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Dementia incidence decreases over time among Framingham Heart Study participants

Incidence of dementia significantly decreased over time among participants in the Framingham Heart Study, according to recent findings.

“As the average life expectancy increases, the prevalence of dementia and associated monetary costs are expected to increase exponentially. A few studies have suggested that the age-specific incidence of dementia (ie, the risk of dementia at any specific age) might be decreasing, but these studies either have shown a trend that failed to reach significance or have relied on comparisons of prevalence data that were ascertained at multiple time points,” Claudia L. Satizabal, PhD, of Boston University School of Medicine, and colleagues wrote.

Researchers determined temporal trends in dementia incidence over three decades among participants in the Framingham Heart Study. Analysis included 5,205 individuals aged 60 years or older.

The age- and sex-adjusted 5-year cumulative hazard rates for dementia were 3.6 per 100 persons during the first epoch (late 1970s and early 1980s), 2.8 per 100 persons during the second epoch (late 1980s and early 1990s), 2.2 per 100 persons during the third epoch (late 1990s and early 2000s) and 2 per 100 persons during the fourth epoch (late 2000s and early 2010s).

Compared with the first epoch, dementia incidence declined by 22%, 38% and 44% during the second, third and fourth epochs, respectively.

Risk reduction was observed only among individuals with at least a high school diploma (HR = 0.77; 95% CI, 0.67-0.88).

Prevalence of most vascular risk factors, excluding obesity and diabetes, and risk for dementia associated with stroke, atrial fibrillation or heart failure decreased over time. However, none of these trends fully explain the decrease in dementia incidence.

“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 researchers 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.” – by Amanda Oldt

Disclosure: Please see the full study for a list of all authors’ relevant financial disclosures.