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A study by Satizabal et al published
in the NEJM found that dementia rates
fell steadily over the past three decades, likely due to declining rates of
heart disease.
The study analyzed data
collected since 1975 from the Framingham Heart Study
and included 5205 persons 60 years of age or older. The authors compared interactions
between epoch and age, sex, apolipoprotein E ε4 status, educational level, as
well as the effects of vascular risk factors such as cardiovascular disease on the
prevalence of dementia.
The 5-year age-and sex-adjusted
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 2.0 per 100 persons during the fourth epoch (late
2000s and early 2010s). Relative to the incidence during the first epoch, the
incidence declined 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. The prevalence of most vascular risk
factors (except obesity and diabetes) and the risk of dementia associated with
stroke, atrial fibrillation, or heart failure have decreased over time, but
none of these trends completely explain the decrease in the incidence of the
disease.
The authors concluded that the
incidence of dementia has declined over the course of three decades.
N Engl J Med 2016; 374:523-532
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