Long-term exposure to air pollution is linked to an increased risk of developing dementia, a new large-scale study by Cambridge University researchers has found. The report, published in The Lancet Planetary Health on Thursday (July 24), is the most comprehensive assessment of its kind, involving a systematic review of 51 studies and drawing on data from more than 29 million participants who had been exposed to air pollutants for at least one year.The findingsThe latest study is the most comprehensive of its kind and found a positive and statistically-significant association between three common air pollutants and dementia.PM2.5: Predominantly produced by vehicle emissions and thermal power plants, PM2.5 is extremely fine particulate matter with a diameter of 2.5 micrometres or less. The study found that for every 10 micrograms per cubic metre (µg/m³) of long-term exposure to PM2.5, an individual’s relative risk of dementia would increase by 17% from the baseline. For context, the average PM2.5 levels at Delhi’s ITO pollution AQI monitoring station over the last 24 hours (as of Saturday, 4 pm) was 77.NO2: Nitrogen dioxide is produced primarily due to the burning of fossil fuels by vehicles, thermal power plants, and various industrial processes. The study found that for every 10 μg/m³ of long-term exposure to nitrogen dioxide, the relative risk of dementia increased by 3%. The average NO2 levels at the ITO station over the last 24 hours (as of Saturday, 4 pm) was 83.Soot: Soot or Black Carbon PM2.5 comes from sources such as vehicle exhaust emissions and burning wood. The study reported that dementia risk jumped by 13% for each 1 μg/m³ of long-term soot exposure. The Central Pollution Control Board does not separately report BC/PM2.5 levels.The explanationOver the years, scientists have proposed several mechanisms to explain how air pollution may cause dementia. These primarily involve inflammation in the brain and oxidative stress (caused by an imbalance between the production of reactive oxygen species and the body’s ability to detoxify them, leading to cellular damage).Both oxidative stress and inflammation play a well-established role in the onset and progression of dementia, and air pollution is thought to trigger these processes through direct entry of pollutants to the brain or via the same mechanisms underlying lung and cardiovascular diseases.Story continues below this adWhy this mattersDementia is a term for several diseases that affect memory, thinking, and the ability to perform daily activities. The illness gets worse over time, and mainly affects older people. According to WHO, some 57 million people had dementia worldwide in 2021, with the number expected to increase to at least 150 million cases by 2050.Also Read | What are the worst polluters in Delhi NCR? Here’s what a TERI report saysThe rise in air pollution, especially in developing countries, might lead to an even sharper rise in cases. WHO data show that 99% of the global population breathes air that exceeds WHO guideline limits and contains high levels of pollutants, with low- and middle-income countries suffering from the highest exposures.“These findings underscore the need for an interdisciplinary approach to dementia prevention. Preventing dementia is not just the responsibility of healthcare: this study strengthens the case that urban planning, transport policy, and environmental regulation all have a significant role to play,” said Dr Christiaan Bredell from the University of Cambridge, and the study’s first author.© The Indian Express Pvt Ltd