A new meta-analysis found prevalence of asthma higher in countries with better air quality, higher income status, and health care access.
A global study on the prevalence of asthma and its impact on specific subgroups found countries with higher air quality, income status, and health care access and quality reported higher asthma rates compared with low- and middle-income countries (LMIC). These findings, study authors wrote, suggest a poor understanding of asthma’s epidemiology, which may result in low diagnosis and underreporting among LMICs.
This research was published in the Journal of Asthma and Allergy.
Because asthma commonly presents as a range of respiratory symptoms such as coughing, wheezing, shortness of breath, and chest tightness, the diagnostic process is often complicated, study authors wrote. Moreover, heterogeneity in clinical practices across the globe in some cases reflects lack of resources and/or medical training, which, in turn, can lead to underreporting and difficulty interpreting prevalence estimates, especially in LMICs.
“The goal of this study was to determine the global prevalence of asthma and its aforementioned phenotypes (EA [eosinophilic asthma] and SA [severe asthma]), along with the prevalence of asthma with AR [allergic rhinitis] or NPs [nasal polyps], and to explore underlying drivers for the observed patterns,” the researchers of the study wrote. “To do this, we examined the scientific literature for studies reporting asthma and subgroup prevalence and compared our results to country-specific qualities like economic status and air quality.”
Data were extracted from the Global Burden of Disease, Injuries, and Risk Factors Study 2019 and a literature review through PubMed in October 2021.
Asthma prevalence values were obtained from 69 countries, based on estimates from 405 sources from epidemiological reports and scientific literature. The targeted literature review included 9 studies with prevalence estimates for the different subgroups, with additional sources included where available per country/disease category. The literature included real-world evidence studies, along with some reviews, to form the base of the pearl-growing technique to find additional sources of the same level of relevance and authority.
Additionally, a qualitative analysis was conducted to include country-specific factors affecting global prevalence distributions. Asthma prevalence values were aggregated according to 2020 Air Quality Index (AQI) values, 2022 World Bank economic status, and 2017 Institute for Health Metrics and Evaluation Healthcare Access and Quality (HAQ) values.
A total of 162 publications were included in the study, with asthma prevalence values ranging across continents from 3.44% (Asia), 3.67% (Africa), 4.90% (South America), 5.69% (Europe), 8.29% (North America), to 8.33% (Oceana).
The global asthma prevalence according to subgroups included:
Furthermore, countries with higher air quality, income status, and health care access and quality reported a higher asthma prevalence. For instance, the United States had the highest asthma prevalence (11.25%) and had good AQI (9.6), while Bangladesh reported the lowest asthma prevalence (1.43%) and had poor AQI (77.1). The researchers explained these results may be attributed to fine-scale geographical variations in air quality that are not captured by AQI, as well as the presence of household pollution that is extremely common in many countries.
However, the researchers also acknowledged that even in countries with higher HAQ, clinicians may still struggle to diagnose and provide care for patients with asthma.
The authors describe study limitations including the possible lack of reliable and accurate data, especially among clinical subgroups of asthma in LMICs. Yet, the findings support existing efforts to standardize health care practices, increase access to care, and improve reporting practices to reduce the global burden of asthma, according to the study.
“This study brought together information on the reported prevalence of asthma and asthma subgroups, as well as country-specific variables of AQI, HAQ, and economic status,” the researchers wrote. “The targeted searches adhered to the methodical pearl-growing technique to identify the most relevant sources of reported asthma subgroup prevalence.”