A study published this week in The Lancet showed that living near high-traffic roads is associated with an increased risk of dementia. The researchers observed nearly 2.2 million adults aged 55 to 85 living in the province of Ontario, Canada. Over a period of 11 years, they monitored which subjects developed dementia based on patient records in local health administration databases. They found that people living within 50 meters of a major road had a 7% higher risk of dementia during the study period compared to those living more than 300 meters away. The risk was even higher for people living near roads in large cities, who had a 12% increased incidence of dementia.
The researchers in this study were careful to control for a variety of demographic factors including socioeconomic status, education, smoking, obesity, and physical activity. When they adjusted for the subjects’ exposure to NO₂ and PM₂.₅, two common types of air pollution, the association was slightly weaker but still remained statistically significant (see this article for more information on the role of air pollution in dementia). This suggests that additional factors, such as other pollutants or noise levels, may play a role in the observed association.
This study has several limitations. Dementia frequently goes undiagnosed, especially in its early stages, so it’s likely that many subjects with dementia were overlooked in the health records. Additionally, the researchers did not account for traffic density in their analysis, instead grouping all included roads into a collective “major roads” category. However, the study’s very large number of subjects gives statistical power to its results. Further research is needed to determine the cause for this association, but if you live near a busy road, you may want to consider investing in a home air filter and/or noise-cancelling headphones.