Are We Underestimating Deaths Related to Household Air Pollution?
New research suggests that air pollution contributes to dementia. The World Health Organization estimates that annually up to 4 million deaths are attributable to household air pollution (HAP) from the use of polluting fuels and technologies, like biomass and kerosene, for cooking. That’s nearly three times the number of deaths caused by malaria and HIV-AIDS combined in 2019. The relationship between HAP and illnesses like pneumonia and heart disease has been well documented. But emerging evidence is also pointing to potentially lethal impacts on the brain, raising the question – is HAP even more harmful than we thought?
Researchers have begun to delve into the damaging impacts of HAP on the brain to help identify important dementia prevention opportunities. Globally, nearly 50 million people suffer from dementia, with approximately 60% living in low- and middle-income countries, where the use of polluting fuels is also most prevalent. The findings from several recent studies highlight the potential of clean cooking interventions to reduce the risk of cognitive decline and impairment, and therefore help prevent the later onset of dementia.
A 2020 Lancet Commission report first identified air pollution as an additional important risk factor for dementia, and two recent studies have explored the relationship between HAP and cognitive decline and impairment, both of which can be early signs and characteristics of dementia, in Chinese adults.
These two studies, one conducted by Deng et al. and one by Luo et al., have helped extend the small evidence base on HAP’s negative impacts on cognition. Both studies used nationally representative datasets containing cognitive scores, which measure cognitive performance across attention, language, memory, and more, combined with fuel use status of older Chinese individuals. They used this data to evaluate whether those who cook with dirty fuels (and are thus exposed to higher HAP) have poorer cognitive outcomes than those who cook with clean fuels.
Both studies found that dirty fuel use was associated with worse cognitive function.
Compared with clean fuel users, dirty fuel users had worse cognitive function across both studies. Luo et al. found that individuals using solid fuels, on average, had a cognition score 8 percentage points lower than clean fuel users. Deng et al. uncovered that biomass fuel use was associated with a significantly higher risk of cognitive impairment and decline.
Interestingly, Deng et al. demonstrated that individuals who switched from using biomass to clean fuels saw a smaller decline in cognitive scores across time than those who stuck with biomass. This finding suggests that switching from cooking with polluting fuels and technologies to cooking with clean solutions may reduce cognitive decline.
Collectively, the studies provide insight into the role of HAP in cognitive outcomes, but the findings should be scaffolded by more robust research.
Although these studies reveal a relationship between HAP and cognition, they are limited by the use of fuel use status as a proxy for exposure to HAP. To further understand the role of HAP in cognitive decline and impairment, research that relates cognitive performance to objective measures of personal exposure to HAP is needed.
The studies suggest that the widespread promotion and adoption of clean cooking technologies could play an important role in reducing the risk for cognitive decline and impairment, which are associated with dementia, among aging populations.