The rate of Alzheimer's disease and other dementias is falling in the United States and some other rich countries — good news about an epidemic that is still growing simply because more people are living to an old age, new studies show.
An American over age 60 today has a 44 percent lower chance of developing dementia than a similar-aged person did roughly 30 years ago, the longest study of these trends in the U.S. concluded.
Dementia rates also are down in Germany, a study there found.
"For an individual, the actual risk of dementia seems to have declined," probably due to more education and control of health factors such as cholesterol and blood pressure, said Dr. Kenneth Langa. He is a University of Michigan expert on aging who discussed the studies Tuesday at the Alzheimer's Association International Conference in Copenhagen.
The opposite is occurring in some poor countries that have lagged on education and health, where dementia seems to be rising.
More than 5.4 million Americans and 35 million people worldwide have Alzheimer's, the most common form of dementia. It has no cure and current drugs only temporarily ease symptoms.
A drop in rates is a silver lining in the so-called silver tsunami — the expected wave of age-related health problems from an older population. Alzheimer's will remain a major public health issue, but countries where rates are dropping may be able to lower current projections for spending and needed services, experts said.
Recent studies from the Netherlands, Sweden and England have suggested a decline, and the new research extends this look to some other parts of the world.
THE UNITED STATES
The federally funded Framingham study tracked new dementia cases among several thousand people 60 and older in five-year periods starting in 1978, 1989, 1996 and 2006. Compared with the first period, new cases were 22 percent lower in the second one, 38 percent lower in the third and 44 percent lower in the fourth one.