The Air Inside Your Home May Be Quietly Eroding Memory in Older Adults, Major Analysis Finds

When scientists warn about air pollution, the picture that usually comes to mind is a smog-choked highway or a factory skyline. But according to a sweeping new systematic review and meta-analysis published in BMC Geriatrics, some of the most consequential air that older adults breathe may be inside their own kitchens and living rooms. The analysis, led by Yiru Guo, Maosheng Tian, and colleagues at Hebei Medical University and collaborating institutions, pooled observational studies covering nearly a quarter of a million older people and found consistent links between indoor air pollution exposure and poorer cognitive function, faster cognitive decline, and higher risks of mild cognitive impairment. The findings arrive at a moment when the world’s population is aging rapidly and when billions of people, particularly in low- and middle-income countries, still cook and heat their homes with solid fuels such as wood, charcoal, and coal.

The research team searched PubMed, Web of Science, Embase, and the Cochrane Library through February 2026, following the PRISMA reporting guidelines and prospectively registering the review on PROSPERO under registration number CRD42024621110. Two reviewers independently screened studies, extracted data, and appraised methodological quality using the Joanna Briggs Institute critical appraisal tools for cross-sectional and cohort designs. From the initial harvest of the literature, twenty-one studies survived the eligibility filter, together encompassing 249,982 participants. That scale matters. Individual studies of indoor air exposure and cognition have often been small, geographically limited, and methodologically heterogeneous, making it difficult to know whether the signals they reported were real or statistical noise. By harmonizing continuous cognitive outcomes to standard deviation units and pooling them with random-effects models, the authors were able to estimate the overall direction and magnitude of the association with far greater precision than any single cohort could provide.

A central technical challenge in this literature is how exposure is measured. Directly monitoring pollutants such as fine particulate matter (PM2.5), nitrogen dioxide, or carbon monoxide inside people’s homes over years is expensive and logistically difficult, so many studies rely on proxies, most commonly the type of fuel used for cooking or heating. The meta-analysis therefore stratified its synthesis by exposure assessment category. Studies using fuel-use proxies, which dominated the evidence base including most of the cohort studies, showed a pooled association with poorer global cognitive function of β = −0.13 (95% confidence interval: −0.16 to −0.09), though with substantial heterogeneity across studies (I² = 86.9%). Studies that used actual pollutant concentration measurements, a smaller and presumably more precise body of evidence, yielded a slightly smaller but notably more consistent estimate: pooled β = −0.10 (95% CI: −0.18 to −0.02) with essentially no heterogeneity (I² = 0%). In plain terms, across both exposure approaches, greater indoor air pollution exposure was associated with worse overall cognitive performance, and the concentration-based findings were strikingly uniform.

Perhaps the most intriguing part of the analysis is what happened when the authors disaggregated cognition into subdomains rather than treating it as a single score. Cognitive science has long recognized that abilities such as memory, executive control, attention, and orientation can decline at different rates and reflect different underlying neural systems. Pooling across studies, the team found poorer memory performance (k = 7 studies; pooled β = −0.09, 95% CI: −0.11 to −0.06; I² = 49.1%), poorer executive-attentional function (k = 3; pooled β = −0.24, 95% CI: −0.27 to −0.20; I² = 15.2%), and poorer mental status (k = 3; pooled β = −0.20, 95% CI: −0.23 to −0.16; I² = 38.9%). Orientation was examined in only one study and therefore could not be pooled. The executive-attentional estimate is particularly eye-catching: a decline of roughly a quarter of a standard deviation is not trivial, and the low heterogeneity suggests the effect was reproduced consistently across the available studies. If indoor pollutants preferentially erode the frontal-executive systems that govern planning, inhibition, and attention, that pattern could offer clues about the biological pathways involved, from cerebrovascular injury to neuroinflammation.

Beyond snapshot measures of cognitive performance, the review also examined clinically meaningful outcomes over time. In analyses of time-to-event data, fuel-use proxy exposure was associated with a 22 percent higher hazard of cognitive decline (pooled hazard ratio = 1.22, 95% CI: 1.14–1.31) and a 24 percent higher hazard of cognitive impairment or mild cognitive impairment (pooled HR = 1.24, 95% CI: 1.11–1.37). Hazard ratios of this magnitude, applied across entire aging populations, translate into a substantial burden of preventable cognitive morbidity. Mild cognitive impairment is often considered a transitional state on the pathway toward dementia, which means that modifiable environmental risk factors that push people into MCI are of intense public health interest. Air pollution has already been implicated in dementia risk in the outdoor context, with epidemiological and toxicological evidence pointing to mechanisms such as systemic inflammation, oxidative stress, and pollution-driven cerebrovascular disease. The new synthesis extends that concern to the indoor environment, where people in many countries spend the overwhelming majority of their time.

The authors were careful about the limits of their evidence, and their caution deserves emphasis. All of the included studies were observational, which means the associations cannot be interpreted as proof of causation. People who burn solid fuels indoors may differ from those who do not in ways that also affect cognition, including socioeconomic status, education, access to healthcare, overall air quality in their region, and reverse causation, in which pre-existing cognitive decline leads households to change cooking or heating practices. The research team addressed some of these concerns statistically. Egger’s regression test for publication bias in the twelve-estimate fuel-use proxy analysis of global cognition was not statistically significant (P = 0.092), suggesting the pooled result was unlikely to be an artifact of small-study effects, and leave-one-out sensitivity analyses supported the direction of the main findings. Supplementary analyses also explored study-level moderators through meta-regression and addressed repeated contributions from shared underlying cohorts, an important technical step given that several large aging surveys, such as the China Health and Retirement Longitudinal Study, the Chinese Longitudinal Healthy Longevity Survey, the Longitudinal Aging Study in India, and the Mexican Health and Aging Study, have each generated multiple publications.

Even so, the evidence base has structural weaknesses that the authors flag clearly. Most included studies, including most cohort studies, relied on fuel-use proxies rather than direct or repeated indoor pollutant measurements, which limits exposure precision and likely contributes to exposure misclassification. Cognitive assessments also varied widely, from screening instruments such as the Mini-Mental State Examination, the Montreal Cognitive Assessment, the Community Screening Instrument for Dementia, and the Ascertain Dementia 8 questionnaire, to broader batteries, complicating cross-study comparability even after harmonization to standard deviation units. The authors’ prescription for future research is correspondingly specific: prospective studies with direct or repeated indoor pollutant measurements and repeated cognitive assessments. Such designs would allow researchers to model cumulative exposure over time, capture temporal sequences more convincingly, and distinguish chronic exposure effects from acute episodes, such as winter heating seasons or periods of heavy cooking smoke.

The public health implications are nonetheless considerable. Household air pollution from solid fuel use remains one of the largest environmental health risks globally, and the populations most exposed, older adults in low- and middle-income countries, are also those least likely to have access to cognitive screening and dementia care services. If the associations observed here reflect even a partially causal relationship, interventions such as cleaner cooking fuels, improved ventilation, improved stoves, and indoor air filtration could represent low-cost, scalable strategies to protect brain health in aging populations. The finding that executive-attentional function showed the largest pooled deficit adds urgency, because these are precisely the capacities that determine whether older adults can manage medications, finances, and independent living. The study was supported by the Hebei Natural Science Foundation and related provincial research programs, with the funders having no role in the design, analysis, or publication decisions, and the authors declared no competing interests.

What makes this meta-analysis resonate beyond the technical literature is the intimacy of its subject. Outdoor air pollution has spawned policy battles over vehicle emissions and industrial regulation, but the air inside a home is shaped by personal circumstances, housing quality, and energy access, factors that regulation reaches far less easily. A grandmother cooking over a charcoal stove in a poorly ventilated kitchen, or an older couple heating a single room with coal through a cold winter, may be absorbing an invisible cognitive toll that accumulates over decades. The evidence assembled by Guo, Tian, Li, and their colleagues does not prove that indoor pollution causes cognitive decline, and they say so explicitly. But it consolidates a scattered literature into a coherent signal spanning a quarter of a million people, spanning multiple cognitive domains, and spanning both performance-based and clinical outcomes. As the global population of adults over sixty continues to expand, the question of what the air in our homes is doing to our brains has moved from a niche research concern to a first-order public health question, and the answer, increasingly, is that we should pay attention to it.

Subject of Research: Association between indoor air pollution exposure and cognitive health outcomes in older adults

Article Title: Indoor air pollution and cognitive health in older adults: a systematic review and meta-analysis

Article References: Guo, Y., Tian, M., Li, Y., Cheng, Z., Niu, Y., Gao, T., Li, S., Wang, S., & Xu, X. (2026). Indoor air pollution and cognitive health in older adults: a systematic review and meta-analysis. BMC Geriatrics. https://doi.org/10.1186/s12877-026-08329-2

Image Credits: AI Generated

DOI: 10.1186/s12877-026-08329-2

Keywords: indoor air pollution, cognitive function, older adults, meta-analysis, systematic review, mild cognitive impairment, cognitive decline, PM2.5, solid fuel use, household air pollution, cognitive ageing, public health