In recently published work in Environment International (DOI: 10.1016/j.envint.2021.106722), my colleagues and I used data from the Gateway to Global Aging Data to investigate how exposure to household air pollution from polluting cooking fuel relates with cognitive function across three low- and middle-income countries. Although many studies have found links between air pollution in the outdoor environment and worse cognitive function, there are fewer researchers studying the potential effects of exposure to pollutants inside the home. Around 3 billion people (primarily in low- and middle-income countries) rely on polluting fuels (such as wood, coal, and dung) for domestic energy. Household combustion of these fuels can expose residents to unsafe levels of air pollution that can be harmful to their health.

Using a sample of 76,000 adults age 50+ from three harmonized studies of aging in Mexico (Mexican Health and Aging Study, MHAS), India (Longitudinal Aging Study in India, LASI), and China (China Health and Retirement Longitudinal Study, CHARLS), we sought to determine whether associations between polluting cooking fuel use and cognition are consistent across settings. Cross-nationally comparative studies are valuable because they strengthen the findings from individual countries and determine whether findings are general or limited to specific contexts and populations. This represents the first cross-nationally comparative study of household air pollution and cognitive function. In all studies, households reporting primarily using polluting fuel (wood, coal, dung, crop residue, or kerosene) were considered to be exposed to household air pollution and cognition was measured using performance on memory, orientation, and constructional praxis tasks.

Our findings show that, across countries, respondents who lived in households that primarily used polluting cooking fuel had worse cognitive function than their counterparts who used clean cooking fuel. These differences were not explained by demographic factors or lower socioeconomic status among households relying on polluting fuel. The differences in cognitive function between those using polluting cooking fuel versus clean cooking fuel were not trivial. They were equivalent to the differences in cognitive function one would expect between individuals separated by 5.5 years of age in India, and 3.3 years of age in both Mexico and China.

Across all countries, effects of polluting cooking fuel were larger for women. This is likely due to gender roles where women are expected to do the majority of the cooking. In data from India, we also found important differences based on the household’s cooking environment. Specifically, effects of polluting cooking fuel were largest when the cooking was done with no ventilation or when polluting cooking fuels were used in a traditional chullah or open fire as opposed to an improved cookstove.

This cross-nationally comparative study suggests that the association between household air pollution from polluting cooking fuel and worse cognitive function is not limited to specific countries. Rather, it is observed across three geographically diverse countries across the globe. The potential harmful effects of polluting cooking fuel on late-life cognitive function are important given the sheer numbers of individuals who rely on polluting fuel in low- and middle-income countries, and the projected population aging in these contexts in coming decades. However, it is encouraging that use of polluting cooking fuel is modifiable. Policy and public health efforts should focus on shifting households to clean cookstoves or clean sources of cooking fuel. This could potentially be achieved through educational interventions, subsidies to lessen the economic barriers to accessing clean fuels and cookstoves, and improvements in infrastructure to supply clean cooking fuels to rural areas.