Drop-Off in Dementia in Northern Manhattan Echoes National Trend

Dementia, including Alzheimer’s disease, is on the decline among northern Manhattan seniors, following national and global trends.

The findings, by researchers at Columbia University Irving Medical Center, were reported last month in the Journal of Alzheimer’s Disease.

The study found a 41 percent drop in dementia risk for seniors from Washington Heights and Inwood who joined a Columbia University-sponsored aging study in 1999 compared with a similar group that enrolled in 1992. Both groups included a multi-ethnic mix of non-Hispanic whites, African-Americans, and Hispanics.

“It’s important to look at a variety of populations so that we can determine if changes in dementia rates are occurring on a local, national, or global trend and to identify both common and population-specific factors that may be contributing to the overall picture,” says James Noble, MD, assistant professor of neurology at Columbia University Irving Medical Center (CUIMC) and co-lead author of the study. “This is especially true in the U.S., where there are often racial, ethnic, and geographic disparities in health that are attributable to a variety of factors, from access to care to education.”

The researchers looked at dementia incidence in more than 4,300 adults over age 65. The risk of dementia fell in all ethnic groups—by 48 percent in African-Americans, 40 percent in whites, and 36 percent in Hispanics. Whites and African-Americans who were 75 and older saw the greatest drop in risk.

The study found a decrease in stroke and smoking rates, particularly in African-Americans and Hispanics. However, some vascular risk factors, including diabetes, hypertension, and heart disease, increased in all groups.

“Though we can’t know for certain, it’s possible that more timely diagnosis and aggressive treatment of vascular risk factors may be an important reason for the decline in dementia rates,” says Dr. Noble.

Increased education in whites and African-Americans, another study finding, may have also played an important role in reducing dementia rates in those groups.

Education may help prevent dementia by increasing cognitive reserve—adaptive changes in the brain that make it more resistant to showing symptoms of neurodegenerative diseases—as one study has suggested. It could also just be a marker for improved overall health.

“We know that there is a complex interaction between some genes and modifiable dementia risk factors,” Dr. Noble says. “Although a study like this cannot determine cause and effect, it suggests that we may want to prioritize research on how education and reduction of vascular risk factors may alleviate the future burden of dementia.”



The study is titled “Secular Trends in the Incidence of Dementia in a Multi-Ethnic Community.”

The other contributors, all from CUIMC, are Nicole Schupf, Jennifer J. Manly, Howard Andrews, Ming-Xing Tang, and Richard Mayeux.

The study was supported by the National Institutes of Health (P01AG07232, R01AG037212, RF1AG054023, and UL1TR001873).

Dr. Noble receives consulting fees from Prophase. The other authors report no financial or other conflicts of interests.