The association between air pollution and cognitive impairment: a systematic review and meta- analysis of global studies.

INTRODUCTION: Air pollution remains one of the most significant global health threats, affecting populations everywhere. Its widespread and persistent presence has long posed serious risks, and its far-reaching effects underscore the significant threat it poses to public health. Although numerous investigations have been conducted worldwide, their outcomes have remained inconsistent and lacked definitive conclusions. Therefore, this systematic review and meta-analysis sought to determine the association between air pollution and cognitive impairment across the globe. METHODS: Databases such as PubMed/MEDLINE, Jane, Science Direct, Cochrane Library, LIVIVO, CINAHL, Global Index Medicus, African Journals Online, Web of Science, HINARI, Semantic Scholar, Google, and Google Scholar were used to retrieve all the relevant articles. Data were analyzed using STATA 17 software to determine the pooled associations between air pollution and cognitive impairment with a 95% confidence interval using a random-effects model. Moreover, the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA 2020) guidelines were followed for this study. RESULT: Fifty-four articles with 711,918 study participants were included in this meta-analysis to determine the association between air pollution and cognitive impairment. The findings of the study indicated that for every 1 µg/m3 increase in PM2.5, PM10, PM1 and black carbon concentration, the cognitive function was decreased by - 0.79 (95% CI β: -0.90, -0.68; I2 = 0.0% and p = 0.730), - 0.48 (95% CI β: -0.82, -0.15; I2 = 99.99% and p = 0.00), - 0.90 (95% CI β: -0.97, -0.82; I2 = 94.60% and p = 0.00), and - 0.53 (95% CI β: -1.03, -0.02; I2 = 99.44% and p = 0.00) respectively. Moreover, the pooled odds of developing cognitive impairment following exposure to a 1 µg/m3 increment in concentration of PM2.5 was 1.02 (95% CI OR: 1.01, 1.02; I2 = 97.02% and p = 0.00). CONCLUSION: Exposure to particulate matter air pollutants such as PM2.5, PM10, PM1, and black carbon was associated with an increased risk of cognitive impairment. The results may have substantial public health significance for preventing cognitive impairment through strong air pollution interventions.