Worldwide, the leading cause of disability and dependence in older adults is dementia. As the life expectancy of the world’s population increases, it is predicted that so will the incidence of dementia. The costs of caring for an aging population needing specialized care due to dementia are expected to increase exponentially.
While study participants with at least a high school diploma exhibited a decreased incidence of dementia and improved cardiovascular health over 20 years, they exhibited an increase in obesity and diabetes over that same time period. Researchers identify that earlier diagnosis and more effective treatment of stroke and heart disease may have contributed to the lower incidence of dementia. Researchers believe there may be a link between stronger hearts and healthier minds.
The Framingham Heart Study began in 1948 by following 5,209 residents living in Framingham, MA. The participants received medical check-ups every two years that included a physician taking detailed history information, a physical examination, and laboratory testing. Beginning in 1971, the offspring of the participants in the original study and the offsprings’ spouses were followed in a special offspring cohort, with their medical assessments occurring every 4 years. Then in 1975 comprehensive neuropsychological testing was conducted on the original study population to assess changes in cognitive health over time.
The researchers evaluated the Framingham Heart Study data in 5-year periods beginning in 1977 and ending in 1994. Since 1977, the incidence of dementia has decreased by an average of 20% per decade in the study population. However, this decline in dementia incidence only occurred in participants who had a high school diploma. Likewise, there was a trend of improved cardiovascular health only in the participants who had at least a high school diploma. While these participants with a high school diploma exhibited a decreased incidence of dementia and improved cardiovascular health, they have exhibited an increased incidence of obesity and diabetes over time. These trends were statistically significant for overall dementia and vascular dementia (type of dementia caused by an impaired supply of blood to the brain, such as in a stroke), but not statistically significant when Alzheimer’s disease patients were evaluated independently. During the first 5-year evaluation period (1975-1979), the risk of dementia among participants who had a stroke was 9 times as high, but in the final 5-year study period (1990-1994) the risk was less than two times as high. Overall, the risk of dementia associated with stroke, atrial fibrillation, or heart failure have decreased over time in the population with a high school diploma, but none of these trends completely explain the decrease in the incidence of dementia. The researchers point out that earlier diagnosis and more effective treatment of stroke and heart disease over time might have contributed to a lower incidence of dementia, especially vascular dementia. The researchers note that they do not have data for some believed risk factors for dementia, such as diet and physical activity, as possible explanations for the observed trends.
Satizabal CL, Beiser AS, Chouraki V, Chêne G, Dufouil C, and Seshadri S. Incidence of Dementia over Three Decades in the Framingham Heart Study. The New England Journal of Medicine. 2016. 374(6): 523-32.