Is Dementia on the Wane?

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In 2014, researchers at the Boston University School of Medicine reported at the Alzheimer’s Association International Conference that the prevalence of dementia among certain populations was decreasing. These findings were not highlighted, in part because the research had not been published in a peer-reviewed journal. And since the specter of a tidal wave of demented baby boomers, draining the coffers of Medicare and Medicaid, is used to raise research funds, this news was met with some wariness.

The work of the Boston University researchers has now been validated; the New England Journal of Medicine published the researchers’ paper last month, confirming that cognitive impairment among the participants in the Framingham Heart Study decreased by 44% over the past 40 years. The average age when cognition issues arise has moved from 80 to 85. This work strikes a very hopeful note at a time when other avenues for effective treatment have been reaching dead ends.

This research stands out from other population based studies because (1) the researchers followed the same population throughout and for more than 40 years, (2) all research subjects underwent cognitive testing at regular intervals, and (3) the researchers could apply consistent diagnostic criteria to all participants to determine the presence of cognitive decline.


Why is dementia on the decline?

The researchers are not sure what has caused the decline in dementia. However, they note that during this same time period, prevalence of stroke, coronary heart disease and atrial fibrillation have also gone down.   Many attribute all these declines to the wide-spread use of statins, blood pressure medication, and healthier diets.


Possible Exception: Education

There was one subset of subjects that did not experience a decline in dementia: those without a high school education.   It is not known why education level influences dementia risk. One theory is that people who have more education develop “cognitive reserves” that protect against cognitive deficits.

Others, noting the many exceptionally well educated individuals who develop cognitive problems think the lack of a high school education is a proxy for other factors that contribute to health problems: lower wages, less medical care, less healthy diets, more stress.


Possible Exception: Race and Ethnicity

The Framingham Heart Study was started in 1948 and its subjects were overwhelmingly white. Subsequent cohorts in the study are the offspring of the original subjects, limiting the possible diversification of the study subjects. There are other studies that seem to indicate that people of color have a higher risk of developing dementia. This research does not establish if race or ethnicity plays a role in development of dementia.


How Hopeful Should We Be?

There is no question that this is good news. It suggests that control of conditions that lead to heart disease will also prevent or delay the onset of dementia. However, this news is tempered by the following:

  1. Although the prevalence of dementia may be decreasing, the number of people over 65, and therefore at risk for dementia, is steadily growing. It may be that there will be fewer people who will be diagnosed with dementia, but dementia will continue to be a major senior health challenge for decades.
  2. Use of statins and blood pressure medication may delay the onset of dementia, but diabetes and obesity may accelerate its onset.
  3. Because researchers will need to raise huge funds to unlock the mysteries of Alzheimer’s and other cognitive impairments, there will be a sharpened need to understand how this disease impacts populations of people in order to best focus on the most effective treatment possibilities.



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