People around the world, particularly in low-income regions, continue to depend on solid fuels such as coal, firewood and agricultural waste for everyday cooking and heating. Burning these materials produces dense indoor air pollution, filling homes with smoke and fine particles that are easily inhaled. Children living in these environments are exposed during crucial periods of brain growth, when developing neural systems are especially vulnerable to environmental harm.
“Nearly 30% of the global population — around 2.4 billion people — still cook without access to clean fuels,” explains University of Helsinki researcher Xu Zong. “Our findings suggest that growing up in a smoke-filled household may damage brain health and reduce cognitive abilities across the lifespan.” The study, published in the international journal Social Science & Medicine, is the first to examine how exposure to indoor air pollution in early childhood affects cognitive performance decades later in adulthood.
The researchers analysed nationally representative data from more than 7,000 Chinese adults aged 45 and older, applying advanced machine learning techniques to uncover long-term patterns. Participants who had been exposed to pollution from solid fuel use in childhood consistently performed worse on cognitive assessments compared with those who grew up in cleaner environments. The impact remained evident even after accounting for a wide range of health and social factors.
The most substantial effects were observed in episodic memory and overall mental functioning, two core components of cognitive health. According to Zong, these results suggest that early exposure may speed up age-related cognitive decline in multiple areas of brain function. Rather than fading over time, the consequences of polluted indoor environments appear to persist well into later life, shaping how the brain ages.
To understand why this occurs, the study explored both biological and socioeconomic pathways. From a biological perspective, childhood exposure was linked to higher rates of being overweight and greater limitations in daily activities in adulthood. These physical health issues can place additional strain on the body and brain, indirectly contributing to poorer cognitive outcomes. Long-term inflammation and reduced physical resilience may play a role in accelerating neurological ageing.
Socioeconomic effects were also substantial. Individuals exposed to indoor pollution as children were more likely to attain lower levels of education and earn less income as adults — both factors strongly associated with faster cognitive decline. The harmful impact was particularly pronounced among men, smokers and regular alcohol users, suggesting that lifestyle-related stress and inflammation may intensify the neurological damage caused by air pollution. Together, these findings highlight how early environmental exposure shapes cognitive health through an intertwined web of physical and social influences.
The researchers argue that reducing reliance on solid fuels should be viewed not only as an environmental or respiratory health priority, but as a long-term investment in brain health. Expanding access to clean household energy, such as electricity and gas, could help protect future generations from lifelong cognitive harm. As Zong notes, supporting clean energy adoption alongside healthier behaviours has the potential to safeguard mental wellbeing across the entire lifespan.
More information: Xu Zong, The long arm of childhood: The association between early-life indoor air pollution exposure and cognitive performance in later life, Social Science & Medicine. DOI: 10.1016/j.socscimed.2025.118662
Journal information: Social Science & Medicine Provided by University of Helsinki
