Sex-Specific and Long-Term Trends of Asthma, Allergic Rhinitis, and Atopic Dermatitis in South Korea, 2007–2022: A Nationwide Representative Study

Allergic diseases, including atopic dermatitis (AD), allergic rhinitis (AR), and asthma, represent a significant global health burden, affecting a substantial portion of the population worldwide [1‒3], which may lead to a significant decline in the quality of life [4]. This situation underscores the importance of understanding the factors associated with allergic diseases, including the role of different variables. According to a previous study, the prevalence of asthma has been reported to be 20% higher specifically in females aged over 35 years on a global scale [5]. Furthermore, another previous study found that females reported a higher history of personal and familial AD [6]. Such a discrepancy may be attributed to the influence of sex hormones on allergic diseases, resulting in a higher incidence of allergies in females post-puberty compared to males [7].

Although it is important to consider sex differences when examining allergic diseases, recent studies have not been designed to investigate the sex-specific and long-term prevalence and risk factors of these allergic diseases, especially during the COVID-19 pandemic. The COVID-19 pandemic has introduced several challenges and changes to healthcare systems and individual health behaviors, which could have influenced the prevalence and management of allergic diseases [8]. For instance, changes in hygiene practices, mask-wearing, and alterations in healthcare access during the pandemic may have had differential impacts on allergic disease prevalence and control across different sexes.

Therefore, this study investigates sex-specific, long-term prevalence, and risk factors of allergic diseases such as AD, AR, and asthma, explicitly considering the influence of sex and several variables before and during the COVID-19 pandemic [9]. The data for this analysis are derived from the Korea National Health and Nutrition Examination Survey (KNHANES), conducted from 2007 to 2022. By conducting this study, we can investigate the long-term prevalence and risk factors of allergic diseases in South Korea, emphasizing sex differences and the potential impact of the COVID-19 pandemic on these conditions.

This study used data from the KNHANES, an annual survey administered by the Korea Disease Control and Prevention Agency from 2007 to 2022 [9]. The KNHANES employs a complex stratified cluster sampling method to ensure representativeness and minimize bias [9]. In addition, the survey applies weighting factors to the collected data, accurately reflecting the Korean population’s distribution, thereby allowing for precise national health and nutrition assessments. Based on previous studies, we included variables that may influence allergic diseases: age, sex, region of residence, body mass index (BMI), education level, household income, and smoking status. For the analysis of sex-specific prevalence in AD, AR, and asthma, a nationally representative sample of 92,135 participants was selected. The survey spanned 16 years, with participant counts per year grouped as follows: 16,768 in 2007–2009; 17,773 in 2010–2012; 22,488 in 2013–2016; 18,548 in 2017–2019; 5,801 in 2020; 5,553 in 2021; and 5,204 in 2022. The study was approved by the Institutional Review Board of the Korea Disease Control and Prevention Agency (2007-02CON-04-P, 2008-04EXP-01-C, 2009-01CON-03-2C, 2010-02CON-21-C, 2011-02CON-06-C, 2012-01EXP-01–2C, 2013-07CON-03–4C, 2013-12EXP-03–5C, 2018-01-03-P-A, 2018-01-03-C-A, 2018-01-03-2C-A, 2018-01-03-5C-A, and 2018-01-03-4C-A), and written informed consent was obtained from all participants. The study was conducted using the principles outlined in the Declaration of Helsinki.

The objective of this study was to assess the overall trends in the sex-specific prevalence of AD, AR, and asthma from 2007 to 2022. Each allergic disease was defined by the question as follows: AD was defined as those who answered “yes” to “Have you ever been diagnosed with AD by a doctor?”; AR was defined as those who answered “yes” to “Have you ever been diagnosed with AR by a doctor?”; Asthma was defined as those who answered “yes” to “Have you ever been diagnosed with asthma by a doctor?” [9] Based on these questions, allergic diseases were determined according to their presence or absence. Furthermore, data were collected on potential risk factors for the onset of allergic diseases, including age, sex, and socioeconomic status [10].

The covariates considered in this study were selected based on previous studies indicating their potential influence on allergic diseases [11]. These covariates included sex, age (19–39, 40–59, and ≥60 years), region of residence (urban and rural) [12], BMI (underweight or normal, and overweight or obese), smoking status (none and current smoking), level of education (high school or lower education, and college or higher education), and household income (low and high). BMI categories were classified according to the Asian-Pacific guidelines into four groups: underweight (<18.5 kg/m²), normal weight (18.5–22.9 kg/m²), overweight (23.0–24.9 kg/m²), and obese (≥25.0 kg/m²) [13, 14]. Furthermore, current smokers were defined as those who engaged in smoking at least once within 1 month.

Using data from the KNHANES from 2007 to 2022, with data grouped annually, we examined trends in the sex-specific prevalence of AD, AR, and asthma. The survey period from 2007 to 2022 was segmented as follows: 2007–2009, 2010–2012, 2013–2016, 2017–2019, 2020, 2021, and 2022, with the pandemic period considered separately. The outcomes of this study were obtained through qualitative data expressed as proportions or percentages. Weighted complex sampling analysis was implemented to ensure precise estimation, minimizing the effect of the difference in the number of participants each year. For statistical analysis, weighted linear or binomial logistic regression models were utilized to compute odds ratios or β-coefficients with a 95% confidence interval (CI). To enhance the reliability of the findings, stratification analysis was carried out, accounting for variables such as age, sex, level of education, region of residence, household income, and smoking in all regression models. Moreover, weighted multivariate regression models were employed to compare the estimates of relevant factors before and during the pandemic. The results were presented in weighted odds ratios and their corresponding 95% CI. All statistical analyses were performed using SAS software (version 9.4; SAS Institute, Cary, NC, USA) with a two-sided test, and significance was considered at a p value <0.05 [15].

This study included a total of 92,135 participants for analysis after excluding 7,306 individuals with missing smoking status, education level, household income, BMI, and weighted data from the total sample of 99,441 survey respondents. The weighted baseline characteristics of the participants are as follows: sex (male, 49.6% [95% CI, 49.3–50.0]) and age (19–39 years, 36.2% [95% CI, 35.5–36.9]; 40–59 years, 39.3% [95% CI, 38.7–39.9]; and ≥60 years, 24.5% [95% CI, 23.9–25.2]; Table 1).

Table 2 and Figure 1 show the sex-specific prevalence of AD, AR, and asthma data comparing the periods before and during the COVID-19 pandemic from 2007 to 2022. For AD, there was an observed increase in prevalence among females, from 3.0% (95% CI, 2.6–3.4) during 2007–2009 to 4.3% (95% CI, 3.4–5.3) in 2022. Males similarly exhibited an increase, from 2.7% (95% CI, 2.2–3.2) in 2007–2009 to 5.0% (95% CI, 3.9–6.1) in 2022. The difference in prevalence between males and females was most pronounced in the case of AR. The rate of females was from 12.9% (95% CI, 12.1–13.7) in 2007–2009 to 19.3% (95% CI, 17.3–21.3) in 2022, while for males, the rate was from 10.5% (95% CI, 9.7–11.4) in 2007–2009 to 15.6% (95% CI, 13.8–17.4) in 2022. As for asthma, the prevalence showed a stable trend in both sexes. Females exhibited similar prevalence rates from 3.2% (95% CI, 2.7–3.6) in 2007–2009 to 3.0% (95% CI, 2.3–3.7) in 2022. Males exhibited a marginal increase from 2.2% (95% CI, 1.8–2.6) in 2007–2009 to 2.6% (95% CI, 1.9–3.3) in 2022.

For both males and females, the trends before the pandemic showed a continuous increase in the prevalence of AD and AR (AD: 2.8% [95% CI, 2.5–3.2] in 2007–2009; 3.6% [95% CI, 3.2–3.9] in 2017–2019; AR: 11.7% [95% CI, 11.1–12.4] in 2007–2009; 15.0% [95% CI, 14.3–15.7] in 2017–2019), while asthma maintained a relatively stable trend (2.7% [95% CI, 2.4–3.0] in 2007–2009; 3.0% [95% CI, 2.7–3.3] in 2017–2019).

During the pandemic, AD and AR also experienced an increase in prevalence (AD: 4.0% [95% CI, 3.4–4.7] in 2020; 4.7% [95% CI, 3.9–5.4] in 2022; AR: 15.8% [95% CI, 14.6–16.9] in 2020; 17.4% [95% CI, 16.0–18.9] in 2022); in contrast, asthma exhibited slight decreases in their trends (2.9% [95% CI, 2.3–3.4] in 2020; 2.8% [95% CI, 2.3–3.3] in 2022; online suppl. Table S1; for all online suppl. material, see https://doi.org/10.1159/000540928). However, there were no statistically significant differences in the prevalence of AD, AR, and asthma between the COVID-19 period and the pre-pandemic period.

Figure 2a–c and online supplementary Table S2 outline total and sex-specific risk factors. The risk factors associated with the prevalence of specific diseases among males and females were found to differ, indicating a broader range of risk factors for females as follows: First, for AD, both sexes exhibited common risk factors, including the age range of 19–39 years and an education level of college or higher. However, smoking and high household income emerged as an additional risk factor for females. Next, regarding AR, individuals aged 19–39 and those with high income and a college education or higher were identified as risk factors for both males and females. Nonetheless, smoking was identified as an additional risk factor for females. Lastly, for asthma, being overweight or obese and smoking were found to be risk factors for females.

Online supplementary Table S3 and Table S4 provide the weighted odds ratios (wORs) for AD, AR, and asthma compared to previous periods. Compared to the period from 2013 to 2016, the prevalence of AD and AR among females increased from 2017 to 2019 (AD: wORs, 1.2 [95% CI, 1.0–1.5]; AR: wORs, 1.1 [95% CI, 1.0–1.2]), while the prevalence of asthma increased among males (wORs, 1.4 [95% CI, 1.1–1.8]). Additionally, in 2020, compared to 2017–2019, there was an increase in the prevalence of AD among male smokers (wORs, 1.3 [95% CI, 0.8 to 2.9]) and an increase in the prevalence of asthma among female smokers (wORs, 2.5 [95% CI, 1.3–5.1]).

This study presents a large-scale analysis of sex-specific and long-term trends in AD, AR, and asthma prevalence over 16 years, from 2007 to 2022, involving 92,135 participants. For both sexes, the prevalence of AD and AR increased before the COVID-19 pandemic and continued to rise during the pandemic. Interestingly, among the three allergic diseases, AR exhibited a significant disparity in prevalence between males and females, with females showing higher rates. Meanwhile, the prevalence of asthma remained stable in both sexes. In addition, in the analysis of AD and AR, common risk factors for both males and females were the age range of 19–39 years and an education level of college or higher. However, females were found to have more risk factors for all three diseases, including smoking. Moreover, for AD, high income was identified as an additional risk factor, and for asthma, being overweight or obese was identified as an additional risk factor for females.

In this study, more risk factors were identified in females than in males. This is likely because females are biologically more sensitive to hormonal and environmental factors than males [16]. Previous studies have shown that allergic diseases are notably more prevalent among females post-puberty [17], mainly due to the significant impact of sex hormones on the prevalence of allergic diseases [18]. For instance, the increase in estrogen levels during the periovulatory stage of the menstrual cycle has been linked to exacerbated nasal congestion and more severe symptoms of rhinitis, contributing to the higher incidence of these conditions in females [19].

Moreover, smoking and obesity not only increase the risk of allergic diseases but also can have more detrimental effects on females than on males due to physiological and hormonal differences [20]. Females are more susceptible to smoking-related respiratory symptoms, potentially owing to hormonal variations and the anti-estrogenic effects of smoking [21]. Additionally, obese females are at a higher risk of developing asthma than males, likely because of obesity’s restrictive impact on lung function [22].

The previous nationwide study conducted in Mexico regarding the shift in the male-to-female ratio in allergic disease before and after adolescence also revealed a higher incidence of the three diseases in females than males in adults [23]. In contrast, the weighted prevalence of AR was reported to be significantly higher in males than in females in a previous study conducted in China (n = 184,326). However, risk factors such as younger age, smoking, higher education level, and higher income were similar to the results of this study [24].

Previous studies have primarily focused on trends and risk factors in children and adolescents, with a particular emphasis on well-known risk factors such as obesity [25, 26]. Furthermore, they have often examined single major allergic diseases, such as asthma, rather than a range of allergic conditions [27]. In contrast, this study distinguishes itself by analyzing representative data to identify long-term trends and risk factors for major allergic diseases, specifically AD, AR, and asthma, in adults. Additionally, by considering these trends and risk factors separately by sex, the study offers valuable insights into the differing manifestations of allergic diseases in males and females.

Given the significant national and financial burdens associated with allergic diseases, policymakers, and healthcare professionals have to manage these conditions effectively [28]. This study identifies several factors that render patients, especially females, more vulnerable to allergic diseases, including smoking, high household income, and overweight or obesity. Therefore, tailored management and interventions considering these factors by sex are essential.

First of all, public health campaigns aimed at promoting healthier lifestyle choices, such as quitting smoking and maintaining a healthy weight, should be implemented. These campaigns should target both sexes but pay special attention to females [29]. Furthermore, it is essential to raise awareness among policymakers and healthcare professionals about the influence of allergic diseases on individuals’ health [30]. Increased funding and resources for study, prevention, and treatment programs targeting allergic diseases can significantly address this challenge.

Developing comprehensive strategies tailored to the specific factors identified in this study is vital for reducing the prevalence of allergic diseases and improving the overall health outcomes of the population. Applying the findings of this study could enhance organizations’ effectiveness in combating allergic diseases.

This study effectively showed sex-specific trends in allergic disease prevalence using 16 years of nationally representative data. In addition, this study is the most updated and comprehensive analysis of the sex-specific prevalence, identifying various vulnerable factors. Notably, this approach allows patients with allergic diseases to recognize different risk factors depending on their sex and assist in managing these factors, such as age, education level, household income, BMI, and smoking. Moreover, this study offers essential insights for health policymakers and professionals on creating sex-specific health interventions, which could improve disease prevention and management efficiency and reducing long-term socioeconomic costs.

This study has certain limitations. First, this study could not attain the AR data from the KNHANES between 2010 and 2012; however, since the analysis is over 13 years, the absence of data for these 3 years may not significantly influence the comparison of overall prevalence by sex [31, 32]. Second, the identification of high income as a female risk factor could stem from the over-representation of individuals with high incomes within the baseline population in this study. Furthermore, a college degree or a higher educational level has also been identified as a risk factor, which may be due to their relatively higher participation in self-reported surveys [33]. Therefore, further investigation is required to determine the degree to which high income and higher education levels are closely associated with the incidence of allergic diseases. Third, our dataset is self-reported; therefore, collecting information on allergic diseases may be subject to reporting biases, potentially leading to an underestimation of prevalence due to biases such as recall, information, and selection biases [34]. In addition, while our analysis can find the correlations between the diseases and various variables, it cannot prove the causality [35]. Last, data were limited to South Koreans, which might restrict the findings’ broader applicability, indicating the necessity of a broader demographic study in the future [36]. Despite this limitation, the study provides valuable country-specific data on allergic diseases, which may vary in characteristics across different nations.

This study provides a comprehensive analysis of sex-specific and long-term trends in the prevalence of AD, AR, and asthma over 16 years, from 2007 to 2022, based on data from 92,135 participants. The findings indicate that the prevalence of both AD and AR increased before the COVID-19 pandemic and continued to rise during the pandemic for both sexes. Notably, AR prevalence was consistently higher in females compared to males, while asthma prevalence remained stable in both sexes throughout the study period. In examining risk factors, it was found that both males and females shared common risk factors for AD and AR, specifically being in the age range of 19–39 years and having a college education or higher. However, females exhibited a greater number of risk factors for all three conditions. Smoking emerged as a common risk factor for females across AD, AR, and asthma. Additionally, high income was identified as an additional risk factor for AD in females, and being overweight or obese was identified as an additional risk factor for asthma in females. Finally, this study underscores the need for sex-specific health interventions and further study to address the intricate impact of socioeconomic factors and lifestyle choices on the prevalence and risk of AD, AR, and asthma.

The study was approved by the Institutional Review Board of the Korea Disease Control and Prevention Agency (2007-02CON-04-P, 2008-04EXP-01-C, 2009-01CON-03-2C, 2010-02CON-21-C, 2011-02CON-06-C, 2012-01EXP-01-2C, 2013-07CON-03-4C, 2013-12EXP-03-5C, 2018-01-03-P-A, 2018-01-03-C-A, 2018-01-03-2C-A, 2018-01-03-5C-A, and 2018-01-03-4C-A), and written informed consent was obtained from all participants. Furthermore, the KNHANES provides public access to its data, which can be utilized as a valuable resource for diverse epidemiological investigations. The study was conducted using the principles outlined in the Declaration of Helsinki.

The authors have no conflicts of interest to declare.

This research was supported by grants from the National Research Foundation of Korea (NRF) funded by the Korean government (MSIT; RS-2023-00248157) and the Ministry of Science and ICT (MSIT), South Korea, under the ITRC (Information Technology Research Center) support program (IITP-2024-RS-2024-00438239) supervised by the IITP (Institute for Information and Communications Technology Planning and Evaluation). The funders had no role in study design, data collection, data analysis, data interpretation, or writing of the report.

Dr. Dong Keon Yon is the senior author, had full access to all of the data in the study, supervised the study, served as a guarantor, and took responsibility for the integrity of the data and the accuracy of the data analysis. All authors approved the final version of the manuscript before submission. Yesol Yim, Hyesu Jo, Selin Woo, and Dong Keon Yon contributed to the study concept and design; acquisition, analysis, or interpretation of data; statistical analysis; and drafting of the manuscript. Yesol Yim, Hyesu Jo, Seoyoung Park, Yejun Son, Jaeyu Park, Hyeon Jin Kim, Sooji Lee, Hayeon Lee, Damiano Pizzol, Lee Smith, Saiah Kim, Jiseung Kang, Selin Woo, and Dong Keon Yon contributed to critical revision of the manuscript for important intellectual content. Yesol Yim and Hyesu Jo contributed equally as the first authors. Selin Woo and Dong Keon Yon contributed equally as the corresponding authors. The corresponding author attests that all listed authors meet the authorship criteria and that no one meeting the criteria has been omitted.

Yesol Yim and Hyesu Jo contributed equally as co-first authors.Edited by: H.-U. Simon, Bern.

Data are publicly available on legal and ethical grounds from the Korea Disease Control and Prevention Agency as open data (https://www.kdca.go.kr/yhs/home.jsp). Further inquiries including the study protocol and statistical code can be directed to the corresponding author, Dong Keon Yon (email: yonkkang@gmail.com).