Asthma Symptom Severity in School-Aged Children: 27-Year Worldwide Trends

Doctor helping patient use inhaler in office
The Global Asthma Network Phase I study of 119,795 school-aged children in 14 countries examined prevalence and severity of asthma symptoms over 3 decades.

Although the overall worldwide prevalence of asthma symptoms has been relatively stable over the past 27 years, about 1 in 20 school-aged children exhibit severe asthma symptoms, indicating a need for better asthma control efforts to lessen avoidable morbidity and mortality from asthma. Moreover, the severity and prevalence of asthma symptoms among children and adolescents varies worldwide according to age group, region, locality, and country income. These were among the results of the Global Asthma Network (GAN) Phase I study, a cross-sectional study of 119,795 school-aged children in 14 countries, recently published in The Lancet.

The GAN study used the same methods as the International Study of Asthma and Allergies in Childhood (ISAAC) Phase III, the only worldwide study of asthma using standardized methods allowing for cross-sectional comparisons of asthma prevalence across populations. Investigators for the GAN study hypothesized that the global burden of asthma symptoms was changing among school-aged children. Accordingly, investigators performed asthma symptom surveillance across the world in 2 different age groups of children, examining trends in the prevalence and severity of symptoms from asthma centers that had completed Global Asthma Network (GAN) Phase I as well as the ISAAC Phase I, ISAAC Phase III, or both. Key personnel at the GAN Global Centre in Auckland, New Zealand, were the same throughout ISAAC Phase I, ISAAC Phase III, and GAN Phase I.

The current analysis includes individuals from 2 age groups: children aged 6 to 7 years and adolescents aged 13 to 14 years. All of these individuals self-completed written questionnaires at school. Using this data, the researchers estimated the 10-year rate of change in prevalence, for each of the 27 center participating in the study, of current wheeze, ever having asthma, severe symptoms of asthma, night cough, and exercise-induced wheeze. Trends were estimated across world regions and income levels with the use of mixed-effects linear regression models.

The 27 centers studied spanned 14 countries in 4 regions: (1) Africa and Eastern Mediterranean, (2) America, (3) Europe, and (4) Southeast Asia and Western Pacific. All centers had completed ISAAC Phase I, Phase III, or both, as well as GAN Phase I methods and data checks.  Individual participants included 74,361 adolescents from 27 centers (response rate, 90%; range, 68% to 100%) and 45,434 children from 19 centers (response rate, 79%; range, 55% to 100%).

Approximately 1 in 10 individuals in both age-groups had experienced wheeze in the prior year, with nearly half of them having severe symptoms. In most of the centers, a change in prevalence of at least 2 SE between ISAAC Phase III and GAN Phase I was observed. From 1993 to 2020, adolescent participants demonstrated a significant reduction in point prevalence per decade in severe asthma symptoms (–0.37; 95% CI, –0.69 to –0.04), as well as an increase in ever having asthma (1.25; 95% CI, 0.67–1.83) and night cough (4.25; 95% CI, 3.06–5.44), the latter of which was also reported among children (3.21; 95% CI, 1.80–4.62).

The prevalence of current wheeze decreased in low-income countries in children (–1.37; 95% CI, –2.47 to –0.27) and in adolescents (–1.67; 95% CI, –2.70 to –0.64), whereas it increased in lower-middle-income countries in children (1.99; 95% CI, 0.33–3.66) and in adolescents (1.69; 95% CI, 0.13–3.25). In upper-middle-income and high-income countries, however, the prevalence of current wheeze remained stable.

The investigators concluded that the high worldwide burden of severe asthma symptoms reported in the current study could be alleviated by providing access to effective treatments for this major worldwide public health issue.

Disclosure: Some of the study authors have declared affiliations with biotech, pharmaceutical, and/or device companies. Please see original reference for a full list of disclosures.


Asher MI, Rutter CE, Bissell K, et al; Global Asthma Network Phase I Study Group. Worldwide trends in the burden of asthma symptoms in school-aged children: Global Asthma Network Phase I cross-sectional study. Lancet. 2021;398(10311):1569-1580. doi:10.1016/S0140-6736(21)01450-1