Dementia incidence declined every decade for past thirty years

For immediate release: August 14, 2020

Boston, MA—Over the past 30 years, the incidence of dementia has declined an average of 13% every decade in people of European ancestry living in the U.S. or Europe, according to a study led by researchers at Harvard T.H. Chan School of Public Health. Using this trend, the researchers estimate that 15 million fewer people could develop dementia by 2040 in high-income countries than if the incidence of the disease remained steady.

“As the populations of the U.S. and Europe age and life expectancy increases, the prevalence of dementia and Alzheimer’s disease has dramatically increased, due to the larger pool of people in the ages of highest risk,” said Lori Chibnik, assistant professor in the Department of Epidemiology at Harvard Chan School. “However, our analysis shows that the incidence, or rate of new cases, has been declining, translating into fewer new dementia and Alzheimer’s disease cases than what we would have expected.”

The study was published in the August 3, 2020 issue of Neurology.

Currently, 47 million people worldwide live with dementia. Due to the rapidly aging population, the number of people living with the disease is expected to triple over the next 30 years, as is the expected socioeconomic burden associated with dementia.

Previous analyses suggested a decline in incidence over the last 40 years, but most studied smaller populations.

In the current study, Chibnik, who is also an assistant professor of neurology at Massachusetts General Hospital, and her co-authors aggregated data from seven studies that included more than 49,000 individuals with up to 27 years of follow-up. In addition to showing a total decline in incidence, the researchers also saw consistent trends across different populations from North America and Europe. In both men and women, incidence decreased, although men had a greater reduction (24%) than women (8%).

The reasons for the decreased incidence are not clear, although several medical interventions that influence blood pressure, cholesterol, and inflammation may have contributed.

The researchers note due to the ethnic background of the participants included in the study, the results may only apply to a minority of the world population, and they recommend that future analyses include more diverse populations.

“The steady decline in incidence over three decades suggests that preventive efforts involving lifestyle education and health interventions such as blood pressure control and antithrombotic medication can offset at least part of the growing burden of dementia from global gains in life expectancy,” said Chibnik. “Providing this evidence of a decline is the first step toward elucidating the factors at play behind that decline and eventually effective interventions to promote brain health.”

Funding for the study is listed at the end of the article.

“27-Year time trends in dementia incidence in Europe and the United States,” Frank J. Wolters, Lori B. Chibnik, Reem Waziry, Roy Anderson, Claudine Berr, Alexa Beiser, Joshua C. Bis, Deborah Blacker, Daniel Bos, Carol Brayne, Jean-François Dartigues, Sirwan K.L. Darweesh, Kendra L. Davis-Plourde, Frank de Wolf, Stephanie Debette, Carole Dufouil, Myriam Fornage, Jaap Goudsmit, Leslie Grasset, Vilmundur Gudnason, Christoforos Hadjichrysanthou, Catherine Helmer, Mohammad Arfan Ikram, M. Kamran Ikram, Erik Joas, Silke Kern, Lewis H. Kuller, Lenore Launer, Oscar Lopez, Fiona E. Matthews, Kevin McRae-McKee, Osorio Meirelles, Thomas H. Mosley, Jr., Matthew P. Pase, Bruce M. Psaty, Claudia L. Satizabal, Sudha Seshadri, Ingmar Skoog, Blossom C.M. Stephan, Hanna Wetterberg, Mei Mei Wong, Anna Zettergren, and Albert Hofman. Neurology®, online August 3, 2020, doi:10.1212/WNL.00000000.

Photo: Shutterstock/Dark Moon Pictures

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Nicole Rura


Harvard T.H. Chan School of Public Health brings together dedicated experts from many disciplines to educate new generations of global health leaders and produce powerful ideas that improve the lives and health of people everywhere. As a community of leading scientists, educators, and students, we work together to take innovative ideas from the laboratory to people’s lives—not only making scientific breakthroughs, but also working to change individual behaviors, public policies, and health care practices. Each year, more than 400 faculty members at Harvard Chan School teach 1,000-plus full-time students from around the world and train thousands more through online and executive education courses. Founded in 1913 as the Harvard-MIT School of Health Officers, the School is recognized as America’s oldest professional training program in public health.