Disparities and inequalities of lower respiratory infections in Iran, 1990-2021: the role of socioeconomic and demographic factors.

Background: Burden of lower respiratory infections (LRIs) is considered the leading health threat worldwide. We aimed to explore the trends and disparities of national and provincial outcomes of LRIs from 1990 to 2021 in Iran.

Methods: we retrieved health-related outcome rates from the Global Burden of Disease (GBD) 2021 Study, including annual age-standardized incidence (ASIR), prevalence (ASPR), deaths (ASDR), and Disability-adjusted life year (ASDALYR) during 1990-2019. To quantify the impact of covariates, the main socioeconomic and demographic factors, as well as the rates of LRIs were calculated by correlation and regression analyses.

Results: In Iran, total all ages deaths of LRIs decreased from 13,549 (95%UI 11,749 - 17,199) in 1990 to 8,596 (7,336-9,573) in 2021. Nationally, the ASIR and ASDR of LRIs decreased by 48.32% (45.02-51.50) and 57.11% (51.41-64.35), respectively, from 1990 to 2021. The highest and lowest ASIR varied among provinces in 2021, from 1,867.95 case (1,720.23-2,008.96) per 100,000 in North Khorasan to 1,077.50 case (988.68-1,175.44) per 100,000 in Ardebil. The ASDALYs decreased by 81.06% (77.15-85.95) for three decades, from 1,509.05 (1,302.85-1,927.77) per 100,000 in 1990 to 285.85 (252.45-315.06) per 100,000 in 2021. Two age groups, children under 5 years and older adults (+ 70 years) had the considerable burden of death and DALYs. Income, urbanization, sociodemographic index (SDI), and human development index (HDI) had the negative correlation with changes of LRIs' outcomes, especially for death (r= -0.60 and r= -0.66) and DALYs rates (r= -0.66 and r= -0.68).

Conclusion: Despite significant decreasing burden of LRIs trend over three decades, there is considerable disparities among provinces, which should be addressed in future studies.