“Interestingly, we were able to establish harmful effects on human health at levels below current air pollution standards,” says first author Giulia Grande, researcher at the Department of Neurobiology, Care Sciences and Society at Karolinska Institutet. “Our findings suggest air pollution does play a role in the development of dementia, and mainly through the intermediate step of cardiovascular disease and especially stroke.”

For the last five years of exposure, the risk of dementia increased by more than 50 percent per interquartile range (IQR) difference in mean PM 2.5 levels and by 14 percent per IQR in nitrogen oxide. Earlier exposures seemed less important. Heart failure and ischemic heart disease both enhanced the dementia risk and stroke explained almost 50 percent of air pollution-related dementia cases, according to the researchers.

Need to optimize treatment of CVD

“Air pollution is an established risk factor for cardiovascular health and because CVD accelerates cognitive decline, we believe exposure to air pollution might negatively affect cognition indirectly,” says Giulia Grande. “In our study, virtually all of the association of air pollution with dementia seemed to be through the presence or the development of CVD, adding more reason to reduce emissions and optimize treatment of concurrent CVD and related risk factors, particularly for people living in the most polluted areas of our cities."

The study was funded by the Swedish National Study on Aging and Care in Kungsholmen, the Swedish Ministry of Health and Social Affairs, the Swedish Research Council, Karolinska Institutet’s funding for doctoral education and the Swedish Research Council for Health, Working Life and Welfare.

Publication

“The role of cardiovascular disease in the association of long-term exposure to air pollution and the risk of dementia,” Giulia Grande, Petter L.S. Ljungman, Kristina Eneroth, Tom Bellander, Debora Rizzuto, JAMA Neurology, online March 30, 2020, doi: 10.1001/jamaneurol.2019.4914