Decades long decline in Dementia

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