Midlife Exposure to Air Pollution Could Impair Brain Health in Older Age

A comprehensive study led by researchers at King's College London's Institute of Psychiatry, Psychology & Neuroscience (IoPPN), highlights the long-term impact of air pollution exposure during midlife on brain health. The research indicates that individuals exposed to higher levels of air pollutants such as nitrogen dioxide (NO2) and particulate matter (PM10) between the ages of 45 and 69 exhibit slower cognitive processing speeds, lower performance on cognitive screening tests, and structural changes in brain anatomy as they age.

Published in The Lancet Healthy Longevity, this study is a collaboration with University College London, University of Leicester, and Alzheimer’s Research UK. It provides compelling evidence that even small reductions in air pollution levels during midlife could help preserve cognitive function and maintain brain structure in older adults.

The research involved analyzing data from 1,761 participants aged 45 and over from the Medical Research Council's National Survey of Health and Development (NSHD). These individuals underwent assessments of verbal memory and processing speed at multiple points from age 43 to 69, as well as a cognitive screening at age 69. Additionally, a subset of participants, aged 69 to 71, received brain scans to evaluate structural changes.

Findings revealed that higher lifetime exposure to pollutants correlated with lower scores on the Addenbrooke's Cognitive Examination (ACE III), which measures various cognitive domains including attention, memory, and language, at age 69. Exposure to nitrogen dioxide (NO2) and particulate matter was associated with slower processing speeds over the years. Notably, these associations persisted even after accounting for childhood cognition and early-life pollution exposure, although no significant link was found with verbal memory.

Neuroimaging analyses showed that increased exposure to nitrogen oxides (NOX) was linked to reduced hippocampal volume—a brain region vital for memory. Elevated levels of NO2 and PM10 were associated with larger ventricular volume, indicating brain tissue shrinkage—a hallmark of cognitive decline and dementia risk.

Prof. Ioannis Bakolis emphasized the public health implications, stating that almost all of the world’s population is exposed to air pollution levels exceeding WHO guidelines, which may contribute to rising dementia rates, projected to reach 153 million people by 2050. Thomas Canning from IoPPN added that reducing exposure to air pollution even during midlife could be instrumental in conserving cognitive function and brain health as we age.

This study underscores the urgency of addressing air quality issues globally, not only for respiratory health but also for long-term brain health and dementia prevention.