Q&A: Asthma and atopic dermatitis trends around the globe

A new study published in The Lancet Respiratory Medicine aimed to provide updated insights into the global, regional, and national burden of asthma and atopic dermatitis from 1990 to 2021. Authors also examined the asthma burden attributable to key modifiable risk factors, including high body mass index (BMI) body mass index, occupational asthmagens, smoking, and nitrogen dioxide pollution. This study also projected trends to 2050.

In this Q&A, we speak with Dr. Jiyeon Oh, IHME collaborator.

This transcript has been lightly edited for clarity

What did the research into Asthma and Atopic Dermatitis set out to do?

Our study aims to provide updated insights into the global, regional, and national burden of asthma and atopic dermatitis from 1990 to 2021. We also examined the asthma burden attributable to key modifiable risk factors, including high BMI [body mass index], occupational asthmagens, smoking, and nitrogen dioxide pollution. Projecting forward to 2050 is essential for long-term health care planning. So, as population growth and environmental changes continue to influence disease patterns, forecasting future trends enables policymakers to allocate resources effectively, implement preventive strategies, and improve health care interventions.

So, we use predictive modeling based on Socio-demographic Index, air pollution levels, and smoking trends to estimate future prevalence.

What were the key findings of your research?

By 2021, an estimated 260 million people had asthma, while 129 million had atopic dermatitis worldwide. While the total number of cases increased due to population growth, the age- standardized prevalence rates actually declined over time.

The first figure presents a world map illustrating the percentage change in the age-standardized prevalence rate of asthma from 1990 to 2021. The most significant decline was observed in Japan and the high-income Asia Pacific region, which could be likely due to advancements in health care access, improved disease management, and public health interventions aimed at reducing asthma triggers.

The second part of the figure shows the percentage change in the age-standardized prevalence rate of atopic dermatitis over the same period. Unlike asthma attacks, atopic dermatitis exhibited minimal change overall. While most regions experienced a decline over the past three decades, Eastern Europe, particularly Russia, showed an increase, which may be attributed to environmental changes, urbanization, or shifts in diagnostic practices.

As a secondary analysis, our decomposition analysis shows that the primary driver of this change is population growth rather than aging or a rise in disease prevalence. This means that while individual risk may be decreasing, the overall number of cases will still rise due to an increasing global population.

How did COVID-19 impact Asthma and Atopic Dermatitis?

We also examined the impacts of the COVID-19 pandemic on these diseases. We found that during the pandemic, the long-term decline in asthma prevalence came to a halt, meaning that the expected reduction in cases was no longer happening.

So this figure illustrates the impact of the COVID-19 pandemic on asthma and atopic dermatitis prevalence trends. The long-term decline in asthma prevalence stagnated during the pandemic globally and across most regions. In contrast, atopic dermatitis prevalence remained stable across all regions. This suggests that the pandemic had a stronger impact on asthma trends, possibly due to lifestyle factors and increased respiratory infections, which is one of the most important triggers for asthma.

How did a country’s place on the socio-demographic index affect the impact of Asthma there?

We found some clear differences depending on SDI levels. First, for asthma, we saw the highest prevalence in high SDI countries. However, the burden of the disease, meaning the impact it has in terms of disability and premature mortality, was actually greater in low SDI settings. This is likely due to differences in health care access, delayed diagnosis, and inadequate treatments in lower-income regions. We also found that different risk factors contributed to the burden of asthma depending on the SDI level of a country.

While high BMI played a dominant role in asthma burden, regardless of the SDI level, it was pronounced in high SDI settings. In contrast, in lower-income regions, occupational asthmagens and smoking were essential contributors to disease burden. So this suggests that intervention strategies should be tailored according to original risk factor profiles in order to be most effective.

What do your projections for Asthma and Atopic Dermatitis through 2050 reveal?

By 2050, asthma cases are projected to rise to 275 million. However, some regions, such as high-income Asia Pacific, Eastern Europe, and Central Europe have expected declines. According to our decomposition analysis, population growth is identified as a primary driver of increasing case numbers worldwide. By 2050, atopic dermatitis cases are expected to rise to 148 million, which is also due to population growth rather than increasing prevalence rates. However, Central Europe, high-income Asia Pacific, East Asia, and Eastern Europe showed a decrease in atopic dermatitis case counts. The age-standardized atopic dermatitis prevalence rate in 2050 is projected to change minimally from 2021.