Air Pollution and Cognitive Impairment across the Life Course in Humans: A Systematic Review with Specific Focus on Income Level of Study Area

Abstract

Cognitive function is a crucial determinant of human capital. The Lancet Commission (2020) has recognized air pollution as a risk factor for dementia. However, the scientific evidence on the impact of air pollution on cognitive outcomes across the life course and across different income settings, with varying levels of air pollution, needs further exploration. A systematic review was conducted, using Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) Guidelines to assess the association between air pollution and cognitive outcomes across the life course with a plan to analyze findings as per the income status of the study population. The PubMed search included keywords related to cognition and to pollution (in their titles) to identify studies on human participants published in English until 10 July 2020. The search yielded 84 relevant studies that described associations between exposure to air pollutants and an increased risk of lower cognitive function among children and adolescents, cognitive impairment and decline among adults, and dementia among older adults with supportive evidence of neuroimaging and inflammatory biomarkers. No study from low- and middle-income countries (LMICs)was identified despite high levels of air pollutants and high rates of dementia. To conclude, air pollution may impair cognitive function across the life-course, but a paucity of studies from reLMICs is a major lacuna in research.

Green Space, Air Pollution, Weather, and Cognitive Function in Middle and Old Age in China

“…The growing evidence suggests that air pollution, especially PM, is associated with cognitive decline ( 12 , 66 ). Our results were mixed on the air pollution effect.…”

Mitigating the impact of air pollution on dementia and brain health: Setting the policy agenda

“…Research on air pollution and brain health is starting to explore this form of vulnerability, as in the case of income inequalities (e.g., Chandra et al, 2022), but based on our umbrella review (in particular, the N = 6 policy papers) evidence is presently lacking (e.g., Delgado-Saborit et al, 2021). This form of vulnerability needs to be a priority.…”

“…New research shows exposure to high levels of air pollutants at critical points in our lives, particularly in early life, is detrimental to brain health across the life course and increases the risk of dementia syndrome and related disorders (e.g., Delgado-Saborit et al, 2021;Guzmán et al, 2022;Ran et al, 2021;Wang et al, 2022;Younan et al, 2022). Examples include global cognition and neurodegenerative disorders, learning in childhood and stroke-related brain damage, and reduction in white matter and neuroinflammation (Chandra et al, 2022;Gartland et al, 2022;Guxens et al, 2018;Killin et al, 2016;Russ et al, 2021).…”

“…Given the global impact of air pollution and PM 2.5 on brain health and dementia, prevention through air quality improvement could lead to better-quality health outcomes, improve productivity and quality of life, and reduce health-related costs 2 (e.g., Calderón-Garcidueñas et al, 2015;Chandra et al, 2022;Chen and Kan, 2022). The WHO estimates that roughly 55 million people have dementia worldwide, at a global cost of roughly $1.3 trillion; and this figure is expected to rise to 139 million by 2050, with an estimated global cost of $2.8 trillion.…”

“…Public health experts call this "systems" impact the "effects of place" (Cummins et al, 2007). Examples include how the causal loop between poverty, living near an industrial air pollution source, and social inequalities across the life course impact cognitive decline and neurodegenerative disorders in older, urban populations (e.g., Chandra et al, 2022;Delgado-Saborit et al, 2021;Shou et al, 2019). Or, how air pollution exposure in early-life impacts adolescent global cognition, due to poor health behaviours, limited access to green space, living in congested housing with poor indoor air quality, and walking to school on highly trafficked roads (e.g., An et al, 2021;Gartland et al, 2022;Johnson et al, 2021;Lopuszanska and Samardakiewicz, 2020;Stenson et al, 2021).…”