The scientific community has known for years that air pollution is linked to an increased risk of dementia. Numerous studies have shown that men and women who live in heavily polluted cities develop cognitive deficits at an earlier age than those who live in more rural areas. Additionally, a small study out of the University of Texas recently linked the pollutant magnetite, an iron ore, with the presence of amyloid deposits in the brain. (Amyloid plaques are a key factor in Alzheimer’s disease.) Air pollution has even been linked to inflammation and changes characteristic of dementia in the brains of children and young adults.
Now a large-scale study, this time from Canada, has shown a correlation between dementia and exposure to heavy automobile traffic. Coordinated by Public Health Ontario and the Institute for Clinical Evaluative Sciences, the study examined the medical records of 6.5 million Ontario residents aged 20 to 85. Researchers looked at the occurrence of three major neurological disorders — dementia, Parkinson’s disease and multiple sclerosis — in the context of where people lived.
The results showed that people who live within 50 meters (.03 miles) of a busy street have a 7 percent higher incidence of dementia than those who live at least 200 meters (0.12 miles) away from heavily traveled roads. The risk of dementia decreased 4 percent for those who lived between 50 and 100 meters away from high-traffic areas. This appears to confirm the link.
Where the subjects lived had no effect on the rates of Parkinson’s disease and multiple sclerosis, the study showed.
Implications for Public Health
The correlation between air pollution and dementia does not establish causation, of course. Scientists theorize that multiple factors, including genetics and lifestyle, contribute to the development of dementia and Alzheimer’s disease. Nevertheless, the Ontario study has serious public health implications, the study authors said.
“Our study is the first in Canada to suggest that pollutants from heavy, day-to-day traffic are linked to dementia,” said Dr. Ray Copes, a co-author of the study and the chief of environmental and occupational health at PHO. “We know from previous research that air pollutants can get into the blood stream and lead to inflammation…This study suggests air pollutants that can get into the brain via the blood stream can lead to neurological problems,” he explained.
Copes suggested that city planners might use this information to inform decisions about traffic routes and residential building design. Moving away from fossil fuels to renewable energy sources to power our automobiles might be a good idea, too.