The GBD Study 2019 offers a comprehensive analysis of health challenges worldwide, covering 369 diseases and injuries along with 87 risk factors from 1990 to 2019, across 204 countries and territories (16). Utilizing robust methodologies, previously detailed in extensive publications, this study highlights trends in epidemiological patterns. The GBD 2019’s extensive dataset, accessible via the Global Health Data Exchange (GHDX) and the interactive GBD Compare platform, serves as an invaluable resource for delineating the evolving landscape of global health challenges, including both fatal and non-fatal health outcomes.

Anemia is defined in this study by age-adjusted reduced hemoglobin levels, following specific criteria for classification. This analysis, spanning the years 1990 to 2019 across 204 nations, calculates the distribution of hemoglobin concentrations, anemia prevalence, and YLDs due to anemia across 37 identified etiologies, covering all genders and 25 age categories. The gradation of anemia into mild, moderate, and severe categories is based on hemoglobin concentration thresholds that vary by age, gender, and pregnancy status, in alignment with World Health Organization standards and adapted for specific demographic nuances.

The assessment of anemia prevalence in children under five utilized demographic health surveys, scholarly articles, and governmental reports. Data were aligned with specific geographic, age, gender, and pregnancy demographics, following GBD study protocols, including adjustments for elevation based on the WHO formula. The method did not alter hemoglobin sample collection or analysis techniques. Spatiotemporal Gaussian process regression and linear mixed-effects models estimated hemoglobin levels and anemia prevalence, applying inverse weighting for model accuracy. Discrepancies were smoothed across various dimensions, enhancing the precision of uncertainty quantification in the final results.

The YLDs calculation for anemia in children under five was conducted by correlating the number of anemia cases at each severity level with severity-specific disability weights. These weights represent the degree of health impairment on a scale from 0 (no impairment) to 1 (death), allowing for a nuanced understanding of anemia’s impact on early childhood development.

Our analysis identified several causes of anemia in children under five, employing a mutually exclusive and collectively exhaustive approach to assign each anemia case to one of the 37 defined causes. This involved utilizing distributions of hemoglobin concentration, overall anemia prevalence by severity, disease prevalence or incidence, and cause-specific hemoglobin shifts derived from extensive research. This detailed methodology facilitates a comprehensive understanding of anemia’s etiology in young children, which is essential for targeted health interventions.

We explored the relationship between anemia prevalence in children under five and socio-economic development, analyzing how anemia’s prevalence and impact on YLDs correlate with the SDI across different regions. Employing meta-regression models, we investigated the potentially non-linear relationships between anemia burden and SDI, identifying countries where anemia prevalence significantly deviates from expectations based on socio-economic status. This multifaceted analysis elucidates the influence of socio-economic factors on anemia prevalence and disability in young children, informing health policy and resource distribution.

Anemia’s impact on the global population of children under five in 2019 was profound, with the total YLDs amounting to 1,252.88 (95% UI: 831.62–1,831.34) per 100,000 population. A nuanced breakdown by severity reveals the differential impact of the condition: mild anemia contributed to a YLDs rate of 69.59 (95% UI: 24.62–152.53) per 100,000 population, moderate anemia presented a considerably higher YLDs rate of 985.46 (95% UI: 646.24–1,450.49) per 100,000 population, and severe anemia resulted in a YLDs rate of 197.82 (95% UI: 132.53–277.80) per 100,000 population (Supplementary Table S1).

Furthermore, the prevalence of anemia in 2019 among this demographic elucidates the extent of its reach. The overall prevalence was reported at a rate of 39,517.75 (95% UI: 38,784.81 - 40,239.62) per 100,000 population. Disaggregating this data by severity, mild anemia exhibited a prevalence rate of 18,880.01 (95% UI: 18,527.70 - 19,193.64) per 100,000, moderate anemia impacted 19,281.86 (95% UI: 18,822.14 - 19,795.88) per 100,000, and severe anemia was less common but still significant, with a prevalence rate of 1,355.87 (95% UI: 1,272.73 - 1,444.12) per 100,000 (Supplementary Table S1).

The analysis reveals stark regional disparities in childhood anemia, correlated with the SDI. Low SDI regions face the most severe burden, with a YLDs rate of 2310.58 per 100,000 population (95%UI: 1,522.92–3,346.29). This rate decreases in low-middle SDI regions to 1,487.04 (95% UI: 975.95–2,185.34), and further to 1,252.88 (95% UI: 831.62–1,831.34) globally. Higher SDI regions experience significantly lower rates, with middle, high-middle, and high SDI regions reporting YLDs of 725.25 (95% UI: 475.04–1,072.18), 448.08 (95% UI: 286.17–679.03), and 159.53 (95% UI: 97.23–251.78) respectively. In terms of prevalence, 67.43% of children under five in low SDI regions suffer from anemia, contrasting with only 14.40% in high SDI areas. Western and Central Sub-Saharan Africa record the highest rates, emphasizing extreme regional disparities in the impact of anemia.

Next, we elucidate the national disparities in the burden and prevalence of anemia among children under the age of 5 years in 2019. Notably, Yemen emerged as the country with the highest YLDs rate for anemia among children under five, registering 4,356.99 YLDs per 100,000 (95%UI: 2,894.25 - 6,249.51). This was closely followed by Burkina Faso with a rate of 4,060.77 YLDs per 100,000 (95% UI: 2,743.77 - 5,856.50), and Bhutan, which recorded a rate of 3,543.98 YLDs per 100,000 (95% UI: 2,266.97 - 5,124.99). Other countries with significant YLDs rates included Mali (3,458.41 YLDs, 95% UI: 2,288.55 - 4,958.01), Sierra Leone (3,085.13 YLDs, 95% UI: 2,019.33 - 4,577.64), and the Central African Republic (2,682.17 YLDs, 95% UI: 1,644.53 - 4,000.34), underscoring the acute burden of anemia in these nations (Figure 1A).

The prevalence of anemia among children under five further illustrates the severe impact of this condition. Bhutan reported the highest prevalence at 96.15% (95% UI: 89.49–100%), closely followed by Yemen with a prevalence of 92.61% (95% UI: 87.99–97.10%), and Burkina Faso at 88.95% (95% UI: 84.75–92.69%). Mali (83.86, 95% UI: 78.97–88.13%), Sierra Leone (81.71, 95% UI: 77.08–86.08%), and the Central African Republic (80.82, 95% UI: 72.86–87.86%) also exhibited high prevalence percentages, indicating a widespread impact across these regions (Figure 1B).

Globally, YLDs attributable to anemia have generally decreased over the past three decades for both genders across all age groups, with males consistently showing higher rates than females. For neonates (0–6 days), male YLDs decreased from 576.08 (95% UI: 369.47 to 859.27) to 541.04 (95% UI: 346.39 to 816.84), while female YLDs went from 336.29 (95% UI: 207.35 to 538.78) to 323.95 (95% UI: 197.22 to 517.40). In the 7–27 days age group, male YLDs saw a temporary rise from 2,557.11 (95% UI: 1,667.66 to 3,760.10) to 2,648.77 (95% UI: 1,745.83 to 3,843.95), contrasting with a decrease in females from 2,426.25 to 2,288.63. Both genders exhibited a downward trend in the 28–364 days category, with male YLDs reducing from 1,645.17 to 1,511.28, and female YLDs from 1,600.82 to 1,413.55. Children aged 1–4 years also saw declines, with male YLDs dropping from 1,556.87 to 1,225.95, and females from 1,455.92 (95% UI: 957.66 to 2,104.46) to 1,153.24 (95% UI: 755.59 to 1,688.78).

Prevalence trends varied by age. Newborns (0–6 days) saw an increase in anemia rates, with male rates rising from 27,938.12 per 100,000 to 29,744.13 per 100,000, and female rates from 23,356.06 per 100,000 to 24,406.13 per 100,000. Infants aged 7–27 days experienced slight increases in prevalence, while those in the 28–364 days group saw minor declines. The most notable decrease occurred in children aged 1–4 years, with male prevalence dropping from 44,744.73 per 100,000 to 38,777.18 per 100,000, and female rates from 41,780.57 per 100,000 to 36,499.94 per 100,000 (Figure 2).

Our findings reveal that dietary iron deficiency emerges as the leading global cause of anemia-related YLDs, followed in significance by hemoglobinopathies and hemolytic anemias. Other notable causes include neglected tropical diseases, malaria, vitamin A deficiency, and unspecified infectious diseases. The highest incidence rates were observed in tropical Latin America, South Asia, and both western and eastern sub-Saharan Africa, indicating geographical variations in anemia etiology.

Significant disparities in the predominant causes of anemia were noted globally and within specific regions (Figure 3A). While dietary iron deficiency was identified as the primary cause of anemia-related YLDs on a global scale and across most regions, the African regions exhibited a higher relative burden from malaria, neglected tropical diseases, and hemoglobinopathies/hemolytic disorders.

A detailed heat map analysis of the prevalence rates attributable to 15 causes of anemia among children under five further corroborates the variability in anemia etiology (Figure 3B). Consistent with the YLDs data, dietary iron deficiency ranked as the foremost contributor to the child anemia burden globally, succeeded by hemoglobinopathies and hemolytic anemias. Other significant causes encompassed neglected tropical diseases, malaria, vitamin A deficiency, and unspecified infectious diseases, with the highest prevalence rates recorded in tropical Latin America, South Asia, and sub-Saharan Africa.

In neonates, hemoglobinopathies are the primary contributors to anemia-related YLDs, accounting for 25% in males and 30% in females, followed by dietary iron deficiency which impacts 30% of males and 36% of females. Vitamin A deficiency affects 13% of males and 15% of females, with malaria contributing to around 9%. During the early infancy stage (7–27 days), dietary iron deficiency dominates, representing 35% of male and 37% of female anemia YLDs, with hemoglobinopathies causing around 12%. Vitamin A deficiency and malaria also contribute, albeit less significantly. For infants aged 28 to 364 days, dietary iron deficiency remains the largest factor, influencing 49% of male and 50% of female YLDs, while hemoglobinopathies affect about 9%. Children aged 1 to 4 years see dietary iron deficiency causing 47% of male and 48% of female anemia YLDs, with hemoglobinopathies contributing to around 6% (Figure 4A).

Prevalence patterns echo these findings, with dietary iron deficiency being most prevalent in neonates, affecting 28% of males and 32% of females, and similarly high figures persist across all age groups. Hemoglobinopathies and vitamin A deficiency remain consistent causes across different ages, while malaria’s impact is relatively lower but persistent (Figure 4B). This comprehensive assessment highlights the varied etiological landscape of anemia, dominated by nutritional deficiencies and genetic disorders across different developmental stages.

Our study reveals a strong inverse relationship between socio-economic development, measured by the SDI, and childhood anemia rates. Regions with lower SDI values, particularly below 0.5 in sub-Saharan Africa and South Asia, experience high anemia YLDs over 2000 per 100,000 population (Figure 5A). In contrast, more developed regions with SDI values above 0.7, such as North America, Europe, and high-income areas in Asia and Latin America, show significantly lower YLDs under 1000 per 100,000 (Figure 5B). The decline in anemia rates correlates with socio-economic improvements, especially noted in East and Southeast Asia from 1990 to 2019. However, Oceania, with a moderate SDI of 0.6, contradicts this trend, suggesting other factors may influence anemia rates. A similar pattern is observed in anemia prevalence, with high rates in low SDI regions and marked reductions in areas with higher SDIs (Figures 5C,D). Overall, the global data confirms that socio-economic advancement plays a crucial role in reducing the impact of childhood anemia.

This study underscores the multifaceted nature of anemia in children under five. Nonetheless, the current study is subject to certain limitations. Although the GBD study provides a comprehensive dataset, it predominantly depends on extant public health records and research, which may be incomplete or less accurate in specific regions. Consequently, estimates of the anemia burden in particular areas or among distinct demographic groups might not be entirely precise. Moreover, the inherent focus of this epidemiological methodology on quantitative metrics, such as incidence rates and YLDs, may result in the underestimation of the qualitative impact of anemia on individual and community well-being. This limitation could obscure significant socio-economic and psychological dimensions of anemia, thereby restricting the scope of the analysis and its implications for public health interventions.