Air Pollution Can Speed Aging, New Study Finds, but Measuring Other Factors Is Challenging

Considering environmental factors is critical to understanding what drives the physical and cognitive declines, the researchers find in broad survey.

Delaying the aging process is a huge business, with anti-aging creams and brain health supplements claiming to slow physical and mental aging contributing to a multibillion dollar industry and researchers examining how video games can slow cognitive decline. 

But identifying external stressors that speed the aging process is just as important as finding ways to delay it. A study published today in Nature Medicine used data about more than 160,000 people in Latin America, Europe, Asia and Africa and found factors including gender equality, local democracy, internal migration and even air quality can affect aging. Notably, they found, exposure to poor air quality can widen the gap between a person’s chronological age and the biological age, a metric defining risk for certain age-associated medical conditions.

The study used multiple datasets, including aging surveys from “40 countries on four different continents,” said co-author Sandra Baez, a professor of psychology and neuroscience at the University of Los Andes in Bogotá, Colombia. Baez and her co-author, Agustin Ibáñez, a professor of global brain health at Trinity College Dublin, extracted information on both preventative factors and risks for brain health. 

They focused particularly on factors associated with dementia. 

Data about preventative factors, such as educational attainment and exercise, and risk factors, including heart disease, hypertension and alcohol consumption, were put into a machine learning model to determine biobehavioral age—a proxy for biological age. Baez said that these drivers can be used to predict biobehavioral age based on neurological health. The researchers referred to the difference between a person’s chronological and biobehavioral age as their “biobehavioral age gap,” which shows neurological stress, Ibáñez said. 

Baez and Ibáñez analyzed how survey participants’ biobehavioral age gap varied based on external conditions like local air quality. The higher a person’s biobehavioral age is compared to their chronological age, the greater the effects of aging they are experiencing. 

“The way that pollution impacts the brain is through, let’s say, inflammation, but political stress also induces inflammation,” Ibáñez said. “The overall idea is to try to understand how physical, social and political factors can have a kind of composite or synergetic effect in the accelerated aging of the people.”

Baez and Ibáñez used country-level measurements of tiny pollution particles called PM2.5 in their research to see how air quality exacerbated aging, both alone and in tandem with other external conditions. They found that combined adverse physical, social and political conditions led to accelerated aging—quadrupling risk for cognitive impairment. Across the entire dataset, poor air quality was statistically more impactful on aging than other social or physical conditions, they found.

“Air quality is as strong, or maybe more, than other very well known problems like gender [discrimination] or migration or socioeconomic inequality,” Ibáñez said.

Air pollution—particularly PM2.5 exposure—is associated with adverse health conditions ranging from dementia to depression to strokes, maladies often associated with aging populations. 

This study also found that accelerated aging from combined physical and social exposures varied regionally. Biobehavioral age gaps in Latin America and Africa were larger than those in Asia or Europe. The authors hypothesize that these larger age gaps are due to higher exposure to poor air quality and greater gender and socioeconomic inequality in Latin American and African countries. They noted, however, that the participants in Africa were limited to Egypt and South Africa, and the results might not be representative of risks across the continent. 

Baez pointed out that structural problems like air pollution exposure and voting access are largely beyond the control of individual choices. 

“It is important to notice here that public health interventions trying to improve the quality of air, the distribution of income, the quality of education, trying to improve the sociopolitical indicators of countries are very important also for brain health and aging,” she said. 

While Baez’s and Ibáñez’s work shows that the aging of bodies and brains might be affected by air quality, there’s debate over whether biobehavioral age gaps actually reflect aging. Most medical experts “don’t agree what aging is,” Ibáñez said.

“There is no such thing as biological age,” said Alan Cohen, professor of environmental health sciences at Columbia University who was not involved in this study. “Aging is a million things. There’s different parts of our bodies that are aging in different ways, and there is no single thing that tells you how all of that is doing on a single scale.”

Cohen views the scale that Baez and Ibáñez use—what they call the biobehavioral age gap—as a weakness. The research inferred aging from people’s behaviors and then compared them to environmental exposures and sociopolitical conditions, but did not directly look at how any of these factors biologically change any body part or organ system.

A better way for age researchers to approximate biological aging is through epigenetics, or the study of how genes turn on or off, Cohen said.

Aging and environmental stressors together create “little marks or annotations on [the human] genome,” Cohen said. Scientists can use the pattern of these markers, known as methyl groups, to determine a person’s exposure to biological stressors like air pollution, and to calculate a measure of biological age, which Cohen noted is usually within three years of someone’s actual chronological age. But replicating a process like this across global populations is not easy.

Individually lab testing the genome of 160,000 people across four continents to determine how air quality, for example, biologically ages someone would be impossible, Cohen said. 

“There is no dataset that looks around the world at all these countries with a big sample and gets you detailed biological information,” Cohen said. “So there isn’t any way [Baez and Ibáñez] could have that kind of gold standard biology to be able to compare anything to.”

Even with perceived weaknesses in the study, Cohen agrees that poor air quality has adverse health effects that could shorten lifespans.

The new study aimed “to find a more accessible and more cheap measure of accelerated aging,” Baez said. That’s why she and Ibáñez calculated “biobehavioral age gap using very simple questions regarding risk factors, protective factors on a global population.”

The diminished duration and quality of life that air pollution can cause is why Ibáñez says that any universal model of the factors that drive aging must include environmental conditions.

“Because if we create a kind of universal model that doesn’t incorporate the environment, we are not going to produce good science, good predictions, good prevention,” Ibáñez said. 

Cover photo:  People travel through dense smog due to air pollution in New Delhi, India, on Nov. 17, 2024. Credit: Salman Ali/Hindustan Times via Getty Images