Dementia Dropping, But Will the Trend Continue?

Since they really don't know why there is absolutely no way to keep it dropping.
http://www.medpagetoday.com/Neurology/Dementia/56128?
The incidence of dementia in the U.S. has fallen over the last 3 decades, but that shouldn't lull providers into a false sense of complacency, researchers said.
In an analysis of data from the Framingham Heart Study, dementia incidence fell about 20% per decade since 1977, driven by declines in vascular dementia -- not Alzheimer's disease, Sudha Seshadri, MD, of Boston University, and colleagues reported in the New England Journal of Medicine
The drop has paralleled improvements in cardiovascular health and risk factor control, even though some contributors to heart disease -- and, potentially, dementia -- such as diabetes and obesity have been on the rise, they said.
Also, the significant declines in dementia were seen only among those who had at least a high school education, they noted.
"Our study offers cautious hope that some cases of dementia might be preventable or at least delayed," they wrote. "However, it also emphasizes our incomplete understanding of the observed temporal trend and the need for further exploration of factors that contribute to this decline in order to better understand and possibly accelerate this beneficial trend."
Researchers contacted by MedPage Today agreed that the findings do imply some hope for prevention, but physicians need to remain vigilant about cardiovascular risk factor control. And incidence can still rise as the population ages, said Alan Lerner, MD, of of UH Case Medical Center, who wasn't involved in the study, but warned that the "fight against dementia is far from over."
"The risk is still palpable, the aging of the population is still real, so in the real world we're still looking for prevention, whether that's secondary prevention for people with established risk factors such as a genetic predisposition or Alzheimer's disease, as well as control of vascular risk factors," Lerner said. "We know what's good for the heart is good for the brain ... so control of cardiovascular risk factors and leading a [healthy lifestyle] are still very important."
"So although in the overall sense the declining incidence of dementia would imply decreased risk," he added, "that risk has not gone away, and we need to continue to be vigilant and work to prevent dementia."
The Framingham Heart Study started in 1948, and dementia has been monitored since 1975. The current analysis included 5,205 people age 60 and up. There were a total of 371 cases of dementia over the study period.
Seshadri and colleagues found that the incidence of dementia fell during four different time periods in the study:

• Late 70s to early 80s: 3.6 per 100
• Late 80s to early 90s: 2.8 per 100
• Late 90s to early 2000s: 2.2 per 100
• Late 2000s to early 2010s: 2.0 per 100

Compared with the first time period, dementia incidence fell by 22%, 38%, and 44% over the next three time periods, respectively, they reported.
The findings also suggest that morbidity has been compressed, researchers said, given that the average age of onset of dementia has been increasing steadily -- from 80 in the earliest period to 85 in the latest.
Yet the overall risk reduction was seen only among those who had at least a high school education, who had about a 23% decline in risk per decade (P<0.001). There was no lowering of risk for those who didn't have a high school diploma, the researchers said.
They cautioned, however, that the proportion of those who didn't have a high school education was low during the last two time periods, so it precluded a deeper investigation into the trends in incidence of dementia in this subgroup.
During the course of the study, rates of cardiovascular events fell, while use of antihypertensives to control cardiovascular risk factors rose -- suggesting that earlier diagnosis and more effective treatment of stroke and heart disease may have contributed to a lower incidence of dementia, particularly vascular dementia. This benefit was also more pronounced in the population that had at least a high school education, the researchers said.
Seshadri and colleagues noted that the decline in incidence of Alzheimer's wasn't significant -- although analyses of dementia subtypes were based on smaller numbers than those for overall dementia, they cautioned.
In an accompanying editorial, David Jones MD, PhD, of Harvard, and Jeremy Greene, MD, PhD, of Johns Hopkins, warned that the data, while they align with other recent research, still reflect only one population sample.
"Whether they are accepted as conclusive evidence of a broad-based reduction in dementia incidence will become clear only over time," they wrote.
Also, since trajectories of chronic disease incidence "reflect complex interactions of many causal factors, it will almost always be uncertain whether decreases will continue or reverse," they added, citing the cardiovascular disease example. While heart disease began to wane in the mid-1960s -- and has continued to do so -- the ongoing increases in obesity and diabetes could reverse that trend. These two trends could affect dementia outcomes as well, they said.
Jason Karlawish, MD, of the University of Pennsylvania, who wasn't involved in the study, noted that the findings suggest researchers may need to revise the methods used to estimate the overall prevalence of dementia.
"We can't assume a static incidence," he said. "The incidence of risk factors is changing as well. Our projections didn't live up to our expectations with cardiovascular disease."