A robust link has been established between long-term ozone exposure and an increased risk of cognitive impairment in older adults, according to a large-scale study published in Environment International.
Air pollution has long been considered a major risk factor for an ageing society. Fine airborne particulate matter can lead to dementia and other cognitive disabilities. But beyond airborne particles, little is known about the way in which other pollutants can pose a similar danger.
The researchers chose to focus on ambient ozone, a highly reactive gas that exists in much of smog at ground level. They then observed health outcomes in nearly 10 000 older adults across China and analysed the extent to which long-term ozone exposure may have impacted their cognitive ability over time.
The results, they found, were startling. For every 10 microgram increase of yearly average ozone exposure, the risk for cognitive impairment grew by more than 10%. Through their analysis, the researchers also found that this association held even when they abstracted away individual risk factors such as smoking, drinking and education level. That is, older adults in China who were exposed to high levels of yearly ozone pollution were more likely to develop cognitive disabilities later in life, no matter what other activities they were involved in.
“Our findings suggest potential benefits in delaying the progression of cognitive decline among older adults if ozone levels are reduced below the new WHO Global Air Quality Guideline for ozone pollution,” said Kai Chen, Ph.D., assistant professor at the Yale School of Public Health and the study’s lead author.
The researchers acknowledged limitations such as observational data being unable to establish a causal link. More research is needed into ozone’s destructive mechanism. And since many older adults in China spend more time indoors, their ozone exposure may be different.
Nonetheless, the findings match what other researchers have found in areas across the globe: Over the past several years, studies have traced a similar link in adults in the United States and in Taiwan, and have also found an association between ozone exposure and other neurological diseases.
The study shows that ozone exposure needs to be curbed worldwide to prevent healthcare systems from being overwhelmed as populations age and pollution increases.
Study co-author Professor Robert Dubrow said what makes this issue more urgent is that “ozone pollution is projected to be worsening under climate change.” Reducing this threat could bring significant benefits to public health and improve quality of life.
Source: Yale University
