ILD, Pulmonary Sarcoidosis Burden Rose Significantly From 1990 to 2021

The global burden of interstitial lung disease (ILD) and pulmonary sarcoidosis increased by 169% from 1990 to 2021, with the greatest impact observed in high sociodemographic index (SDI) countries, according to a study published in BMC Public Health.¹

Characterized by varying degrees of inflammation or fibrosis, there are about 200 types of ILDs, with idiopathic pulmonary fibrosis being the most common. Patients with certain ILD types face a poor prognosis, with untreated survival typically ranging from 3 to 5 years post diagnosis.

In contrast, pulmonary sarcoidosis is a granulomatous lung disease of unknown origin that can lead to respiratory failure. Its progression is unpredictable, and treatment outcomes are often unsatisfactory.

Globally, respiratory diseases account for about one-third of the workload in primary health care facilities, contributing to the increasing burden of non-communicable diseases. The Global Alliance Against Chronic Respiratory Diseases aims to reduce this burden by addressing conditions like ILD and pulmonary sarcoidosis.

Given the prolonged disease course and poor prognosis associated with ILD and pulmonary sarcoidosis, the researchers emphasized the need to analyze trends in their global burden and correlations with social development. To address this, they conducted a comprehensive analysis of the Global Burden of Diseases Study (GBD) 2021, which assessed burden trends and examined SDI-related health inequalities from 1990 to 2021²; the GBD 2021 data set included data on disability-adjusted life-years (DALYs) across 371 diseases and injuries.

The increase in the global burden of interstitial lung disease (ILD) and pulmonary sarcoidosis had the greatest impact on countries with a high socio-demographic index (SDI). | Image Credit: flashmovie - stock.adobe.com

The researchers extracted DALY data for ILD and pulmonary sarcoidosis from 1990 to 2021, stratified by age, sex, year, location, and SDI.¹ Data were obtained from 5 SDI quintiles (high, high-middle, middle, low-middle, and low), 21 GBD regions, and 204 countries/territories, across 20 age groups ranging from 5 or younger to 95 or older. DALYs were calculated by summing years lived with disability and years of life lost.

The SDI, a composite indicator of development status, combines per capita income, average education level, and fertility rates among females younger than 25. In this study, the SDI represented the development level of each country. Additionally, the researchers performed a decomposition analysis to explore DALY changes from 1990 to 2021, attributing observed differences to population size, epidemiological change, and population structure.

Health inequalities were assessed using the slope index of inequality (SII) and concentration index, representing the degree of absolute and relative inequalities, respectively. Using an appropriate regression model, the SII represented DALY differences between the countries with the highest SDI and those with the lowest SDI.

Conversely, the concentration index, a relative measure of inequality and positive values, indicated a concentration of DALYs among countries with high SDI. The researchers noted that greater absolute values of both the SII and concentration index indicate higher levels of inequality.

As measured in DALYs, the total burden of ILDs and pulmonary sarcoidosis was estimated at 4,042,150 (95% CI, 3,489,795-4,516,883) in 2021, an increase of 169.3% (95% uncertainty interval [UI], 134.8-218.2) from 1990. Therefore, the age-standardized DALY rate increased from 37.1 (95% UI, 30.6-45.4) per 100,000 in 1990 to 47.6 (95% UI, 41.3-53.2) in 2021.

Also, the researchers noted that males and those aged 70 to 74 experienced a higher burden of ILDs and pulmonary sarcoidosis; the DALY rates increased progressively with age. In particular, the high-SDI quintile showed the greatest increase in the age-standardized DALY rate from 1990 to 2021 (53.4%; 95% UI, 45.1-62.2).

Of the 21 GBD regions, South Asia (1,312,644; 95% UI, 890,806-1,740,639), high-income North America (582,575; 95% UI, 532,853-621,775), and Western Europe (526,090; 95% UI, 478,286-559,276) were most heavily affected in 2021. At the national level, India (1,124,248; 95% UI, 750,835-1,523,499), the US (524,808; 95% UI, 478,755-560,667), and Japan (383,903; 95% UI, 335,660-419,248) were the countries with the highest DALYs in 2021. However, the highest age-standardized DALY rate was observed in Peru (246.2 per 100,000; 95% UI, 178.3-317.8), while the lowest was in the Philippines (2.1 per 100,000; 95% UI, 1.5-2.6).

According to the decomposition analysis, there was a notable increase in ILDs and pulmonary sarcoidosis DALYs across the 5 SDI quintiles, with the largest increase observed in the high-SDI quintile. DALY increases due to population growth were most pronounced in the low-SDI (95.8%) and low-middle-SDI (51.3%) quintiles.

Based on the SII, the disparity in DALY rates between countries with the highest SDI vs those with the lowest SDI increased significantly, from 19.6 (95% CI, 11.6-27.5) in 1990 to 53.4 (95% CI, 39.7-67.1) in 2021. Therefore, countries with higher SDI experienced a higher burden of ILDs and pulmonary sarcoidosis. Lastly, the concentration index indicated relative inequality rose from 0.15 (95% CI, 0.08-0.21) in 1990 to 0.24 (95% CI, 0.16-0.32) in 2021.

The researchers acknowledged their limitations, one being that low-income countries lack accurate diagnostic tools and complete disease registries. Consequently, they may have underestimated the burden of ILDs and pulmonary sarcoidosis in low-income countries. Despite their limitations, the researchers expressed confidence in their findings, using them to suggest areas for further research.

“Future work should focus on obtaining more accurate and available epidemiological data on ILDs and pulmonary sarcoidosis, especially in low-income regions and countries,” the authors concluded. “The economic burden of ILDs and pulmonary sarcoidosis should also be further studied.”

References

1. Chen S, Li Y. Global health inequalities in the burden of interstitial lung disease and pulmonary sarcoidosis from 1990 to 2021. BMC Public Health. 2024;24(1):2892. doi:10.1186/s12889-024-20430-y
2. GBD 2021 Diseases and Injuries Collaborators. Global incidence, prevalence, years lived with disability (YLDs), disability-adjusted life-years (DALYs), and healthy life expectancy (HALE) for 371 diseases and injuries in 204 countries and territories and 811 subnational locations, 1990-2021: a systematic analysis for the Global Burden of Disease Study 2021. Lancet. 2024;403(10440):2133-2161. doi:10.1016/S0140-6736(24)00757-8