Fungal skin diseases (FSD) caused by dermatophytes and non-dermatophytes are among the most prevalent dermatological conditions, primarily affecting the skin, hair, and nails (1). According to the Global Burden of Disease (GBD) 2019, the global prevalence of FSD reached 1.65 billion, with an age-standardized prevalence rate (ASPR) of 21.4% and an age-standardized incidence rate (ASIR) of 21.2%, posing a significant challenge to global public health (2). Dermatophyte infections, predominantly caused by species of Trichophyton, Epidermophyton, Microsporum, and Nannizzia, are the primary pathogens responsible for skin, hair, and nail infections globally, accounting for 60%–70% of all cases (3, 4). The epidemiology of these infections is dynamic, varying by geographic location and specific populations, with incidence rates as high as 36.6%–78.4% in certain regions (5, 6). The prevalence of FSD caused by non-dermatophytes ranges from 0.8% to 65.8% (7, 8). In recent years, the incidence of non-dermatophyte infections has been steadily increasing, with studies in regions such as Thailand, Brazil, and Sri Lanka have reported that non-dermatophytes account for as much as 51.6%–68.2% of FSD (8, 9). Additionally, infections caused by Candida and Malassezia are on the rise, particularly among immunocompromised individuals, such as those with HIV/AIDS (10). The prevalence of FSD varies with age and gender (11–13). The incidence of FSD is highly variable due to factors such as climate, socioeconomic status, urban environment, migration, animal distribution, and cultural habits (1). Additionally, increasing research indicates that the incidence of chronic and persistent FSD has risen. This is not only associated with an increase in the prevalence of drug-resistant pathogens (14, 15) but may also be closely related to factors such as patients’ immune dysfunction (such as HIV, diabetes, systemic use of corticosteroids or immunosuppressants), natural immune deficiencies (such as CARD9 gene mutations), occupational exposure, climate change, and improvements in diagnostic tests and medical care (16).

FSD can significantly reduce patients’ quality of life, with disease severity being directly correlated with quality of life deterioration. This imposes a substantial burden on patients, their families, and national healthcare systems. Notably, skin and subcutaneous diseases are globally recognized as the fourth largest health problem, with FSD contributing the highest burden in most regions (2, 14). FSD can also have a substantial negative impact on patients' psychosocial health by reducing self-esteem, leading to embarrassment and social withdrawal (17). Additionally, the discomfort and inflammation associated with FSD may impair patients' ability to perform daily activities and even lead to disability (18). Severe FSD, if untreated or poorly managed, can result in secondary infections and significant morbidity, such as bacterial cellulitis and ulcers, thereby increasing mortality rates among patients with bacterial skin infections (19). Therefore, it is imperative to assess the burden caused by FSD to initiate targeted intervention campaigns globally.

In previous assessments, FSD was often discussed as part of the broader disease burden of Skin Diseases. Currently, only one study based on the GBD 2017 data has addressed FSD specifically (20). The study included only two indicators: prevalence and DALYs, analyzing the global burden of FSD. It utilized the DALYs metric to explore the current status of FSD across different age groups, genders, and high-burden countries. However, the study did not examine the changes in the burden of FSD over the past few decades. Furthermore, a comprehensive assessment of the burden of FSD based on GBD 2021 data remains largely unreported. Therefore, there is a need for a thorough description and analysis of the current global status of FSD and its trends over time. Based on the latest data from the 2021 GBD study, we evaluated the prevalence, incidence, and disability-adjusted life years (DALYs) for FSD at global, regional, and national levels from 1990 to 2021. Additionally, we analyzed the differences in the burden of FSD across various age groups and genders. By understanding the latest spatial distribution and temporal trends of FSD globally, we aim to inform policy-making, establish more rational and effective resource allocation, and implement disease prevention and control measures. This effort seeks to improve health disparities, enhance patients' quality of life, reduce avoidable healthcare costs, alleviate the disease burden, and potentially prompt action from policymakers.

Our research findings indicate that over the past 32 years, the global cases of prevalence, incidence, and DALYs of FSD have significantly increased by approximately 68%. This growth may be associated with a 45% increase in the global population, as well as improvements in public health systems and enhanced information reporting capabilities (23). Concurrently, the ASPR, ASIR, and ASDR of FSD are also showing an upward trend, indicating a worsening burden of FSD-related diseases globally. This trend may be attributed to the limited variety of antifungal drugs available (24) and the increasing resistance of various dermatophytes to these treatments (25), leading to a significant rise in globally treatment-resistant FSD. Notably, in 2021, the number of incidents of FSD is approximately three times higher than the number of prevalent cases, indicating a surge in new cases. We hypothesize that this increase may be linked to the global COVID-19 pandemic. Studies have shown that COVID-19 is a new risk factor for fungal infections, as its impact on the human immune system and treatments for COVID-19 can weaken the body's defences against fungi (26).

The study results indicate that in 2021, the number of FSD-related cases, ASPR, ASIR, and ASDR in developing regions was higher than those in developed regions. Research has shown that developed regions have a greater number of social determinants of health (SDOH), which are associated with an increased risk of FSD (27). Further analysis revealed that the middle SDI regions had the highest cases of FSD, accounting for 30% of the global. Over the past 32 years, the increase in the number of FSD-related cases in developing regions has exceeded that in developed regions. Overall, the burden of FSD is higher in developing regions, particularly in middle SDI regions, and this disparity is likely to widen in the future. Several factors may contribute to this phenomenon: Firstly, developing regions have large population bases and often face poorer socioeconomic conditions, which create favourable conditions for the transmission of FSD pathogens. Crowded living conditions facilitate close and prolonged contact between individuals, increased exposure to animal vectors, suboptimal hygiene, poor environmental sanitation, and a lack of public awareness about FSD pathogens, all of which can elevate infection risk (28, 29). Secondly, dermatophytes thrive in warm and humid environments, making them more common in tropical and subtropical regions (30), where many developing countries are located. Thirdly, in high SDI, robust healthcare systems are typically in place. Conversely, healthcare infrastructure in developing countries is often inadequate, and access to medical care is limited, which can result in misdiagnosis or delayed diagnosis of infections (31). Moreover, with changes in the socioeconomic conditions of these regions, there is an increase in reported triggering factors and disease diagnoses of FSD. The ongoing development of tourism and immigration hotspots also contributes to the epidemiological shift of FSD, further complicating its treatment (32, 33). Prolonged wearing of enclosed clothing can exacerbate dermatophyte infections, and clothing as a vector for dermatophytes poses a significant health risk. For example, a study found that FSD pathogens were isolated from clothing in the thriving second-hand clothing markets in Kenya, and as the markets become increasingly popular in certain African countries, potentially contributing to the rise of FSD in these regions (34). Therefore, it is necessary to devise country-specific strategies to reduce the burden of FSD. These strategies may include enhancing public health education, strengthening epidemiological surveillance, improving healthcare systems, advancing diagnostic technologies, and promoting interdisciplinary research to develop more effective prevention and treatment methods.

In 2021, the absolute highest number of FSD-related cases was reported in South Asia, while the highest ASPR was observed in Western Sub-Saharan Africa. Simultaneously, this region also had relatively high cases and showed a relatively high percentage change, indicating a heavy burden of FSD in these regions. This aligns with previous research (20), which attributes the high burden to the persistent prevalence of FSD in these areas, as well as to factors such as medical service levels, economic conditions, climate, and cultural background. Furthermore, studies have indicated that global warming may increase the incidence and transmission of skin fungal infections (35, 36). These findings underscore the urgency for governments in these regions to implement measures such as enhancing health education, providing accessible medical services, and promoting healthy lifestyles to mitigate this adverse trend. Our study reveals significant differences in the percentage change in FSD-related cases over the past 32 years across different countries. Countries in high SDI regions especially exhibit a marked polarization, with disparities up to 33-fold. India and China, the world's two most populous countries, had the highest number of FSD-related cases in 2021, accounting for 18% of the global population each. Although a decrease in ASPR, ASIR, and ASDR has been shown in India and China since 1990, these countries still account for the highest absolute FSD cases. Recent studies have reported a significant increase in the prevalence of dermatophytosis in India over the past decade, with prevalence rates ranging from 6.0% to 61.5%. Among these cases, 5%–10% of new cases of dermatophytosis have been identified as chronic and recurrent (3, 5). Additionally, research indicates an increasing number of reports of disseminated trichosporonosis worldwide, including in India (37). Furthermore, a notable epidemiological shift from T. rubrum to Trichophyton (T.) indotineae has been observed in India (38). Tinea capitis, one of the most common FSDs worldwide, primarily affects preadolescent children, especially boys. In 2021, China had 250 million children under the age of 14 (12, 39). Conversely, the declining trend in a few countries may reflect the positive impact of healthcare and public health management efforts in raising public health awareness, enhancing preventive measures, and improving disease outcomes (33). Ongoing monitoring of trends in these countries could help inform global strategies to alleviate the FSD burden.

Consistent with previous reports (20), the global burden of FSD, especially in developing countries, is higher among males than females and remains relatively stable, particularly in younger age groups. However, this trend reverses in older age groups (>65 years). Among the 5 SDI regions, the number of FSD-related cases is higher in males than females in low, low-middle, and middle SDI regions, whereas it is higher in females in high-middle and high SDI regions. In terms of age, consistent with previous research findings, the number of FSD-related prevalence, incidence, and DALY cases peak at ages 5–9 globally, while the ASR of these indicators shows a sharp increase in the 60–64 age group. The age groups at which FSD peaks cases in low SDI and low-middle SDI, middle SDI, high-middle SDI, and high SDI regions are 5–9 years, 45–49 years, and 70–74 years, respectively. This phenomenon is primarily due to poor personal hygiene, the use of local barbers, and close contact with playmates and siblings in younger age groups, increasing the risk of disease transmission. Elderly individuals are more susceptible to fungal infections due to factors such as declining physical function, decreased immune function, and multiple chronic comorbidities (40, 41). Furthermore, males in developing regions, as the primary household labour force, are more prone to occupational exposure. However, with age, the risk of infection decreases as men are less likely to engage in fungus-prone occupations (42). Conversely, women are more likely to keep pets, increasing the risk of zoonotic dermatophyte infections (43). With the improvement of SDI, the peak age for FSD-related cases has gradually shifted toward older age groups. This shift may also be related to females having a longer life expectancy than males and the ageing population in developed countries. There is a significant negative correlation between the ASR of FSD and SDI. In countries with lower SDI, the ASR of FSD has declined more markedly, possibly attributed to the increasing attention to the diagnosis, prevention, and treatment of FSD in these regions.

FSD not only occurs as a primary disease but also serves as a source of infection, transmitted directly or indirectly to close contacts through contaminated domestic or public environments, thereby further increasing the disease burden. In recent years, the increasing number of immunocompromised patients and the globalization of travel have led to rising incidence rates of FSD outside endemic regions. Concurrently, the global rise and spread of antifungal resistance, particularly among dermatophytes showing resistance to terbinafine, have caused significant healthcare challenges worldwide (44). On the other hand, the high failure rate of antifungal therapy poses greater challenges for the treatment of non-dermatophyte fungal infections (45). Furthermore, the ongoing COVID-19 pandemic has further exacerbated the incidence and treatment challenges of FSD. Therefore, enhanced monitoring and diagnosis of FSD, as well as increased public awareness and education on FSD and antifungal resistance, are essential. Public health intervention measures should promptly adapt to changes in factors and patterns of disease analysis and promote research and innovation in FSD prevention, diagnosis, treatment, and intervention measures. Efforts should also be made to promote research and development of novel antifungal drugs, and based on the latest distribution characteristics in various countries and regions, formulate targeted and effective comprehensive control strategies for FSD, striving to reduce the significant burden of FSD.

This study has several limitations. Firstly, the data primarily originate from disease reports and healthcare institutions, which may result in the inclusion of cases predominantly focusing on specific types of skin fungal infections. Additionally, the lack of more detailed clinical information may lead to incomplete or inaccurate data, potentially introducing bias in the burden assessment. Secondly, the data obtained from the GBD study heavily relies on statistical modelling methods, particularly in countries lacking original data, which may influence the accuracy of the results. Lastly, the assessment of FSD burden is complex, and the definition of disability weights remains quite superficial, making reliable “measurability” of disabilities very challenging. Additionally, the lack of mandatory reporting for fungal diseases, poor diagnostic test performance, and limited diagnostic capabilities of clinicians in certain regions may impact the reported global incidence of FSD. Therefore, when analyzing the burden of FSD using the GBD database, it is crucial to interpret the results with caution. It is recommended that other data sources and field surveys be integrated for a more accurate and comprehensive assessment.

Overall, the global burden of FSD has significantly increased from 1990 to 2021. The burden of FSD is negatively correlated with the SDI across regions and specific countries. Developing countries, particularly in middle SDI regions, exhibited a significantly higher burden of FSD compared to developed countries. While most countries experienced a declining trend in disease burden, a few countries, such as Mexico, are experiencing an upward trend in burden. The global burden of FSD is higher in males than in females, but this trend reverses in older age groups (>65 years). Additionally, as SDI improved, the age group at which FSD-related cases peak is gradually shifting towards older age groups. These findings highlight the necessity of developing targeted prevention and treatment strategies and rationally allocating healthcare resources to address the considerable variations in FSD burden across different geographic locations, genders, and populations.