Global burden of influenza lower respiratory tract infections in children younger than 5 years from 1990 to 2021

Introduction

Influenza lower respiratory tract infections (LRTIs) are classified as infectious diseases that occur in the trachea, bronchus, bronchi and alveoli. These infections are transmitted by droplet or contact (1,2), and are susceptible to severe illness in children, the elderly and immunocompromised populations. They have always been a central global public health problem (3,4). As the fourth leading cause of death on a global scale, LRTIs are the leading cause of death in low-income countries, causing nearly 2 million deaths annually, with a disproportionate number of deaths occurring in children under the age of 5 years (5,6). Among the numerous LRTI pathogens, influenza virus, as one of the three most deadly pathogens, has been in the spotlight due to three major characteristics (7-9). Firstly, its rapid mutation and ability to spread across seasons lead to persistent epidemics. Secondly, influenza often acts synergistically with co-transmissible pathogens, exacerbating the risk of respiratory complications. Thirdly, influenza prevention and control are affected by differences in socio-economic development levels, resource availability and pathogen epidemiological characteristics among regions, showing significant imbalances and serious problems such as the lack of targeting strategies for high-risk populations. This dismal reality underscores the imperative for in-depth research on influenza-LRTIs. Only by elucidating their epidemiological evolution and socioeconomic drivers can precise intervention strategies be formulated.

LRTI in children under the age of five is attributable to a multitude of biological and sociological factors. These include an underdeveloped immune system, a high risk of exposure in congregate living environments, and the lifelong respiratory sequelae that may result from early infection. These factors combine to elevate the risk of morbidity and death rate in this group (10,11). Despite the advances in vaccination and clinical care, 57 of 204 countries worldwide reported more than 60 deaths per 100,000 children under 5 years of age from LRTI in 2021, revealing persistent deficiencies in prevention systems and access to care (12,13). The extant literature on the subject is limited to short-term epidemiological analyses. The failure to systematically analyse the long-term spatial and temporal heterogeneity of death rate and death and disability-adjusted life years (DALYs) has a direct impact on the achievement of Sustainable Development Goal (SDG) 3.2 of slowing down the progression of avoidable deaths in children by 2030 (14).

In consideration of the aforementioned points, the present study employs Global Burden of Disease (GBD) 2021 data with the objective of enhancing the existing body of knowledge on the subject by conducting a comprehensive examination of the global, regional, and national burden of influenza LRTI in children under five years of age from 1990 to 2021. The study analyses trends in death rate and DALYs, stratified by sex, age, socio-demographic index (SDI), and geographic region. Utilising data from the GBD study, a comprehensive evaluation of the evolution of the burden of influenza LRTIs over three decades is conducted, with a focus on both the progress achieved and the persistent challenges that remain. The results of this study will contribute to the ongoing discussion on reducing the global burden of paediatric respiratory infections and support evidence-based policymaking.

Methods

Study design

This is a study based on the 2021 GBD estimate. We study the gender distribution of the burden of disease from 1990 to 2021 and analyze year-to-year changes in death rates and DALY rates. We describe global, regional, and national trends in the number of deaths, death rates, number of DALYs, and DALY rates for influenza LRTIs in children younger than 5 years from 1990 to 2021. In addition to examining disease burden and trends, we analyzed the impact of SDI on the burden of influenza LRTIs, along with the inequality analysis across different SDI regions. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments.

Data source and collection

We used the Global Health Data Exchange (GHDx) query tool [VizHub-GBD Results (healthdata.org), accessed March 2025] to collect rates and numbers of influenza LRTIs deaths and DALYs in children under 5 years of age (15). To address potential bias from the global sex ratio at birth, we also extracted sex-specific population estimates for each age group from the GBD 2021 database (https://ghdx.healthdata.org/gbd-2021) to serve as denominators for rate calculations. We collected data on age, sex, SDI, 21 GBD regions and 204 countries and territories. In the GBD website, the data is organized into nine sections, namely GBD estimates, etiology, measure, metric, cause, location, age, sex, and years. In our study, the etiology was first selected in the GBD estimate section and influenza in the etiology section. Next, we check deaths and DALYs in the measure section, select number and rate in the metric section, and select lower respiratory infections in the cause section. We selected Global, 21 GBD regions, 5 SDI regions and 204 countries and territories for the region section and limited the population of this study to children younger than five years old, and selected male, female and both for sex. Finally, data from 1990 to 2021 were selected.

Regions and demographics

A total of 204 countries and territories were grouped into 21 GBD regions by their geographical proximity and similarity in morbidity characteristics, including East Asia, Western Europe, Central Latin America, North America and other GBD regions. The SDI is an indicator representing the sum of economic, educational and fertility rates, and is divided into five parts, namely, the low SDI region, the low-middle SDI region, the middle SDI region, the high-middle SDI region and the high SDI region. At the same time, 204 countries and territories are classified into 5 SDI regions according to their economic, educational and fertility levels. We categorized children under five years of age into six age groups: 0–6 days, 7–27 days, 1–5 months, 6–11 months, 12–23 months, and 2–4 years in order to study the age distribution of the disease burden.

Statistical analysis

Influenza is a cause of LRTIs in the GBD framework and is estimated to be a component of the overall burden of lower respiratory infections. We chose death and DALY as measures, and the detailed estimation process is described in previous studies (12,16). The absolute number and rate of influenza LRTIs were reported alongside 95% uncertainty intervals (UI), derived from the 25th and 975th percentile values obtained through 1,000 sampling iterations. All data analyses in this study were performed using R software (version 4.4.1), and all graphical visualizations were performed using R software (version 4.4.1) and GraphPad Prism (version 8.0.2).

Results

Burden and trends of influenza LRTIs at global levels

Globally, the number of deaths of children under 5 years of age due to influenza LRTIs has decreased by 83.46% from 167,009 (95% UI: 142,224–194,162) in 1990 to 27,615 (95% UI: 20,128–36,852) in 2021, and the death rate has decreased by 84.41% from 26.94 (95% UI: 22.94–31.32) per 100,000 in 1990 to 4.2 (95% UI: 3.06–5.60) per 100,000 in 2021 (Table 1). The DALYs of influenza LRTIs displayed a similar trend, with the number of DALYs decreasing by 83.47% from 14,888,626 (95% UI: 12,684,580–17,312,190) in 1990 to 2,460,833 (95% UI: 1,796,287–3,280,725) in 2021, and the DALY rate declined by 84.43% from 2,401.63 (95% UI: 2,046.10–2,792.57) per 100,000 people in 1990 to 373.89 (95% UI: 272.92–498.46) per 100,000 people in 2021 (Table 2).

Distribution by age and sex

In 1990, the age group with the highest number of deaths and DALYs from influenza LRTIs among children younger than 5 years was 1–5 months, followed by 2–4 years, 12–23 months, 7–27 days, 6–11 months, and the least was 0–6 days. In 2021, the age group with the highest number of deaths and DALYs from influenza LRTIs among children younger than 5 years is 1–5 months, followed by 2–4 years, 6–11 months, 12–23 months, 0–6 days, and the least was 7–27 days. For each age group, the number of deaths and DALYs in 2021 are substantially lower than in 1990 (Figure 1).

Figure 1 The global number of death and DALYs for influenza LRTIs in children under five years of age by age and sex group, 1990 and 2021. (A) The number of deaths in 1990. (B) The number of DALYs in 1990. (C) The number of deaths in 2021. (D) The number of DALYs in 2021. DALY, disability-adjusted life year; LRTI, lower respiratory tract infection.

Among children younger than five years of age, the number of deaths and DALYs, rates of death and DALY for influenza LRTIs tended to be greater for boys than for girls in all age groups. Even after accounting for the fact that the global population of boys under five (approximately 348 million in 2021) is larger than that of girls (approximately 327 million), the sex-specific death rates remained significantly higher in males (Table 3). In 2021, among children of all age groups, the largest gender gap in deaths was observed in the 0–6 days group, which male deaths were 1.5 times higher than female deaths (Figures 1,2). When converted to rates, the mortality risk for male neonates in the 0–6 days group remained approximately 1.4 times higher than that for females. This confirms that the higher burden in boys is driven by increased biological or clinical vulnerability rather than just a larger population base (Table 3).

Figure 2 Number of deaths and DALYs, rate of death and DALY for influenza LRTIs in children under five years of age, by sex group, globally, 1990–2021. (A) The number and rate of death, 1990–2021. (B) The number and rate of DALY, 1990–2021. DALY, disability-adjusted life year; LRTI, lower respiratory tract infection.

Distribution by region

2021 Influenza LRTIs in low SDI regions have the highest number of deaths 15,591 (95% UI: 10,768–21,301) and the highest number of DALYs 1,386,514 (95% UI: 958,649–1,892,242). Rates of death and DALY show decreasing trends from 1990 to 2021 in all SDI regions, with the highest rate of decrease in the high-middle SDI regions (83.37% per 100,000 decline in death rate and 83.38% per 100,000 decline in DALY rate). The low SDI region, although experiencing a significant decline in death rate and DALY rate (98.13% per 100,000 decline in death rate and 98.15% per 100,000 decline in DALY rate), still has the highest death rate and DALY rate in 2021, with a death rate of 9.42 (per 100,000, 95% UI: 6.5–12.86) and a DALY rate of 837.39 (per 100,000, 95% UI: 578.98–1,142.83) (Tables 1,2). Death and DALY rates globally and in the five SDI regions have shown a downward trend over the last 32 years, with the largest decreases in the low SDI regions, but death and DALY rates in the low SDI regions and low-middle SDI regions are still above the global level (Figure 3).

Figure 3 Rate of death rate and DALY for influenza LRTIs in children under five years of age, by SDI group, 1990–2021. (A) Death rate, 1990–2021. (B) DALY rate, 1990–2021. DALY, disability-adjusted life year; LRTI, lower respiratory tract infection; SDI, socio-demographic index.

The GBD region with the highest number of deaths from influenza LRTIs in 2021 was Western Sub-Saharan Africa at 10,145 (95% UI: 5,989–15,505), followed by South Asia at 9,382 (95% UI: 4,674–14,967). The highest death rate from influenza LRTIs in 2021 in the GBD region was Western Sub-Saharan Africa at 12.69 (per 100,000, 95% UI: 7.49–19.39), followed by Central Sub-Saharan Africa at 7.41 (per 100,000, 95% UI: 3.57–12.01). All GBD regions have shown a significant downward trend in death rate from influenza LRTIs over the past 32 years, with the top three declining regions being High-income Asia Pacific (100.00%), Australasia (100.00%), Central Europe (99.84%) (Table 1). Besides, the GBD region with the highest number of DALY from influenza LRTIs in 2021 was Western Sub-Saharan Africa at 900,693 (95% UI: 532,481–1,376,529), South Asia at 839,480 (95% UI: 418,144–1,340,129), and Eastern Sub-Saharan Africa at 419,801 (95% UI: 270,190–618,104). Western Sub-Saharan Africa (1,126.46 per 100,000, 95% UI: 665.95–1,721.56) had the highest DALY rate from influenza LRTIs in 2021 in the GBD region. DALY rates in all DBD regions have shown a decreasing trend over the past 32 years, with the largest decrease in High-income Asia Pacific (99.96%) and the smallest decrease in Western Sub-Saharan Africa (80.07%).

The burden of influenza LRTIs in children under five exhibited significant socioeconomic inequality, consistently showing a negative correlation with the SDI and being disproportionately concentrated in low-SDI regions. Specifically, the Slope Index of Inequality (SII) increased from −4,703.6 in 1990 to −581.9 in 2021, indicating a substantial narrowing of absolute disparities between regions. Meanwhile, the concentration index (CI) decreased from −0.46 in 1990 to −0.61 in 2021, and the concentration curve shifted noticeably upward, reflecting a deepening of relative inequality in the distribution of the disease burden (Figure 4).

Figure 4 Health inequality of influenza LRTIs in children under five years of age, 1990 and 2021. (A) SII in DALY rates. (B) Concentration curves of DALYs. DALY, disability-adjusted life year; LRTI, lower respiratory tract infection; SDI, socio-demographic index; SII, Slope Index of Inequality.

For different countries and regions, Niger had the highest DALY rate of 10,285.99 (95% UI: 7,422.79–13,524.10) in 1990, in addition the countries with DALY over 5,237.79 were, in descending order, Guinea, Lao People’s Democratic Republic, Cambodia, Sierra Leone, Nigeria, Timor-Leste, Liberia, Central African Republic, Afghanistan, Nepal, Burkina Faso, Myanmar, Mongolia, Azerbaijan, Ethiopia, Angola, Chad, Rwanda, United Republic of Tanzania, South Sudan. Central African Republic had the highest DALY rate of 2,013.85 (95% UI: 929.86–3,372.60) in 2021, while the other countries with DALY over 661.78 are Chad, Burkina Faso, South Sudan, Nigeria, Guinea, Benin, Somalia, Togo, Sierra Leone, United Republic of Tanzania, Cameroon, Mali, Eritrea, Malawi, Zambia, Pakistan, Comoros (Figure 5).

Figure 5 The rates of DALY for influenza LRTIs in children under five years of age among 204 countries and territories, 1990 and 2021 (per 100,000 population). (A) The rate of DALY per 100,000 population, 1990. (B) The rate of DALY per 100,000 population, 2021. DALY, disability-adjusted life year; LRTI, lower respiratory tract infection.

Discussion

Key findings and global disparities

It is acknowledged that this is a field of research that has a recognised methodology. Utilising data from the GBD 2021 study, a comprehensive global analysis of the burden and trends of influenza LRTIs in children under five from 1990 to 2021 has been conducted. This analysis has included the estimation of death rate and DALYs for the study period, as well as the analysis of spatial and temporal heterogeneity. The analysis has focused on exploring disparities in death rate and DALYs across different age groups, sexes, sociodemographic regions and geographical areas. The following core findings have been revealed:

The analysis of data reveals significant disparities in death rates according to age and gender. The study finds infants aged 1–5 months to be the demographic with the highest death rates, occupying the top position in terms of total deaths both in 1990 and 2021. Furthermore, neonatal death rates (0–6 days) exhibited an upward trend in 2021, indicating a potential gap in the quality of perinatal care (Figure 1). A gender analysis revealed that the death rate and DALY rates for boys were significantly higher than for girls, suggesting that differences in immune development and risk of behavioural exposures may be associated with the need for targeted prevention and control strategies (Figure 2).

The GBD has shown a general decline, yet this decline varies significantly between different regions. From 1990 to 2021, the global number of deaths among children under 5 years of age due to influenza LRTIs decreased by 83.46%. The death rate decreased by 84.41% (from 26.94/100,000 to 4.2/100,000), and the DALY rate decreased by 84.43%, indicating the overall effectiveness of public health interventions (Tables 1,2). However, regions exhibiting low SDI continue to experience the highest burden of disease, with death rates (9.42/100,000) and DALY rates (837.39/100,000) in 2021 being 235 and 209 times higher, respectively, than those observed in regions characterised by high SDI (Figure 3). Western sub-Saharan Africa (12.69/100,000 deaths) and South Asia (5.92/100,000 deaths) in particular have been identified as regions of particular concern with regard to the transmission of the disease (Figure 5).

Socioeconomic inequality exerts a pivotal influence on the distribution of diseases, as evidenced by a stratified analysis of SDI. High-SDI regions have attained a death rate of 0.04/100,000 through the optimisation of healthcare resources, while low-SDI regions have achieved a 69.37% reduction in death rate. Nevertheless, these regions still account for 56.5% of global deaths in absolute terms, a disparity largely attributable to their substantial population sizes, limited vaccine coverage, and insufficient healthcare infrastructure (15,591 deaths). The rapid progress observed in middle- and high-SDI regions (83.37% death rate reduction) underscores the decisive role of healthcare investment and system capacity, whereas the slower improvement in low-SDI regions highlights the persistent imbalance in global health resource allocation and intervention effectiveness (Figure 3).

Furthermore, the socioeconomic inequality analysis of the disease burden underscores the substantial progress achieved by public health interventions over the past three decades, which have collectively contributed to narrowing the absolute health disparities across regions with different socioeconomic development levels. This is quantitatively demonstrated by the notable increase in SII from −4,703.6 in 1990 to −581.9 in 2021. However, alongside this absolute improvement, CI decreased from −0.46 to −0.61, accompanied by a distinct upward shift in the concentration curve, indicating that the disease burden has become increasingly concentrated among populations in lower-SDI regions. This pattern suggests that although health outcomes have improved across all regions, the relative burden is progressively shifting toward the most socioeconomically disadvantaged groups (Figure 4).

Mechanisms underlying disparities

This study suggests that the global decline in influenza-associated LRTIs may result from synergistic effects of multifaceted interventions. Vaccination reduces susceptible populations through direct protection of high-risk groups and indirect transmission chain disruption, though global coverage remains below WHO’s 75% target. Notably, childhood influenza vaccination rates in high-income countries have significantly increased (e.g., U.S. coverage rose from 51% to 59% between 2010 and 2017) (17,18). Rational antiviral use mitigates severe outcomes, with early oseltamivir administration demonstrating dose-dependent efficacy in controlling clustered transmission (19). Baloxavir marboxil (BXM) shows dual clinical-public health benefits by reducing viral shedding and shortening infectious duration, with modeling predicting reduced seasonal influenza incidence in China (20,21). Public health measures disrupt transmission through multiple pathways: hand hygiene interventions decreased acute respiratory infection incidence by 20–50% in low-income countries (22), while maternal-neonatal health programs lower infant influenza hospitalization risk via placental antibody transfer (23). Enhanced surveillance networks and tiered healthcare systems enable early case identification and optimized resource allocation (24).

However, the high burden in low-SDI regions reflects structural inequities: Suboptimal vaccine coverage stems from inadequate healthcare resources. Deficiencies in cold chain logistics compromise influenza vaccine delivery—a Ugandan study revealed widespread use of outdated, poorly maintained cold chain equipment in public facilities, with nearly 50% of health workers lacking temperature monitoring knowledge (25). Ethiopian data showed only 50% of health institutions maintained standardized cold chain management, exacerbated by transportation challenges and power shortages in remote areas (26). Globally, low-middle income countries exhibit fourfold higher influenza-related severe illness risks versus high-income nations due to vaccine resource gaps (27). Inadequate basic sanitation amplifies exposure risks. The lack of access to water, sanitation, and hygiene (WASH) services—including disinfection facilities and waste management systems—accelerates viral spread—studies indicate substantial WASH deficiencies in public healthcare facilities across 46 least-developed countries (28). Low vaccination rates among healthcare workers in such environments elevate their roles as transmission vectors, increasing cross-infection risks for both providers and patients (29). Rapid viral evolution interacts dynamically with resource disparities. Delayed vaccine strain updates in low-SDI regions, coupled with limited antiviral accessibility, reduce intervention efficacy compared to developed areas (30). These intersecting factors perpetuate a “cycle of vulnerability”, underscoring urgent needs for equitable resource allocation, infrastructure modernization, and coordinated multipathogen prevention strategies.

The observed age and sex disparities may stem from immune developmental stages: infants aged 1–5 months exhibit heightened vulnerability to severe outcomes due to maternal antibody decay and immature adaptive immunity. While maternal influenza vaccination enables placental/lactational antibody transfer, their half-life varies with vaccine strains and gestational timing (31). A(H1N1)pdm09-specific antibodies decline below the protective threshold (1:40) within 2 postnatal months (32). Concurrent immunological deficits in this age group include limited T-cell receptor diversity (20% of adult levels) (33), delayed interstitial macrophage maturation, impaired monocyte recruitment, and insufficient interferon-gamma (IFN-γ) secretion—collectively compromising viral clearance and elevating pneumonia risks (34). Male biological predisposition and behavioral patterns synergistically increase exposure. Biologically, X-chromosome haploinsufficiency limits immune regulatory genes (e.g., TLR7, CD40L), manifesting as lower respiratory mucosal IgA levels and delayed antibody responses compared to female counterparts (35,36). Epidemiologically, boys demonstrate 30% longer outdoor activity duration, particularly in lower socioeconomic households (37), enhancing pathogen exposure. Notably, cultural preferences for male child prioritization in healthcare access may confound true biological sex differences in certain regions (38).

Public health and policy implications

Vaccination, antibiotic treatment and hand hygiene promotion have been shown to be effective in reducing the burden of disease. However, in order to reduce the burden of disease due to influenza LRTIs in children under five years of age and to achieve SDG 3.2, greater focus is required on areas with low SDIs and on high-risk populations. Influenza vaccination should be prioritised and promoted in LRTI areas, especially for infant family members. A substantial body of research has demonstrated that the provision of influenza vaccination to all household contacts of infants aged between 0 and 6 months results in a significant reduction in the risk of influenza-like illness and severe acute respiratory infections in infants, with effectiveness rates of 48.9% and 76.9%, respectively (39). However, the lack of biochemical testing capacity in primary health care facilities in low- and middle-income countries (LMICs) hinders comprehensive diagnosis (40). Consequently, there is an imperative to enhance the capacity of primary health care systems and ensure universal access to rapid diagnostic tools to mitigate misdiagnosis and the exacerbation of the disease. Placental IgG transfer constitutes a pivotal mechanism of neonatal passive immunity (41), and for high-risk age groups such as newborns and infants, neonatal care ought to be integrated with maternal and child health services, including breastfeeding support, nutritional interventions, and an early warning system for respiratory infections, with a view to reducing the risk of infections through mother-to-child antibody transmission and early immunization in order to break the chain of disease progression. Furthermore, entrenched gender stereotypes and social norms represent significant drivers of health inequalities (42), which must be mitigated through the implementation of gender-sensitive policies, such as the improvement of access to healthcare for girls and the elimination of cultural biases. On a global scale, there is a necessity to combine the investment of resources by international organisations with the specific cause-of-death spectrum of low-income countries, such as Africa (dominated by infections) and Asia (dominated by perinatal complications) (43,44), through financial support, technology transfer, and equitable distribution of vaccines. These interventions must focus on cross-sectoral collaboration, data-driven decision-making and community participation to ensure accurate targeting of resources and sustainability of interventions, ultimately reducing health inequities and safeguarding children’s rights to survival and development.

Limitations and future directions

This study provides critical insights into the global burden of influenza LRTIs in children under five, but is not without its limitations. These include reliance on retrospective GBD estimates, which are prone to data gaps and diagnostic inconsistencies in low-resource settings, an ecological design that limits causal inference, insufficient exploration of SDI-specific drivers (e.g., economic, educational, or healthcare factors) and contextual risks (e.g., vaccination coverage), and a lack of granularity in analysing short-term epidemic fluctuations or mechanisms underlying sex/age disparities. Future research should prioritize the integration of primary surveillance data to validate estimates, the employment of causal models to identify modifiable risks, the conducting of stratified analyses of SDI components and contextual factors (e.g., urban/rural disparities), and the incorporation of dynamic modelling of seasonal trends and co-infections. Intervention-focused studies, including cost-effectiveness evaluations of vaccines or maternal health programs, alongside investigations into biological vulnerabilities (e.g., immune development) and social determinants (e.g., gender-based care inequities), are essential to refine equitable strategies for reducing the enduring burden in high-risk populations and regions.

Conclusions

This study reveals a significant decline in the global burden by analysing death rate and DALYs of global influenza-associated LRTIs in children under 5 years of age from 1990 to 2021 (84.41% decline in death rate and 84.43% decline in DALY rate). This trend is consistent with the overall decline in non-coronavirus disease 2019 (non-COVID-19) lower respiratory infections in the GBD 2021 study (12), but this study further focuses on the influenza-specific burden and clarifies the unique phenomenon of lagging progress but the largest declines in low SDI regions, with infants 1–5 months of age consistently being the most at-risk group, with a refined analysis by sub-SDIs and geographic regions. The findings indicate that both death rate and DALY rates were found to be significantly higher for boys than for girls, suggesting that despite the global progress that has been made, the burden of influenza LPIs remains an inequitable marker that disproportionately affects children in resource-poor settings. Addressing this issue necessitates multisectoral collaboration with a focus on ensuring vaccine equity, strengthening healthcare systems, and implementing gender-sensitive policies. By aligning with SDG 3.2, the international community can translate these insights into tangible reductions in preventable child death rate, ensuring that no area is left behind.

Acknowledgments

We gratefully acknowledge all members of the GBD Collaborative Network for their contributions to the 2021 GBD Study.

Footnote

Peer Review File: Available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-aw-2363/prf

Funding: This study was supported by the Fundamental Research Funds for the Central Public Welfare Research Institutes (No. ZB2025018), Noncommunicable Chronic Diseases-National Science and Technology Major Project: “Implementation Research on the Promotion Action of Chronic Disease Prevention and Control Techniques” (No. 2023ZD0509800), and Project II “Research on Mechanisms, Models, and Approaches to Promote Traditional Chinese Medicine Appropriate Techniques for Chronic Disease Prevention and Control” (No. 2023ZD0509802).

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jtd.amegroups.com/article/view/10.21037/jtd-2025-aw-2363/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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