A Distinct Low Lung Function Trajectory from Childhood to the Fourth Decade of Life

Childhood Asthma: Advances Using Machine Learning and Mechanistic Studies

A paradigm shift brought by the recognition that childhood asthma is an aggregated diagnosis that comprises several different endotypes underpinned by different pathophysiology, coupled with advances in understanding potentially important causal mechanisms, offers a real opportunity for a step change to reduce the burden of the disease on individual children, families, and society. Data-driven methodologies facilitate the discovery of "hidden" structures within "big healthcare data" to help generate new hypotheses. These findings can be translated into clinical practice by linking discovered "phenotypes" to specific mechanisms and clinical presentations. Epidemiological studies have provided important clues about mechanistic avenues that should be pursued to identify interventions to prevent the development or alter the natural history of asthma-related diseases. Findings from cohort studies followed by mechanistic studies in humans and in neonatal mouse models provided evidence that environments such as traditional farming may offer protection by modulating innate immune responses and that impaired innate immunity may increase susceptibility. The key question of which component of these exposures can be translated into interventions requires confirmation. Increasing mechanistic evidence is demonstrating that shaping the microbiome in early life may modulate immune function to confer protection. Iterative dialogue and continuous interaction between experts with different but complementary skill sets, including data scientists who generate information about the hidden structures within "big data" assets, and medical professionals, epidemiologists, basic scientists, and geneticists who provide critical clinical and mechanistic insights about the mechanisms underpinning the architecture of the heterogeneity, are keys to delivering mechanism-based stratified treatments and prevention.

Pulmonary Consequences of Prenatal Inflammatory Exposures: Clinical Perspective and Review of Basic Immunological Mechanisms

Chorioamnionitis, a potentially serious inflammatory complication of pregnancy, is associated with the development of an inflammatory milieu within the amniotic fluid surrounding the developing fetus. When chorioamnionitis occurs, the fetal lung finds itself in the unique position of being constantly exposed to the consequent inflammatory meditators and/or microbial products found in the amniotic fluid. This exposure results in significant changes to the fetal lung, such as increased leukocyte infiltration, altered cytokine, and surfactant production, and diminished alveolarization. These alterations can have potentially lasting impacts on lung development and function. However, studies to date have only begun to elucidate the association between such inflammatory exposures and lifelong consequences such as lung dysfunction. In this review, we discuss the pathogenesis of and fetal immune response to chorioamnionitis, detail the consequences of chorioamnionitis exposure on the developing fetal lung, highlighting the various animal models that have contributed to our current understanding and discuss the importance of fetal exposures in regard to the development of chronic respiratory disease. Finally, we focus on the clinical, basic, and therapeutic challenges in fetal inflammatory injury to the lung, and propose next steps and future directions to improve our therapeutic understanding of this important perinatal stress.

COPD: To Be or Not to Be, That is the Question

As our knowledge on the natural history of chronic obstructive pulmonary disease (COPD) progresses, a conceptual model simply based on an accelerated decline of lung function in adult life in response to smoking has become inadequate to capture the complexity of this disease, and increasing attention is being given to possible contributions from events or alterations of developmental processes that take place earlier in life. In addition, a remarkable heterogeneity has emerged among the pathobiological mechanisms that are involved in different phenotypes of COPD, suggesting that an effective disease management will require individualized treatment approaches largely based on the underlying biological mechanisms (endotypes). In this review, we will discuss the many faces of COPD from an epidemiological, pathobiological, and clinical standpoint and argue that airflow limitation encompasses a number of manifestations that are too diverse to be still clustered under the same diagnostic label.

Fifty Years of Progress in the Epidemiology of Chronic Obstructive Pulmonary Disease: A Review of National Heart, Lung, and Blood Institute-Sponsored Studies

Our understanding of the epidemiology of chronic obstructive pulmonary disease (COPD), including such metrics as incidence, prevalence, risk factors, outcome, and comorbidities has increased greatly over the past 50 years. Much of this increase is attributable to National Heart Blood and Lung Institute (NHLBI)-sponsored studies. This paper will review 13 of these key studies and their contribution to our understanding of COPD in the last half century.

Severe asthma during childhood and adolescence: A longitudinal study

BACKGROUND

Morbidity and mortality associated with childhood asthma are driven disproportionately by children with severe asthma. However, it is not known from longitudinal studies whether children outgrow severe asthma.

OBJECTIVE

We sought to study prospectively whether well-characterized children with severe asthma outgrow their asthma during adolescence.

METHODS

Children with asthma were assessed at baseline with detailed questionnaires, allergy tests, and lung function tests and were reassessed annually for 3 years. The population was enriched for children with severe asthma, as assessed by the American Thoracic Society/European Respiratory Society guidelines, and subject classification was reassessed annually.

RESULTS

At baseline, 111 (59%) children had severe asthma. Year to year, there was a decrease in the proportion meeting the criteria for severe asthma. After 3 years, only 30% of subjects met the criteria for severe asthma (P < .001 compared with enrollment). Subjects experienced improvements in most indices of severity, including symptom scores, exacerbations, and controller medication requirements, but not lung function. Surprisingly, boys and girls were equally likely to has resolved asthma (33% vs 29%). The odds ratio in favor of resolution of severe asthma was 2.75 (95% CI, 1.02-7.43) for those with a peripheral eosinophil count of greater than 436 cells/μL.

CONCLUSIONS

In longitudinal analysis of this well-characterized cohort, half of the children with severe asthma no longer had severe asthma after 3 years; there was a stepwise decrease in the proportion meeting severe asthma criteria. Surprisingly, asthma severity decreased equally in male and female subjects. Peripheral eosinophilia predicted resolution. These data will be important for planning clinical trials in this population.

Inception of early-life allergen-induced airway hyperresponsiveness is reliant on IL-13+CD4+ T cells

Airway hyperresponsiveness (AHR) is a critical feature of wheezing and asthma in children, but the initiating immune mechanisms remain unconfirmed. We demonstrate that both recombinant interleukin-33 (rIL-33) and allergen [house dust mite (HDM) or Alternaria alternata] exposure from day 3 of life resulted in significantly increased pulmonary IL-13⁺CD4⁺ T cells, which were indispensable for the development of AHR. In contrast, adult mice had a predominance of pulmonary Lin^negCD45⁺CD90⁺IL-13⁺ type 2 innate lymphoid cells (ILC2s) after administration of rIL-33. HDM exposure of neonatal IL-33 knockout (KO) mice still resulted in AHR. However, neonatal CD4^creIL-13 KO mice (lacking IL-13⁺CD4⁺ T cells) exposed to allergen from day 3 of life were protected from AHR despite persistent pulmonary eosinophilia, elevated IL-33 levels, and IL-13⁺ ILCs. Moreover, neonatal mice were protected from AHR when inhaled Acinetobacter lwoffii (an environmental bacterial isolate found in cattle farms, which is known to protect from childhood asthma) was administered concurrent with HDM. A. lwoffii blocked the expansion of pulmonary IL-13⁺CD4⁺ T cells, whereas IL-13⁺ ILCs and IL-33 remained elevated. Administration of A. lwoffii mirrored the findings from the CD4^creIL-13 KO mice, providing a translational approach for disease protection in early life. These data demonstrate that IL-13⁺CD4⁺ T cells, rather than IL-13⁺ ILCs or IL-33, are critical for inception of allergic AHR in early life.

Distinct asthma phenotypes with low maximal attainment of lung function on cluster analysis

OBJECTIVE

Asthma is a heterogeneous disease with varying clinical presentations, severity and ability to achieve asthma control. The present study aimed to characterize clinical phenotypes of asthma in an Indian cohort of subjects using a cluster analysis approach.

METHODS

Patients with confirmed asthma (N = 100) and at least 6-months of follow-up data, identified by retrospective chart review, were included in this study. Demographics, age at disease onset, disease duration, body mass index, serial spirometry and allergen sensitization were assessed. Asthma control was assessed prospectively using Global Initiative for Asthma and Asthma Control Test. R version 3.4.3 was used for statistical analysis. Ward's minimum-variance hierarchical clustering method was performed using an agglomerative (bottom-up) approach. To compare differences between clusters, analysis of variance using Kruskal-Wallis test (continuous variables) and chi-square test (categorical variables) was used.

RESULTS

Cluster analysis of 100 treatment-naive patients with asthma identified four clusters. Cluster 1, (N = 40), childhood onset of disease, normal body weight, equal gender distribution and achieved normal lung function. Cluster 2 (N = 16) included adolescent disease-onset, obese, majority males and had poor attainment of maximum lung functions. Cluster 3 (N = 20) were older, late-onset of disease, obese, majority male and had poor attainment of maximum lung function. Cluster 4 (N = 24) had adult-onset of disease, obese, predominantly female and achieved normal lung function.

CONCLUSIONS

In an Indian cohort of well-characterized patients with asthma, cluster analysis identified four distinct clinical phenotypes of asthma, two of which had poor attainment of maximum lung functions.

SERPINA1 gene polymorphisms in a population-based ALSPAC cohort

BACKGROUND

There is an association between persistent preschool wheezing phenotypes and school-age asthma. These wheezing/asthma phenotypes likely represent clinical entities having specific genetic risk factors. The SERPINA1 gene encodes α ₁ -antitrypsin (AAT), and mutations in the gene are important in the pathophysiology of pulmonary diseases. We hypothesized that there might be an association between SERPINA1 gene polymorphisms and the risk of developing wheezing/school age asthma.

OBJECTIVE

To examine 10 single nucleotide polymorphisms (SNPs) of SERPINA1 (rs6647, rs11832, rs17580, rs709932, rs1243160, rs2854254, rs8004738, rs17751769, rs28929470, and rs28929474) and relate them to childhood wheezing phenotypes and doctor-diagnosed asthma in the population-based Avon Longitudinal Study of Parents and Children (ALSPAC) cohort.

METHODS

Wheeze data, reports of physician-diagnosed asthma and data on the SERPINA1 gene SNPs, were available for 7964 children. Binary logistic regression was used to assess the associations between allele prevalence and wheezing and asthma phenotypes. P values were adjusted to account for multiple hypotheses using the Benjamini-Hochberg false discovery rate.

RESULTS

Only within a subgroup of children with asthma who had no prior diagnosis of preschool wheeze was there a trend for association between rs28929474 (Glu342Lys, Pi*Z causing AAT deficiency; P = .0058, adjusted P = .058). No SNP was associated with wheezing and asthma in those with preschool wheeze.

CONCLUSION

Analyzed SNPs in SERPINA1 are not associated with wheezing/asthma phenotypes. Only rs28929474, the most common pathologic SNP (Pi*Z) in the SERPINA1 gene, might be associated with a risk of developing school-age asthma without exhibiting preschool wheeze.

Severe asthma phenotypes and endotypes

Current management of severe asthma relying either on guidelines (bulk approach) or on disease phenotypes (stratified approach) did not improve the burden of the disease. Several severe phenotypes are described: clinical, functional, morphological, inflammatory, molecular and microbiome-related. However, phenotypes do not necessarily relate to or give insights into the underlying pathogenetic mechanisms which are described by the disease endotypes. Based on the major immune-inflammatory pathway involved type-2 high, type-2 low and mixed endotypes are described for severe asthma, with several shared pathogenetic pathways such as genetic and epigenetic, metabolic, neurogenic and remodelling subtypes. The concept of multidimensional endotyping as un unbiased approach to severe asthma is discussed, together with new tools and targets facilitating the shift from the stratified to the precision medicine approach.

Socioeconomic circumstances and respiratory function from childhood to early adulthood: a systematic review and meta-analysis

OBJECTIVE

Disadvantaged socioeconomic circumstances in early life have the potential to impact lung function. Thus, this study aimed to summarise evidence on the association between socioeconomic circumstances and respiratory function from childhood to young adulthood.

DESIGN

Systematic review and meta-analysis.

METHODS

Following the Preferred Reporting Items for Systematic Review and Meta-analysis guidelines, Medline, ISI-Web of Science and Scopus were searched from inception up to January 2018. Original studies on the association between socioeconomic circumstances and respiratory function in early ages (ie, participants younger than 25 years of age) were investigated. Two investigators independently evaluated articles, applied the exclusion criteria, extracted data and assessed the risk of bias using the Newcastle-Ottawa Scale. A meta-analysis of the standardised mean difference and 95% CI in respiratory function between participants from different socioeconomic circumstances was conducted, using a random-effects model.

RESULTS

Thirty-three papers were included in this review and 23 showed that disadvantaged socioeconomic circumstances were significantly associated with reduced respiratory function. The meta-analysis including seven papers showed a significant difference of -0.31 (95% CI -0.42 to -0.21) litres in forced expiratory volume in the first second between children, adolescents and young adults from disadvantaged versus advantaged socioeconomic circumstances. Specifically a difference of -0.31 (95% CI -0.51 to -0.10) litres in girls and -0.43 (95% CI -0.51 to -0.35) litres in boys was observed.

CONCLUSIONS

Children, adolescents and young adults from disadvantaged socioeconomic circumstances had lower respiratory function, and boys presented higher respiratory health inequalities. This information contributes to explain the social patterning of respiratory diseases, and might enable health policy makers to tackle respiratory health inequalities at early ages.

Distinctive lung function trajectories from age 10 to 26 years in men and women and associated early life risk factors - a birth cohort study

Pre-bronchodilator lung function including forced vital capacity (FVC), forced expiratory flow in 1 second (FEV1), their ratio (FEV1/FVC), and forced expiratory flow 25-75% (FEF25-75) measured at age 10, 18, and 26 years in the Isle of Wight birth cohort was analyzed for developmental patterns (trajectories). Early life risk factors before the age of 10 years were assessed for the trajectories.

METHOD

Members of the birth cohort (1989/90) were followed at age 1, 2, 4, 10, 18, and 26 years. Allergic sensitization and questionnaire data were collected. Spirometry tests were performed and evaluated according to the American Thoracic Society (ATS) criteria at 10, 18, and 26 years. To identify developmental trajectories for FVC, FEV1, FEV1/FVC, and FEF25-75 from 10 to 26 years, a finite mixture model was applied to the longitudinal lung function data, separately for males and females. Associations of early life factors with the respective lung function trajectories were assessed using log-linear and logistic regression analyses.

RESULTS

Both high and low lung function trajectories were observed in men and women. FVC continued to grow beyond 18 years in men and women, whereas FEV1 peaked at age 18 years in female trajectories and in one male trajectory. For the FEV1/FVC ratios and FEF25-75 most trajectories appeared highest at age 18 and declined thereafter. However, the low FEV1/FVC trajectory in both sexes showed an early decline at 10 years. Lower birth weight was linked with lower lung function trajectories in males and females. Eczema in the first year of life was a risk factor for later lung function deficits in females, whereas the occurrence of asthma at 4 years of age was a risk factor for later lung function deficits in males. A positive skin prick test at age four was a risk for the low FEV1 trajectory in females and for the low FEV1/FVC trajectory in males.

CONCLUSION

Men and women showed distinctive lung function trajectories and associated risk factors. Lower lung function trajectories can be explained by not achieving maximally attainable function at age 18 years and by a function decline from 18 to 26 years.

Involvement of epigenetic modification in epithelial immune responses during respiratory syncytial virus infection

The epithelial cells of bronchi (BECs) act as a protective wall against potential pathogens and foreign particles that controls many aspects of respiratory immune response. The BECs act as not only a physical protecting wall of the airways but also as a significant part of both the innate and adaptive immune responses. Many kind of epithelium-associated communicating pathways which are triggered by genetic and environmental causating agents get involved in development of respiratory tract abnormalities. Epigenetic dysregulation is one potential mechanism which may mediate between adverse in early life exposures such as severe infections and immunological function deficits in later life. Epigenetic factors which regulate the respiratory tract lining structure and role are also an attractive area to assess the susceptibility of respiratory tract diseases. Several studies show that the key genes in epithelium-related signaling pathways have epigenetic modifications. The interactions mediating the relationship between severe bronchiolitis caused by RSV and their adverse consequences in childhood are broadly understood as immunological in nature, however, are yet to be fully uncovered. Thus, our study explained the immune action of epithelium and RSV-triggered immune imbalance of epithelium through epigenetic modifications in the mechanism of airway hyperresponsiveness.

Lung function trajectories and chronic obstructive pulmonary disease: current understanding and knowledge gaps

PURPOSE OR REVIEW

Population-based studies have shown a significant heterogeneity in patients with chronic obstructive pulmonary disease (COPD), regarding both the attainment of maximal lung function and the subsequent decline over time. This review will highlight recent advances in the understanding of lung function trajectory in COPD, focusing on factors that influence peak adult lung function, markers of accelerated lung function decline and pharmacologic interventions in early phases of the disease.

RECENT FINDINGS

Recent data have shown that individuals with lower lung function early in life will go on to develop lower forced expiratory volume in 1 s (FEV1) in adulthood. Smoking can amplify the effect of specific childhood exposures on maximal adult lung function. Clinical symptoms such as chronic mucous hypersecretion and the biomarker club cell secretory protein have been associated with lung function decline over time. New computed tomography imaging markers also show promise as a way to detect early small airway disease, but need to be examined more longitudinally. In addition to these advances, a slower decline in FEV1 has been demonstrated in two randomized clinical trials studying tiotropium and inhaled fluticasone.

SUMMARY

A better understanding of lung function development and eventual decline in those at risk for progression to COPD will aide in a precision medicine approach, in which markers for those at risk of low maximal lung function and accelerated decline are identified. Targeted therapy can then be used early to modify disease activity and outcomes.

Club Cell Secretory Protein Deficiency Leads to Altered Lung Function

RATIONALE

CC16 (club cell secretory protein-16), a member of the secretoglobin family, is one of the most abundant proteins in normal airway secretions and has been described as a serum biomarker for obstructive lung diseases.

OBJECTIVES

To determine whether low CC16 is a marker for airway pathology or is implicated in the pathophysiology of progressive airway damage in these conditions.

METHODS

Using human data from the birth cohort of the Tucson Children's Respiratory Study, we examined the relation of circulating CC16 levels with pulmonary function and responses to bronchial methacholine challenge from childhood up to age 32 years. In wild-type and CC16-/- mice, we set out to comprehensively examine pulmonary physiology, inflammation, and remodeling in the naive airway.

MEASUREMENTS AND MAIN RESULTS

We observed that Tucson Children's Respiratory Study participants in the lowest tertile of serum CC16 had significant deficits in their lung function and enhanced airway hyperresponsiveness to methacholine challenge from 11 years throughout young adult life. Similarly, CC16-/- mice had significant deficits in lung function and enhanced airway hyperresponsiveness to methacholine as compared with wild-type mice, which were independent of inflammation and mucin production. As compared with wild-type mice, CC16-/- mice had significantly elevated gene expression of procollagen type I, procollagen type III, and α-smooth muscle actin, areas of pronounced collagen deposition and significantly enhanced smooth muscle thickness.

CONCLUSIONS

Our findings support clinical observations by providing evidence that lack of CC16 in the lung results in dramatically altered pulmonary function and structural alterations consistent with enhanced remodeling.

Pathophysiological Mechanisms of Asthma

The recent Lancet commission has highlighted that "asthma" should be used to describe a clinical syndrome of wheeze, breathlessness, chest tightness, and sometimes cough. The next step is to deconstruct the airway into components of fixed and variable airflow obstruction, inflammation, infection and altered cough reflex, setting the airway disease in the context of extra-pulmonary co-morbidities and social and environmental factors. The emphasis is always on delineating treatable traits, including variable airflow obstruction caused by airway smooth muscle constriction (treated with short- and long-acting β-2 agonists), eosinophilic airway inflammation (treated with inhaled corticosteroids) and chronic bacterial infection (treated with antibiotics with benefit if it is driving the disease). It is also important not to over-treat the untreatable, such as fixed airflow obstruction. These can all be determined using simple, non-invasive tests such as spirometry before and after acute administration of a bronchodilator (reversible airflow obstruction); peripheral blood eosinophil count, induced sputum, exhaled nitric oxide (airway eosinophilia); and sputum or cough swab culture (bacterial infection). Additionally, the pathophysiology of risk domains must be considered: these are risk of an asthma attack, risk of poor airway growth, and in pre-school children, risk of progression to eosinophilic school age asthma. Phenotyping the airway will allow more precise diagnosis and targeted treatment, but it is important to move to endotypes, especially in the era of increasing numbers of biologicals. Advances in -omics technology allow delineation of pathways, which will be particularly important in TH2 low eosinophilic asthma, and also pauci-inflammatory disease. It is very important to appreciate the difficulties of cluster analysis; a patient may have eosinophilic airway disease because of a steroid resistant endotype, because of non-adherence to basic treatment, and a surge in environmental allergen burden. Sophisticated -omics approaches will be reviewed in this manuscript, but currently they are not being used in clinical practice. However, even while they are being evaluated, management of the asthmas can and should be improved by considering the pathophysiologies of the different airway diseases lumped under that umbrella term, using simple, non-invasive tests which are readily available, and treating accordingly.

Prenatal Household Air Pollution Alters Cord Blood Mononuclear Cell Mitochondrial DNA Copy Number: Sex-Specific Associations

Background: Associations between prenatal household air pollution (HAP) exposure or cookstove intervention to reduce HAP and cord blood mononuclear cell (CBMC) mitochondrial deoxyribonucleic acid copy number (mtDNAcn), an oxidative stress biomarker, are unknown. Materials and Methods: Pregnant women were recruited and randomized to one of two cookstove interventions, including a clean-burning liquefied petroleum gas (LPG) stove, or control. Prenatal HAP exposure was determined by serial, personal carbon monoxide (CO) measurements. CBMC mtDNAcn was measured by quantitative polymerase chain reaction. Multivariable linear regression determined associations between prenatal CO and cookstove arm on mtDNAcn. Associations between mtDNAcn and birth outcomes and effect modification by infant sex were explored. Results: LPG users had the lowest CO exposures (p = 0.02 by ANOVA). In boys only, average prenatal CO was inversely associated with mtDNAcn (β = -14.84, SE = 6.41, p = 0.03, per 1ppm increase in CO). When examined by study arm, LPG cookstove had the opposite effect in all children (LPG β = 19.34, SE = 9.72, p = 0.049), but especially boys (β = 30.65, SE = 14.46, p = 0.04), as compared to Control. Increased mtDNAcn was associated with improved birth outcomes. Conclusions: Increased prenatal HAP exposure reduces CBMC mtDNAcn, suggesting cumulative prenatal oxidative stress injury. An LPG stove intervention may reverse this effect. Boys appear most susceptible.

Life Cycle of Childhood Asthma: Prenatal, Infancy and Preschool, Childhood, and Adolescence

Asthma is a heterogeneous developmental disorder influenced by complex interactions between genetic susceptibility and exposures. Wheezing in infancy and early childhood is highly prevalent, with a substantial minority of children progressing to established asthma by school age, most of whom are atopic. Adolescence is a time of remission of symptoms with persistent lung function deficits. The transition to asthma in adulthood is not well understood.

Lung function in a cohort of 5-year-old children born very preterm

OBJECTIVE

We assessed lung function and respiratory health in an area-based prospective cohort of preschool children born very preterm.

DESIGN

Lung function was measured by interrupter respiratory resistance (Rint) and forced oscillation technique (FOT) (respiratory resistance (Rrs8), reactance (Xrs8), and area under the reactance curve (AX)) at a median age of 5.2 years in a cohort of 194 children born at 22-31 weeks of gestational age (GA) in Tuscany, Italy. Respiratory symptoms and hospitalizations were also assessed.

RESULTS

Mean (SD) lung function Z-scores were impaired in preterm children for Rint (0.72 (1.13)), Xrs8 (-0.28 (1.34)), and AX (0.29 (1.41)). However, only a relatively small proportion of children (14.5-17.4%) had values beyond the 95th centile or below the 5th. Children with bronchopulmonary dysplasia (BPD) (n = 24) had slightly but not significantly impaired lung function indices in comparison with those without BPD (n = 170). In a multivariable analysis, lower GA was associated with worse lung function indices. Fifty-five percent of children had a history of wheezing ever and 21% had been hospitalized in their lifetime because of lower respiratory infections; 31% had wheezing in the last 12 months and this was associated with increased Rrs8 (P = 0.04) and AX (P = 0.08), and with decreased Xrs8 (P = 0.04) Z-scores.

CONCLUSIONS

Irrespectively of BPD preschool children born very preterm had impaired lung function indices, as measured by Rint and FOT, and a slightly higher burden of respiratory problems than the general population. GA seems to be crucial for lung development.

Respiratory syncytial virus hospitalization and incurred morbidities the season after prophylaxis

OBJECTIVES

The primary objective of this study was to determine the incidence and incurred morbidities of Respiratory syncytial virus (RSV)-related hospitalization (RSVH), the season following completion of prophylaxis.

METHODS

A retrospective study was conducted of all infants enrolled in a prophylaxis clinic in one institution during the 2009 to 2014 RSV seasons. RSV infection was identified by Diseases codes and confirmed by RSV-positivity. Data were classified into five groups based on indications for prophylaxis. The incidence of RSVH was calculated. For each subgroup, differences in characteristics between children with and without RSVH were analyzed by independent t test or chi-square test.

RESULTS

During five RSV seasons, 827 infants were enrolled. RSVH incidence the season following prophylaxis was 2.1% (n=17/827). Children with chronic lung disease (CLD) had the highest RSVH incidence (7.7%; n=4/52) followed by preterms 33 to 35 weeks gestation (2.5%; n=4/162), those with complex medical disorders (2.2%; n=3/135), those with congenital heart disease (1.5%; n=1/66) and preterms less than or equal to 32 weeks gestation (1.2%; n=5/412). There was no statistically significant association between indications for prophylaxis and RSVH (Fisher exact test, P=0.060). The odds of RSVH were 4.9 times greater (odds ratio [OR]=4.9; 95% CI: 1.53, 15.55; P=0.007) in CLD compared to those without CLD. The median length of RSVH stay was 4 days; 58.8% (n=10/17) required oxygen (median 1 day); 29.4% (n=5/17) required intensive care.

CONCLUSIONS

Infants with CLD are at highest risk for RSVH in the season postprophylaxis and may merit palivizumab for more than two seasons dependent on disease severity. However, larger prospective studies are necessary to confirm the findings before embarking on a strategy of providing prophylaxis for a third RSV season.

Prenatal nitrate air pollution exposure and reduced child lung function: Timing and fetal sex effects

BACKGROUND

Prenatal particulate air pollution exposure may alter lung growth and development in utero in a time-sensitive and sex-specific manner, resulting in reduced lung function in childhood. Such relationships have not been examined for nitrate (NO3-).

METHODS

We implemented Bayesian distributed lag interaction models (BDLIMs) to identify sensitive prenatal windows for the influence of NO3- on lung function at age 7 years, assessing effect modification by fetal sex. Analyses included 191 mother-child dyads. Daily ambient NO3- exposure over pregnancy was estimated using a hybrid chemical transport (Geos-Chem)/land-use regression model. Spirometry was performed at mean (SD) age of 6.99 (0.89) years, with forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) z-scores accounting for child age, sex, height and race/ethnicity.

RESULTS

Most mothers were Hispanic (65%) or Black (22%), had ≤ high school education (67%), and never smoked (71%); 17% children had asthma. BDILMs adjusted for maternal age and education and child's asthma identified an early sensitive window of 6-12 weeks gestation, during which increased NO3- was significantly associated with reduced FEV1 z-scores specifically among boys. BDLIM analyses demonstrated similar sex-specific patterns for FVC.

CONCLUSION

Early gestational NO3- exposure is associated with reduced child lung function, especially in boys.

RSV infection and respiratory sequelae

INTRODUCTION

The association between respiratory syncytial virus (RSV) infections and long-term respiratory sequelae has long been recognized. It is estimated that individuals with a history of RSV bronchiolitis have 2- to 12-fold higher risk of developing asthma. Although this risk tends to decrease with age, persistent airway obstruction and hyperresponsiveness are observed even 30 years after RSV infection.

EVIDENCE ACQUISITION

Our data search strategy was designed to address the following questions: What is the epidemiological evidence available on the association between RSV infection and long-term respiratory morbidity? What are the potential pathogenic pathways linking RSV infection to long-term respiratory morbidity? Are there any host genetic backgrounds that can predispose to both severe RSV lower respiratory tract infection and asthma? Are antiviral therapies and RSV prevention measures effective in reducing respiratory morbidities?

EVIDENCE SYNTHESIS

This article reviews the recent scientific literature on the epidemiological association and pathogenic links between early RSV infection and long-term respiratory morbidities.

CONCLUSIONS

Nowadays, asthma is increasingly considered a heterogeneous disease, caused by interactions between several host and environmental factors. Understanding the specific causative role of respiratory viruses, and the pathogenic mechanisms through which bronchiolitis predisposes to asthma, is a challenging, but essential starting point for the development of prevention and treatment strategies potentially capable of preserving lung function.

Translating Asthma: Dissecting the Role of Metabolomics, Genomics and Personalized Medicine

The management of asthma has largely stagnated over the last 25 years, but we are at the dawning of a new age wherein -omics technology can help us manage the disease objectively and rationally. Even in this new scientific age, getting the basics of asthma management right remains essential. The new technologies which can be applied to multiple biological samples include genomics (study of the genome), transcriptomics (gene transcription), lipidomics, proteomics and metabolomics (lipids, proteins and metabolites, respectively) and breathomics, using exhaled breath as a source of biomarkers, which is of particular interest in view of its non-invasive nature in pediatrics. Important applications will include the diagnosis of airways disease, including its components; the pathways driving airway pathology; monitoring the response to treatment; and measuring future risk (asthma attacks, poor lung growth trajectory). With the advent of a wide range of novel biologicals to treat asthma, -omics technology to personalize therapy will be especially important. The U-BIOPRED (Europe) and SARP (USA) groups have been most active in this field, especially using bronchoscopically obtained samples to perform cluster analyses to define new asthma endotypes. However, stability over time and consistency between investigators is imperfect. This is perhaps unsurprising; results of biomarker studies in asthma will be a composite of the underlying disease, the (variable) effects of adverse drivers such as allergen exposure and pollution, the effects of treatment, and the effects of adherence or otherwise to treatment. Ultimately, the aim should be an exhaled breath based tool with a rapid result that can be used as a routine in the clinic. However, at the moment, there are as yet no clinical applications in children of -omics technology.

Nutrition and Lung Growth

Experimental evidence from animal models and epidemiology studies has demonstrated that nutrition affects lung development and may have a lifelong impact on respiratory health. Chronic restriction of nutrients and/or oxygen during pregnancy causes structural changes in the airways and parenchyma that may result in abnormal lung function, which is tracked throughout life. Inadequate nutritional management in very premature infants hampers lung growth and may be a contributing factor in the pathogenesis of bronchopulmonary dysplasia. Recent evidence seems to indicate that infant and childhood malnutrition does not determine lung function impairment even in the presence of reduced lung size due to delayed body growth. This review will focus on the effects of malnutrition occurring at critical time periods such as pregnancy, early life, and childhood, on lung growth and long-term lung function.

Prediction models for the development of COPD: a systematic review

Early identification of people at risk of developing COPD is crucial for implementing preventive strategies. We aimed to systematically review and assess the performance of all published models that predicted development of COPD. A search was conducted to identify studies that developed a prediction model for COPD development. The Checklist for Critical Appraisal and Data Extraction for Systematic Reviews of Prediction Modelling Studies was followed when extracting data and appraising the selected studies. Of the 4,481 records identified, 30 articles were selected for full-text review, and only four of these were eligible to be included in the review. The only consistent predictor across all four models was a measure of smoking. Sex and age were used in most models; however, other factors varied widely. Two of the models had good ability to discriminate between people who were correctly or incorrectly classified as at risk of developing COPD. Overall none of the models were particularly useful in accurately predicting future risk of COPD, nor were they good at ruling out future risk of COPD. Further studies are needed to develop new prediction models and robustly validate them in external cohorts.

Protective effect of breastfeeding on recurrent cough in adulthood

RATIONALE

Breastfeeding protects from respiratory infections in early life but its relationship to recurrent cough and other respiratory outcomes in adult life is not well established.

METHODS

Infant feeding practices were assessed prospectively in the Tucson Children's Respiratory Study, a non-selected birth cohort and categorised into formula from birth or introduced <1 month, formula introduced ≥1 to <4 months and exclusive breastfeeding for ≥4 months. Infant feeding was assessed as an ordinal variable representing an increasing dose of breastmilk across the three categories. Recurrent cough was defined at 22, 26 and 32 years as ≥2 episodes of cough without a cold lasting 1 week during the past year. Covariates included participant sex, race/ethnicity and smoking as well as parental smoking, education, age and asthma. Covariates were evaluated as potential confounders for the relation between infant feeding and adult outcomes.

RESULTS

Of the 786 participants, 19% breastfed <1 month, 50% breastfed ≥1 to <4 months and 31% breastfed ≥4 months. The prevalence of recurrent cough at 22, 26 and 32 years was 17%, 15% and 16%, respectively. Each ordinal increase in breastfeeding duration was associated with a decreased risk of recurrent cough in adult life: adjusted OR=0.71, (95% CI: 0.56 to 0.89), p=0.004. Additional adjustment for concurrent adult asthma, wheeze, smoking and lung volume did not change these results.

CONCLUSION

Longer duration of breastfeeding reduces the risk of recurrent cough in adult life, regardless of smoking and other respiratory symptoms, suggesting long-term protective effects on respiratory health.

Early life determinants of lung function change from childhood to adolescence

RATIONALE

Little is known about how perinatal and childhood factors influence lung function change between childhood and adolescence.

OBJECTIVES

To investigate possible early life predictors of change in FEV₁ between age 8 and 16 years. In addition, to investigate possible predictors of having persistently low lung function (FEV₁ <25th percentiles both at age 8 and 16) up to adolescence.

METHODS

The BAMSE birth cohort study collected data throughout childhood on environmental factors, individual characteristics, and spirometric measures at 8 and 16 years (n = 1425). Associations between early life predictors (n = 31) and FEV₁ increase between 8 and 16 years were assessed with linear regression. Predictors of having persistently low lung function were examined.

RESULTS

Few factors were consistently associated with altered lung function growth, although low birth weight, asthma heredity (paternal), secondhand smoke in infancy, and season of birth had a significant impact (p-value ≤0.01). The majority of subjects stayed however within the same category of lung function between ages 8 and 16 years (in total 821/1425 = 58%). Predictors associated with having persistently low lung function were gestational age, secondhand smoke (at 2 and 8 years of age), and factors related to lower respiratory tract infections in infancy.

CONCLUSIONS

In summary, rather few exposures in childhood were identified to have a significant impact on lung function growth between childhood and adolescence. Our data support previous study findings indicating that lung function development is influenced by factors before birth and in infancy, including second hand tobacco smoke.

Asthma across the lifespan: Time for a paradigm shift

We have a unique opportunity to significantly reduce the worldwide burden of asthma in children and affect respiratory outcomes in adults. However, this will require a paradigm shift that is directed at altering the natural history of asthma, reducing asthma exacerbations, and preventing long-term adverse outcomes of childhood asthma. Attention should continue to be directed toward minimizing risk, as well as impairment, with a goal to achieve optimal control. Based on several National Institutes of Health studies conducted over the last 10 years, we now have the tools necessary to accomplish this goal. The tools include assessment of lung function over time or defining trajectories of lung growth, the Composite Asthma Severity Index score, a panel of useful biomarkers, the Seasonal Asthma Exacerbation Prediction Index score, and rapidly advancing technology that includes adherence monitoring. Future guideline revisions should consider incorporating recommendations to follow spirometry over time and defining trajectories of lung growth to assess risk for reduced lung growth and early decline, asthma burden by using biomarkers to select and monitor therapy, assessment of social determinants of health, evaluation of risk for seasonal exacerbations, and consideration of electronic adherence monitoring for difficult-to-manage asthma. Guidelines should continue to include a core dedicated to the diagnosis and treatment of intermittent and mild and moderate persistent asthma and include additional sections dedicated to the management of severe asthma.

Lung function trajectories from pre-school age to adulthood and their associations with early life factors: a retrospective analysis of three population-based birth cohort studies

BACKGROUND

Maximal lung function in early adulthood is an important determinant of mortality and COPD. We investigated whether distinct trajectories of lung function are present during childhood and whether these extend to adulthood and infancy.

METHODS

To ascertain trajectories of FEV₁, we studied two population-based birth cohorts (MAAS and ALSPAC) with repeat spirometry from childhood into early adulthood (1046 participants from 5-16 years and 1390 participants from 8-24 years). We used a third cohort (PIAF) with repeat lung function measures in infancy (V'_maxFRC) and childhood (FEV₁; 196 participants from 1 month to 18 years of age) to investigate whether these childhood trajectories extend from early life. We identified trajectories using latent profile modelling. We created an allele score to investigate genetic associations of trajectories, and constructed a multivariable model to identify their early-life predictors.

FINDINGS

We identified four childhood FEV₁ trajectories: persistently high, normal, below average, and persistently low. The persistently low trajectory (129 [5%] of 2436 participants) was associated with persistent wheezing and asthma throughout follow-up. In genetic analysis, compared with the normal trajectory, the pooled relative risk ratio per allele was 0·96 (95% CI 0·92-1·01; p=0·13) for persistently high, 1·01 (0·99-1·02; p=0·49) for below average, and 1·05 (0·98-1·13; p=0·13) for persistently low. Most children in the low V'_maxFRC trajectory in infancy did not progress to the low FEV₁ trajectory in childhood. Early-life factors associated with the persistently low trajectory included recurrent wheeze with severe wheezing exacerbations, early allergic sensitisation, and tobacco smoke exposure.

INTERPRETATION

Reduction of childhood smoke exposure and minimisation of the risk of early-life sensitisation and wheezing exacerbations might reduce the risk of diminished lung function in early adulthood.

FUNDING

None.

Early life insults as determinants of chronic obstructive pulmonary disease in adult life

Background

Early life events may predispose to the development of chronic lung disease in adulthood.

Aim

To provide an update on current knowledge of early nongenetic origins of COPD.

Materials and methods

Systematic literature review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

Results

A total of 16 studies, comprising 69,365 individuals, met the predefined criteria and were included in the present review. Studies have shown that in utero tobacco exposure, low birth weight, preterm birth, and respiratory diseases, primarily asthma and pneumonia, in early childhood are associated with lung function impairment later in childhood, and by that predispose to subsequent development of COPD, although the causal association between childhood respiratory diseases and COPD has been questioned in one study. Environmental tobacco exposure has also been shown to have negative impact on lung function in childhood possibly leading to COPD in adulthood, although it is at present not possible to clearly distinguish between the impact of active and the environmental tobacco exposure on subsequent development of COPD.

Conclusion

Tobacco exposure in utero and early life is a risk factor for subsequent development of COPD. Furthermore, low birth weight, lower respiratory tract infections and asthma, including wheezy bronchitis, in childhood also seem to be important determinants for later development of COPD. Early life insults may, therefore, be crucial to COPD development.

Classification of Pediatric Asthma: From Phenotype Discovery to Clinical Practice

Advances in big data analytics have created an opportunity for a step change in unraveling mechanisms underlying the development of complex diseases such as asthma, providing valuable insights that drive better diagnostic decision-making in clinical practice, and opening up paths to individualized treatment plans. However, translating findings from data-driven analyses into meaningful insights and actionable solutions requires approaches and tools which move beyond mining and patterning longitudinal data. The purpose of this review is to summarize recent advances in phenotyping of asthma, to discuss key hurdles currently hampering the translation of phenotypic variation into mechanistic insights and clinical setting, and to suggest potential solutions that may address these limitations and accelerate moving discoveries into practice. In order to advance the field of phenotypic discovery, greater focus should be placed on investigating the extent of within-phenotype variation. We advocate a more cautious modeling approach by "supervising" the findings to delineate more precisely the characteristics of the individual trajectories assigned to each phenotype. Furthermore, it is important to employ different methods within a study to compare the stability of derived phenotypes, and to assess the immutability of individual assignments to phenotypes. If we are to make a step change toward precision (stratified or personalized) medicine and capitalize on the available big data assets, we have to develop genuine cross-disciplinary collaborations, wherein data scientists who turn data into information using algorithms and machine learning, team up with medical professionals who provide deep insights on specific subjects from a clinical perspective.

COPD: time to improve its taxonomy?

Due to well-conducted epidemiological studies and advances in genetics, molecular biology, translational research, the advent of computed tomography of the lungs and bioinformatics, the diagnosis of chronic obstructive pulmonary disease (COPD) as a single entity caused by susceptibility to cigarette smoke is no longer tenable. Furthermore, the once-accepted concept that COPD results from a rapid and progressive loss of lung function over time is not true for a sizeable proportion of adults with the disease. Now we know that some genetic predisposition and/or different environmental interactions (nutritional, infectious, pollution and immunological) may negatively modulate post-natal lung development and lead to poorly reversible airflow limitation later in life, consistent with COPD. We believe it is time to rethink the taxonomy of this disease based on the evidence at hand. To do so, we have followed the principles outlined in the 1980s by J.D. Scadding who proposed that diseases can be defined by four key characteristics: 1) clinical description (syndrome), 2) disorder of structure (morbid anatomy), 3) disorder of function (pathophysiology) and 4) causation (aetiology). Here, we propose a pragmatic approach to the taxonomy of COPD based on different processes that result in a similar syndromic presentation. It can accommodate changes over time, as the pathobiology that may lead to COPD expands. We hope that stakeholders in the field may find it useful to better define the patients now boxed into one single entity, so that specific studies can be designed and conducted for each type of COPDs.

Lung function in early adulthood and health in later life: a transgenerational cohort analysis

BACKGROUND

Early life events can affect health in later life. We hypothesised that low lung function (FEV₁ <80% predicted) in early adulthood (25-40 years) is associated with higher prevalence and earlier incidence of respiratory, cardiovascular, and metabolic abnormalities, and premature death.

METHODS

In this cohort analysis, we tested this hypothesis using data from the Framingham Offspring Cohort (FOC) and validated our observations in CARDIA (an independent cohort) and GenIII (which includes the direct descendants of FOC participants). These were three general population cohorts that included men and women, who were regularly and prospectively followed up to collect extensive clinical, physiological, biological, and imaging information. Main outcomes were prevalence (in early adulthood) and incidence (during follow-up) of comorbidity, and all-cause mortality. χ² test, unpaired t test, Fisher's exact test, and Cox proportional hazards models were used for data analysis. Differential dropout rates during follow-up were regarded as a potential source of bias.

FINDINGS

We found that 111 (10%) of 1161 participants in FOC, 338 (13%) of 2648 participants in CARDIA, and 71 (4%) of 1912 participants in GenIII had FEV₁ of less than 80% predicted at the age of 25-40 years. These individuals also had higher prevalence of respiratory, cardiovascular, and metabolic abnormalities in early adulthood; higher and earlier (about a decade) incidence of comorbidities during follow-up (39 years vs 47 years in FOC; 30 years vs 37 years in CARDIA, p<0·0001); and higher all-cause mortality than individuals with normal lung function in early adulthood (in FOC, hazard ratio 2·3 [95% CI 1·4-3·7], p=0·001), which was independent of, but additive with, cumulative smoking exposure. In GenIII, we observed that individuals with at least one parent stratified as having low lung function in early adulthood in FOC (n=115) had lower FEV₁ in early adulthood (10% had FEV₁ of less than 80% predicted; this proportion was 3% in those with both parents classified as normal in FOC [n=248]; p<0·0001); and early adulthood FEV₁ of GenIII participants was related (R²=0·28, p<0·0001) to FOC parents' average FEV₁ in early adulthood.

INTERPRETATION

Low peak lung function in early adulthood is common in the general population and could identify a group of individuals at risk of early comorbidities and premature death.

FUNDING

Fondo de Investigacion Sanitaria, Sociedad Española de Neumologia y Cirurgia Torácica, Formació Personal Investigador, Agencia de Gestió d'Ajuts de Recerca 2016, and AstraZeneca Foundation Young Researcher Award.

Combined Impact of Smoking and Early-Life Exposures on Adult Lung Function Trajectories

RATIONALE

Both adverse early-life exposures and adult smoking can negatively influence adult lung function trajectory, but few studies consider how the impact of early-life exposures may be modified by subsequent smoking.

METHODS

The Medical Research Council National Survey of Health and Development is a nationally representative cohort, initially of 5,362 individuals, followed since enrollment at birth in March 1946. Using data collected prospectively across life and multilevel modeling, we investigated how the relationships between early-life exposures (infant lower respiratory infection, manual social class, home overcrowding, and pollution exposure) and FEV₁ and FVC trajectories between ages 43 and 60-64 years were influenced by smoking behavior.

MEASUREMENTS AND MAIN RESULTS

Among 2,172 individuals, there were synergistic interactions of smoking with infant respiratory infection (P = 0.04) and early-life home overcrowding (P = 0.009), for FEV₁ at 43 years. Within smoker-stratified models, there were FEV₁ deficits among ever-smokers associated with infant lower respiratory infection (-108.2 ml; P = 0.001) and home overcrowding (-89.2 ml; P = 0.002), which were not evident among never-smokers (-15.9 ml; P = 0.69 and -13.7 ml; P = 0.70, respectively). FVC modeling, including 1,960 individuals, yielded similar results. FEV₁ decline was greater in smokers (P < 0.001), but there was no effect of any early-life exposure on FEV₁ decline. Neither smoking nor early-life exposures were associated with FVC decline.

CONCLUSIONS

Besides accelerating adult FEV₁ decline, cigarette smoking also modifies how early-life exposures impact on both midlife FEV₁ and FVC. These findings are consistent with smoking impairing pulmonary development during adolescence or early adulthood, thereby preventing catch-up from earlier acquired deficits.

Chronic obstructive pulmonary disease with mild airflow limitation: current knowledge and proposal for future research - a consensus document from six scientific societies

Chronic obstructive pulmonary disease (COPD) is a leading cause of mortality and morbidity worldwide, with high and growing prevalence. Its underdiagnosis and hence under-treatment is a general feature across all countries. This is particularly true for the mild or early stages of the disease, when symptoms do not yet interfere with daily living activities and both patients and doctors are likely to underestimate the presence of the disease. A diagnosis of COPD requires spirometry in subjects with a history of exposure to known risk factors and symptoms. Postbronchodilator forced expiratory volume in 1 second (FEV₁)/forced vital capacity <0.7 or less than the lower limit of normal confirms the presence of airflow limitation, the severity of which can be measured by FEV₁% predicted: stage 1 defines COPD with mild airflow limitation, which means postbronchodilator FEV₁ ≥80% predicted. In recent years, an elegant series of studies has shown that "exclusive reliance on spirometry, in patients with mild airflow limitation, may result in underestimation of clinically important physiologic impairment". In fact, exercise tolerance, diffusing capacity, and gas exchange can be impaired in subjects at a mild stage of airflow limitation. Furthermore, growing evidence indicates that smokers without overt abnormal spirometry have respiratory symptoms and undergo therapy. This is an essential issue in COPD. In fact, on one hand, airflow limitation, even mild, can unduly limit the patient's physical activity, with deleterious consequences on quality of life and even survival; on the other hand, particularly in younger subjects, mild airflow limitation might coincide with the early stage of the disease. Therefore, we thought that it was worthwhile to analyze further and discuss this stage of "mild COPD". To this end, representatives of scientific societies from five European countries have met and developed this document to stimulate the attention of the scientific community on COPD with "mild" airflow limitation. The aim of this document is to highlight some key features of this important concept and help the practicing physician to understand better what is behind "mild" COPD. Future research should address two major issues: first, whether mild airflow limitation represents an early stage of COPD and what the mechanisms underlying the evolution to more severe stages of the disease are; and second, not far removed from the first, whether regular treatment should be considered for COPD patients with mild airflow limitation, either to prevent progression of the disease or to encourage and improve physical activity or both.

Recent advances in understanding lung function development

Recent years have witnessed critical contributions to our understanding of the determinants and long-term implications of lung function development. In this article, we review studies that have contributed to advances in understanding lung function development and its critical importance for lung health into adult life. In particular, we have focused on early life determinants that include genetic factors, perinatal events, environmental exposures, lifestyle, infancy lower respiratory tract infections, and persistent asthma phenotypes. Longitudinal studies have conclusively demonstrated that lung function deficits that are established by school age may track into adult life and increase the risk of adult lung obstructive diseases, such as chronic obstructive pulmonary disease. Furthermore, these contributions have provided initial evidence in support of a direct influence by early life events on an accelerated decline of lung function and an increased susceptibility to its environmental determinants well into adult life. As such, we argue that future health-care programs based on precision medicine approaches that integrate deep phenotyping with tailored medication and advice to patients should also foster optimal lung function growth to be fully effective.