Key risk factors of asthma-like symptoms are mediated through infection burden in early childhood

The role of the early-life gut microbiome in childhood asthma

Asthma is a chronic disease affecting millions of children worldwide, and in severe cases requires hospitalization. The etiology of asthma is multifactorial, caused by both genetic and environmental factors. In recent years, the role of the early-life gut microbiome in relation to asthma has become apparent, supported by an increasing number of population studies, in vivo research, and intervention trials. Numerous early-life factors, which for decades have been associated with the risk of developing childhood asthma, are now being linked to the disease through alterations of the gut microbiome. These factors include cesarean birth, antibiotic use, breastfeeding, and having siblings or pets, among others. Association studies have highlighted several specific microbes that are altered in children developing asthma, but these can vary between studies and disease phenotype. This demonstrates the importance of the gut microbial ecosystem in asthma, and the necessity of well-designed studies to validate the underlying mechanisms and guide future clinical applications. In this review, we examine the current literature on the role of the gut microbiome in childhood asthma and identify research gaps to allow for future microbial-focused therapeutic applications in asthma.

Respiratory morbidity before and during the COVID-19 pandemic from birth to 18 months in a Swedish birth cohort

BACKGROUND

Respiratory infections in early life are an identified risk factor for asthma. We hypothesized that infection-prevention measures during the coronavirus disease 2019 (COVID-19) pandemic influenced the risk of respiratory morbidity and aeroallergen sensitization in early childhood.

OBJECTIVE

We compared respiratory morbidity and aeroallergen sensitization in children born before and during the pandemic.

METHODS

We compared a COVID-19 category (exposed children; n = 1661) to a pre-COVID-19 category (nonexposed children; n = 1676) by using data from the prospective population-based NorthPop Birth Cohort study in Sweden. Data on respiratory morbidity and concomitant medication were retrieved from national registers. Prospectively collected data on respiratory morbidity using web-based questionnaires at 9 and 18 months of age were applied. At age 18 months, serum IgE levels to aeroallergens were determined (n = 1702).

RESULTS

The risk of developing any respiratory tract infection (adjusted odds ratio [aOR] = 0.33 [95% CI, 0.26-0.42]), bronchitis (aOR = 0.50 [95% CI, 0.27-0.95]) and croup (aOR = 0.59 [95% CI, 0.37-0.94]) were decreased in the COVID-19 category. The risk of wheeze in the first 9 months was lower in the COVID-19 category (aOR = 0.70 [95% CI, 0.55-0.89]). There were also fewer prescriptions of antibiotics in the COVID-19 category. The prevalence of aeroallergen sensitization was similar between categories.

CONCLUSION

Children born during the COVID-19 pandemic demonstrated significantly decreased risks of respiratory infections and prescribed antibiotics until 18 months of age compared to children born before the COVID-19 pandemic. Whether this will affect the risk of developing asthma in childhood is being followed.

Burden of Infections in Early Life and Risk of Infections and Systemic Antibiotics Use in Childhood

Importance

A high infection burden in early childhood is common and a risk factor for later disease development. However, longitudinal birth cohort studies investigating early-life infection burden and later risk of infection and antibiotic episodes are lacking.

Objective

To investigate whether early-life infection burden is associated with a later risk of infection and systemic antibiotic treatment episodes in childhood.

Design, Setting, and Participants

This longitudinal cohort study of children from birth to age 10 or 13 years included data from the Danish population-based Copenhagen Prospective Studies on Asthma in Childhood (COPSAC) birth cohort between November 2008 to November 2010. Children were monitored for infection diagnoses and systemic antibiotic prescriptions from national databases until February 1, 2024, by which time they had completed the age 10- or 13-year visit. Children with immune deficiencies or congenital diseases were excluded.

Exposures

Daily diary-registered common infection episodes of cold, acute otitis media, tonsillitis, pneumonia, gastroenteritis, and fever episodes from birth to 3 years.

Main Outcome and Measures

After age 3 years, the incidence of moderate to severe infection diagnoses and systemic antibiotic prescriptions were estimated using adjusted incidence rate ratios (AIRRs) calculated from quasi-Poisson regression models. All analyses were adjusted for social and environmental confounders.

Results

A total of 614 children (317 male [51.6%]) with diary data from birth to 3 years had completed follow-up until age 10 or 13 years. No differences in baseline characteristics between the children having vs not having available diary data were noted. Children with a high vs low burden of diary-registered infections between birth and 3 years (ie, equal to and above vs below the median of 16) had an increased risk of later moderate to severe infections (181 vs 87 episodes; AIRR, 2.39; 95% CI, 1.52-3.89) and systemic antibiotic treatments (799 vs 623 episodes; AIRR, 1.34; 95% CI, 1.07-1.68) until age 10 or 13 years. Each diary infection episode also increased the later risk of moderate to severe infections (AIRR, 1.05; 95% CI, 1.02-1.08) and systemic antibiotic treatments (AIRR, 1.02; 95% CI, 1.01-1.04). Subtype analyses showed significant associations between each cold, acute otitis media, pneumonia, gastroenteritis, and fever episode between birth and 3 years and risk of later moderate to severe infections or systemic antibiotic treatments.

Conclusions and relevance

This longitudinal cohort study suggests that early-life infection burden may continue throughout childhood and is associated with later antibiotic treatments independent of social and environmental risk factors. These findings are important for prognosis and follow-up of children experiencing a high burden of common infections in early life.

Burden and Subtypes of Early Life Infections Increase the Risk of Asthma

BACKGROUND

Early life respiratory tract infections have been linked to the development of asthma, but studies on the burden and subtypes of common infections in asthma development are sparse.

OBJECTIVE

To examine the association between burden of early life infections, including subtypes, with the risk of asthma from age 3 to 10 years and lung function at age 10 years.

METHODS

We included 662 children from the Copenhagen Prospective Studies on Asthma in Childhood 2010 birth cohort, for whom infections such as colds, acute tonsillitis, acute otitis media, pneumonia, gastroenteritis, and fever were registered prospectively in daily diaries at age 0 to 3 years and asthma was diagnosed longitudinally from age 3 to 10 years. The association between the burden of infection and subtypes and risk of asthma was analyzed by generalized estimating equations.

RESULTS

The children experienced a median of 16 infections (interquartile range, 12-23 infections) at age 0 to 3 years. Children with a high burden of infections (above the median) had an increased risk of asthma at age 3 to 10 years (adjusted odds ratio = 3.61; 95% CI, 2.39-5.45; P < .001), which was driven by colds, pneumonia, gastroenteritis, and fever episodes (P < .05) but not by acute otitis media and tonsillitis. Lower lung function measures at age 10 years were associated with the burden of pneumonia but not the overall infection burden. The association between colds and the risk of asthma was significantly higher in children with allergic rhinitis at age 6 years (P interaction = .032).

CONCLUSION

A high burden of early life infections in terms of colds, pneumonia, gastroenteritis, and fever is associated with an increased risk of developing asthma, particularly in children with respiratory allergy. Strategies to diminish these early life infections may offer a path for the primary prevention of childhood asthma.

Genetics of preschool wheeze and its progression to childhood asthma

Wheezing is a common and heterogeneous condition in preschool children. In some countries, the prevalence can be as high as 30% and up to 50% of all children experience wheezing before the age of 6. Asthma often starts with preschool wheeze, but not all wheezing children will develop asthma at school age. At this moment, it is not possible to accurately predict which wheezing children will develop asthma. Recently, studying the genetics of wheeze and the childhood-onset of asthma have grown in interest. Childhood-onset asthma has a stronger heritability in comparison with adult-onset asthma. In early childhood asthma exacerbations, CDHR3, which encodes the receptor for Rhinovirus C, was identified, as well as IL33, and the 17q locus that includes GSDMB and ORMDL3 genes. The 17q locus is the strongest wheeze and childhood-onset asthma locus, and was shown to interact with many environmental factors, including smoking and infections. Finally, ANXA1 was recently associated with early-onset, persistent wheeze. ANXA1 may help resolve eosinophilic inflammation. Overall, despite its complexities, genetic approaches to unravel the early-onset of wheeze and asthma are promising, since these shed more light on mechanisms of childhood asthma-onset. Implicated genes point toward airway epithelium and its response to external factors, such as viral infections. However, the heterogeneity of wheeze phenotypes complicates genetic studies. It is therefore important to define accurate wheezing phenotypes and forge larger international collaborations to gain a better understanding of the pathways underlying early-onset asthma.