Preterm Birth with Childhood Asthma: The Role of Degree of Prematurity and Asthma Definitions

Asthma, classical conditioning, and the autonomic nervous system - a hypothesis for why children wheeze

Paediatric asthma is an increasing global healthcare problem for which current treatments are not always effective. This review explores how abnormal triggering of the autonomic diving reflex might be important in explaining research findings and the real-world experience of asthma. It hypothesises that the way in which stress during pregnancy is associated with childhood asthma could be through effects on the developing nervous system. This results in increased parasympathetic responsiveness and specifically, excessive triggering of the diving reflex in response to wetting and cooling of the face and nose as occurs with upper airway infections and allergic rhinitis. In aquatic mammals the reflex importantly includes the contraction of airway smooth muscle to minimise lung volume and prevent nitrogen narcosis from diving at depth. Misfiring of this reflex in humans could result in the pathological airway narrowing that occurs in asthma. The diving reflex, and possibly also smooth muscle, is a vestigial remnant of our aquatic past. The hypothesis further suggests that classically conditioned reflex responses to neutral cues and contexts that were present at the same time as the stimuli that initially caused symptoms, become of themselves ongoing triggers of recurrent wheeze. Symptoms occurring in this way, irrespective of the presence of allergens and ongoing airway sensitisation, explain why allergen avoidance is poorly effective in alleviating wheeze and why asthma is made worse by stress. Interventions to suppress the diving reflex and to prevent reflex conditioned wheezing could result in more effective asthma management.

How Schools Can Help Address Social Determinants of Health in Asthma Management

Schools are in a unique position to address social determinants of health (SDOHs) in pediatric asthma management because of their potential to provide resources and facilitate collaboration with health care providers and services for children at risk within their community. SDOHs include economic factors, educational attainment and health literacy, neighborhood factors and the built environment, social and community aspects including discrimination and racism, and health care access and quality. These factors have a significant impact on asthma health in children, and certain populations such as minoritzed populations and those living in high-poverty environments have been shown to be at greater risk for adverse effects of SDOHs on asthma outcomes. School-based asthma programs address several SDOHs including health literacy, the built environment, and health care quality and access and have been shown to improve asthma outcomes. Key components include connection between the school and the health care team, self-management education, and directly observed therapy. School nurses play a key role in directing and managing effective programs because they can evaluate and support a student's health while considering the effect of SDOHs at interpersonal, institutional, community, and policy levels.

Are Babies Born Preterm High-Risk Asthma Candidates?

Among preterm infants, the risk of developing asthma is a matter of debate. This review discusses the state of the art of poorly understood prematurity-associated asthma. Impaired pulmonary function is common in children born prematurely. Preterm infants are prone to developing viral respiratory tract infections, bronchiolitis in the first year of life, and recurrent viral wheezing in preschool age. All of these conditions may precede asthma development. We also discuss the role of both atopic sensitization and intestinal microbiome and, consequently, immune maturation. Diet and pollution have been considered to better understand how prematurity could be associated with asthma. Understanding the effect of factors involved in asthma onset may pave the way to improve the prediction of this asthma phenotype.

Relation of Maternal Pre-Pregnancy Factors and Childhood Asthma: A Cross-Sectional Survey in Pre-School Children Aged 2-5 Years Old

Background and Objectives: Asthma constitutes a constant, prolonged, inflammation-related pulmonary disorder in childhood with serious public health concerns. Several maternal risk factors can enhance the prevalence of its development in this stage of life; however, the currently available data remain contradictory and/or inconsistent. We aim to evaluate the potential impacts of mothers' sociodemographic, anthropometric and prenatal and perinatal factors on the prevalence of developing asthma in pre-school children. Materials and Methods: This is a retrospective cross-sectional survey, which includes 5133 women and their matched pre-school children. Childhood asthma was diagnosed using validated questionnaires. Statistical analysis was accomplished to evaluate whether maternal sociodemographic, anthropometric and prenatal and perinatal factors can increase the probability of childhood asthma in pre-school age. Results: A prevalence of 4.5% of childhood asthma was recorded in pre-school age. Maternal age and pre-pregnancy overweight and obesity, caesarean section, gestational diabetes and hypertension and not breastfeeding were associated with childhood asthma after adjustment for multiple confounding factors. Conclusion: Our research showed that several maternal factors increase the prevalence of childhood asthma in pre-school age. Suitable and effective health policies and strategies should be taken into account to confront the predominant maternal factors that increase its prevalence in pre-school age.

Maternal exposure to urinary polycyclic aromatic hydrocarbons (PAH) in pregnancy and childhood asthma in a pooled multi-cohort study

BACKGROUND

Prenatal exposure to polycyclic aromatic hydrocarbons (PAH) may increase risk of pediatric asthma, but existing human studies are limited.

OBJECTIVES

We estimated associations between gestational PAHs and pediatric asthma in a diverse US sample and evaluated effect modification by child sex, maternal asthma, and prenatal vitamin D status.

METHODS

We pooled two prospective pregnancy cohorts in the ECHO PATHWAYS Consortium, CANDLE and TIDES, for an analytic sample of N = 1296 mother-child dyads. Mono-hydroxylated PAH metabolites (OH-PAHs) were measured in mid-pregnancy urine. Mothers completed the International Study on Allergies and Asthma in Childhood survey at child age 4-6 years. Poisson regression with robust standard errors was used to estimate relative risk of current wheeze, current asthma, ever asthma, and strict asthma associated with each metabolite, adjusted for potential confounders. We used interaction models to assess effect modification. We explored associations between OH-PAH mixtures and outcomes using logistic weighted quantile sum regression augmented by a permutation test to control Type 1 errors.

RESULTS

The sociodemographically diverse sample spanned five cities. Mean (SD) child age at assessment was 4.4 (0.4) years. While there was little evidence that either individual OH-PAHs or mixtures were associated with outcomes, we observed effect modification by child sex for most pairs of OH-PAHs and outcomes, with adverse associations specific to females. For example, a 2-fold increase in 2-hydroxy-phenanthrene was associated with current asthma in females but not males (RRfemale = 1.29 [95 % CI: 1.09, 1.52], RRmale = 0.95 [95 % CI: 0.79, 1.13]; pinteraction = 0.004). There was no consistent evidence of modification by vitamin D status or maternal asthma.

DISCUSSION

This analysis, the largest cohort study of gestational PAH exposure and childhood asthma to date, suggests adverse associations for females only. These preliminary findings are consistent with hypothesized endocrine disruption properties of PAHs, which may lead to sexually dimorphic effects.

Boston Birth Cohort Profile: Rationale and Study Design

In 1998, the Boston Birth Cohort (BBC) was initiated at Boston Medical Center (BMC) in response to persistently high rates of preterm birth (PTB, defined as birth before 37 weeks of gestation) in the US population and the longstanding profound PTB disparity among Black, Indigenous, and people of color (BIPOC). The BBC encompasses two linked study protocols: The Preterm Birth Study serves as the baseline recruitment in the BBC. It aims to address fundamental questions about the causes and consequences of PTB. The study oversamples preterm babies using a case/control study design, in which cases are defined as mothers who deliver a preterm and/or low birthweight baby (<2500 grams regardless of gestational age). Controls are enrolled at a 2:1 control/case ratio and matched by maternal age (±5 years), self-reported race and ethnicity, and date of delivery (± 7 days for case delivery). From inception, it was designed as a comprehensive gene-environmental study of PTB. As a natural extension, the Children's Health Study, under a separate but linked IRB protocol, is a longitudinal follow-up study of the participants who were recruited at birth in the Preterm Birth Study and who continue pediatric care at BMC. This linked model allows for investigation of early life origins of pediatric and chronic disease in a prospective cohort design. The BBC is one of the largest and longest NIH-funded prospective birth cohort studies in the US, consisting of 8733 mother-child dyads enrolled in the Preterm Birth Study at birth, and of those, 3,592 children have been enrolled in the Children's Health Study, with a median follow-up of 14.5 years. The BBC mirrors the urban, under-resourced and underrepresented BIPOC population served by BMC. A high proportion of BBC children were born prematurely and had chronic health conditions (e.g., asthma, obesity and elevated blood pressure) in childhood. The BBC's long-term goal has been to build a large, comprehensive database (epidemiological, clinical, multi-omics) and biospecimen repository to elucidate early life origins of pediatric and chronic diseases and identify modifiable upstream factors (e.g., psychosocial, environmental, nutritional) to improve health across the life course for BIPOC mothers and children.

Boston Birth Cohort profile: rationale and study design

In1998, the Boston Birth Cohort (BBC) was initiated at Boston Medical Center (BMC) in response to persistently high rates of preterm birth (PTB, defined as birth before 37 weeks of gestation) in the US population and the longstanding profound PTB disparity among Black, Indigenous, and people of color (BIPOC). The BBC encompasses two linked study protocols: The PTB Study serves as the baseline recruitment in the BBC. It aims to address fundamental questions about the causes and consequences of PTB. The study oversamples preterm babies using a case/control study design, in which cases are defined as mothers who deliver a preterm and/or low birthweight baby (<2500 grams regardless of gestational age). Controls are enrolled at a 2:1 control/case ratio and matched by maternal age (±5 years), self-reported race and ethnicity, and date of delivery (± 7 days for case delivery). From inception, it was designed as a comprehensive gene-environmental study of PTB. As a natural extension, the Children's Health Study, under a separate but linked Institutional Review Board protocol, is a longitudinal follow-up study of the participants who were recruited at birth in the PTB Study and who continue pediatric care at BMC. This linked model allows for investigation of early life origins of pediatric and chronic disease in a prospective cohort design. The BBC is one of the largest and longest National Institutes of Health-funded prospective birth cohort studies in the United States, consisting of 8733 mother-child dyads enrolled in the PTB Study at birth, and of those, 3592 children have been enrolled in the Children's Health Study, with a median follow-up of 14.5 years. The BBC mirrors the urban, underresourced, and underrepresented BIPOC population served by BMC. A high proportion of BBC children were born prematurely and had chronic health conditions (e.g., asthma, obesity, and elevated blood pressure) in childhood. The BBC's long-term goal has been to build a large, comprehensive database (epidemiological, clinical, and multiomics) and biospecimen repository to elucidate early life origins of pediatric and chronic diseases and identify modifiable upstream factors (e.g., psychosocial, environmental, and nutritional) to improve health across the life course for BIPOC mothers and children.

Factors associated with recurrent wheezing in the first year of life among premature newborns from Neonatal Intensive Care Units

Abstract Objectives: to determine the prevalence and factors associated with recurrent wheezing in the first year of life among premature newborns from Neonatal Intensive Care Units, in the city of Montes Claros, northern Minas Gerais. Methods: cross-sectional study, with data collection from medical records of a follow-up clinic, interviews with mothers and, eventually, search in hospital records. Bivariate analyzes were carried out between sociodemographic and clinical characteristics and recurrent wheezing. Variables associated up to the level of 20% were analyzed by binary logistic regression, and associations defined by the Odds Ratio and respective 95% confidence intervals. Only variables associated with a 5% significance level were maintained in the final model of logistic regression. Results: among 277 infants studied, about one fifth (21.3%) were extremely low birth weight preterm and more than half (60.7%) had birth weight below 1500 grams. The prevalence of recurrent wheezing was 14.4% (CI95% = 10.3-18.4). Mechanical ventilation (OR = 2.12; CI95% = 1.09-4.76; p = 0.030) and oxygen therapy time ≥ 15 days (OR = 2.49; CI95%= 1.12-5.00; p = 0.010) were the risk factors for the event. Conclusions: there is a high prevalence of recurrent wheezing in the evaluated group and the associated variables reiterate the risk of prolonged oxygen therapy and mechanical ventilation for premature newborns.

Asthma clustering methods: a literature-informed application to the children's health study data

OBJECTIVE

The heterogeneity of asthma has inspired widespread application of statistical clustering algorithms to a variety of datasets for identification of potentially clinically meaningful phenotypes. There has not been a standardized data analysis approach for asthma clustering, which can affect reproducibility and clinical translation of results. Our objective was to identify common and effective data analysis practices in the asthma clustering literature and apply them to data from a Southern California population-based cohort of schoolchildren with asthma.

METHODS

As of January 1, 2020, we reviewed key statistical elements of 77 asthma clustering studies. Guided by the literature, we used 12 input variables and three clustering methods (hierarchical clustering, k-medoids, and latent class analysis) to identify clusters in 598 schoolchildren with asthma from the Southern California Children's Health Study (CHS).

RESULTS

Clusters of children identified by latent class analysis were characterized by exhaled nitric oxide, FEV₁/FVC, FEV₁ percent predicted, asthma control and allergy score; and were predictive of control at two year follow up. Clusters from the other two methods were less clinically remarkable, primarily differentiated by sex and race/ethnicity and less predictive of asthma control over time.

CONCLUSION

Upon review of the asthma phenotyping literature, common approaches of data clustering emerged. When applying these elements to the Children's Health Study data, latent class analysis clusters-represented by exhaled nitric oxide and spirometry measures-had clinical relevance over time.

Telomere length shortening in hospitalized preterm infants: A pilot study

Leukocyte telomere length is a biomarker of aging-related health risks. Hospitalized preterm infants frequently experience elevated oxidative stress and inflammation, both of which contribute to telomere shortening. Our aim was to examine changes in telomere length during neonatal intensive care unit (NICU) hospitalization in a cohort of preterm infants <32 weeks' gestation. We conducted a longitudinal study of 10 infants (mean gestational age 27 weeks, range 23.5 to 29, at birth). We isolated DNA from dried blood spots and used Real Time Quantitative PCR to measure relative leukocyte telomere length in triplicate at three time points for each participant. From birth to discharge, infants experienced an average decline in relative telomere length of 0.021 units per week (95% CI -0.040, -0.0020; p = 0.03), after adjustment for gestational age at birth. Our results suggest a measurable decline in telomere length during NICU hospitalization. We speculate that telomere length change may convey information about NICU exposures that carry short- and long-term health risks.

Gaining a deeper understanding of social determinants of preterm birth by integrating multi-omics data

In the US, high rates of preterm birth (PTB) and profound Black-White disparities in PTB have persisted for decades. This review focuses on the role of social determinants of health (SDH), with an emphasis on maternal stress, in PTB disparity and biological embedding. It covers: (1) PTB disparity in US Black women and possible contributors; (2) the role of SDH, highlighting maternal stress, in the persistent racial disparity of PTB; (3) epigenetics at the interface between genes and environment; (4) the role of the genome in modifying maternal stress-PTB associations; (5) recent advances in multi-omics studies of PTB; and (6) future perspectives on integrating multi-omics with SDH to elucidate the Black-White disparity in PTB. Available studies have indicated that neither environmental exposures nor genetics alone can adequately explain the Black-White PTB disparity. Preliminary yet promising findings of epigenetic and gene-environment interaction studies underscore the value of integrating SDH with multi-omics in prospective birth cohort studies, especially among high-risk Black women. In an era of rapid advancements in biomedical sciences and technologies and a growing number of prospective birth cohort studies, we have unprecedented opportunities to advance this field and finally address the long history of health disparities in PTB. IMPACT: This review provides an overview of social determinants of health (SDH) with a focus on maternal stress and its role on Black-White disparity in preterm birth (PTB). It summarizes the available literature on the interplay of maternal stress with key biological layers (e.g., individual genome and epigenome in response to environmental stressors) and significant knowledge gaps. It offers perspectives that such knowledge may provide deeper insight into how SDH affects PTB and why some women are more vulnerable than others and underscores the critical need for integrating SDH with multi-omics in prospective birth cohort studies, especially among high-risk Black women.

Polydrug Use During Pregnancy and Preterm Birth in a Low-Income, Multiethnic Birth Cohort, Boston, 1998-2018

OBJECTIVE

The opioid epidemic in the United States increasingly affects women of reproductive age and has resulted in a rise in concurrent polydrug use. The objective of this study was to investigate the effect of this polydrug use on preterm birth in a multiethnic birth cohort.

METHODS

We analyzed data from 8261 mothers enrolled in the Boston Birth Cohort from 1998 to 2018 in Boston, Massachusetts. We grouped substances used during pregnancy based on their primary effects (stimulant or depressant) and assessed independent and combined associations with smoking on preterm birth.

RESULTS

Of 8261 mothers, 131 used stimulant drugs and 193 used depressant drugs during pregnancy. The preterm birth rate was 27.5% (2271 of 8261) in the sample. Mothers who smoked had 35% increased odds of preterm birth across adjusted models. Mothers who used stimulant drugs without smoking were not at increased risk of preterm delivery compared with mothers who used neither (odds ratio [OR] = 0.69; 95% confidence interval [CI], 0.19-1.98), whereas mothers who used depressant drugs without smoking had more than twice the odds of having preterm delivery (OR = 2.31; 95% CI, 1.19-4.44), and infants were at risk of a 1-week reduction in gestational age (OR = -1.05; 95% CI, -2.07 to -0.03). Concurrently smoking and using depressant drugs was associated with increased odds of preterm birth (OR = 1.83; 95% CI, 1.28-2.61), as was concurrently smoking and using stimulant drugs (OR = 1.73; 95% CI, 1.14-2.59).

CONCLUSIONS

Using stimulant drugs and depressant drugs during pregnancy is a risk factor for preterm birth. The individual and combined effects of using these drugs with smoking must be considered together to reduce the risk of preterm birth in the United States.

Inner-City Asthma in Childhood

The inner-city is a well-established and well-studied location that includes children at high risk for high asthma prevalence and morbidity. A number of intrinsic and extrinsic risk factors contribute to asthma in inner-city populations. This review seeks to explore these risk factors and evaluate how they contribute to increased asthma morbidity. Previous literature has identified risk factors such as race and ethnicity, prematurity, obesity, and exposure to aeroallergens and pollutants. Environmental and medical interventions aimed at individual risk factors and specific asthma phenotypes have contributed to improved outcomes in the inner-city children with asthma.

New Directions in Pediatric Asthma

Childhood asthma affects many children placing them at significant risk for health care utilization and school absences. Several new developments relevant to the field of pediatric asthma have occurred over the last 5 years; yet, there is much more to learn. It is poorly understood how to prevent the disease, optimally address environmental challenges, or effectively manage poor adherence. Moreover, it is not clear how to customize therapy by asthma phenotype, age group, high risk groups, or severity of disease. Highlights of advances in pediatric asthma are reviewed and multiple essential areas for further exploration and research are discussed.

Inner-City Asthma in Children

Asthma in inner-city children is often severe and difficult to control. Residence in poor and urban areas confers increased asthma morbidity even after adjusting for ethnicity, age, and gender. Higher exposure to household pests, such as cockroaches and mice, pollutants and tobacco smoke exposure, poverty, material hardship, poor-quality housing, differences in health care quality, medication compliance, and heath care access also contribute to increased asthma morbidity in this population. Since 1991, the National Institutes of Allergy and Infectious Diseases established research networks: the National Cooperative Inner-City Asthma Study (NCICAS), the Inner-City Asthma Study (ICAS), and the Inner-City Asthma Consortium (ICAC), to improve care for this at risk population. The most striking finding of the NCICAS is the link between asthma morbidity and the high incidence of allergen sensitization and exposure, particularly cockroach. The follow-up ICAS confirmed that reductions in household cockroach and dust mite were associated with reduction in the inner-city asthma morbidity. The ICAC studies have identified that omalizumab lowered fall inner-city asthma exacerbation rate; however, the relationship between inner-city asthma vs immune system dysfunction, respiratory tract infections, prenatal environment, and inner-city environment is still being investigated. Although challenging, certain interventions for inner-city asthma children have shown promising results. These interventions include family-based interventions such as partnering families with asthma-trained social workers, providing guidelines driven asthma care as well as assured access to controller medication, home-based interventions aim at elimination of indoor allergens and tobacco smoke exposure, school-based asthma programs, and computer/web-based asthma programs.

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 Life Weight Gain and Development of Childhood Asthma in a Prospective Birth Cohort

RATIONALE

The prevalence of childhood asthma has been increasing worldwide in parallel with childhood obesity.

OBJECTIVES

We investigated whether there is a temporal relationship between early life weight gain (reflecting growth velocity) and early life body mass index (BMI) attained status (reflecting accumulative weight) with future risk of asthma in the Boston Birth Cohort.

METHODS

This report includes 1,928 children from the Boston Birth Cohort with a mean age of 7.8 years (standard deviation, 3.3 yr), enrolled at birth and followed prospectively. Asthma was defined using physician diagnosis code (International Classification of Diseases, Ninth Revision, Clinical Modification code 493.xx) in children 2 years and older. We categorized the children by their weight gain trajectory on the basis of changes in z-scores: slow (less than -0.67), on track (-0.67 to 0.67), rapid (0.67-1.28), and extremely rapid (>1.28); and by their BMI attained status (underweight, normal weight, and overweight) during the first 4, 12, and 24 months. Poisson regression models with robust variance estimation were applied to examine the relationship between early life weight gain/attained BMI and asthma.

RESULTS

During the first 4 months of life, 37% had on-track weight grain, 22% had slow weight gain, 15% had rapid weight gain, and 26% had extremely rapid weight gain. At 4 months, 61% were normal weight, 7% were underweight, and 32% were overweight. In adjusted analyses, extremely rapid early life weight gain during the first 4 and 24 months of life were each associated with increased risks of asthma (risk ratio, 1.34 for extremely rapid weight gain at 4 months; 95% confidence interval [CI], 1.06-1.70; risk ratio, 1.32 for extremely rapid weight gain at 24 months; 95% CI, 1.00-1.75) Similarly, overweight at 4, 12, and 24 months were each associated with an increased risk of asthma. Analyses that further adjusted for birthweight or preterm birth showed similar findings.

CONCLUSIONS

In this predominantly urban U.S. low-income minority birth cohort, excessive early life weight gain and overweight status were both associated with an increased risk of asthma in childhood.

Phenotypical characterization of human rhinovirus infections in severely premature children

BACKGROUND

Human Rhinovirus (HRV) has been identified as the most common cause of acute respiratory infections and hospitalizations in premature children. It is unclear if premature children are more susceptible to HRV due to their decreased pulmonary reserve or because they have enhanced lower airway reactivity to HRV.

METHODS

We conducted a retrospective analysis of the clinical respiratory presentation of all PCR-confirmed HRV infections in full-term and premature children aged ≤3 years in our institution. Standardized respiratory distress scores were developed to examine lower airway obstruction (i.e., wheezing, hyperinflation, and sub-costal retractions) along with markers of decreased pulmonary reserve (hypoxemia and tachypnea) in young children with HRV infections. Demographic and clinical variables were obtained from reviewing electronic medical records (EMR).

RESULTS

This study included a total of 205 children; 71% of these children were born full-term (>37 weeks gestation), 10% preterm (32-37 weeks) and 19% severely premature (<32 weeks). Our results demonstrated that: 1) HRV infections in the first 3 years of life were associated with higher overall respiratory distress scores in severely premature children relative to children born preterm or full-term; 2) HRV-infected severely premature children ≤3 years old were more likely to have lower airway obstruction than HRV-infected children born preterm or full-term; and 3) other clinical signs of respiratory distress such as tachypnea and hypoxemia were not more common in severely premature than in preterm and full-term children during an HRV infection.

CONCLUSIONS

Our results indicate that HRV infections in severely premature children are associated with lower airway obstruction rather than hypoxemia or tachypnea. The latter suggests that enhanced airway reactivity is the underlying mechanism for the increased susceptibility to HRV in severely premature children. Longitudinal studies are needed to understand why premature babies develop airway hyper-reactivity to HRV and the long-term effects of early HRV infection in this population.

Association of Long-term Exposure to Airborne Particulate Matter of 1 μm or Less With Preterm Birth in China

IMPORTANCE

Airborne particulate matter pollution has been associated with preterm birth (PTB) in some studies. However, most of these studies assessed only populations living near monitoring stations, and the association of airborne particulate matter having a median diameter of 1 μm or less (PM1) with PTB has not been studied.

OBJECTIVE

To evaluate whether PM1 concentrations are associated with the risk of PTB.

DESIGN, SETTING, AND PARTICIPANTS

This national cohort study used National Free Preconception Health Examination Project data collected in 324 of 344 prefecture-level cities from 30 provinces of mainland China. In total, 1 300 342 healthy singleton pregnancies were included from women who were in labor from December 1, 2013, through November 30, 2014. Data analysis was conducted between December 1, 2016, and April 1, 2017.

EXPOSURES

Predicted weekly PM1 concentration data collected using satellite remote sensing, meteorologic, and land use information matched with the home addresses of pregnant women.

MAIN OUTCOMES AND MEASURES

Preterm birth (<37 gestational weeks). Gestational age was assessed using the time since the first day of the last menstrual period. Cox proportional hazards regression analysis was used to examine the associations between trimester-specific PM1 concentrations and PTB after controlling for temperature, seasonality, spatial variation, and individual covariates.

RESULTS

Of the 1 300 342 singleton live births at the gestational age of 20 to 45 weeks included in this study, 104 585 (8.0%) were preterm. In fully adjusted models, a PM1 concentration increase of 10 μg/m3 over the entire pregnancy was significantly associated with increased risk of PTB (hazard ratio [HR], 1.09; 95% CI, 1.09-1.10), very PTB as defined as gestational age from 28 through 31 weeks (HR, 1.20; 95% CI, 1.18-1.23), and extremely PTB as defined as 20 through 27 weeks' gestation (HR, 1.29; 95% CI, 1.25-1.34). Pregnant women who were older (30-50 years) at conception (HR, 1.13; 95% CI, 1.11-1.14), were overweight before pregnancy (HR, 1.13; 95% CI, 1.11-1.15), had a rural household registration (HR, 1.09; 95% CI, 1.09-1.10), worked as farmers (HR, 1.10; 95% CI, 1.09-1.11), and conceived in autumn (HR, 1.48; 95% CI, 1.46-1.50) appeared to be more sensitive to PM1 exposure than their counterparts.

CONCLUSIONS AND RELEVANCE

Results from this national cohort study examining more than 1.3 million births indicated that exposure to PM1 air pollution was associated with an increased risk of PTB in China. These findings will provide evidence to inform future research studies, public health interventions, and environmental policies.

Demographic and neonatal risk factors for childhood asthma in the USA

OBJECTIVE

Asthma is the most common chronic condition diagnosed among children worldwide according to the World Health Organization (WHO). This study evaluated on a longitudinal basis prospectively collected medical records for demographic and neonatal information among United States (US) children diagnosed with childhood asthma in comparison to controls.

DESIGN

The Vaccine Safety Datalink (VSD) database was examined to identify cases (n = 5907) diagnosed with International Classification of Disease, ninth revision (ICD-9) healthcare provider diagnosed childhood asthma (493.xx) and controls (n = 11,662).

PATIENTS

All cases and controls were health maintenance organization (HMO)-enrolled from birth until diagnosis or sufficient time to ensure that they were unlikely to receive a diagnosis, respectively.

MAIN OUTCOME MEASURES

Child's gestational age in weeks at birth, birth weight in grams, maternal age in years at birth, Appearance-Pulse-Grimace-Activity-Respiration (APGAR) score at 1 minute and 5 minutes following birth, gender, and race.

RESULTS

The study results revealed childhood asthma was diagnosed significantly more frequently among males than females, and significantly more frequently among minority populations (Black > Hispanic > Native American > Asian) than White populations. Cases diagnosed with childhood asthma had significantly decreased mean values for the following neonatal risk factors: gestational age, maternal age, birth weight, and APGAR scores at 1 and 5 minutes following birth in comparison to controls.

CONCLUSIONS

This study offers healthcare providers important demographic and neonatal factors significantly associated with childhood asthma, and should help aid in the early diagnosis and treatment of childhood asthma.

Palivizumab Prophylaxis in Preterm Infants and Subsequent Recurrent Wheezing. Six-Year Follow-up Study

RATIONALE

Respiratory syncytial virus (RSV) induces not only infantile recurrent wheezing but also potentially atopic asthma.

OBJECTIVES

To test the effect of RSV infection on development of subsequent atopic asthma, we evaluated whether palivizumab, an anti-RSV monoclonal antibody, by preventing severe RSV disease in the first year of life, could impact subsequent recurrent wheezing and atopic asthma at 6 years of age.

METHODS

During the 2007 to 2008 RSV season, the decision to administer palivizumab was made based on standard medical practice and an observational prospective multicenter (n = 52) case-control study in preterm infants with a gestational age between 33 and 35 weeks followed from 0 to 3 years (preceding Committee on Recurrent Wheezing study). The 52 investigators at hospitals then followed these subjects until 6 years of age, reported here (Effects of Preventive Treatment for Respiratory Syncytial [RS] Virus Infection During Infancy on Later Atopic Asthma in Preterm Infants; Scientific Committee for Elucidation of Infantile Asthma). Parents of study subjects reported the infants' physicians' assessment of recurrent wheezing, using a report card and a novel mobile phone-based reporting system using the Internet. The primary endpoint was the incidence of atopic asthma.

MEASUREMENTS AND MAIN RESULTS

Of 444 preterm infants enrolled, 349 received palivizumab during the first year of life. At 6 years, atopic asthma was not different in the groups: 15.3 and 18.2% of infants in the treated and untreated groups, respectively (P = 0.57). On the other hand, physician-diagnosed recurrent wheezing was observed in 15.3 and 31.6% in the treated and untreated groups, respectively (P = 0.003).

CONCLUSIONS

Palivizumab prophylaxis administered to preterm infants did not suppress the onset of atopic asthma but resulted in a significantly lower incidence of recurrent wheezing during the first 6 years. Clinical trial registered with www.clinicaltrials.gov (NCT 01545245).

Urban residence, neighborhood poverty, race/ethnicity, and asthma morbidity among children on Medicaid

BACKGROUND

Although poor-urban (inner-city) areas are thought to have high asthma prevalence and morbidity, we recently found that inner cities do not have higher prevalent pediatric asthma. Whether asthma morbidity is higher in inner-city areas across the United States is not known.

OBJECTIVE

This study sought to examine relationships between residence in poor and urban areas, race/ethnicity, and asthma morbidity among children with asthma who are enrolled in Medicaid.

METHODS

Children aged 5 to 19 enrolled in Medicaid in 2009 to 2010 were included. Asthma was defined by at least 1 outpatient or emergency department (ED) visit with a primary diagnosis code of asthma over the 2-year period. Urbanization status was defined at the county level and neighborhood poverty at the zip-code level. Among children with asthma, logistic models were created to examine the effects of urbanization, neighborhood poverty, and race/ethnicity on rates of asthma outpatient visits, ED visits, and hospitalizations.

RESULTS

This study included 16,860,716 children (1,534,820 with asthma). Among children enrolled in Medicaid, residence in inner-city areas did not confer increased risk of prevalent asthma in either crude or adjusted analyses, but it was associated with significantly more asthma-related ED visits and hospitalizations among those with asthma in crude analyses (risk ratio, 1.48; 95% CI, 1.24-1.36; and 1.97; 95% CI, 1.50-1.72, respectively) and when adjusted for race/ethnicity, age, and sex (adjusted risk ratio, 1.23; 95% CI, 1.08-1.15; and 1.62; 95% CI, 1.26-1.43). Residence in urban or poor areas and non-Hispanic black race/ethnicity were all independently associated with increased risk of asthma-related ED visits and hospitalizations.

CONCLUSIONS

Residence in poor and urban areas is an important risk factor for asthma morbidity, but not for prevalence, among low-income US children.

Asthma as a disruption in iron homeostasis

Over several decades, asthma has evolved from being recognized as a single disease to include a diverse group of phenotypes with dissimilar natural histories, pathophysiologies, responses to treatment, and distinctive molecular pathways. With the application of Occam's razor to asthma, it is proposed that there is one cause underlying the numerous phenotypes of this disease and that the responsible molecular pathway is a deficiency of iron in the lung tissues. This deficiency can be either absolute (e.g. asthma in the neonate and during both pregnancy and menstruation) or functional (e.g. asthma associated with infections, smoking, and obesity). Comparable associations between asthma co-morbidity (e.g. eczema, urticaria, restless leg syndrome, and pulmonary hypertension) with iron deficiency support such a shared mechanistic pathway. Therapies directed at asthma demonstrate a capacity to impact iron homeostasis, further strengthening the relationship. Finally, pathophysiologic events producing asthma, including inflammation, increases in Th2 cells, and muscle contraction, can correlate with iron availability. Recognition of a potential association between asthma and an absolute and/or functional iron deficiency suggests specific therapeutic interventions including inhaled iron.

Maternal smoking in pregnancy and its influence on childhood asthma

Maternal smoking in pregnancy (MSP) is a large modifiable risk factor for pregnancy related mortality and morbidity and also the most important known modifiable risk factor for asthma. This review summarises the effects of MSP throughout infancy, childhood and adolescence with regards to asthma (development and severity). Firstly, the direct damage caused by nicotine on fetal lung development, fetal growth and neuronal differentiation is discussed, as well as the indirect effects of nicotine on placental functioning. Secondly, the effects of MSP on later immune functioning resulting in increased infection rate are summarised and details are given on the effects of MSP modulating airway hyperreactivity, reducing lung function and therefore increasing asthma morbidity. Furthermore, epigenetic effects are increasingly being recognised. These can also result in transgenerational detrimental effects induced by cigarette smoke. In summary, the causal relationship between MSP and asthma development is well documented and presents a major health problem for generations to come. The high prevalence of MSP is alarming and epigenetic effects of nicotine on immune functioning potentiate this danger. A considerable part of the increase in asthma prevalence worldwide is due to MSP.

The respiratory consequences of early-term birth and delivery by caesarean sections

In England and Wales, 19% of live births in 2012 were at 37-38 weeks' gestation, equating to nearly 140 000 early-term births each year. Since caesarean sections (CS) are often performed at early-term gestations, this accounts for some of the increased proportion of the early-term births. Infants born early-term are at an increased risk of neonatal respiratory morbidity particularly if they are delivered by caesarean section. The long term lung function data are limited but available data suggest that early-term delivery is associated with respiratory morbidity in childhood. CS also appears to be associated with increased neonatal morbidity and future development of respiratory symptoms. However, future studies need to confirm the independent effects of caesarean sections and early-term deliveries particularly for long term outcomes as both are likely to affect the respiratory system differently.