Temporal trends in anemia and particulate matter air pollution by sex and country-level income: Longitudinal evidence from 185 countries, 1990-2021.

Anemia remains a major global health concern with multifactorial causes and consequences across income levels. Evidence linking environmental factors, such as particulate matter (PM2.5) air pollution, to anemia is limited. This study examined longitudinal associations between PM2.5 air pollution and anemia prevalence across 185 countries from 1990 to 2021, focusing on sex and income-level differences. Secondary data on PM2.5 exposure, anemia prevalence, socioeconomic indices (Socio-demographic Index [SDI], Healthcare Access and Quality [HAQ], Sustainable Development Goals [SDGs]), and health-related factors (iron, vitamin A, calcium, zinc deficiencies, and kidney dysfunction) were analyzed using joinpoint regression and generalized estimating equations (GEEs). Globally, anemia prevalence rose by 8% in males and 9% in females over 32 years, with substantial variation by income group. Upper-middle-income countries achieved the greatest reductions in anemia disability-adjusted life years (DALYs), while low-income countries showed the largest PM2.5 declines (5%). Generalized estimating equation analysis found significant associations between anemia prevalence and PM2.5 pollution (β = 2.18, p = .002), income level (β = 1.25, p = .025), and female sex (β = 1.14, p = .033). Particulate matter exposure rose most steeply in lower-middle-income countries (2008-2012) but declined in high-income countries (2015-2019). Despite declining PM2.5 exposure, global anemia prevalence has increased. Addressing air pollution alongside other health-related factors is essential, particularly in low-income countries.