Does air pollution contribute to the risk of dementia? And if so, what steps can you take to protect yourself?
A recent study published in The Lancet suggests that living near a major roadway may raise the risk of dementia. Researchers found that residents in Ontario had about 7% higher risk of developing dementia if they lived within 50 meters of a major roadway . This recent study joins several other reports associating higher exposure to air pollution—such as that from car exhaust—with higher risk of dementia [2-5] or lower average cognitive function in older adults (reviewed in ).
This was an observational study, so the researchers can establish an association but not a cause and effect relationship between air pollution and dementia risk. It's possible that people exposed to more air pollution share other similarities, such as socioeconomic factors, which could cause harm. The researchers did, however, try to control for such factors and found no explanation other than air pollution for their results . It's important to consider that in controlled laboratory experiments, air pollutants have caused damage consistent with Alzheimer's disease and other dementias [7-10].
The World Health Organization estimates that air pollution contributes to approximately 2.6 million premature deaths each year, mainly from heart disease, stroke, lung cancer, and respiratory illness. Even relatively low exposure may shorten average lifespan by several months, based on studies in European and North American countries . Research has shown that harmful pollutants such as sulfur-dioxide, nitrogen dioxide, ozone, carbon monoxide, and fine particulate matter (PM2.5) can penetrate and lodge deep within the respiratory tract. Resulting respiratory illness or damage to the cardiovascular system can cause chronic inflammation that might also lead to increased risk of dementia .
If you are concerned about your exposure to air pollution, there are things you can do to protect your health and your brain. The drastic step of moving away from a major road is not always feasible, particularly if it means leaving a community you enjoy. Other steps can help you monitor and reduce your exposure to air pollution.
While these steps can help, your exposure to air pollution is still affected by others. The good news is that air quality can be improved even as industry expands. For example, average PM2.5 levels in the US declined by 37% from 2000–2015, based on EPA measurements. Technological innovation is helping to lower emissions and reduce pollution. New approaches to old ideas, such as more vegetation in urban planning, could help as well. While common tactics such as occasional trees have minimal influence, one model predicted that ambitious vegetation planting in street canyons could reduce street-level concentrations of pollutants by up to 60% .
Dr. Penny Dacks was previously the Director of Aging and Alzheimer’s Disease Prevention at the Alzheimer's Drug Discovery Foundation. She was trained in neuroscience at the Mount Sinai School of Medicine, the University of Arizona, and Queen's University (Canada) with individual fellowships from the National Institute of Health, the Evelyn F. McKnight Brain Research Foundation, the ARCS Foundation and the Hilda and Preston Davis Foundation. She has authored over 18 peer-reviewed scientific articles and is a member of the Society for Neuroscience, the Gerontological Society of America, the Endocrine Society and the Association for Women in Science.
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American Heart Association –
Risks of air pollution outside and inside the home
World Health Organization –
Interactive map of pollution worldwide
Environmental Protection Agency –
Pollution forecast within the U.S.
California EPA Air Resources Board –
Information and community action fact sheets
Union of Concerned Scientists –
Pollution from vehicles and potential solutions