New findings on the relationship between air pollution and dementia

Previous research has shown a link between exposure to air pollution and the risk of dementia. in his dissertation Air pollution and dementia in low-exposure areas–the role of noise, smell, and the APOE gene John Anderson, a doctoral student in the Department of Psychology at Umeå University, is deepening knowledge of what this connection looks like.

– I checked whether traffic noise, the sense of smell and the genetic risk factor for dementia are of any importance in this regard. Dementia is a common disease that not only costs society a lot of money, but also causes a lot of human suffering. The number of people with dementia will increase because our life expectancy is increasing. In addition, the proportion of the world’s population living in cities is increasing and is therefore exposed to higher levels of air pollution. Therefore, it will also be important to study the links between pollution and dementia, says John Anderson.

Some are more sensitive to harmful air pollution

In his research, John Anderson used data from the Betula Project, a large study on aging and health that has been ongoing in Umeå since 1988. He also collaborated with researchers from SMHI, and at the Department of Public Health and Clinical Medicine at Umeå University. The latter has developed models that describe levels of small particles and traffic noise over Umeå and the surrounding area.

The studies in the thesis show that long-term exposure to higher levels of air pollution, both nitrogen oxides and small particles, is associated with an increased risk of dementia even at the relatively low levels found in Umeå. Simplified, one can say that a person who lives in one of the most polluted areas of Umeå has a 40% higher risk of developing dementia than someone who lives in one of the least polluted areas, which is in line with previous research. However, what is new is that we can see that those with an impaired sense of smell, or those who carry the APOE-ε4 variant gene, are more sensitive to the harmful effects of air pollution. In fact, we saw no significant association between pollution and dementia in those with a better sense of smell, or in those without APOE-4.

The findings also show that traffic noise does not appear to contribute to an increased risk of dementia, and that exposure to air pollution is unrelated to an impaired sense of smell.

It is important to note here that we cannot comment on whether these results also apply to regions with higher levels of air pollution. I investigated Umeå in my research, a city with relatively good air quality. Research on the link between air pollution and dementia has been done in larger and more polluted cities, such as Mexico City, Taipei and London, and it would be interesting to deepen knowledge of areas with lower levels of pollution, says John Anderson.

The problem of car movement in urban environments

John Anderson points out that his results should not be interpreted as a call for everyone carrying the APOE-e4 genetic variant to move out of town.

Instead, these results should be seen as another argument that vehicle traffic should be reduced in urban environments, even in a relatively small city like Umeå. Unfortunately, it is not enough to replace gasoline-powered cars with electric ones. The particles that lead to harmful effects on the brain largely come from road wear, especially when we drive with studded tires in winter. But if we succeed in reducing vehicular traffic, it can potentially have remarkable positive effects on the health of the people of Ume.

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