Sex and socioeconomic inequalities in global asthma burden attributable to major risk factors, 1990-2021

Asthma remains a major global health issue, and modelled estimates suggest that its burden attributable to modifiable risk factors is unevenly distributed by sex and socioeconomic context. We aimed to assess long-term sex and socioeconomic inequalities in asthma burden attributable to major risk factors from 1990 to 2021.

Using Global Burden of Disease (GBD) 2021 modelled estimates, we analysed asthma-specific disability-adjusted life years (DALYs), years of life lost (YLLs), deaths, and average years of life lost (AYLL; derived as YLLs divided by deaths) attributable to "All risk factors" as a GBD-defined aggregate category, and to four individual risk factors examined separately: high body-mass index (BMI), smoking, occupational asthmagens, and nitrogen dioxide (NO₂) pollution. Temporal trends were evaluated using Joinpoint regression. Changes in DALYs were decomposed into the effects of population growth, population ageing, and epidemiological change using Das Gupta decomposition. Socioeconomic inequalities across levels of the Socio-demographic Index (SDI) were assessed using the slope index of inequality (SII) and concentration index (CI).

From 1990 to 2021, global asthma DALYs attributable to All risk factors, as defined in the GBD risk-attribution framework, increased by 8.6%, mainly reflecting population growth and ageing, whereas the age-standardized DALY rate (ASDR) declined, with an estimated annual percentage change (APC) of -1.8% per year. Male DALYs decreased by 2.2%, whereas female DALYs increased by 24.6%. Among the four specific risk factors assessed individually, high BMI accounted for the largest DALY burden, while occupational asthmagens accounted for the greatest AYLL. Point-estimate inequality trends suggested narrowing absolute and relative inequalities for most risk factors, but occupational asthmagen-attributable burden showed persistent or widening inequalities, particularly in lower-SDI settings.

Based on modelled GBD estimates, these findings suggest that equity-oriented strategies targeting modifiable risk exposures may help reduce asthma burden and promote global respiratory health equity.