A new study has found that dementia rates among people 65 and older in England and Wales have plummeted by 25% over the past two decades, to 6.2% from 8.3%, a trend that researchers say is probably occurring across developed countries and that could have major social and economic implications for families and societies.
Another recent study, conducted in Denmark, found that people in their 90s who were given a standard test of mental ability in 2010 scored substantially better than people who had reached their 90s a decade earlier. Nearly one-quarter of those assessed in 2010 scored at the highest level, a rate twice that of those tested in 1998. The percentage of subjects severely impaired fell to 17% from 22%.
The British study, published Tuesday in The Lancet, and the Danish one, which was released last week, also in The Lancet, soften alarms sounded by advocacy groups and some public health officials who have forecast a rapid rise in the number of people with dementia, as well as in the costs of caring for them.
Yet experts on aging said the studies also confirmed something they had suspected but had difficulty proving: that dementia rates would fall and mental acuity improve as the population grew healthier and better educated. The incidence of dementia is lower among those better educated, and among those who control their blood pressure and cholesterol, possibly because some dementia is caused by ministrokes and other vascular damage. So as populations controlled cardiovascular risk factors better and had more years of schooling, it made sense that the risk of dementia might decrease. A half-dozen previous studies had hinted that the rate was falling, but they had flaws that led some to doubt the conclusions.
{{/usCountry}}Yet experts on aging said the studies also confirmed something they had suspected but had difficulty proving: that dementia rates would fall and mental acuity improve as the population grew healthier and better educated. The incidence of dementia is lower among those better educated, and among those who control their blood pressure and cholesterol, possibly because some dementia is caused by ministrokes and other vascular damage. So as populations controlled cardiovascular risk factors better and had more years of schooling, it made sense that the risk of dementia might decrease. A half-dozen previous studies had hinted that the rate was falling, but they had flaws that led some to doubt the conclusions.
{{/usCountry}}Researchers said the two new studies were the strongest, most credible evidence yet that their hunch had been right. Dallas Anderson, an expert on the epidemiology of dementia at the National Institute on Aging, the principal financer of dementia research in the United States, said the new studies were “rigorous and are strong evidence.”
“It’s terrific news,” said Dr. P. Murali Doraiswamy, an Alzheimer’s researcher at Duke University, who was not involved in the new studies. It means, he said, that the common assumption that every successive generation will have the same risk for dementia does not hold true.
But Maria Carrillo, vice president of medical and scientific relations at the Alzheimer’s Association, an advocacy group, was not convinced that the trends were real or that they held for the United States.
The studies assessed dementia, which includes Alzheimer’s disease but also other conditions that can make mental functioning deteriorate. Richard Suzman, the director of the division of behavioral and social research at the National Institute on Aging, said it was not possible to know from the new studies whether Alzheimer’s was becoming more or less prevalent. NYT