The declining rate is linked to higher levels of education and better control of heart disease and high blood pressure
At a time when the only medical treatments available for dementia are providing, at best, a little help, there is some good news about this dreaded disease.
Studies in England, Wales, Denmark and the United States have found that dementia rates are going down.
In England and Wales, it was found that dementia rates have plummeted by 25 percent over the last 20 years among people 65 years and older. Researchers say the same trend is probably occurring across all developed countries.
Meanwhile, in a study in Denmark people in their 90s given a standard test of mental ability scored significantly higher than people in that same age group a decade earlier.
Nearly one-quarter of those tested in 2010 scored at the highest level, twice that of those tested in 1998. At the same time, the percentage of subjects who were severely impaired dropped to 17 percent in 2008 from 22 percent in 19988.
Both of these studies were reported in the Lancet.
As well, a study on dementia rates reported in the Journal of the American Medical Association showed similar trends.
In this study, dementia rates fell to 8.8 percent from 11.6 percent over the 12 year span.
Put another way, if the rate of dementia in 2012 had been what it was in 2000, more than one million additional people would be living with dementia in the U.S.
This is definitely good news, but why is it happening?
Researchers believe the answer may be one or a combination of factors.
People reaching age 65 or 95 are probably going to be better educated than those of the same age 20 or even 10 years earlier.
“More years of formal education is associated with a reduced risk of dementia, likely through multiple causal pathways, including a direct effect on brain development and function (i.e., the building of ‘cognitive reserve’), health behaviours, as well as the general health advantages of having more wealth and opportunities,” the JAMA study says.
The number of people with less than a high school diploma in the U.S. decreased to 21 percent in 2012 from 33 percent in 2000. As well, the proportion of those with a college degree or higher rose to 24 percent from 17 percent.
Also, better control of risk factors for heart disease, high blood pressure and high cholesterol may play a role. Controlling these factors could help reduce the risk of vascular-related dementia, which may be because some dementia is caused by mini-strokes and other vascular damage.
Several researchers had previously suspected these trends, and a half dozen previous studies had hinted that the rate of dementia was falling.