Framingham Study Suggests Dementia Rates May Be Falling

Many experts predict that as people live longer, the prevalence of dementia will climb. However, a study published in the New England Journal of Medicine now suggests the incidence of dementia may be falling.

Researchers from Boston University School Medicine analyzed data from 5,205 people aged 60 and older who were participants in the Framingham Heart Study, a community-based, longitudinal cohort study that was initiated in 1948. Since 1975, the cognitive status of the original cohort has been regularly monitored via the Mini-Mental State Examination, neurological and neuropsychological examinations, and subjective memory questioning.

By using statistical models adjusted for age and sex, the researchers determined the incidence of dementia during each of four distinct time periods: from the late 1970s to early 1980s (first epoch), from the late 1980s to early 1990s (second epoch), from the late 1990s to the early 2000s (third epoch), and from the late 2000s to the early 2010s (fourth epoch). The researchers also examined the interactions between epoch and age, sex, apolipoprotein E ε4 status, and educational level.

The researchers found a progressive decline in dementia over the 30-year period, with incidence rates, relative to the first epoch, declining by 22%, 38%, and 44% during the second, third, and fourth epochs, respectively. This risk reduction was observed only among persons who had at least a high school diploma. In parallel with the trend toward a lower incidence of dementia, participants in the Framingham Heart Study also had improvements in most indicators of cardiovascular health, with the exception of a trend toward increasing prevalence of diabetes and obesity.

“Although projections suggest an exploding burden of dementia over the next four decades owing to an increasing number of older persons at risk, primary and secondary prevention might be key to diminishing the magnitude of this expected increase,” the authors wrote. “Our study offers cautious hope that some cases of dementia might be preventable or at least delayed. 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.”

For related information, see the Psychiatric News article “Cardiovascular Risk Factors May Serve as Early Indicator of Cognitive Decline.”

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Cancer Survivors Have Lower Alzheimer’s Risk

New results from the Framingham Heart Study suggest that cancer survivors have a lower risk of developing Alzheimer’s disease. Researchers reported online March 12 in the BMJ the results of their 1986 to 1990 study of 1,278 participants with and without a history of cancer who were aged 65 or older and free of dementia at baseline. They concluded that cancer survivors had a lower risk of Alzheimer’s disease than those without cancer, and patients with Alzheimer’s disease had a lower risk of incident cancer. The risk of Alzheimer’s disease was lower in survivors of smoking-related cancers and was not primarily explained by survival bias. “This pattern for cancer is similar to that seen in Parkinson’s disease and suggests an inverse association between cancer and neurodegeneration,” said the researchers.

Learn more about the neurodegeneration associated with Alzheimer’s disease in the Clinical Manual of Alzheimer Disease and Other Dementias, available from American Psychiatric Publishing here.

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