Polluting cooking fuel users may be at a higher risk of cognitive impairment finds study in Karnataka

The Hindu

07-07-2025

A recent study published in The Lancet Regional Health - Southeast Asia has found that polluting cooking fuel users may be at a higher risk for cognitive impairment.
Highlighting the need for policies promoting the adoption of clean cooking fuel/technology, the study found that rural females, who tend to be more exposed than males, could have greater vulnerability to household air pollution's (HAP) adverse effects on the brain.
A team of researchers from the Centre for Brain Research at the Indian Institute of Science (IISc) in Bengaluru and University of Chicago, United States, used baseline data from participants of the ongoing prospective cohort study, Centre for Brain Research - Srinivaspura Aging, Neuro Senescence, and COGnition (CBR-SANSCOG). Data was collected between January 2018 and December 2023. Under the CBR-SANSCOG cohort, adults aged over 45 years from the villages of Srinivaspura taluk in Kolar district of Karnataka were recruited. Of the sample size of 4,145 adults, as many as 994 participants who passed the MRI quality control were included in the MRI analysis.
Household air pollution
HAP is a specific type of indoor air pollution, which primarily results from the use of polluting cooking technology - coal stoves, biomass stoves, chullahs (earthen stoves) and polluting fuels such as firewood, cow dung cake, coal, lignite or charcoal, and kerosene, in and around the house, leading to the production of gaseous toxins.
While HAP from polluting cooking fuels, a rampant issue in rural India, is suspected to be a significant modifiable risk factor for cognitive impairment, evidence supported by neuroimaging in this population was lacking.
'Our study aimed to explore the relationship between polluting cooking technology, as a proxy for HAP, and cognitive performance, and brain morphology in the Srinivaspura cohort. We hypothesised that HAP exposure is associated with poorer cognitive performance and adverse brain morphology in this population. We also examined how factors such as age and sex affected this association and complemented our findings with insights from structural brain MRI,' one of the authors from the CBR team told The Hindu.
Cognitive functions
According to the study, only polluting cooking technology users had significantly lower scores in global cognition, visuospatial ability and executive functions, whereas at least one polluting cooking technology user had lower scores in global cognition only, compared to the clean cooking technology users.
'This study noted significantly poorer performance in global and domain-specific cognitive functions among polluting cooking technology users. Moreover, polluting cooking technology use was significantly associated with lower hippocampus volumes in females, the region which is primarily implicated in Alzheimer's disease (AD) pathology,' the CBR team said.
'When solid fuels are burned indoors for cooking, especially in poorly ventilated spaces, air pollutants like oxides of carbon, nitrogen, sulphur, heavy metals, volatile organic compounds, and suspended particulate matter are released. These pollutants have been implicated in adversely affecting brain health via different mechanisms. The primary mechanisms may be related to inflammation and oxidative stress, wherein ultrafine air pollutants affect the brain directly by entering the brain through the olfactory bulb or by crossing the blood–brain barrier (BBB),' the study noted.
The impact of household air pollution on health
According to the World Health Organization (WHO), 3.2 million premature deaths occurred worldwide from illnesses attributed to HAP as of 2020. These include ischaemic heart disease, stroke and chronic pulmonary conditions. In India, as of 2019, 0.81 million deaths were attributed to HAP.
The 2019–21 National Family Health Survey-5 reported that 41.4% of households in India lacked access to clean cooking fuels. This disparity was more pronounced in rural areas, wherein 56.8% of households utilised polluting cooking fuels, compared to 10.3% in urban areas.
In Karnataka, 30.7% of rural households relied on unclean cooking fuel in 2019–20. A 2017 nationwide study found that deaths and DALYs (disability-adjusted life years) due to HAP in Karnataka were significantly higher than those caused by ambient particulate matter pollution, contrasting with the trends in most other States.
Modifiable risk factor
While a large body of evidence exists documenting the effects of air pollution on cardiovascular and pulmonary health, its impact on cognition and brain health is only recently being explored. Besides the well-recognised risk factors for cognitive impairment, such as age, genetic predisposition, and cardiovascular diseases, increasing evidence suggests that air pollution is a modifiable risk factor.
'Our study echoes the findings from a harmonised analysis of ageing studies across India, China and Mexico that revealed poorer cognitive function among polluting cooking fuel users. It is among the first few studies to produce findings specific to a rural Indian setting. Recent findings from cross-sectional data of the Longitudinal Aging Study in India (LASI) showed that HAP was negatively associated with cognitive functioning among rural residents, particularly in older rural women. Another study among rural adults in South India found a higher prevalence of cognitive impairment among polluting cooking fuel users,' the study added.