Lifestyle, genetics and age all play a role in the development of neurodegenerative diseases like Alzheimer’s. But environmental factors like air pollution may play an even bigger role in a person’s risk of dementia than researchers previously thought.
In a new study out of Sweden, researchers found that both heart disease and exposure to air pollution significantly increased the risk for developing dementia.
“[E]vidence concerning the association of exposure to air pollution and brain pathology is growing, in particular regarding neurodegeneration, excessive oxidative stress, and neuroinflammation,” the authors wrote in the study.
“In addition, epidemiological and experimental evidence demonstrate an association of higher levels of pollutants in the air with faster cognitive decline.”
The researchers examined 2,927 people who were involved in the Swedish National Study on Aging and Care in Kungsholmen from 2001-2013. The participants had lived in central Stockholm from 2001 to 2004, and were over the age of 60. The researchers then followed up on the participants every few years, up until 2013 to track their association to developing dementia.
The results showed that higher levels of exposure to air pollution — specifically a type known as particulate matter — correlated with an increased dementia incidence. The researchers also found that people who had developed heart disease seemed to increase that risk even further.
“This study found that long-term exposure to air pollution was associated with a higher risk of dementia,” the authors concluded.
“Heart failure and ischemic heart disease appeared to enhance the association between air pollution and dementia, whereas stroke seemed to be an important intermediate condition between the association of air pollution exposure with dementia,” they continued.
Past research has found links between air pollution and a slew of health issues, from asthma to cancer. But there’s also been growing evidence to show that exposure to air pollution can contribute to neurodegeneration and inflammation. One 2020 study found that living close to major roads and highways can raise a person’s risk of dementia.
The latest study found that even in the neighborhood in Sweden where participants lived, which had lower levels of air pollution than current air pollution standards, there was still a negative effect on their health.
“Interestingly, we were able to establish harmful effects on human health at levels below current air pollution standards,” Giulia Grande, a researcher at the Department of Neurobiology, Care Sciences and Society at Karolinska Institutet and a lead author of the study, said in a statement.
And having heart disease appeared to make that risk even greater, hinting at the importance of both air pollution reduction measures and lifestyle changes to improve heart health.
“From a policy point of view, this result is encouraging because it might imply that reducing air pollutant levels today could yield better outcomes already in the shorter term, reinforcing the need for appropriately set air quality standards,” the authors wrote.