The 2019 GBD study was used to analyze the global, regional, and country urticaria burden from 1990 to 2019. The Institute for Health Metrics and Evaluation (IHME) coordinates the GBD study, which assesses illness, injury, and risk factor burden in 204 nations and territories. The GBD Results tool, an online data repository, provided the latest GBD estimations for our investigation.

To estimate the prevalence, incidence, and DALYs of urticaria, we used DisMod-MR 2.1, a Bayesian meta-regression tool developed by the IHME for modeling disease epidemiology. This tool allows for the integration of various data sources, including surveys, administrative records, and published studies, while accounting for potential biases and heterogeneity in the data.

The Socio-demographic Index (SDI) is a composite indicator expressed on a scale of 0 to 1 of development status that is strongly correlated with health outcomes. It is the geometric mean of indices of lag-distributed income per capita, mean years of schooling for individuals aged 15 years or more, and total fertility rate for individuals aged less than 25 years. A location with an SDI of 0 indicates a theoretical minimum level of development status relevant to health outcomes, while a location with an SDI of 1 indicates a theoretical maximum level.

The SDI is stratified into quintiles to provide nuanced distinctions in sociodemographic development. Specifically, a low SDI spans from 0 to 0.454743, followed by a low-middle SDI ranging from 0.454743 to 0.607679. The middle SDI encompasses values between 0.607679 and 0.689504. Subsequently, the high-middle SDI covers the range of 0.689504 to 0.805129, and finally, a high SDI is defined from values of 0.805129 up to 1.

The GBD study divides the world into 21 regions based on geographical location and epidemiological similarity. These regions are further subdivided into 204 countries and territories. In our analysis, we assessed the burden of urticaria for each region and country, enabling us to identify areas with the highest disease burden and potential targets for intervention.

Urticaria prevalence, incidence, and DALYs were computed for each SDI, area, and nation. We generated age-standardized estimated annual percentage changes (EAPCs) to quantify urticaria incidence, prevalence, and DALYs. Age-standardized incidence, prevalence, and DALY rates of urticaria were compared across populations after they were adjusted for potential age structure confounding by applying the age-specific rates for each location, gender, and year to a GBD world standard population.

The EAPC is a widely used measure of the age-standardized rate trend over a specified time interval [14]. We fitted a regression line to the natural logarithm of the age-standardized rate to calculate the EAPC: y = α + βx + ε, where y = ln (age-standardized rate) and x = calendar year. This was then expressed as a percentage: 100 × (eβ − 1). The 95% CI of the EAPC was calculated to reflect the temporal trend in the age-standardized rate. An upward trend in the age-standardized rate was indicated when the EAPC and the lower boundary of the 95% CI were positive, while a downward trend was indicated when the EAPC and the upper boundary of the 95% CI were negative. We calculated the EAPCs for age-standardized incidence rates, age-standardized prevalence rates, and age-standardized DALY rates of urticaria to reflect their temporal trends. All data analyses were conducted using R (version 4.2.1; R Foundation for Statistical Computing) and Origin (2022 version; OriginLab).

Our research is based on the secondary analysis of data derived from the 2019 GBD study. This comprehensive study integrated data from a diverse array of primary sources, including various surveys, censuses, vital statistics, and other health-related data sets that previously received ethical approval from their respective institutional review boards. Given that our study leverages secondary data, which is an aggregation and anonymization of these primary data sets, our analysis did not necessitate a separate institutional review board approval or exemption [14].

From 1990 to 2019, the global age-standardized prevalence, incidence, and DALY rates of urticaria remained stable, with women having higher rates than men. The number of cases, DALYs, and incidence increased during this period. In 2019, 65.14 million people had urticaria, with a prevalence of 841.88 per 100,000 population and an age-standardized prevalence rate of 865.51 per 100,000 population. The global DALY rate was 50.39 per 100,000 population, with an age-standardized rate of 51.91 per 100,000 population. Compared to 1990, the global age-standardized prevalence, incidence, and DALY rates increased by 2.92, 4.84, and 0.31 per 100,000 population, respectively, in 2019 (Figure 1; Multimedia Appendix 1, Tables S1 and S2).

In 2019, low-middle SDI regions had the highest age-standardized prevalence, incidence, and DALY rates, while high SDI regions had the lowest. Middle SDI regions experienced the most significant percentage changes from 1990 to 2019 in all 3 health indicators. All levels of SDI showed a decline in age-standardized DALY rates over the past 30 years, especially for the high-middle SDI group, which decreased from 52.25 per 100,000 population in 1990 to 51.18 per 100,000 population in 2019. However, the decline in the low-middle SDI group was smaller, from 54.44 per 100,000 population in 1990 to 54.72 per 100,000 population in 2019. Overall, the age-standardized DALY rates for women were higher than those for men in all SDI groups. In terms of different SDI groups, the high SDI group consistently had the lowest age-standardized DALY rates, while the low SDI group consistently had the highest rates. The age-standardized DALY rates for women were consistently higher than those for men, especially in the high SDI and high-middle SDI groups (Figure 2; Multimedia Appendix 1, Table S1).

Incidence rates declined for all SDI groups, with the greatest decrease observed in the high-middle SDI group, from 1534.30 per 100,000 population in 1990 to 1499.49 per 100,000 population in 2019. However, the change in incidence in the low-middle SDI group was not obvious, from 1613.38 per 100,000 population in 1990 to 1613.91 per 100,000 population in 2019. Women had higher incidence rates than men, especially in high SDI and high-middle SDI groups. Prevalence rates remained stable across different SDI levels, with women having higher rates than men. In 2019, Central Europe had the highest age-standardized prevalence, incidence, and DALY rates, while Western Europe had the lowest. From 1990 to 2019, all 21 regions showed stable age-standardized rates but increasing DALY, prevalence, and incidence numbers, with South Asia and East Asia having significantly higher numbers (Figure 2-3; Multimedia Appendix 1, Table S1).

The DALYs of urticaria varied significantly between countries and territories. In 2019, the lowest rate, 27.1 (95% uncertainty interval [UI] 17.7-38.1) per 100,000 population, was reported for Portugal, while the highest rate, 92.0 (95% UI 60.3-130.2) per 100,000 population, was reported for Nepal. The data include the DALY numbers for each country and territory in 2019, with India having the highest number at 749,495.9 (95% UI 490,301.3-1,074,876.0), followed by China at 576,544.5 (95% UI 379,886.1-818,597), Pakistan at 180,580.9 (95% UI 117,789.7-263,500.0), and the United States at 153,479.1 (95% UI 102,752.9-213,697.0), among others. The countries and territories with the lowest DALY numbers included Tokelau (0.60, 95% UI 0.39-0.87), Niue (0.67, 95% UI 0.43-0.96), and Nauru (4.74, 95% UI 3.09-6.93). From 1990 to 2019, the annual percentage change in age-standardized DALY rate differed, with the highest decrease in Qatar at –0.0719% (EAPC –0.0719, 95%CI –0.0906 to –0.0532) (Figure 4-5; Multimedia Appendix 1, Table S3).

For incidence, the age-standardized rate and number of new cases also varied widely across countries and territories. In 2019, out of 204 countries and territories, Portugal reported the lowest rate, 818.2 (95% UI 728.6-917.3) per 100,000 population, while Nepal had the highest rate, 2665.5 (95% UI 2904.2-2445.1) per 100,000 population. Incident cases in the 204 countries and territories varied greatly, ranging from as low as 17.8 (95% UI 15.6-20.5) in Tokelau to as high as 22,065,409 (95% UI 19,265,922-25,287,089) in India. Between 1990 and 2019, the annual percentage change in age-standardized incidence rate varied across countries and territories, with Qatar having the highest decrease at –0.0774% (EAPC –0.0774, 95% CI –0.0961 to –0.0587) (Figure 4-5; Multimedia Appendix 1, Table S3).

In terms of prevalence, there was considerable variation in age-standardized rates and the number of cases across countries and territories. Portugal reported the lowest age-standardized prevalence rate, 456.4 (95% UI 406.2-512.2) per 100,000 people in 2019, while Nepal reported the highest rate, 1534.6 (95% UI 1416.2-1662.5) per 100,000 people. Prevalence numbers for the 204 countries and territories ranged widely, from as low as 10.0 (95% UI 8.7-11.5) in Tokelau to as high as 12,552,793 (95% UI 10,916,085-14,379,341) in India. From 1990 to 2019, annual percentage changes in age-standardized prevalence rate varied across countries and territories. Qatar had the highest decrease, with a decline of 0.0795% (EAPC –0.0795, 95% CI –0.0988 to –0.0603) (Figure 4-5; Multimedia Appendix 1, Table S3).

We analyzed global data on rates and numbers for DALYs, prevalence, and incidence across age groups between 1990 and 2019. Rates were higher in younger age groups, decreased with age, and slightly increased in the oldest groups. Women had higher rates than men. A general increase in rates and numbers was observed across age groups between 1990 and 2019 that was more pronounced in younger populations and women. The largest increases occurred in age groups younger than 40 years, while the smallest increases were in groups older than 70 years. In both age groups, women consistently had higher numbers for DALYs, prevalence, and incidence, indicating an overall rising trend in disease burden, prevalence, and incidence (Multimedia Appendix 2, Figure S1).

Regional and SDI-level urticaria disease burden were also analyzed, focusing on rates and numbers for DALYs, prevalence, and incidence across age groups and genders. The youngest age group generally had the highest rates and numbers, decreasing with age. Women consistently had higher rates and numbers across most age groups and regions. Significant regional and SDI-level variations existed, with regions like South Asia, Western sub-Saharan Africa, North Africa, and the Middle East having higher burdens. Central and Eastern Europe had higher rates and numbers than Western Europe. DALY numbers decreased with age across SDI regions and genders, with women having higher numbers. DALY rate trends were similar, but differences between SDI regions and genders were less pronounced (Multimedia Appendix 2, Figures S2-S5).

At the SDI level, urticaria prevalence rates were analyzed across age groups, genders, and SDI regions. The rates were highest in the low-middle SDI group and generally decreased with age, with women consistently having higher rates. High and high-middle SDI groups had lower prevalence rates than low and low-middle groups. The prevalence number also decreased with age and was higher in women. High SDI and high-middle SDI regions had lower prevalence numbers (Multimedia Appendix 2, Figure S6).

Urticaria incidence rates varied across age groups and SDI regions, with women generally having higher rates. The highest incidence rate was in children younger than 5 years, and rates decreased with age. Low-middle SDI regions had the highest incidence rates, while middle SDI regions had the lowest. Incidence numbers followed similar trends, with higher numbers in low SDI and low-middle SDI regions and a decrease with age. The incidence was consistently higher in women across all groups (Multimedia Appendix 2, Figure S7).