For millions of Indian women, the kitchen is where the day begins and ends. Bent over a clay chulha, feeding firewood or dung cakes into the flame, they cook for their families in poorly ventilated rooms thick with smoke. The lungs pay a well-documented price. But now science asks a far more disturbing question: what is this smoke doing to the brain?
A landmark study published in The Lancet Regional Health – Southeast Asia — the first of its kind in rural India — provides a deeply alarming answer. Researchers at the Centre for Brain Research, Indian Institute of Science (IISc), Bengaluru have produced neuroimaging evidence linking household air pollution (HAP) from cooking fuels to both cognitive decline and measurable structural changes in the brain, including a smaller hippocampus in women — the very region devastated by Alzheimer’s disease.
The Study: What Was Done and Where
The research draws on the CBR-SANSCOG (Centre for Brain Research – Srinivaspura Aging, Neuro Senescence, and COGnition) study — an ongoing large cohort from the villages of Srinivaspura in Kolar district, Karnataka. Most participants are from farming communities with limited formal education and represent one of the most rural, under-studied ageing populations in South Asia.
Baseline cross-sectional data from 4,145 participants aged 45 years and above was analysed. Researchers grouped participants by cooking fuel type: those using only clean fuels (LPG, electricity), those using at least one polluting source alongside clean fuels, and those using exclusively polluting technologies — firewood, cow dung cakes, crop residue, and coal.
Cognitive performance was assessed through computerised, culturally adapted test batteries covering global cognition, memory, attention, language, visuospatial ability, and executive function. A subset of 994 participants also underwent 3-Tesla MRI scanning to measure regional brain volumes and white matter hyperintensities — structural markers of brain ageing and vascular damage.
Key Numbers at a Glance
- 4,145 adults aged ≥45 years studied in rural Karnataka
- 994 participants underwent high-resolution 3-Tesla brain MRI scans
- 30.7% of rural Karnataka households still rely on polluting cooking fuels (NFHS-5)
- 56.8% of all rural Indian households use polluting cooking fuels
What the Data Revealed
Significant Cognitive Decline Across Multiple Domains
Even participants using a mix of clean and polluting fuels showed measurably worse cognitive performance than clean-fuel-only users. Those relying exclusively on polluting fuels showed the steepest decline across several domains:
- Global cognition: 0.28 standard deviations lower in exclusive polluting fuel users; 0.10 SD lower even in mixed-fuel users
- Visuospatial ability (geometric figure matching): 0.28 SD lower in only-polluting users
- Executive function (semantic association tests): 0.25 SD lower in only-polluting users
- HMSE dementia screening: significantly lower scores across age groups, including those under 60
Brain Scans Confirm the Damage — Especially in Women
While MRI analysis of the full sample found no significant group differences in overall brain volumes, the picture changed sharply when researchers analysed women separately. Female users of polluting cooking fuels had hippocampal volumes 0.18 standard deviations smaller than women using clean fuels — a neurologically significant finding with direct implications for dementia risk.
The hippocampus — a small, seahorse-shaped structure deep in the temporal lobe — is the brain’s primary centre of learning and memory. It is the first region to atrophy in Alzheimer’s disease. Its measurable shrinkage in women exposed to HAP is not merely a statistical result: it is a neurological warning sign.
Why Women Suffer the Greatest Neurological Burden
The sex disparity is not coincidental — it is structural. In rural agrarian households across India, cooking is overwhelmingly women’s work. Women spend hours each day in small, poorly ventilated kitchens, inhaling far higher concentrations of toxic pollutants than their male counterparts. The study’s sex-stratified analysis confirmed exactly what the exposure pattern predicts: no significant cognitive or brain volume associations were found in men, while women showed both cognitive impairment and measurable structural brain changes.
Burning biomass fuels in poorly ventilated spaces releases harmful pollutants including carbon oxides, nitrogen oxides, sulphur oxides, heavy metals, and fine particulate matter (PM2.5) — all of which can penetrate the bloodstream and reach the brain, triggering neuroinflammation and oxidative stress.
This finding places HAP alongside other well-established gendered health burdens in rural India. Clean cooking fuel interventions must be understood not merely as energy policy, but as women’s health policy and dementia prevention strategy.
A Quiet Crisis at Scale
India is ageing rapidly. By 2050, over 300 million Indians will be above 60 years of age. The country already carries one of the world’s largest dementia burdens. Despite the Pradhan Mantri Ujjwala Yojana (PMUY) — which distributed free LPG connections to millions of low-income households — rural adoption remains incomplete. High refill costs, supply disruptions, and cultural preferences drive many families back to biomass. In rural Karnataka, almost one in three households still depends on traditional polluting fuels.
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 trends in most other states. HAP is not a background risk in rural India. It is a frontline public health emergency.
Why This Study Matters
- First in India: The first study to use brain MRI in a rural Indian population to examine how HAP structurally alters the brain
- Scale: Over 4,100 participants — one of the largest rural ageing brain cohorts in South Asia
- Neuroimaging proof: Moves beyond cognitive testing to deliver biological, structural confirmation of brain harm
- Modifiable risk: Unlike age or genetics, cooking fuel choice is changeable — making this a preventable cause of cognitive decline
- Policy relevance: Directly informs Ujjwala Yojana, Swachh Bharat, and rural health literacy programmes
- Lancet Commission aligned: Confirms and extends the 2020 Lancet Commission finding that air pollution is a modifiable dementia risk factor
What Must Change — Policy and Action Agenda
The researchers are explicit in their policy call: promoting clean cooking fuel and technology adoption is imperative. But distribution alone is insufficient. Evidence-based action requires:
- Subsidise LPG refill costs to prevent households reverting to biomass after the initial adoption subsidy
- Launch community health literacy campaigns linking polluting cooking to brain and cognitive health — especially targeting women
- Integrate HAP exposure screening into geriatric and primary care assessments in rural health facilities
- Scale ventilated kitchen construction where full clean-fuel transition is not yet immediately feasible
- Include HAP as a recognised dementia risk factor in India’s National Programme for Health Care of the Elderly (NPHCE)
- Expand cognitive screening in HAP-heavy rural districts as a preventive neurological health initiative
Conclusion
Every morning, across thousands of villages in Karnataka — and hundreds of millions of homes across low- and middle-income countries — women crouch over smoky stoves and cook. They do not know that the smoke is quietly reshaping the architecture of their brains. They do not know that the hippocampus, the seat of all memory, may be slowly shrinking.
This study gives us the evidence to act. The question now is whether policymakers, health systems, and communities will respond with the urgency this quiet crisis deserves.
The data will keep coming. But the women are cooking right now. We cannot afford to wait for perfect evidence before making thoughtful, life-saving choices.
Source: Mitra S, Sagiraju M, Pradhan H, Yao D, Pinto JM, Sundarakumar JS; CBR-SANSCOG Study Team. The cognitive toll of household air pollution: cross-sectional associations between polluting cooking fuel use, cognitive functions and brain MRI in a rural aging population from Karnataka, India. Lancet Reg Health Southeast Asia. 2025 Jun 28;39:100624. doi: 10.1016/j.lansea.2025.100624. PMID: 40672781.
⚠️ Medical Disclaimer: This article is for educational and public health awareness purposes only. It does not constitute medical advice. Please see our Medical Disclaimer for full details.
Leave a Comment