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By Thomas Westerholm
Life & Trends Reporter
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Air pollution has long been linked to cardiovascular and respiratory illnesses, but new research suggests it may also significantly impair brain health—especially when exposure occurs during midlife.
Researchers from University College London and King's College London published a study in The Lancet Healthy Longevity that identified the ages of 45 to 69 as a critical window during which air pollution is linked to cognitive decline and structurally damaging changes in the brain.
Researchers followed participants in the study for nearly three decades, measuring exposure to pollutants like nitrogen dioxide and particulate matter, while assessing memory and processing speeds.
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They found that ambient air pollution can affect cognitive aging and increase dementia risk even before clinical symptoms emerge.
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Why It Matters
The global dementia burden is rising rapidly.
Cases of the cognitive disease are projected to triple from 57 million to 153 million by 2050, according to the 2024 Lancet Commission, and identifying risk factors is crucial to slowing the trend.
"Air pollution has been called the invisible killer and is the number one environmental threat to health in the world," study lead author Thomas Canning told Newsweek in an email.
"The mortality burden of air pollution is not new—according to the chief medical officer's annual report in England, it is estimated to be between 26,000 and 38,000 premature deaths a year, but in addition to this, many people suffer avoidable chronic ill health.
"This mortality has been linked to the effect of dirty air on the heart and lungs from cradle to death, but there is now an increasing body of evidence that suggests that air pollution isn't great for our brain either, with evidence suggested by our current and previous seminal research on these associations from the early developmental years now reaching up to later life."
What To Know
The study found that midlife exposure to nitrogen dioxide was associated with an 8.12-point decrease in processing speed on a 15-item recall task.
Higher exposure levels also correlated with a 0.59-point reduction on the Addenbrooke's Cognitive Examination III, a standardized test for cognitive impairment.
These effects remained noteworthy even after adjusting for childhood cognitive ability and earlier-life exposure, suggesting that midlife may be a uniquely vulnerable period for adults living with air pollution.
"Childhood is a really pivotal time, but evidence prior to this study was also very clear about the risk to older adults due to the vulnerability of older age," Canning told Newsweek.
"With the use of a novel 70-year follow-up period of people born in 1946, this study helped to clarify for the first time that exposure to air pollution in midlife was a risk to cognition and the brain in older age after taking into account a large number of lifelong socio-economic and clinical measures, as well taking into account exposure to air pollution from early childhood."
What People Are Saying
"It's really clear that air pollution at any exposure level is bad for many health problems—whether that's in children or adults," Canning told Newsweek.
"Air pollution, like climate change, is not a problem to be entirely resolved or mitigated by scientists alone, but an issue deeply embedded into our individual and societal decisions and the power relations of our political systems.
"Air pollution is a risk factor that is easily modifiable, and action can start at any level. There are many different ways that even local government can reduce it, and we know these changes work."
What's Next
Scientists in an accompanying Lancet commentary on the study noted, "Realistically, air pollution cannot be reduced by individual action but only through public health approaches."
"Dementia-specific recommendations might include building/locating care homes away from busy roads, improving guidelines for healthcare professionals on considering the impact of the environment on their patients, and the development of behavioral interventions such as nature prescribing for dementia patients," Canning added.
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