Global, regional, and national disability-adjusted life years and prevalence of lymphatic filariasis from 1990 to 2021: A trend and health inequality analysis based on the global burden of disease study 2021

Abstract

Lymphatic filariasis (LF) is a neglected tropical disease predominantly affecting marginalized populations in resource-limited settings. It can lead to long-term deformities, disabilities, and reduced economic productivity. This study examines differences in Disability-Adjusted Life Year (DALY) and prevalence of LF across countries and regions and predicts future trends. Trends were analyzed based on demographic factors and epidemiological changes, and cross-national health inequalities in LF were quantified. Using data from the Global Burden of Disease (GBD) 2021 database, this study evaluated trends in age-standardized LF DALY rates and prevalence from 1990 to 2021, employing estimated annual percentage change. The study also assessed the relative contributions of aging, population growth, and epidemiological changes in LF burden trends. To quantify absolute and relative cross-country inequalities, the Slope Index of Inequality (SII) and Concentration Index (CI) were applied. Additionally, Bayesian age-period-cohort models were used to predict LF case numbers and prevalence from 2022 to 2030. The findings indicated that, in 2021, LF burden varied by age, sex, and region, with the highest prevalence among individuals aged 15-49 years, males, and populations in low SDI regions. The global age-standardized prevalence and DALY rates of LF declined between 1990 and 2021, and predictions suggest this downward trend will continue through 2030. Potential changes adjusted by aging and population growth were the primary drivers of reductions in the number of LF cases and DALYs. Over the past few decades, the LF burden has concentrated in underdeveloped and disadvantaged regions. However, cross-national inequalities in LF are narrowing rapidly. These results emphasize the urgent need for sustained health interventions and public health policies to eliminate LF, particularly in low-income, high-risk regions such as Oceania. Targeted efforts are essential to improving the health and well-being of marginalized populations.

Fig 1. The age-standardized prevalence (per 100,000) of lymphatic filariasis, among 67 countries and territories in 2021.

The shapefiles used for spatial visualization are sourced from Natural Earth. The terms of free use for these shapefiles can be found at: https://www.naturalearthdata.com/about/terms-of-use/, the shapefiles available at: https://www.naturalearthdata.com/downloads/10m-cultural-vectors/10m-admin-0-countries/.

Fig 2. The crude prevalence and DALY rates (per 100,000), number of cases and DALYs of lymphatic filariasis, by age group, sex, at the global level, in 1990 (A, B) and 2021 (C, D).

The bar graphs represent the number and the error bars indicate the 95% uncertainty intervals; The smooth line fitted using the loess function represents the trend of age-standardized rates and error envelope indicate the 95% confidence intervals. Abbreviations: DALYs, Disability adjusted life years.

Fig 3. Changes in DALYs number of lymphatic filariasis according to population-level determinants including aging, population growth and epidemiological change, by sex, SDI quintiles, from 1990 to 2021 at the global level and.

(A) Both sex (B) Male (C) Female. Abbreviations: SDI, socio-demographic index; DALYs, disability adjusted life years.

Fig 4. Changes in DALYs number of lymphatic filariasis according to population-level determinants including aging, population growth and epidemiological change, by sex, GBD regions, from 1990 to 2021 at the global level and.

(A) Both sex (B) Male (C) Female. Abbreviations: SDI, socio-demographic index; DALYs, disability adjusted life years.

Fig 5. Health inequality regression curves for the age-standardized (A) DALY rates and (B) prevalence of lymphatic filariasis, at the global level, in 1990 and 2021.

The smooth line fitted using the generalized linear model represents the trend of crude rates ranked by SDI and error envelope indicate the 95% confidence intervals. Abbreviations: DALYs, Disability adjusted life years. Abbreviations: SDI, socio-demographic index; DALYs, disability adjusted life years.

Fig 6. Concentration curves curves for the age-standardized (A) DALY rates and (B) prevalence of lymphatic filariasis, at the global level, in 1990 and 2021.

The smooth line fitted using the loess funtion represents the concentration curve and error envelope indicate the 95% confidence intervals. Abbreviations: SDI, socio-demographic index; DALYs, disability adjusted life years.

Fig 7. The global change trends of lymphatic filariasis age-standardized cases from 1990 to 2021, and its predicted trends between 2022 and 2030.

The posterior distribution 95% credibility intervals for age-standardized prevalence rate are plotted with colors.