Infant lung function predicts asthma persistence and remission in young adults

Heterogeneity of Airway Smooth Muscle Remodeling in Asthma

Rationale: Ventilatory defects in asthma are heterogeneous and may represent the distribution of airway smooth muscle (ASM) remodeling. Objectives: To determine the distribution of ASM remodeling in mild-severe asthma. Methods: The ASM area was measured in nine airway levels in three bronchial pathways in cases of nonfatal (n = 30) and fatal asthma (n = 20) and compared with control cases without asthma (n = 30). Correlations of ASM area within and between bronchial pathways were calculated. Asthma cases with 12 large and 12 small airways available (n = 42) were classified on the basis of the presence or absence of ASM remodeling (more than two SD of mean ASM area of control cases, n = 86) in the large or small airway or both. Measurements and Main Results: ASM remodeling varied widely within and between cases of nonfatal asthma and was more widespread and confluent and more marked in fatal cases. There were weak correlations of ASM between levels within the same or separate bronchial pathways; however, predictable patterns of remodeling were not observed. Using mean data, 44% of all asthma cases were classified as having no ASM remodeling in either the large or small airway despite a three- to 10-fold increase in the number of airways with ASM remodeling and 81% of asthma cases having ASM remodeling in at least one large and small airway. Conclusions: ASM remodeling is related to asthma severity but is heterogeneous within and between individuals and may contribute to the heterogeneous functional defects observed in asthma. These findings support the need for patient-specific targeting of ASM remodeling.

Growth of the airway smooth muscle layer from late gestation to childhood is mediated initially by hypertrophy and subsequently hyperplasia

Background and objective

The airway smooth muscle (ASM) layer thickens during development. Identifying the mechanism(s) for normal structural maturation of the ASM reveals pathways susceptible to disease processes. This study characterized thickening of the ASM layer from foetal life to childhood and elucidated the underlying mechanism in terms of hypertrophy, hyperplasia and extracellular matrix (ECM) deposition.

Methods

Airways from post‐mortem cases were examined from seven different age groups: 22–24 weeks gestation, 25–31 weeks gestation, term (37–41 weeks gestation), <0.5 year, 0.5–1 year, 2–5 years and 6–10 years. The ASM layer area (thickness), the number and size of ASM cells and the volume fraction of ECM were assessed by planimetry and stereology.

Results

From late gestation to the first year of life, normalized ASM thickness more than doubled as a result of ASM hypertrophy. Thereafter, until childhood, the ASM layer grew in proportion to airway size, which was mediated by ASM hyperplasia. Hypertrophy and hyperplasia of ASM were accompanied by a proportional change in ECM such that the broad composition of the ASM layer was constant across age groups.

Conclusion

These data suggest that the mechanisms of ASM growth from late gestation to childhood are temporally decoupled, with early hypertrophy and subsequent proliferation. We speculate that the developing airway is highly susceptible to ASM thickening in the first year of life and that the timing of an adverse event will determine structural phenotype.

A period of rapid hypertrophic airway smooth muscle growth occurs in the first year of life, representing a critical window for disruption by disease processes and/or opportunity for clinical intervention.

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Tidal Breathing Pulmonary Function of Children With Allergic Rhinitis

In order to investigate the characteristics of tidal breathing pulmonary function in children with allergic rhinitis, and explore its role in the relationship between allergic rhinitis and asthma, we conducted this prospective study from January 4, 2016 to January 30, 2019 in Wuhan children's hospital. In this study, 49 children with simple allergic rhinitis were enrolled in the AR group; 50 children with allergic rhinitis concomitant with asthma were enrolled in the AR&A group; 43 healthy children were recruited in the control group. For individuals in each group, the assessment of tidal breath pulmonary function was performed after enrollment. Then participants in the AR group and control group were followed up for 1 year to observe their frequency of wheezing attacks. The parameters of tI/tE, tPTEF/tE, and VPTEF/VE of AR group were significantly higher than AR&A group (P < 0.001). The reduced proportion of tPTEF/tE and VPTEF/VE. in AR group were higher than that in control group (30.61% vs. 11.63%, P < 0.001; 24.49% vs. 11.63%, P < 0.001, respectively). The proportion of patients with reduced tPTEF/tE and VPTEF/VE who occurred recurrent wheezing was higher than that of patients with normal pulmonary function in AR group(P = 0.008). In conclusion, some children with allergic rhinitis has impaired tidal breathing pulmonary function. Tidal breathing pulmonary function test plays an important role in the diagnosis and assessment of children's airway allergic diseases (AR and asthma).

Small airway dysfunction is an independent dimension of wheezing disease in preschool children

BACKGROUND

Whether small airway dysfunction (SAD), which is prevalent in asthma, helps to characterize wheezing phenotypes is undetermined. The objective was to assess whether SAD parameters obtained from impedance measurement and asthma probability are linked.

METHODS

One hundred and thirty-nine preschool children (mean age 4.7 years, 68% boys) suffering from recurrent wheezing underwent impulse oscillometry that allowed calculating peripheral resistance and compliance of the respiratory system (markers of SAD) using the extended RIC model (central and peripheral resistance, inertance, and peripheral compliance). Children were classified using the probability-based approach of GINA guidelines (few, some, and most having asthma). A principal component analysis (PCA) that determined the dimensions of wheezing disease evaluated the links between SAD and asthma probability.

RESULTS

Forty-seven children belonged to the few, 28 to the some, and 64 to the most having asthma groups. Whereas their anthropometrics and measured parameters were similar, the most having asthma group exhibited the lowest mean value of airway inertance after bronchodilator probably due to airway inhomogeneities. PCA characterized four independent dimensions including a peripheral resistance (constituted by baseline peripheral compliance, Frs, R5Hz, R5-20Hz, X5Hz, and AX), a central resistance (baseline central resistance, R20Hz), anthropometrics (age and height), and asthma probability (wheezing patterns and therapeutic steps). Thus, PCA showed that the SAD markers were independent from clinical dimensions and were unable to differentiate wheezing phenotypes.

CONCLUSIONS

Lung function parameters obtained from impulse oscillometry and asthma probability were belonging to independent dimensions of the wheezing disease.

Wheezing-Related Relevant Factors and the Role of Viral Bronchiolitis

Bronchiolitis is a virus-associated infection of the lower respiratory tract exhibiting signs and symptoms of airway obstruction. Respiratory Syncytial Virus (RSV) is responsible in most cases; however, different rhinoviruses have also been implicated. Specific viruses and time until the first infection, severity of the respiratory condition, and atopic status have a determinant role in the recurrence of wheezing and asthma development. Genetics, lung function, atopic condition, the role of microbiota and environment, pollution, and obesity are considered in the present review. Emergency room visits and hospitalizations because of severe wheezing and smoking during pregnancy among others were identified as risk factors for significant morbidity in our population. Approaching determinant conditions like genetics, allergy, antiviral immunity, and environmental exposures such as farm vs. urban and viral virulence provides an opportunity to minimize morbidity of viral illness and asthma in children.

Early age exposure to moisture and mould is related to FeNO at the age of 6 years

BACKGROUND

Exposure to indoor moisture damage and visible mold has been found to be associated with asthma and respiratory symptoms in several questionnaire-based studies by self-report. We aimed to define the prospective association between the early life exposure to residential moisture damage or mold and fractional exhaled nitric oxide (FeNO) and lung function parameters as objective markers for airway inflammation and asthma in 6-year-old children.

METHODS

Home inspections were performed in children's homes when infants were on average 5 months old. At age 6 years, data on FeNO (n = 322) as well as lung function (n = 216) measurements were collected. Logistic regression and generalized additive models were used for statistical analyses.

RESULTS

Early age major moisture damage and moisture damage or mold in the child's main living areas were significantly associated with increased FeNO levels (>75th percentile) at the age of 6 years (adjusted odds ratios, 95% confidence intervals, aOR (95% CI): 3.10 (1.35-7.07) and 3.16 (1.43-6.98), respectively. Effects were more pronounced in those who did not change residential address throughout the study period. For lung function, major structural damage within the whole home was associated with reduced FEV1 and FVC, but not with FEV1/FVC. No association with lung function was observed with early moisture damage or mold in the child's main living areas.

CONCLUSION

These results underline the importance of prevention and remediation efforts of moisture and mold-damaged buildings in order to avoid harmful effects within the vulnerable phase of the infants and children's immunologic development.

Cord blood group 2 innate lymphoid cells are associated with lung function at 6 weeks of age

Objective

Offspring born to mothers with asthma in pregnancy are known to have lower lung function which tracks with age. Human group 2 innate lymphoid cells (ILC2) accumulate in foetal lungs, at 10‐fold higher levels compared to adult lungs. However, there are no data on foetal ILC2 numbers and the association with respiratory health outcomes such as lung function in early life. We aimed to investigate cord blood immune cell populations from babies born to mothers with asthma in pregnancy.

Methods

Cord blood from babies born to asthmatic mothers was collected, and cells were stained in whole cord blood. Analyses were done using traditional gating approaches and computational methodologies (t‐distributed stochastic neighbour embedding and PhenoGraph algorithms). At 6 weeks of age, the time to peak tidal expiratory flow as a percentage of total expiratory flow time (tPTEF/tE%) was determined as well as Lung Clearance Index (LCI), during quiet natural sleep.

Results

Of 110 eligible infants (March 2017 to November 2019), 91 were successfully immunophenotyped (82.7%). Lung function was attempted in 61 infants (67.0%), and 43 of those infants (70.5% of attempted) had technically acceptable tPTEF/tE% measurements. Thirty‐four infants (55.7% of attempted) had acceptable LCI measurements. Foetal ILC2 numbers with increased expression of chemoattractant receptor‐homologous molecule (CRTh2), characterised by two distinct analysis methodologies, were associated with poorer infant lung function at 6 weeks of age.”

Conclusion

Foetal immune responses may be a surrogate variable for or directly influence lung function outcomes in early life.

Fetal Growth Restriction and Asthma: Is the Damage Done?

Trajectories of airway remodeling and functional impairment in asthma are consistent with the notion that airway pathology precedes or coincides with the onset of asthma symptoms and may be present at birth. An association between intrauterine growth restriction (IUGR) and asthma development has also been established, and there is value in understanding the underlying mechanism. This review considers airway pathophysiology as a consequence of IUGR that increases susceptibility to asthma.

Pharmacological ablation of the airway smooth muscle layer-Mathematical predictions of functional improvement in asthma

Airway smooth muscle (ASM) plays a major role in acute airway narrowing and reducing ASM thickness is expected to attenuate airway hyper‐responsiveness and disease burden. There are two therapeutic approaches to reduce ASM thickness: (a) a direct approach, targeting specific airways, best exemplified by bronchial thermoplasty (BT), which delivers radiofrequency energy to the airway via bronchoscope; and (b) a pharmacological approach, targeting airways more broadly. An example of the less well‐established pharmacological approach is the calcium‐channel blocker gallopamil which in a clinical trial effectively reduced ASM thickness; other agents may act similarly. In view of established anti‐proliferative properties of the macrolide antibiotic azithromycin, we examined its effects in naive mice and report a reduction in ASM thickness of 29% (p < .01). We further considered the potential functional implications of this finding, if it were to extend to humans, by way of a mathematical model of lung function in asthmatic patients which has previously been used to understand the mechanistic action of BT. Predictions show that pharmacological reduction of ASM in all airways of this magnitude would reduce ventilation heterogeneity in asthma, and produce a therapeutic benefit similar to BT. Moreover there are differences in the expected response depending on disease severity, with the pharmacological approach exceeding the benefits provided by BT in more severe disease. Findings provide further proof of concept that pharmacological targeting of ASM thickness will be beneficial and may be facilitated by azithromycin, revealing a new mode of action of an existing agent in respiratory medicine.

Structure and function of small airways in asthma patients revisited

Small airways (<2 mm in diameter) are probably involved across almost all asthma severities and they show proportionally more structural and functional abnormalities with increasing asthma severity. The structural and functional alterations of the epithelium, extracellular matrix and airway smooth muscle in small airways of people with asthma have been described over many years using in vitro studies, animal models or imaging and modelling methods. The purpose of this review was to provide an overview of these observations and to outline several potential pathophysiological mechanisms regarding the role of small airways in asthma.

The economic burden of medical treatment of children with asthma in China

Background

At present, there are few studies on the economic burden and medical treatment of children with asthma in China. Thus this study aimed to investigate the economic burden of medical treatment of children with asthma in China.

Method

The 2015 China Medical Insurance Research Association (CHIRA) database was searched for patients with asthma from 0 to 14 years old. A cross-sectional study with cost analysis was conducted.

Results

The annual per capita direct medical cost was RMB 525 (US$75) related to asthma. Totaling 58% of the medical expenditure for asthma was covered by insurance in China, the majority of which were direct medical costs. Those that have the highest rates of using antibiotics were central China (100.0%), children aged 3 years and under (63.6%), as well as fourth-tier and fifth-tier cities (77.1%). Outpatient clinics (98.58% vs 1.42%, P < 0.01), tertiary hospitals (62.08% vs 37.92%, P < 0.01), and general hospitals (72.27% vs 27.73%, P < 0.01) were more often visited than the inpatient clinics, secondary and primary as well as the specialized clinics, respectively.

Conclusion

The economic burden of childhood asthma in China is relatively low, and the national medical insurance reduces their economic burden to a large extent. Abuse of antibiotics in treating asthma was found in China. There remain opportunities to strengthen the hierarchical medical system, reducing hospitalization and emergency visits, and ultimately reducing the economic burden of children with asthma.

Childhood asthma increases respiratory morbidity, but not all-cause mortality in adulthood: The Busselton Health Study

BACKGROUND

Long-term childhood asthma studies that investigate adult outcomes other than lung function are lacking. This study examines the associations of childhood asthma and the occurrence of respiratory events and all-cause mortality in adulthood.

METHODS

A cohort of 4430 school children (aged to 17 years) who attended the Busselton Health Study between 1967 and 1983 were analysed. Self-reported history of asthma was determined using questionnaires. Participants were followed until 2014 for respiratory disease-related events (hospital admissions or death) and all-cause mortality using the Western Australia Data Linkage System. Cox regression models were used to investigate the impact of childhood asthma on respiratory events and all-cause mortality in adulthood. A subgroup of 2153 participants who re-attended a survey in young adulthood was also analysed.

RESULTS

A total of 462 (10%) of the cohort had childhood asthma. During follow-up 791 participants experienced a respiratory event and 140 participants died. Childhood asthma was associated with an increased risk of respiratory events in adulthood (unadjusted HR 1.84, 95% CI 1.52 to 2.23; P < 0.0001). The result remained significant after adjusting for adult-onset asthma, FEV₁, body mass index, smoking, dusty job, hay fever, and respiratory symptoms (adjusted HR 1.68, 95% CI 1.07 to 2.64; P = 0.0247). Childhood asthma was not associated with all-cause mortality in adulthood (unadjusted HR 1.08, 95% CI 0.63 to 1.84; P = 0.7821).

CONCLUSION

Childhood asthma is associated with increased risk of respiratory disease-related hospital admissions and death but not all-cause mortality in adulthood.

Asthma: Pharmacological degradation of the airway smooth muscle layer

Asthma: A disease characterised by excessive and variable airway narrowing, and pathologies of inflammation and remodelling, particularly thickening of the airway smooth muscle (ASM). Treatment approaches dilate narrowed airways and reduce inflammation; however, remodelling seems largely neglected. This review considers the evolution of remodelling in asthma and whether conventional hypotheses that inflammation causes ASM thickening has mislead the medical community into thinking that anti-inflammatories will remedy this ASM defect. There is instead reasonable evidence that ASM thickening occurs independently of inflammation, such that therapies should employ strategies to directly modify ASM growth. Lessons have been learned from the use of untargeted bronchial thermoplasty and there should also be consideration of pharmacological therapies to ablate ASM. We discuss several new approaches to target ASM remodelling in asthma. A major current obstacle is our inability to image the ASM layer and assess treatment response. In this regard, polarisation-sensitive optical coherence tomography offers future promise.

Inflammatory mechanisms linking maternal and childhood asthma

Asthma is a chronic inflammatory airway disease characterized by airway hyperresponsiveness, inflammation, and remodeling. Asthma often develops during childhood and causes lifelong decrements in lung function and quality of life. Risk factors for childhood asthma are numerous and include genetic, epigenetic, developmental, and environmental factors. Uncontrolled maternal asthma during pregnancy exposes the developing fetus to inflammatory insults, which further increase the risk of childhood asthma independent of genetic predisposition. This review focuses on the role of maternal asthma in the development of asthma in offspring. We will present maternal asthma as a targetable and modifiable risk factor for childhood asthma and discuss the mechanisms by which maternal inflammation increases childhood asthma risk. Topics include how exposure to maternal asthma in utero shapes structural lung development with a special emphasis on airway nerves, how maternal type-2 cytokines such as IL-5 activate the fetal immune system, and how changes in lung and immune cell development inform responses to aero-allergens later in life. Finally, we highlight emerging evidence that maternal asthma establishes a unique "asthma signature" in the airways of children, leading to novel mechanisms of airway hyperreactivity and inflammatory cell responses.

Persistent Asthma from Childhood to Adulthood Presents a Distinct Phenotype of Adult Asthma

BACKGROUND

In approximately 30% of children with asthma, the condition persists into adulthood. The longer duration of asthma in these patients is a risk factor for poor asthma control. However, the characteristics of adult patients with asthma that has persisted since childhood are not well documented.

OBJECTIVE

We sought to compare the clinical characteristics among patients with adult-onset asthma, patients who outgrew childhood asthma but relapsed, and patients with persistent asthma since childhood.

METHODS

We conducted a cross-sectional study of adult patients with asthma who visited our hospital. We classified them into 3 groups: those with adult-onset asthma (adult-onset), those who had remitted childhood asthma that relapsed (relapsed), and those who had asthma that had persisted since childhood (persistent). The clinical characteristics of these groups were compared.

RESULTS

A total of 1443 patients were enrolled. The persistent group was younger and included fewer patients with a smoking history. There were statistically significant differences among the 3 groups in the percentages of patients with a family history of asthma and comorbidities of allergic rhinitis and atopic dermatitis. The proportion of patients with severe asthma differed among the 3 groups (31% in the adult-onset group, 34% in the relapsed group, and 40% in the persistent group; P = .015). The values of forced expiratory flow at 75% of vital capacity were lower in the persistent group than the relapsed or adult-onset group. A multivariable logistic regression analysis (dependent variable: severe asthma) in each group revealed that the factors associated with severe asthma differed among the adult-onset, relapsed, and persistent groups. When we established an overall model that included interaction terms of cohort-by-other factors, there was a trend that comorbidity of allergic rhinitis affected the severity of asthma differently in the relapsed group compared with the other groups.

CONCLUSION

The clinical phenotype of asthma that persists from childhood to adulthood seems to be a distinct phenotype of adult asthma.

A modern approach to identifying and characterizing child asthma and wheeze phenotypes based on clinical data

‘Asthma’ is a complex disease that encapsulates a heterogeneous group of phenotypes and endotypes. Research to understand these phenotypes has previously been based on longitudinal wheeze patterns or hypothesis-driven observational criteria. The aim of this study was to use data-driven machine learning to identify asthma and wheeze phenotypes in children based on symptom and symptom history data, and, to further characterize these phenotypes. The study population included an asthma-rich population of twins in Sweden aged 9–15 years (n = 752). Latent class analysis using current and historical clinical symptom data generated asthma and wheeze phenotypes. Characterization was then performed with regression analyses using diagnostic data: lung function and immunological biomarkers, parent-reported medication use and risk-factors. The latent class analysis identified four asthma/wheeze phenotypes: early transient wheeze (15%); current wheeze/asthma (5%); mild asthma (9%), moderate asthma (10%) and a healthy phenotype (61%). All wheeze and asthma phenotypes were associated with reduced lung function and risk of hayfever compared to healthy. Children with mild and moderate asthma phenotypes were also more likely to have eczema, allergic sensitization and a family history of asthma. Furthermore, those with moderate asthma phenotype had a higher eosinophil concentration (β 0.21, 95%CI 0.12, 0.30) compared to healthy and used short-term relievers at a higher rate than children with mild asthma phenotype (RR 2.4, 95%CI 1.2–4.9). In conclusion, using a data driven approach we identified four wheeze/asthma phenotypes which were validated with further characterization as unique from one another and which can be adapted for use by the clinician or researcher.

Mechanical Abnormalities of the Airway Wall in Adult Mice After Intrauterine Growth Restriction

Developmental abnormalities of airways may impact susceptibility to asthma in later life. We used a maternal hypoxia-induced mouse model of intrauterine growth restriction (IUGR) to examine changes in mechanical properties of the airway wall. Pregnant BALB/c mice were housed under hypoxic conditions (10.5% O₂) from gestational day (GD) 11 to GD 17.5 (IUGR; term, GD 21). Following hypoxic exposure, mice were returned to a normoxic environment (21% O₂). A control group of pregnant mice were housed under normoxic conditions throughout pregnancy. At 8 weeks postnatal age, offspring were euthanized and a tracheasectomy performed. Tracheal segments were studied in organ baths to measure active airway smooth muscle (ASM) stress to carbachol and assess passive mechanical properties (stiffness) from stress-strain curves. In a separate group of anesthetized offspring, the forced oscillation technique was used to examine airway mechanics from relative changes in airway conductance during slow inflation and deflation between 0 and 20 cmH₂O transrespiratory pressure. From predicted radius-pressure loops, storage and loss moduli and hysteresivity were calculated. IUGR offspring were lighter at birth (p < 0.05) and remained lighter at 8 weeks of age (p < 0.05) compared with Controls. Maximal stress was reduced in male IUGR offspring compared with Controls (p < 0.05), but not in females. Sensitivity to contractile agonist was not affected by IUGR or sex. Compared with the Control group, airways from IUGR animals were stiffer in vitro (p < 0.05). In vivo, airway hysteresivity (p < 0.05) was increased in the IUGR group, but there was no difference in storage or loss moduli between groups. In summary, the effects of IUGR persist to the mature airway wall, where there are clear abnormalities to ASM contractile properties and passive wall mechanics. We propose that mechanical abnormalities of the airway wall acquired through disrupted fetal growth impact susceptibility to disease.

Mechanical Abnormalities of the Airway Wall in Adult Mice After Intrauterine Growth Restriction

Developmental abnormalities of airways may impact susceptibility to asthma in later life. We used a maternal hypoxia-induced mouse model of intrauterine growth restriction (IUGR) to examine changes in mechanical properties of the airway wall. Pregnant BALB/c mice were housed under hypoxic conditions (10.5% O₂) from gestational day (GD) 11 to GD 17.5 (IUGR; term, GD 21). Following hypoxic exposure, mice were returned to a normoxic environment (21% O₂). A control group of pregnant mice were housed under normoxic conditions throughout pregnancy. At 8 weeks postnatal age, offspring were euthanized and a tracheasectomy performed. Tracheal segments were studied in organ baths to measure active airway smooth muscle (ASM) stress to carbachol and assess passive mechanical properties (stiffness) from stress-strain curves. In a separate group of anesthetized offspring, the forced oscillation technique was used to examine airway mechanics from relative changes in airway conductance during slow inflation and deflation between 0 and 20 cmH₂O transrespiratory pressure. From predicted radius-pressure loops, storage and loss moduli and hysteresivity were calculated. IUGR offspring were lighter at birth (p < 0.05) and remained lighter at 8 weeks of age (p < 0.05) compared with Controls. Maximal stress was reduced in male IUGR offspring compared with Controls (p < 0.05), but not in females. Sensitivity to contractile agonist was not affected by IUGR or sex. Compared with the Control group, airways from IUGR animals were stiffer in vitro (p < 0.05). In vivo, airway hysteresivity (p < 0.05) was increased in the IUGR group, but there was no difference in storage or loss moduli between groups. In summary, the effects of IUGR persist to the mature airway wall, where there are clear abnormalities to ASM contractile properties and passive wall mechanics. We propose that mechanical abnormalities of the airway wall acquired through disrupted fetal growth impact susceptibility to disease.

Mechanical Abnormalities of the Airway Wall in Adult Mice After Intrauterine Growth Restriction

Developmental abnormalities of airways may impact susceptibility to asthma in later life. We used a maternal hypoxia-induced mouse model of intrauterine growth restriction (IUGR) to examine changes in mechanical properties of the airway wall. Pregnant BALB/c mice were housed under hypoxic conditions (10.5% O₂) from gestational day (GD) 11 to GD 17.5 (IUGR; term, GD 21). Following hypoxic exposure, mice were returned to a normoxic environment (21% O₂). A control group of pregnant mice were housed under normoxic conditions throughout pregnancy. At 8 weeks postnatal age, offspring were euthanized and a tracheasectomy performed. Tracheal segments were studied in organ baths to measure active airway smooth muscle (ASM) stress to carbachol and assess passive mechanical properties (stiffness) from stress-strain curves. In a separate group of anesthetized offspring, the forced oscillation technique was used to examine airway mechanics from relative changes in airway conductance during slow inflation and deflation between 0 and 20 cmH₂O transrespiratory pressure. From predicted radius-pressure loops, storage and loss moduli and hysteresivity were calculated. IUGR offspring were lighter at birth (p < 0.05) and remained lighter at 8 weeks of age (p < 0.05) compared with Controls. Maximal stress was reduced in male IUGR offspring compared with Controls (p < 0.05), but not in females. Sensitivity to contractile agonist was not affected by IUGR or sex. Compared with the Control group, airways from IUGR animals were stiffer in vitro (p < 0.05). In vivo, airway hysteresivity (p < 0.05) was increased in the IUGR group, but there was no difference in storage or loss moduli between groups. In summary, the effects of IUGR persist to the mature airway wall, where there are clear abnormalities to ASM contractile properties and passive wall mechanics. We propose that mechanical abnormalities of the airway wall acquired through disrupted fetal growth impact susceptibility to disease.

Prodromal clinical, demographic, and socio-ecological correlates of asthma in adults: a 10-year statewide big data multi-domain analysis

Objectives: To identify prodromal correlates of asthma as compared to chronic obstructive pulmonary disease and allied-conditions (COPDAC) using a multi domain analysis of socio-ecological, clinical, and demographic domains.Methods: This is a retrospective case-risk-control study using data from Florida's statewide Healthcare Cost and Utilization Project (HCUP). Patients were grouped into three groups: asthma, COPDAC (without asthma), and neither asthma nor COPDAC. To identify socio-ecological, clinical, demographic, and clinical predictors of asthma and COPDAC, we used univariate analysis, feature ranking by bootstrapped information gain ratio, multivariable logistic regression with LogitBoost selection, decision trees, and random forests.Results: A total of 141,729 patients met inclusion criteria, of whom 56,052 were diagnosed with asthma, 85,677 with COPDAC, and 84,737 with neither asthma nor COPDAC. The multi-domain approach proved superior in distinguishing asthma versus COPDAC and non-asthma/non-COPDAC controls (area under the curve (AUROC) 84%). The best domain to distinguish asthma from COPDAC without controls was prior clinical diagnoses (AUROC 82%). Ranking variables from all the domains found the most important predictors for the asthma versus COPDAC and controls were primarily socio-ecological variables, while for asthma versus COPDAC without controls, demographic and clinical variables such as age, CCI, and prior clinical diagnoses, scored better.Conclusions: In this large statewide study using a machine learning approach, we found that a multi-domain approach with demographics, clinical, and socio-ecological variables best predicted an asthma diagnosis. Future work should focus on integrating machine learning-generated predictive models into clinical practice to improve early detection of those common respiratory diseases.

Transition From Phasic to Tonic Contractility in Airway Smooth Muscle After Birth: An Experimental and Computational Modeling Study

Fetal airway smooth muscle (ASM) exhibits phasic contractile behavior, which transitions to a more sustained "tonic" contraction after birth. The timing and underlying mechanisms of ASM transition from a phasic to a tonic contractile phenotype are yet to be established. We characterized phasic ASM contraction in preterm (128 day gestation), term (~150 day gestation), 1-4 month, 1 yr, and adult sheep (5yr). Spontaneous phasic activity was measured in bronchial segments as amplitude, frequency, and intensity. The mechanism of phasic ASM contraction was investigated further with a computational model of ASM force development and lumen narrowing. The computational model comprised a two-dimensional cylindrical geometry of a network of contractile units and the activation of neighboring cells was dependent on the strength of coupling between cells. As expected, phasic contractions were most prominent in fetal airways and decreased with advancing age, to a level similar to the level in the 1-4 month lambs. Computational predictions demonstrated phasic contraction through the generation of a wave of activation events, the magnitude of which is determined by the number of active cells and the strength of cell-cell interactions. Decreases in phasic contraction with advancing age were simulated by reducing cell-cell coupling. Results show that phasic activity is suppressed rapidly after birth, then sustained at a lower intensity from the preweaning phase until adulthood in an ovine developmental model. Cell-cell coupling is proposed as a key determinant of phasic ASM contraction and if reduced could explain the observed maturational changes.

Early Lung Function and Future Asthma

Asthmatic adults with lower lung function have been described as having had this worse condition early in life. Lung function is reduced in children with persistent asthma and continues low throughout adult life. The challenge is to know if impaired lung function is a risk factor of asthma, as a consequence of special congenital characteristics of the airways, or whether asthmatic patients suffer a loss in lung function as early as 9 years of age as a consequence of very precocious remodeling of the airways. The loss is so early in life that it is probably a congenital characteristic, however there is not a cut-off point with clinical interest to predict risk of asthma later in life. There are contradictory results regarding whether asthmatic children lose lung function as a consequence of the airway remodeling by the illness itself. This aspect seemed to be shown for children at risk-the offspring of asthmatic mothers. The early BHR seems to be very frequent even in healthy infants, but is probably not a risk factor for asthma years later; except in the offspring of asthmatic mothers in which it has been shown. There are still many uncertainties in this field; so, more research is needed in order to better understand the pathophysiology of asthma, the early risk factors and to design new therapeutic targets and early interventions to change the natural history of the disease.

Prevalence of allergic sensitization, hay fever, eczema, and asthma in a longitudinal birth cohort

Purpose

The aim of this study was to longitudinally assess the prevalence of allergic sensitization, asthma, eczema and hay fever from infancy to adulthood in a single cohort.

Participants and methods

This prospective study is based on a longitudinal birth cohort of 253 participants, with respiratory and immunological assessments at 1, 6, 11, 18 and 24 years of age. Subjects were recruited from an urban maternity hospital. Retention rates varied from 45% to 72% at follow-up assessments. Asthma diagnosis was based on physician diagnosis of asthma and symptoms/medications in the previous 12 months. Allergic sensitization was defined by the positive skin prick test. Hay fever and eczema were based on a questionnaire.

Results

The prevalence of allergic sensitization rose from 19% (n=33) at 1 year of age to 71% (n=77) at 24 years of age. The rate of asthma halved from 25% at 6 years of age to 12%–15% between 11 and 24 years of age, but the prevalence of allergic sensitization among those with asthma doubled from 50% at 6 years of age to 100% at 24 years of age. Hay fever rates rose throughout childhood from 7% at 6 years of age to 44% at 24 years of age, while the prevalence of eczema reduced from 25% at 6 years of age to 16% at 24 years of age. Parental atopy doubled the odds of asthma in their offspring by 24 years of age (odds ratio [OR]= 2.63, 95% CI 1.1–6.2, p=0.029). In all, 74% of those with asthma at 24 years of age also reported hay fever. The relationship between eczema and asthma was only significant up to 11 years of age, and the relationship between hay fever and asthma was stronger in adolescence and early adulthood than in early childhood.

Conclusion

Patterns of atopic disorders vary throughout childhood. Although the prevalence of allergic sensitization and hay fever rose throughout childhood and the prevalence of asthma reduced, the strength of their relationship with asthma increased with age.

Incidence of asthma in young adults from Castellon, Spain: A prospective cohort study

BACKGROUND

The objective was to estimate the incidence of asthma in young adults from 13-15 years old to 23-25 years old, and associated factors.

METHODS

In 2012, a population-based prospective cohort study was carried out in Castellon from the cohort who had participated in the International Study of Asthma and Allergy in Childhood in 1994 and 2002. A telephone survey was undertaken using the same questionnaires. A new case of asthma was defined as a participant free of the disease in 2002 who suffered asthma, was diagnosed with asthma, or took medications against asthma based on self-report from 2002 to 2012.

RESULTS

The mean age of participants was 24.9±0.6 with a follow-up of 79.1%. Asthma cumulative incidence was 3.4%: 44 new cases occurred among 1280 participants. The incidence was higher in females than males with relative risk (RR)=2.02 (95% confidence interval [CI] 1.1-3.8). A significant decrease of asthma incidence density was observed (8.2 cases to 3.5 cases per 1000 person/year). Factors associated with the incidence of asthma were allergic rhinitis (RR=4.05; 95% CI 1.7-9.6), bronchitis (RR=2.13; 95% CI 1.0-4.5), mother's age at time of birth (RR=0.87; 95% CI 0.8-0.9) and a pet other than a dog or cat (RR=0.42; 95% CI 0.2-0.9). For gender, some variations in the risk factors were observed.

CONCLUSIONS

A significant decrease in the incidence of asthma was observed. Several risk and protective factors were found.

Foetal growth restriction in mice modifies postnatal airway responsiveness in an age and sex-dependent manner

Epidemiological studies demonstrate an association between intrauterine growth restriction (IUGR) and asthma; however the underlying mechanism is unknown. We investigated the impact of maternal hypoxia-induced IUGR on airway responsiveness in male and female mice during juvenility and adulthood. Pregnant BALB/c mice were housed under hypoxic conditions for gestational days 11-17.5 and then returned to normoxic conditions for the remainder of pregnancy. A control group was housed under normoxic conditions throughout pregnancy. Offspring were studied at 2 weeks (juveniles) and 8 weeks (adults), where lung volume was assessed by plethysmography, airway responsiveness to methacholine determined by the forced oscillation technique and lungs fixed for morphometry. IUGR offspring were lighter at birth, exhibited "catch-up growth" by 2 weeks, but were again lighter in adulthood. IUGR males were "hyper-responsive" at 2 weeks and "hypo-responsive" as adults, in contrast with IUGR females who were hyper-responsive in adulthood. IUGR males had increased inner and total wall thickness at 2 weeks which resolved by adulthood, while airways in IUGR females were structurally normal throughout life. There were no differences in lung volume between Control and IUGR offspring at any age. Our data demonstrate changes in airway responsiveness as a result of IUGR that could influence susceptibility to asthma development and contribute to sexual dimorphism in asthma prevalence which switches from a male dominated disease in early life to a female dominated disease in adulthood.

Pathophysiology of severe asthma: We've only just started

Severe asthma is defined by the high treatment requirements to partly or fully control the clinical manifestations of disease. It remains a problem worldwide with a large burden for individuals and health services. The key to improving targeted treatments, reducing disease burden and improving patient outcomes is a better understanding of the pathophysiology and mechanisms of severe disease. The heterogeneity, complexity and difficulties in undertaking clinical studies in severe asthma remain challenges to achieving better understanding and better outcomes. In this review, we focus on the structural, mechanical and inflammatory abnormalities that are relevant in severe asthma.

Pre-natal and post-natal exposure to pet ownership and lung function in children: The Seven Northeastern Cities Study

To evaluate the association between pre-natal and post-natal exposure to pet ownership and lung function in children, a cross-sectional study named Seven Northeastern Cities (SNEC) study was conducted. In this study, children's lung function including the forced expiratory volume in 1 second (FEV₁ ), forced vital capacity (FVC), maximal mid-expiratory flow (MMEF), and peak expiratory flow (PEF) were measured by spirometers, and pet ownership situations were collected by questionnaire. Analyzed by multiple logistic regression and generalized linear modeling, we found that for all subjects, pet exposure in the first 2 years of life was significantly associated with lung function impairment of FVC<85% predicted (adjusted odds ratio [aOR]=1.28; 95% confidence interval [CI]: 1.01, 1.63). For current pet exposure, the increased odds of lung function impairment ranged from 35% (aOR=1.35; 95%CI: 1.12, 1.62) for FVC<85% predicted to 57% (aOR=1.57; 95%CI: 1.29, 1.93) for FEV₁ <85% predicted. The in utero exposure was not related to lung function impairment. Compared with other pets, higher odds were observed among children with dogs. When stratified by gender, girls with current pet exposure were more likely to have lung function impairment than boys. It implies self-reported exposures to pets were negatively associated with lung function among the children under study.