Risk Factors and Age-Related Patterns of Asthma-Like Symptoms in Early Childhood

Understanding the childhood origins of asthma and chronic obstructive pulmonary disease: Insights from birth cohorts and studies across the life-span

Birth cohorts have identified modifiable risk factors for asthma and respiratory health in children and adults, demonstrating the important role and pathways through which early-life events influence not only child outcomes but also adult health, disease, and mortality. This focused literature update from 2021 to 2024 summarizes birth cohort studies across the life-span that contribute to our understanding of risk factors for and the childhood origins of asthma and chronic obstructive pulmonary disease that may inform prevention efforts. We conclude that there are critical periods of developmental plasticity and susceptibility during which early-life events and exposures likely have the greatest impact on the development of asthma and chronic obstructive lung disease phenotypes, and that there are important prenatal and early childhood exposures, which, if modified, might be candidates for improving respiratory health across the life-span. Birth cohorts have been and will continue to be critical to advancing our understanding of lung health and disease across the life-span, including asthma and chronic obstructive pulmonary disease. As child mortality declines and the human population ages, data from birth cohort studies are needed to inform strategies for optimizing healthy longevity, including the investment in understanding the lifelong consequences of adverse prenatal and early childhood exposures.

The Impact of the Indoor Environment on Childhood Asthma

PURPOSE OF REVIEW

This manuscript reviews the impact of important indoor environmental exposures on pediatric asthma, with a focus on recent literature in the field.

RECENT FINDINGS

Studies continue to support an association between numerous indoor aeroallergens and air pollutants found in homes and schools and increased asthma morbidity overall. Several recent home and school intervention studies have shown promise, though results have been overall mixed. Indoor environmental exposures contribute to the development of asthma and impact asthma morbidity. Further research is needed to improve our understanding of how to optimize mitigation of these indoor exposures to significantly affect asthma outcomes.

Diagnostic Accuracy of FEF25-75 for Bronchial Hyperresponsiveness in Patients with Suspected Asthma and/or Allergic Rhinitis: A Systematic Review and Meta-analysis

BACKGROUND

Some studies have suggested that the forced expiratory flow between 25 and 75% of vital capacity (FEF25-75) can be used as an early marker of bronchial hyperresponsiveness (BHR) in asthma and allergic rhinitis (AR), but is highly variable. Here, we aimed to assess whether the FEF25-75 can be used to diagnose BHR in patients with asthma-like symptoms and AR.

METHODS

PubMed, EMBASE, Web of Science, Wiley Online Library, Cochrane Library, SinoMed, CNKI, and Wanfang Data were searched to acquire eligible studies. Articles published before 30 Sep 2023 were included. Quality Assessment of Diagnostic Accuracy Studies 2 was used to evaluate the risk of bias and application concern of the included articles. Data were pooled using random-effects models. The univariable meta-regression and subgroup analyses were used to explore the sources of heterogeneity.

RESULTS

Twenty-five studies were included, describing 12,310 patients with asthma-like symptoms and AR. In terms of the FEF25-75, the pooled sensitivity and specificity were 0.56(95% CI 0.47-0.65) and 0.86 (95% CI 0.80-0.90), respectively. In addition, the pooled diagnostic odds ratio (DOR) was 8.00 (95% CI 6-10) and the area under the curve (AUC) was 0.80 (95% CI 0.76-0.83). Furthermore, we performed the univariable meta-regression and subgroup analyses, indicating that the disease types and ethnicity may be the sources of heterogeneity.

CONCLUSION

This meta-analysis showed that if BPT cannot be performed a value of FEF25-75 < 65% of predicted may suggest the presence of BHR in patients with suspected asthma and /or AR.

Levels of total IgE versus specific IgE during childhood for defining and predicting T2-high asthma

Background

T2-high asthma is characterized by elevated blood eosinophils (b-eos), and/or fractional exhaled nitric oxide (FeNO), and/or being "allergy-driven", which is not well-defined.

Objective

To investigate the role of total and specific immunoglobulin E (tIgE/sIgE) for defining and predicting T2-high asthma in childhood as biomarkers of "allergy-driven".

Methods

We utilized data from the COPSAC2000 (n = 411) and COPSAC2010 (n = 700) mother-child cohorts with repeated measurements of tIgE, sIgE, b-eos and FeNO through childhood. We defined T2-high asthma by elevated b-eos (≥0.3 × 109/L) and/or FeNO (≥20 ppb) and analyzed association with elevated tIgE (age-specific cut-offs) and sIgE (≥0.35 kU/L) using logistic regression at ages 7/10/13/18 years. Further, we analyzed the association between elevated tIgE and sIgE at age 0-4 years and later risk of T2-high asthma using logistic regression and ROC models.

Results

Elevated tIgE was associated with risk of T2-high asthma at all time points, whereas elevated sIgE showed similar results at ages 10/13/18 years. There was no overall model fit preference for a combination of tIgE and sIgE instead of tIgE or sIgE alone using Vuong's Likelihood-Ratio-Test, Akaike or Bayesian Information Criterion. Further, elevated tIgE at age 0-4 years was associated with later risk of T2-high asthma at all time points (AUC = 0.63-0.70, sensitivity = 0.62-0.81, specificity = 0.57-0.78), whereas elevated sIgE at 0-4 years was only associated with T2-high asthma at 18 years (AUC = 0.66, sensitivity = 0.45, specificity = 0.88). There were no significant differences in AUC values between tIgE and sIgE (DeLong's test).

Conclusion

Elevated tIgE and sIgE are equally useful stand-alone biomarkers for defining and predicting risk of T2-high asthma in childhood.

Symptom trajectories in infancy for the prediction of subsequent wheeze and asthma in the BILD and PASTURE cohorts: a dynamic network analysis

BACKGROUND

Host and environment early-life risk factors are associated with progression of wheezing symptoms over time; however, their individual contribution is relatively small. We hypothesised that the dynamic interactions of these factors with an infant's developing respiratory system are the dominant factor for subsequent wheeze and asthma.

METHODS

In this dynamic network analysis we used data from term healthy infants from the Basel-Bern Infant Lung Development (BILD) cohort (435 neonates aged 0-4 weeks recruited in Switzerland between Jan 1, 1999, and Dec 31, 2012) and replicated the findings in the Protection Against Allergy Study in Rural Environments (PASTURE) cohort (498 infants aged 0-12 months recruited in Germany, Switzerland, Austria, France, and Finland between Jan 1, 2002, and Oct 31, 2006). BILD exclusion criteria for the current study were prematurity (<37 weeks), major birth defects, perinatal disease of the neonate, and incomplete follow-up period. PASTURE exclusion criteria were women younger than 18 years, a multiple pregnancy, the sibling of a child was already included in the study, the family intended to move away from the area where the study was conducted, and the family had no telephone connection. Outcome groups were subsequent wheeze, asthma, and healthy. The first outcome was defined as ever wheezed between the age of 2 years and 6 years. Week-by-week correlations of the determining factors with cumulative symptom scores (CSS) were calculated from weeks 2 to 52 (BILD) and weeks 8 to 52 (PASTURE). The complex dynamic interaction between the determining factors and the CSS was assessed via dynamic host-environment correlation network, quantified by a simple descriptor: trajectory function G(t). Wheeze outcomes at age 2-6 years were compared in 335 infants from BILD and 437 infants from PASTURE, and asthma outcomes were analysed at age 6 years in a merged cohort of 783 infants.

FINDINGS

CSS was significantly different for wheeze and asthma outcomes and became increasingly important during infancy in direct comparison with all determining factors. Weekly symptoms were tracked for groups of infants, showing a non-linear increase with time. Using logistic regression classification, G(t) distinguished between the healthy group and wheeze or asthma groups (area under the curve>0·97, p<0·0001; sensitivity analysis confirmed significant CSS association with wheeze [BILD p=0·0002 and PASTURE p=0·068]) and G(t) was also able to distinguish between the farming and non-farming exposure groups (p<0·0001).

INTERPRETATION

Similarly to other risk factors, CSS had weak sensitivity and specificity to identify risks at the individual level. At group level however, the dynamic host-environment correlation network properties (G(t)) showed excellent discriminative ability for identifying groups of infants with subsequent wheeze and asthma. Results from this study are consistent with the 2018 Lancet Commission on asthma, which emphasised the importance of dynamic interactions between risk factors during development and not the risk factors per se.

FUNDING

The Swiss National Science Foundation, the Kühne Foundation, the EFRAIM study EU research grant, the FORALLVENT study EU research grant, and the Leibniz Prize.

Increasing awareness regarding the relationship between environmental exposures and allergic disease

This review highlights studies from the past 3 years that add to the understanding of the impact of environmental exposures on allergic disease. These include aeroallergens, air quality, prenatal or early-life exposures, and occupational exposures. Recent studies have focused on the relationship between the environment, the microbiome, and allergic disease, and new therapeutic options have also been reviewed. Lastly, there has been significant recent research improving our knowledge of the link between health disparities and environmental exposures. These scientific advances have resulted in a better understanding that sets the foundation for current and future research dedicated to improving health outcomes by modifying environmental exposures.

Genetic predisposition to high BMI increases risk of early life respiratory infections and episodes of severe wheeze and asthma

BACKGROUND

High body mass index (BMI) is an established risk factor for asthma, but the underlying mechanisms remain unclear.

OBJECTIVE

To increase understanding of the BMI-asthma relationship by studying the association between genetic predisposition to higher BMI and asthma, infections and other asthma traits during childhood.

METHODS

Data were obtained from the two ongoing Copenhagen Prospective Studies on Asthma in Childhood (COPSAC) mother-child cohorts. Polygenic risk scores for adult BMI were calculated for each child. Replication was done in the large-scale register-based Integrative Psychiatric Research (iPSYCH) cohort using data on hospitalisation for asthma and infections.

RESULTS

In the COPSAC cohorts (n=974), the adult BMI polygenic risk score was significantly associated with lower respiratory tract infections (incidence rate ratio (IRR) 1.20, 95% CI 1.08-1.33, false discovery rate p-value (pFDR)=0.005) at age 0-3 years and episodes of severe wheeze (IRR 1.30, 95% CI 1.06-1.60, pFDR=0.04) at age 0-6 years. Lower respiratory tract infections partly mediated the association between the adult BMI polygenic risk score and severe wheeze (proportion mediated: 0.59, 95% CI 0.28-2.24, p-value associated with the average causal mediation effect (pACME)=2e-16). In contrast, these associations were not mediated through the child's current BMI and the polygenic risk score was not associated with an asthma diagnosis or reduced lung function up to age 18 years. The associations were replicated in iPSYCH (n=114 283), where the adult BMI polygenic risk score significantly increased the risk of hospitalisations for lower respiratory tract infections and wheeze or asthma throughout childhood to age 18 years.

CONCLUSION

Children with genetic predisposition to higher BMI had increased risk of lower respiratory tract infections and severe wheeze, independent of the child's current BMI. These results shed further light on the complex relationship between body mass BMI and asthma.

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.

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

BACKGROUND

Risk factors of asthma-like symptoms in childhood may act through an increased infection burden because infections often trigger these symptoms.

OBJECTIVE

We sought to investigate whether the effect of established risk factors of asthma-like episodes in early childhood is mediated through burden and subtypes of common infections.

METHODS

The study included 662 children from the Copenhagen Prospective Studies on Asthma in Childhood 2010 mother-child cohort, in which infections were registered prospectively in daily diaries from age 0 to 3 years. The association between established risk factors of asthma-like episodes and infection burden was analyzed by quasi-Poisson regressions, and mediation analyses were performed for significant risk factors.

RESULTS

In the first 3 years of life, the children experienced a median of 16 (interquartile range, 12-23) infectious episodes. We found that the infection burden significantly (PACME < .05) mediated the association of maternal asthma (36.6% mediated), antibiotics during pregnancy (47.3%), siblings at birth (57.7%), an asthma exacerbation polygenic risk score (30.6%), and a bacterial airway immune score (80.2%) with number of asthma-like episodes, whereas the higher number of episodes from male sex, low birth weight, low gestational age, and maternal antibiotic use after birth was not mediated through an increased infection burden. Subtypes of infections driving the mediation were primarily colds, pneumonia, gastroenteritis, and fever, but not acute otitis media or acute tonsillitis.

CONCLUSIONS

Several risk factors of asthma-like symptoms in early childhood act through an increased infection burden in the first 3 years of life. Prevention of infectious episodes may therefore be beneficial to reduce the burden of asthma-like symptoms in early childhood.

Bacteria and viruses and their role in the preschool wheeze to asthma transition

Wheezing is the cardinal symptom of asthma; its presence early in life, mostly caused by viral infections, is a major risk factor for the establishment of persistent or recurrent disease. Early-life wheezing and asthma exacerbations are triggered by common respiratory viruses, mainly rhinoviruses (RV), and to a lesser extent, respiratory syncytial virus, parainfluenza, human metapneumovirus, coronaviruses, adenoviruses, influenza, and bocavirus. The excess presence of bacteria, several of which are part of the microbiome, has also been identified in association with wheezing and acute asthma exacerbations, including haemophilus influenza, streptococcus pneumoniae, moraxella catarrhalis, mycoplasma pneumoniae, and chlamydophila pneumonia. While it is not clear when asthma starts, its characteristics develop over time. Airway remodeling already appears between the ages of 1 and 3 years of age even prior to the presence of atopic inflammation or an asthma diagnosis. The role of genetic defect or variations hampering the airway epithelium in response to environmental stimuli and severe disease morbidity are now considered as major determinants for early structural changes. Repeated viral infections can induce and perpetuate airway hyperresponsiveness. Allergic sensitization, that often precedes infection-induced wheezing, shifts inflammation toward type-2, while common respiratory infections themselves promote type-2 inflammation. Nevertheless, most children who wheeze with viral infections during infancy and during preschool years do not develop persistent asthma. Multiple factors, including illness severity, viral etiology, allergic sensitization, and the exposome, are associated with disease persistence. Here, we summarize current knowledge and developments in infection epidemiology of asthma in children, describing the known impact of each individual agent and mechanisms of transition from recurrent wheeze to asthma.

Ambient fine particulate matter and allergic symptoms in the middle-aged and elderly population: results from the PIFCOPD study

BACKGROUND

The associations between short- and long-term exposure to ambient fine particulate matter with an aerodynamic diameter ≤ 2.5 µm (PM_2.5) and allergic symptoms in middle-aged and elderly populations remain unclear, particularly in China, where most cities have severe air pollution.

METHODS

Participants (n = 10,142; age = 40-75 years) were recruited from ten regions in China from 2018 to 2021 for the Predictive Value of Inflammatory Biomarkers and Forced Expiratory Volume in 1 s (FEV₁) for Chronic Obstructive Pulmonary Disease (PIFCOPD) study. Short-term (lag0 and lag0-7 day) and long-term (1-, 3- and 5-year) PM_2.5 concentrations at residences were extracted from the air pollutant database known as Tracking Air Pollution (TAP) in China. Multivariate logistic regression models were used to estimate associations for short- and long-term PM_2.5 exposure concentrations and long-term exposure models were additionally adjusted for short-term deviations.

RESULTS

A 10 µg/m³ increase in PM_2.5 on the day the allergic symptoms questionnaire was administered (lag0 day) was associated with higher odds of allergic nasal (1.09, 95% CI 1.05, 1.12) and eye symptoms (1.08, 95% CI 1.05, 1.11), worsening dyspnea caused by allergens (1.06, 95% CI 1.02, 1.10), and ≥ 2 allergic symptoms (1.07, 95% CI 1.03, 1.11), which was similar in the lag0-7 day concentrations. A 10 µg/m³ increase in the 1-year average PM_2.5 concentration was associated with an increase of 23% for allergic nasal symptoms, 22% for eye symptoms, 20% for worsening dyspnea caused by allergens, and 21% for ≥ 2 allergic symptoms, similar to the 3- and 5-year average PM_2.5 concentrations. These associations between long-term PM_2.5 concentration and allergic symptoms were generally unchanged after adjustment for short-term deviations.

CONCLUSIONS

Short- and long-term exposure to ambient PM_2.5 was associated with an increased risk of allergic nasal and eye symptoms, worsening dyspnea caused by allergens, and ≥ 2 allergic symptoms.

TRIAL REGISTRATION

Clinical trial ID: NCT03532893 (29 Mar 2018).