What Does New NEJM Study on Dementia Really Mean?

What Does New NEJM Study on Dementia Really Mean?

Jason Karlawish Parses Cognitive Decline Trends


Jason Karlawish, MD

In a column in Forbes and a video posted to the University of Pennsylvania Memory Center website, Perelman School of Medicine Professor Jason Karlawish discusses a new study that found the risk of developing dementia has declined over the last 30 years.

Karlawish, MD, a Senior Fellow at the Leonard Davis Institute of Health Economics (LDI) and Co-Director of the Penn Memory Center, noted that the findings run counter to widespread assumptions and policymaker predictions that dementia is on the increase in a population that is living longer.

Significant 30 year decline
Originally published in the New England Journal of Medicine, the study, led by Claudia Satizabal, PhD, of the Boston University School of Medicine, used data from the NIH-funded Framingham Heart Study. In 1977 that project began tracking a large group of older adults who were free of dementia and, over the next three decades, documented the development of dementia among them. During that period the rate at which dementia developed declined from 3.6 cases per 100 persons to 2 cases per 100 persons.

In another column in Forbes, Karlawish predicts the newly launched U.S. national plan to prevent Alzheimer's by 2025 will result in more accurate genetic and brain scanning tests to predict individual risk for the disease. This will happen simultaneously with now-underway large clinical trials exploring new Alzheimer's related drugs.

"The promise of Alzheimer’s disease prevention," Karlawish continued, "is that someday, as part of a routine evidence-based exam, we’ll undergo tests to determine whether we're at risk. If we are, prescriptions will follow for drugs that slow cognitive decline. This marriage of a test and a drug -- the popular term is a 'theranostic' -- is akin to the cholesterol-test-into-statin-drug duet that typifies life after 50." 

However, Karlawish, who is an Alzheimer's disease specialist, noted that the study data also shows that while the general risk of dementia declined, the risk of dementia specifically caused by Alzheimer's did not.

'Another provocative finding'
"The study shows that the risk of dementia caused by vascular disease explains most of the decline in dementia risk," he said in his video. "It also has another provocative finding. Namely, that this reduction in the risk of developing dementia was only seen in individuals who had at least a high school education. That's very interesting because it's saying that an exposure occurring no later than the ages of 18 and 24 years of age has a real influence on your cognitive health 50 years later."

He said that it appeared to be yet another bit of data demonstrating how education "leads to subsequent social and economic opportunities or lack of opportunities that can influence health and well being with aging."

Policymakers and scientists may also find an important message in the findings, Karlawish suggested. 

New scientific approach needed
"This study," he continued, "shows that efforts to project the future prevelance of dementia need to be revisited," he said. "Currently our approaches rely on using a static estimate on what the risk is. We assume the risk now is the risk that will be 30 years from now and using that, we project how many people will have dementia in 30 or 40 years...we're going to have to switch from simpler methods to probably some more complicated micro-simulation methods."