can expect, and help families to plan better for their loved one's care.