Fewer New Cases of Dementia in Last Four Decades

Despite worries of an increase in dementia cases over the next few decades due to an aging population, a new study suggests that the rate of new cases of dementia actually may be decreasing. The most noticeable decline was found in new cases of stroke-related dementia.

The findings, based on data from the Framingham Heart Study (FHS), provide hope that some cases of dementia might be preventable or delayed and encourages funding agencies and the scientific community to further explore demographic, lifestyle and environmental factors underlying this positive trend.

FHS participants have been continuously watched for signs of cognitive decline and dementia since 1975. Thanks to a rigorous collection of information, FHS researchers have been able to diagnose Alzheimer’s disease and other dementias using a consistent set of criteria. These include FHS exams, outside clinical records, interviews with family members, and the examination of participants suspected of having a neurological problem.

Looking at four distinct periods in the late 1970s, late 1980s, 1990s, and 2000s, the researchers found that there was a progressive decline in cases of dementia at a given age, with an average reduction of 20 percent per decade since the 1970s.

The most noticeable decline was among cases of dementia caused by vascular diseases, such as stroke. There also was a decreasing impact of heart diseases, which suggests the importance of effective stroke treatment and prevention of heart disease. Interestingly, the decline in dementia incidence was found only in individuals with high school education and above.

Currently, there are no effective treatments to prevent or cure dementia, said corresponding author Sudha Seshadri, M.D., professor of neurology at Boston University School of Medicine and FHS senior investigator. But she said this study offers hope that some of the dementia cases might be preventable — or at least delayed — through primary (keep the disease process from starting) or secondary (keep it from progressing to clinically obvious dementia) prevention.

“Effective prevention could diminish in some measure the projected explosion in the number of persons affected with the disease in the next few decades,” Seshadri said.

The authors note that the sample population is overwhelmingly of European ancestry and that further studies are needed to extend the findings to other populations. Furthermore, the researchers did not look at the effects of key variables such as changes in diet and exercise.

Despite these limitations, “it is very likely that primary and secondary prevention and better management of cardiovascular diseases and stroke, and their risk factors, might offer new opportunities to slow down the currently projected burden of dementia for the coming years ” said Dr. Carole Dufouil, Inserm research director in Bordeaux (France).

Yet, the researchers caution that this does not mean that the total number of persons with dementia will decrease anytime soon. Since baby boomers are aging and people are living longer, the burden of dementia will continue to grow.

The findings are published in the New England Journal of Medicine.

Source: Boston University Medical Center

 
Dementia photo by shutterstock.