Potential asthma risk factors do not account for global asthma symptom prevalence patterns and time trends in children and adolescents
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Published on: August 7, 2017
Charlotte E Rutter1, Richard J Silverwood1,2, Neil Pearce1
1Department of Medical Statistics, London School of Hygiene and Tropical Medicine, UK.
Insights
Asthma prevalence trends globally are not explained by common risk factors like diet or screen time. Country income influences prevalence, but significant unexplained variation remains, highlighting the complexity of childhood asthma.
Area of Science:
- Epidemiology
- Environmental Health
- Pediatrics
Background:
- Global asthma prevalence surveys were conducted between 1990 and 2020 by the International Study of Asthma and Allergies in Childhood (ISAAC) and the Global Asthma Network (GAN).
- These surveys focused on adolescents (13-14 years) and children (6-7 years) to investigate asthma symptom prevalence and trends.
Purpose of the Study:
- To assess whether potential asthma risk factors explain global asthma symptom prevalence trends over a 30-year period.
- To estimate the global asthma symptom prevalence in 2019 and identify factors associated with variations.
Main Methods:
- Mixed-effects linear regression models were employed to analyze associations between center-level risk factor prevalence and asthma symptom prevalence.
- Models estimated the relationship between risk factors and both mid-point prevalence and changes per decade, alongside overall 2019 prevalence.
Main Results:
- For adolescents, decreasing asthma prevalence showed weak associations with reduced fast-food consumption and television viewing. Higher prevalence was linked to frequent TV viewing and truck traffic.
- For children, no risk factors correlated with prevalence trends, but truck traffic and early-life paracetamol use were linked to higher mid-point prevalence.
- Estimated 2019 prevalence was 12.8%, with lower rates in low-income countries compared to higher-income nations. Risk factors did not alter these estimates.
Conclusions:
- Identified potential asthma risk factors do not adequately explain global prevalence patterns or temporal trends.
- While country income correlates with prevalence differences, a substantial unexplained variation persists, indicating other contributing factors.
- Further research is needed to understand the complex etiology of global asthma symptom prevalence.
Background:
The International Study of Asthma and Allergies in Childhood (ISAAC) and the Global Asthma Network (GAN) conducted a series of global asthma prevalence surveys, between 1990 and 2020, in adolescents aged 13-14 and children aged 6-7 years. We used them to assess whether potential asthma risk factors explain global asthma symptom prevalence trends over this period.
Method:
We fitted mixed-effects linear regression models to estimate associations between centre-level risk factor prevalence and both the mid-point asthma symptom prevalence and the change per decade. We also estimated the 2019 asthma symptom prevalence across all included centres.
Results:
For adolescents, across 50 centres in 26 countries there was weak evidence that decreasing asthma prevalence over time was associated with regular fast-food consumption and frequent television viewing. However, frequent television viewing, along with heavy truck traffic, were associated with higher prevalence of asthma symptoms at the study mid-point. For children, across 41 centres in 21 countries, no risk factors were associated with time trends in asthma symptom prevalence, but truck traffic and paracetamol in the first year of life were associated with higher mid-point prevalence.We estimated the 2019 asthma symptom prevalence, across a total of 124 centres, to be 12.8% (11.4%, 14.2%) with little evidence of a difference by age. Low-income countries had lower prevalence (children 5.2% [2.5%, 7.8%], adolescents 5.3% [2.8%, 7.8%]), than lower-middle-, upper-middle- and high-income countries (all approximately 14-15%). Including risk factors in the models did not change the estimates.
Conclusion:
Potential asthma risk factors do not seem to explain the global prevalence patterns or time trends. Country income accounts for some of the differences, but the unexplained variation is very high.
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