Relationship between birth weight and adult lung function: controlling for maternal factors

Long-term pulmonary and neurodevelopmental impairment in a fetal growth restriction rabbit model

Fetal growth restriction (FGR) remains one of the main obstetrical problems worldwide, with consequences beyond perinatal life. Animal models with developmental and structural similarities to the human are essential to understand FGR long-term consequences and design novel therapeutic strategies aimed at preventing or ameliorating them. Herein, we described the long-term consequences of FGR in pulmonary function, structure, and gene expression, and characterized neurodevelopmental sequelae up to preadolescence in a rabbit model. FGR was induced at gestational day 25 by surgically reducing placental blood supply in one uterine horn, leaving the contralateral horn as internal control. Neonatal rabbits born near term were assigned to foster care in mixed groups until postnatal day (PND) 21. At that time, one group underwent pulmonary biomechanical testing followed by lung morphometry and gene expression analysis. A second group underwent longitudinal neurobehavioral assessment until PND 60 followed by brain harvesting for multiregional oligodendrocyte and microglia quantification. FGR was associated with impaired pulmonary function and lung development at PND 21. FGR rabbits had higher respiratory resistance and altered parenchymal biomechanical properties in the lungs. FGR lungs presented thicker alveolar septal walls and reduced alveolar space. Furthermore, the airway smooth muscle content was increased, and the tunica media of the intra-acinar pulmonary arteries was thicker. In addition, FGR was associated with anxiety-like behavior, impaired memory and attention, and lower oligodendrocyte proportion in the frontal cortex and white matter. In conclusion, we documented and characterized the detrimental pulmonary function and structural changes after FGR, independent of prematurity, and beyond the neonatal period for the first time in the rabbit model, and describe the oligodendrocyte alteration in pre-adolescent rabbit brains. This characterization will allow researchers to develop and test therapies to treat FGR and prevent its sequelae.

Associations between birth weight and lung function in a Japanese adult population: The tohoku medical megabank community-based cohort study

BACKGROUND

Birth weight, as a measure of intrauterine growth, is commonly used in epidemiological studies and is reported to be associated with adult lung function. However, findings regarding this association in previous studies have been inconsistent. Furthermore, no studies have reported associations stratified by age or smoking status, or adjusted for eosinophil count or other parameters related to type 2 airway inflammation.

METHODS

This cross-sectional study included 2632 men and 7237 women aged ≥20 years living in Miyagi Prefecture, Japan. Lung function was assessed based on spirometry. Birth weight data were obtained through a questionnaire survey. Analysis of covariance was used to evaluate the associations between birth weight and lung function, adjusting for potential confounders. Stratified analyses by age and smoking status were also conducted, together with a sub-analysis for low birth-weight participants.

RESULTS

Birth weight was positively associated with forced expiratory volume in 1 s (FEV1) for both sexes and with vital capacity in women, after adjusting for height, age, smoking status, and parameters related to type 2 airway inflammation. The stratified analysis for smoking status revealed associations in never-smokers and ex-smokers. When stratified by age, the associations were confirmed in middle-aged participants. The effect of smoking status on the FEV1 of low birth-weight participants was not significant.

CONCLUSIONS

Our analysis of a large, Japanese adult population showed that birth weight was independently and positively associated with adult lung function, even after adjustment for age, height, smoking status, and parameters related to type 2 airway inflammation.

Early Origins of Chronic Obstructive Pulmonary Disease: Prenatal and Early Life Risk Factors

The main risk factor for chronic obstructive pulmonary disease (COPD) is active smoking. However, a considerable amount of people with COPD never smoked, and increasing evidence suggests that adult lung disease can have its origins in prenatal and early life. This article reviews some of the factors that can potentially affect lung development and lung function trajectories throughout the lifespan from genetics and prematurity to respiratory tract infections and childhood asthma. Maternal smoking and air pollution exposure were also analyzed among the environmental factors. The adoption of preventive strategies to avoid these risk factors since the prenatal period may be crucial to prevent, delay the onset or modify the progression of COPD lung disease throughout life.

Risk Factors Affecting Development and Persistence of Preschool Wheezing: Consensus Document of the Emilia-Romagna Asthma (ERA) Study Group

Wheezing at preschool age (i.e., before the age of six) is common, occurring in about 30% of children before the age of three. In terms of health care burden, preschool children with wheeze show double the rate of access to the emergency department and five times the rate of hospital admissions compared with school-age asthmatics. The consensus document aims to analyse the underlying mechanisms involved in the pathogenesis of preschool wheezing and define the risk factors (i.e., allergy, atopy, infection, bronchiolitis, genetics, indoor and outdoor pollution, tobacco smoke exposure, obesity, prematurity) and the protective factors (i.e., probiotics, breastfeeding, vitamin D, influenza vaccination, non-specific immunomodulators) associated with the development of the disease in the young child. A multidisciplinary panel of experts from the Emilia-Romagna Region, Italy, addressed twelve key questions regarding managing preschool wheezing. Clinical questions have been formulated by the expert panel using the PICO format (Patients, Intervention, Comparison, Outcomes). Systematic reviews have been conducted on PubMed to answer these specific questions and formulate recommendations. The GRADE approach has been used for each selected paper to assess the quality of the evidence and the degree of recommendations. Based on a panel of experts and extensive updated literature, this consensus document provides insight into the pathogenesis, risk and protective factors associated with the development and persistence of preschool wheezing. Undoubtedly, more research is needed to improve our understanding of the disease and confirm the associations between certain factors and the risk of wheezing in early life. In addition, preventive strategies must be promoted to avoid children's exposure to risk factors that may permanently affect respiratory health.

The Epidemiology and Mechanisms of Lifetime Cardiopulmonary Morbidities Associated With Pre-Pregnancy Obesity and Excessive Gestational Weight Gain

Obesity has reached pandemic proportions in the last few decades. The global increase in obesity has contributed to an increase in the number of pregnant women with pre-pregnancy obesity or with excessive gestational weight gain. Obesity during pregnancy is associated with higher incidence of maternal co-morbidities such as gestational diabetes and hypertension. Both obesity during pregnancy and its associated complications are not only associated with immediate adverse outcomes for the mother and their newborns during the perinatal period but, more importantly, are linked with long-term morbidities in the offsprings. Neonates born to women with obesity are at higher risk for cardiac complications including cardiac malformations, and non-structural cardiac issues such as changes in the microvasculature, e.g., elevated systolic blood pressure, and overt systemic hypertension. Pulmonary diseases associated with maternal obesity include respiratory distress syndrome, asthma during childhood and adolescence, and adulthood diseases, such as chronic obstructive pulmonary disease. Sequelae of short-term complications compound long-term outcomes such as long-term obesity, hypertension later in life, and metabolic complications including insulin resistance and dyslipidemia. Multiple mechanisms have been proposed to explain these adverse outcomes and are related to the emerging knowledge of pathophysiology of obesity in adults. The best investigated ones include the role of obesity-mediated metabolic alterations and systemic inflammation. There is emerging evidence linking metabolic and immune derangements to altered biome, and alteration in epigenetics as one of the intermediary mechanisms underlying the adverse outcomes. These are initiated as part of fetal adaptation to obesity during pregnancy which are compounded by rapid weight gain during infancy and early childhood, a known complication of obesity during pregnancy. This newer evidence points toward the role of specific nutrients and changes in biome that may potentially modify the adverse outcomes observed in the offsprings of women with obesity.

Intrauterine growth retardation and lung function of very prematurely born young people

OBJECTIVES

To assess if intrauterine growth retardation (IUGR) was associated with reduced lung function at 16-19 years.

WORKING HYPOTHESIS

Very prematurely born young people who had IUGR would have reduced lung function postpuberty.

STUDY DESIGN

Prospective follow-up study.

PATIENT-SUBJECT SELECTION

One hundred and fifty-nine 16-19 year olds born before 29 weeks of gestation; 37 had IUGR.

METHODOLOGY

Lung function tests were performed: spirometry was used to assess forced expiratory volume in one second (FEV1), forced expiratory flow at 75%, 50% and 25% of expired vital capacity (FEF75, FEF50 and FEF25), peak expiratory flow (PEF) and forced vital capacity (FVC). Functional residual capacity (FRCpleth) total lung capacity (TLCpleth) and residual volume (RVpleth) were measured. Alveolar function was assessed by diffusion capacity within the lungs of carbon monoxide (DLCO). Impulse oscillometry was used to assess respiratory resistance and lung clearance index to assess ventilation homogeneity. Exercise capacity was assessed using a shuttle sprint test.

RESULTS

After adjustment for BMI, the mean FEV-1/FVC, FEF75, FEF25-75, FRCpleth and RVpleth were poorer in those who had had IUGR, with differences between 0.56 and 0.75 z-scores. After further adjustment for BPD and postnatal corticosteroid use, only the difference in RVpleth z-scores remained statistically significant, adjusted difference (95% CI): 0.66 (0.18,1.13). Exercise capacity was lower in those with IUGR and this was more pronounced in males (p=0.04).

CONCLUSIONS

At 16-19 years of age, those who had IUGR had poorer lung function and exercise capacity compared with those with adequate intrauterine growth.

Intrauterine growth restriction leads to a high-corticosterone producing offspring: An implication for pulmonary infection susceptibility

AIMS

Although intrauterine growth restriction (IUGR) impairs immune system homeostasis and lung development, its relationship with the susceptibility to pulmonary infections remains unclear. Thus, this study aimed to investigate the impact of IUGR on acute lung inflammatory response induced by bacterial stimulus.

MATERIALS AND METHODS

Pregnant female Wistar rats were subjected to 50% caloric-protein food restriction during gestation. To mimic bacterial lung infection, adult male offspring (12 weeks old) were challenged with a single lipopolysaccharide (LPS) intranasal instillation, and 6 h later, we assessed the acute inflammatory response. Normal birth weight (NBW) animals represent the control group.

KEY FINDINGS

LPS instillation increased the protein levels in the airways of both the NBW and low birth weight (LBW) groups, indicating vascular leakage. LBW animals exhibited a lower number of neutrophils, reduced production of interleukin-6 and macrophage-inflammatory protein-2 and decreased upregulation of intercellular adhesion molecule-1 gene expression in lung tissues. Further analysis revealed that the LBW group produced lower levels of prostaglandin-E₂ and failed to secrete leukotriene-B₄ upon LPS stimulation, which correlated with impaired cyclooxygenase-2 and 5-lipoxygenase expression. These results were probably associated with their inability to upregulate the expression of Toll-like receptor-4 and downstream signaling proteins, such as nuclear factor kappa-B, in the lungs. The LBW group also exhibited abnormal airway thickening and high corticosterone levels under basal conditions.

SIGNIFICANCE

This study suggests that IUGR-induced foetal programming in LBW offspring threatens HPA axis physiology and corticosterone biodisponibility, and impairs the innate response to bacterial antigens, increasing future susceptibility to pulmonary infection.

Perinatal Nutritional and Metabolic Pathways: Early Origins of Chronic Lung Diseases

Lung development is not completed at birth, but expands beyond infancy, rendering the lung highly susceptible to injury. Exposure to various influences during a critical window of organ growth can interfere with the finely-tuned process of development and induce pathological processes with aberrant alveolarization and long-term structural and functional sequelae. This concept of developmental origins of chronic disease has been coined as perinatal programming. Some adverse perinatal factors, including prematurity along with respiratory support, are well-recognized to induce bronchopulmonary dysplasia (BPD), a neonatal chronic lung disease that is characterized by arrest of alveolar and microvascular formation as well as lung matrix remodeling. While the pathogenesis of various experimental models focus on oxygen toxicity, mechanical ventilation and inflammation, the role of nutrition before and after birth remain poorly investigated. There is accumulating clinical and experimental evidence that intrauterine growth restriction (IUGR) as a consequence of limited nutritive supply due to placental insufficiency or maternal malnutrition is a major risk factor for BPD and impaired lung function later in life. In contrast, a surplus of nutrition with perinatal maternal obesity, accelerated postnatal weight gain and early childhood obesity is associated with wheezing and adverse clinical course of chronic lung diseases, such as asthma. While the link between perinatal nutrition and lung health has been described, the underlying mechanisms remain poorly understood. There are initial data showing that inflammatory and nutrient sensing processes are involved in programming of alveolarization, pulmonary angiogenesis, and composition of extracellular matrix. Here, we provide a comprehensive overview of the current knowledge regarding the impact of perinatal metabolism and nutrition on the lung and beyond the cardiopulmonary system as well as possible mechanisms determining the individual susceptibility to CLD early in life. We aim to emphasize the importance of unraveling the mechanisms of perinatal metabolic programming to develop novel preventive and therapeutic avenues.

Impaired Respiratory Health and Life Course Transitions From Health to Chronic Lung Disease

Primary prevention and interception of chronic lung disease are essential in the effort to reduce the morbidity and mortality caused by respiratory conditions. In this review, we apply a life course approach that examines exposures across the life span to identify risk factors that are associated with not only chronic lung disease but also an intermediate phenotype between ideal lung health and lung disease, termed "impaired respiratory health." Notably, risk factors such as exposure to tobacco smoke and air pollution, as well as obesity and physical fitness, affect respiratory health across the life course by being associated with both abnormal lung growth and lung function decline. We then discuss the importance of disease interception and identifying those at highest risk of developing chronic lung disease. This work begins with understanding and detecting impaired respiratory health, and we review several promising molecular biomarkers, predictive symptoms, and early imaging findings that may lead to a better understanding of this intermediate phenotype.

Patterns of respiratory health services utilization from birth to 5 years of children who experienced adverse birth outcomes

Introduction

Adverse birth outcomes have important consequences for future lung health. We evaluated patterns of respiratory health services utilization in early childhood among children born preterm (PTB), small and large for gestational age at term (SGA and LGA, respectively), and appropriate-for-gestational age at term.

Materials and methods

We conducted a population-based retrospective cohort study using administrative health data of all singleton live births in Alberta, Canada between 2005–2010. Data on hospitalizations and emergency department (ED) visits from birth to 5 years were collected for asthma, bronchitis, bronchiolitis, croup, influenza, pneumonia, and other acute upper and lower respiratory tract infections (other URTI and other LRTI, respectively). Adjusted rate ratios were estimated for respiratory ED visits and hospitalizations for adverse birth outcomes using the appropriate-for-gestational age at term group as reference. Age-specific trajectories of total respiratory health services utilization rates for each group were estimated in Poisson models.

Results

A total of 293,764 episodes of respiratory care from 206,994 children were analyzed. Very PTB children had the highest rates of health services use for all respiratory conditions, particularly for asthma, pneumonia, and bronchiolitis hospitalizations. Moderate/late PTB children also had elevated ED visits and hospitalizations for all respiratory conditions. Children born SGA showed high rates of ED visits for other LRTI, and of hospitalizations for bronchitis, bronchiolitis, and other URTI. Children born LGA had high rates of croup and other URTI ED visits, and of bronchiolitis and bronchiolitis hospitalizations. Age-specific trajectories showed a decreasing trend in the rates of total respiratory health service utilization from birth to five years of age for all groups studied. Children born PTB and LGA at term significantly required more respiratory health services over time compared to the reference group.

Conclusion

Patterns of paediatric respiratory health services utilization vary according to gestational age and fetal growth.

Respiratory Health of Pacific Youth: An Observational Study of Associated Risk and Protective Factors Throughout Childhood

BACKGROUND

Respiratory disease is the third most common cause of death in New Zealand, with Pacific people living in New Zealand bearing the greatest burden of this type of disease. Although some epidemiological outcomes are known, we lack the specifics required to formulate targeted and effective public health interventions. The Pacific Islands Families (PIF) birth cohort study is a study that provides a unique source of data to assess lung function and current respiratory health among participants entering early adulthood and to examine associations with early life events during critical periods of growth.

OBJECTIVE

This paper aims to provide an overview of the design, methods, and scope of the Respiratory Health of Pacific Youth Study, which uses the overall PIF study cohort aged 18-19 years.

METHODS

From 2000-2019, the PIF study has followed, from birth, the growth, and the development of 1398 Pacific children born in Auckland, New Zealand. Participants were nested within the overall PIF study (at ages 18-19 years) from June 2018, and assessments were undertaken until mid-November 2019. The assessments included respiratory and general medical histories, a general physical examination, assessment of lung function (forced expiratory volume and forced vital capacity), self-completed questionnaires (St George's Respiratory Questionnaire, European Quality of Life 5 Dimensions-3 Level, Epworth Sleepiness Scale for Children and Adolescents, and Leicester Cough Questionnaire), blood tests (eosinophils, Immunoglobulin E, Immunoglobulin G, Immunoglobulin A, Immunoglobulin M, and C-reactive protein), and chest x-rays. Noninferential analyses will be carried out on dimensionally reduced risk and protective factors and confounders.

RESULTS

Data collection began in June 2018 and ended in November 2019, with a total of 466 participants recruited for submission of the paper. Collection and collation of chest x-ray data is still underway, and data analysis and expected results will be published by November 2020.

CONCLUSIONS

This is the first longitudinal observational study to address the burden of respiratory disease among Pacific youth by determining factors in early life that impose long-term detriments in lung function and are associated with the presence of respiratory illness. Identifying risk factors and the magnitude of their effects will help in adopting preventative measures, establishing whether any avoidable risks can be modified by later resilient behaviors, and provide baseline measurements for the development of respiratory disease in later adult life. The study results can be translated into practice guidelines and inform health strategies with immediate national and international impact.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/18916.

Early childhood malnutrition trajectory and lung function at preadolescence

OBJECTIVE

Chronic undernutrition is a common phenomenon in Bangladesh. However, information is grossly lacking to report the correlation between chronic undernutrition trajectory and lung function in children. The aim of the current study was to understand the association between early-childhood chronic undernutrition trajectory and lung function at preadolescence.

DESIGN

The current study is a part of the 9-year follow-up of a large-scale cohort study called the Maternal and Infant Nutrition Interventions in Matlab.

SETTINGS

The current study was conducted in Matlab, a sub-district area of Bangladesh that is located 53 km south of the capital, Dhaka.

PARTICIPANTS

A total of 517 children participated in lung function measured with a spirometer at the age of 9 years. Weight and height were measured at five intervals from birth till the age of 9 years.

RESULTS

Over half of the cohort have experienced a stunting undernutrition phenomenon up to 9 years of age. Children who were persistently or intermittently stunted showed lower forced expiratory volume (ml/s) than normal-stature children (P < 0·05). Children who exhibited catch-up growth throughout 4·5 years from the stunted group showed similar lung function with normal counterparts, and a better lung function than in children with the same growth velocity or who had faltering growth. In the multivariable models, similar associations were observed in children who experienced catch-up growth than their counterparts after adjusting for covariates.

CONCLUSION

Our data suggest that catch-up growth in height during early childhood is associated with a better lung function at preadolescence.

Health gradients in emergency visits and hospitalisations for paediatric respiratory diseases: A population-based retrospective cohort study

BACKGROUND

Socio-economically deprived children face a disproportionate burden of respiratory diseases. The association between area-level material and social deprivation and emergency department (ED) visits and hospitalisations for paediatric respiratory diseases has not been explored.

OBJECTIVES

We evaluated health inequalities in emergency department (ED) visits and hospitalisations for paediatric respiratory diseases according to material and social deprivation indexes.

METHODS

This population-based retrospective cohort study deterministically linked birth, ED visits and hospitalisation data, and census-based, area-level deprivation indexes for all singleton children born in the province of Alberta, Canada, between 2005 and 2010 who had at least one recorded ED visit or hospitalisation for respiratory diseases in their first five years of life. We classified ED visits and hospitalisations for seven respiratory diseases by deprivation indexes. Concentration indexes (CInd) and area-level concentration curves measured health gradients across deprivation groups. Rate ratios (RR) evaluated associations between deprivation indexes and respiratory episodes of care.

RESULTS

The study cohort included 198 572 newborns. The highest CInd were found in ED visits for other acute lower respiratory tract infections (oLRTI; CInd -0.22, 95% confidence interval [CI] -0.32, -0.12) and bronchiolitis (CInd -0.21, 95% CI -0.29, -0.12), and for pneumonia hospitalisations (CInd -0.23, 95% CI -0.33, -0.13). Croup ED visits had a low inequality degree. Compared to social deprivation, the material deprivation index presented a more consistent health gradient of increased episodes of care with increasing deprivation. oLRTI ED visits (RR 2.60, 95% CI 2.34, 2.92) and pneumonia hospitalisations (RR 2.57, 95% CI 2.31, 2.86) presented the largest inequalities between the least and most materially deprived groups.

CONCLUSIONS

We found a concentration of ED visits and hospitalisations for paediatric respiratory diseases in the most deprived groups. However, health inequalities are present across the material and social deprivation spectrum. Compared to the social deprivation index, the material index presented clearer paediatric respiratory health gradients.

Rural Residence and Poverty Are Independent Risk Factors for Chronic Obstructive Pulmonary Disease in the United States

RATIONALE

In developing countries, poor and rural areas have a high burden of chronic obstructive pulmonary disease (COPD), and environmental pollutants and indoor burning of biomass have been implicated as potential causal exposures. Less is known about the prevalence of COPD in the United States with respect to urban-rural distribution, poverty, and factors that uniquely contribute to COPD among never-smokers.

OBJECTIVES

To understand the impact of urban-rural status, poverty, and other community factors on COPD prevalence nationwide and among never-smokers.

METHODS

We studied a nationally representative sample of adults in the National Health Interview Survey 2012-2015, with data linkage between neighborhood data from the U.S. Census's American Community Survey and the National Center for Health Statistics Urban-Rural Classification Scheme. The main outcome was COPD prevalence.

MEASUREMENTS AND MAIN RESULTS

The prevalence of COPD in poor, rural areas was almost twice that in the overall population (15.4% vs. 8.4%). In adjusted models, rural residence (odds ratio [OR], 1.23; P < 0.001) and census-level poverty (OR, 1.12; P = 0.012) were both associated with COPD prevalence, as were indicators of household wealth. Among never-smokers, rural residence was also associated with COPD (OR, 1.34; P < 0.001), as was neighborhood use of coal for heating (OR, 1.09; P < 0.001).

CONCLUSIONS

In a nationally representative sample, rural residence and poverty were risk factors for COPD, even among never-smokers. The use of coal for heating was also a risk factor for COPD among never-smokers. Future disparities research to elucidate contributors to COPD development in poor and rural areas, including assessments of heating sources and environmental pollutants, is needed.

Timing of secondhand smoke, pet, dampness or mould exposure and lung function in adolescence

BACKGROUND

The relevance of timing of exposure in the associations of secondhand tobacco smoke (SHS), pets, and dampness or mould exposure with lung function is unclear. We investigated the relevance of timing of these exposures for lung function in adolescence.

METHODS

We used data from participants of the Dutch Prevention and Incidence of Asthma and Mite Allergy (PIAMA) cohort with spirometric measurements at ages 12 and 16 years (n=552). Data on residential exposure to SHS, pets, and dampness or mould were obtained by repeated parental questionnaires. We characterised timing of exposure through longitudinal patterns using latent class growth modelling and assessed associations of these patterns with FEV₁ and FVC at ages 12 and 16 and FEV₁ and FVC growth between ages 12 and 16 using linear regression models.

RESULTS

Childhood SHS exposure was associated with reduced FEV₁ growth/year (95% CI) (-0.34% (-0.64% to -0.04%)). Late childhood and early life pet exposure was associated with increased FEV₁ growth (0.41% (0.14% to 0.67%)) and reduced FVC growth (-0.28% (-0.53% to -0.03%)), respectively, compared with very low exposure. Early life dampness or mould exposure was associated with reduced lung function growth. All time windows of SHS exposure tended to be associated with lower attained lung function and pet exposure tended to be associated with higher FEV₁.

CONCLUSION

SHS exposure during childhood could lead to reduced lung function growth and lower attained lung function in adolescence. While pet exposure in late childhood may not adversely affect lung function, early childhood pet exposure may slow down FVC growth in adolescence.

The LEAD (Lung, Heart, Social, Body) Study: Objectives, Methodology, and External Validity of the Population-Based Cohort Study

BACKGROUND

The Lung, hEart, sociAl, boDy (LEAD) Study (ClinicalTrials.gov; NCT01727518; http://clinicaltrials.gov) is a longitudinal, observational, population-based Austrian cohort that aims to investigate the relationship between genetic, environmental, social, developmental and ageing factors influencing respiratory health and comorbidities through life. The general working hypothesis of LEAD is the interaction of these genetic, environmental and socioeconomic factors influences lung development and ageing, the risk of occurrence of several non-communicable diseases (respiratory, cardiovascular, metabolic and neurologic), as well as their phenotypic (ie, clinical) presentation.

METHODS

LEAD invited from 2011-2016 a random sample (stratified by age, gender, residential area) of Vienna inhabitants (urban cohort) and all the inhabitants of six villages from Lower Austria (rural cohort). Participants will be followed-up every four years. A number of investigations and measurements were obtained in each of the four domains of the study (Lung, hEart, sociAl, boDy) including data to screen for lung, cardiovascular and metabolic diseases, osteoporosis, and cognitive function. Blood and urine samples are stored in a biobank for future investigations.

RESULTS

A total of 11.423 males (47.6%) and females (52.4%), aged 6-80 years have been included in the cohort. Compared to governmental statistics, the external validity of LEAD with respect to age, gender, citizenship, and smoking status was high.

CONCLUSIONS

In conclusion, the LEAD cohort has been established following high quality standards; it is representative of the Austrian population and offers a platform to understand lung development and ageing as a key mechanism of human health both in early and late adulthood.

Sex-specific differences in the association between birth weight and lung volume in Japanese young adults

BACKGROUND

Fetal growth disturbances may influence adult lung function and can lead to pulmonary diseases in adulthood. Although the results of previous studies are controversial, low birth weight seems to be associated with poor adult lung function. This study aimed to assess previously unknown information about the sex-specific association between birth weight and adult lung volume in the Japanese population.

METHODS

We evaluated pulmonary parameters in 200 consenting young medical students (age, 20-29 years) with a never smoking history at Kochi University. Subjects whose lung function was not sufficiently examined or those with evidence of current or previous respiratory diseases were excluded (n=7). All students underwent spirometry, and their weight records at birth or 3 years of age were obtained from their maternal and child handbooks. Associations between the spirometric parameters and birth/3-year weights were statistically analyzed.

RESULTS

We evaluated 91 male and 102 female students. Their mean age was 23.3 years. Assessment revealed that birth weight significantly correlated with the percent predicted value of forced vital capacity (%FVC; r_s=0.17, p=0.018) but not with the forced expiratory volume in 1 s/FVC ratio. Sex-specific analysis revealed significant correlations between birth weight and %FVC in males (r_s=0.22, p=0.041) but not in females. Body weight at the age of 3 years also significantly correlated with %FVC only in males (r_s=0.32, p=0.021).

CONCLUSIONS

Birth weight is significantly associated with pulmonary function in Japanese young adults. The associations are especially significant in males.

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.

As Long as the Breath Lasts: In Utero Exposure to Ramadan and the Occurrence of Wheezing in Adulthood

While prenatal exposure to Ramadan has been shown to be negatively associated with general physical and mental health, studies on specific organs remain scarce. In this study, we explored whether Ramadan exposure during pregnancy affects the occurrence of wheezing, a main symptom of obstructive airway disease. Using data from the Indonesian Family Life Survey collected between 1997 and 2008 (waves 2-4), we compared wheezing occurrence among adult Muslims who had been in utero during Ramadan with that in adult Muslims who had not been in utero during Ramadan. Wheezing prevalence was higher among adult Muslims who had been in utero during Ramadan, independent of the pregnancy phase in which the exposure to Ramadan occurred. Moreover, this association tended to increase with age, being strongest among those aged about 45 years or older. This is in line with fetal programming theory, suggesting that impacts of in utero exposures often manifest only after reproductive age. Particularly strong associations were detected for smokers. The respiratory system of prenatally exposed Muslims thus seems to perform worse in mitigating later ex utero harmful influences such as smoking. This study suggests that exposure to Ramadan during pregnancy may have lasting consequences for adult lung functionality.

Lung development

Epidemiological studies have demonstrated an association between maternal vitamin D deficiency and an increased risk of chronic lung disease in offspring. While vitamin D and UV induced non-vitamin D pathways have the capacity to modulate immune function, this relationship may also be explained by an effect on lung development which is an independent predictor of lung function and the risk of lung disease later in life. To date there are not sufficient data to support the role of non-vitamin D pathways in this association, while in vivo and in vitro data suggest that there is a causal relationship between vitamin D and lung development. However, equivocal results in recent high profile clinical trials have dampened enthusiasm for vitamin D as an important public health intervention for improving lung development. In this narrative review we summarise our current understanding of the link between UV exposure, vitamin D and lung development.

Birth Weight and Lung Function in Adulthood: A Systematic Review and Meta-analysis

RATIONALE

There is evidence suggesting that birth weight may influence lung function in adulthood, but it is unclear whether it might differentially affect restrictive (FVC) and obstructive (FEV₁/FVC) patterns.

OBJECTIVES

To summarize evidence available on the association of birth weight, weight at 1 year, and weight gain in the first year of life with FVC and FEV₁/FVC in adulthood.

METHODS

We performed a systematic review of the literature by searching MEDLINE, EMBASE, and Web of Science through January 2015. Data were combined using inverse-variance weighted meta-analysis with random effects models and between-study heterogeneity evaluated. We conducted a priori subgroup or sensitivity analyses by age, country wealth, ethnicity, sex, and smoking. We evaluated risk of bias using the Newcastle Ottawa Scale and reporting bias using funnel plots.

RESULTS

Eighteen articles were included in the review and 13 in the meta-analyses. Most studies were from high-income countries, and all had a low risk of bias. We found strong evidence of an association of birth weight with adult FVC, a 59.4 ml higher FVC in adulthood per kilogram increase in birth weight (95% confidence interval, 43.3-75.5), with no evidence of heterogeneity. Evidence of an association of birth weight with FEV₁/FVC was weaker and showed some inconsistency across studies. Only one study investigated weight at 1 year, and another one reported weight gain in the first year.

CONCLUSIONS

Our meta-analyses show strong and consistent evidence of an association of birth weight with adult FVC, a measure of restrictive impairment, with much weaker evidence for airflow obstruction.

Lung Development and Aging

The onset of chronic obstructive pulmonary disease (COPD) can arise either from failure to attain the normal spirometric plateau or from an accelerated decline in lung function. Despite reports from numerous big cohorts, no single adult life factor, including smoking, accounts for this accelerated decline. By contrast, five childhood risk factors (maternal and paternal asthma, maternal smoking, childhood asthma and respiratory infections) are strongly associated with an accelerated rate of lung function decline and COPD. Among adverse effects on lung development are transgenerational (grandmaternal smoking), antenatal (exposure to tobacco and pollution), and early childhood (exposure to tobacco and pollution including pesticides) factors. Antenatal adverse events can operate by causing structural changes in the developing lung, causing low birth weight and prematurity and altered immunological responses. Also important are mode of delivery, early microbiological exposures, and multiple early atopic sensitizations. Early bronchial hyperresponsiveness, before any evidence of airway inflammation, is associated with adverse respiratory outcomes. Overlapping cohort studies established that spirometry tracks from the preschool years to late middle age, and those with COPD in the sixth decade already had the worst spirometry at age 10 years. Alveolar development is now believed to continue throughout somatic growth and is adversely impacted by early tobacco smoke exposure. Genetic factors are also important, with genes important in lung development and early wheezing also being implicated in COPD. The inescapable conclusion is that the roots of COPD are in early life, and COPD is a disease of childhood adverse factors interacting with genetic factors.

Are preterm-born survivors at risk of long-term respiratory disease?

BACKGROUND

To evaluate the long-term impact of preterm birth on respiratory function in female patients born preterm, we undertook spirometric examinations twice, as they reached the age of puberty, then follow-up examinations of part of the same cohort in adulthood. We sought evidence that preterm birth is correlated with poorer spirometric results into adulthood.

METHODS

A total of 70 girls (aged 12.2 ± 1.5 years in 1997) who had been born preterm (at 34.7 ± 1.86 weeks, none having experienced bronchopulmonary dysplasia) took part in spriometric examinations in 1997 and again in 1998. Of those, after a gap of 17 years, a group of 12 were successfully recontacted and participated in the 2015 examination as adults (then aged 27.6 ± 2.6 years, born at 34.5 ± 1.92 weeks). We compared spirometric results across the adolescent and adult examinations, and compared the adult results with an adult reference group.

RESULTS

The percentage values of FEV1 (forced expiratory volume in 1 s), FVC (forced vital capacity) and MVV (maximal voluntary ventilation) showed significant improvement between the two examinations in the early adolescent period. In adulthood, FEV1%pred (percentage predicted forced expiratory volume in 1 s) showed no statistically significant difference. The mean values of both FVC and FVC%pred (percentage predicted forced vital capacity) for the preterm-born group were lower than for the reference group, but this was not statistically significant. The preterm-born group showed lower values of such parameters as forced expiratory flow at 25-75% of FVC, MEF25 (maximal expiratory flow at 25% of forced vital capacity) and FEV1/FVC as compared with the reference group, but again without statistical significance.

CONCLUSIONS

(1) A somewhat below-norm level of respiratory parameters among preterm-born girls entering pubescence may attest to continued negative impact on their respiratory system. (2) A significant improvement in their spirometric results 1 year later may indicate that pubescence helps compensate for the earlier negative effect of preterm birth. (3) No significant differences were seen in lung function in preterm-born adults as compared with a reference group of adults, although the preterm-born group did exhibit lower values of all parameters studied and more frequent obstructive disorders.

Maternal obesity mediated predisposition to respiratory complications at birth and in later life: understanding the implications of the obesogenic intrauterine environment

More women than not are entering pregnancy either overweight or obese. This presents a significant health care burden with respect to maternal morbidities and offspring complications at birth and in later life. In recent years it has also become clear that maternal obesity is an even greater global health problem than anticipated, because the effects are not limited to the mother but are also programmed in the fetus, known as the 'intergenerational cycle of obestiy'. Despite a large body of epidemiological evidence reporting outcomes of obese pregnancies, including offspring respiratory complications, much less is known about the molecular effects of maternal obesity on fetal lung development. This review focuses on the influence of altered substrate supply associated with the obesogenic intrauterine environment on fetal lung development. Understanding the molecular mechanisms contributing to altered fetal lung development will lead to improved respiratory outcomes for offspring at birth and in later life.

Relationship between birth weight, maternal smoking during pregnancy and childhood and adolescent lung function: A path analysis

BACKGROUND

Low birth weight and gestational maternal smoking have been linked with reduced lung function in children in many cross sectional studies. However, these associations have not yet been assessed with repeated measurements of lung function. Our aim was to investigate the effects of birth weight, gestational age, and gestational maternal smoking on lung function in children at age 10 and 18 years.

METHODS

In the Isle of Wight birth cohort spirometry was performed at age 10 and 18 years. Information on birth weight and gestational age were obtained from hospital records. Mothers were asked about smoking during pregnancy. We employed linear mixed models to estimate the effect of these risk factors on repeated measurements of lung function. We considered maternal asthma, sex, neonatal intensive care unit admission, height, socio-economic status, personal smoking in participants at age 18, body mass index and environmental tobacco smoke exposure as potential confounders. Finally, we used path analysis to determine links between birth weight, gestational age and gestational maternal smoking on lung function at age 10 and 18 years.

RESULTS

Linear mixed models showed that with every 1 kg increase in birth weight, Forced expiratory volume in one second (FEV₁) increased by 42.6 ± 17.2 mL and Forced expiratory flow between 25% and 75% (FEF_25-75) of Forced vital capacity (FVC) increased by 95.5 ± 41.2 mL at age 18 years after adjusting for potential confounders. Path analysis suggested that birth weight had positive direct effects on FEV₁ and FEF_25-75 and positive indirect effect on FVC at 10 years which were carried forward to 18 years. Additionally, results also suggested a positive association between gestational age and FEV₁, FVC and FEF_25-75 at ages 10 and 18 years and an inverse association between gestational smoke exposure and FEV₁/FVC ratio and FEF_25-75 at age 18 years.

CONCLUSIONS

Higher birth weight and gestational age were associated with higher FEV₁, FVC and FEF_25-75 and maternal smoking during pregnancy was associated with reduced FEV₁/FVC ratio and FEF_25-75. The use of path analysis can improve our understanding of underlying "causal" pathways among different prenatal and childhood factors that affect lung function in both pre-adolescent and adolescent periods.

Before the first breath: prenatal exposures to air pollution and lung development

Various environmental contaminants are known to impair the growth trajectories of major organs, indirectly (gestational exposure) or directly (postnatal exposure). Evidence associates pre-gestational and gestational exposure to air pollutants with adverse birth outcomes (e.g., low birth weight, prematurity) and with a wide range of diseases in childhood and later in life. In this review, we explore the way that pre-gestational and gestational exposure to air pollution affects lung development. We present results in topics underlining epidemiological and toxicological evidence. We also provide a summary of the biological mechanisms by which air pollution exposure possibly leads to adverse respiratory outcomes. We conclude that gestational and early life exposure to air pollutants are linked to alterations in lung development and function and to other negative respiratory conditions in childhood (wheezing, asthma) that may last into adulthood. Plausible mechanisms encompass changes in maternal physiology (e.g., hypoxia, oxidative stress and inflammation) and DNA alterations in the fetus. Evidence for pre-gestational and gestational effects on the lung is scarce compared with that on early life exposure and further studies are needed. However, the suggested mechanisms are credible and the evidence of pre-gestational and gestational air pollution exposure is robust for adverse birth outcomes. Air pollutants might change lung developmental trajectories of the unborn child predisposing it to diseases later in life highlighting the urgent need for controls on urban air pollution levels worldwide.

Intrauterine growth restriction predicts lower lung function at school age in children born very preterm

OBJECTIVE

Children born preterm have lower lung function compared with term-born children. Intrauterine growth restriction (IUGR) may predispose individuals to chronic obstructive pulmonary disease. The purpose of this observational study was to investigate the role of IUGR as predictor of lung function at school age in children born very preterm. We further studied the difference in lung function between term-born and preterm-born children with distinct morbidities.

DESIGN

Preterm-born children and age-matched and sex-matched term-born comparison groups (88 of each) were studied at the mean age of 11 years. Spirometry and diffusing capacity of the lung for carbon monoxide (DLCO) were recorded. All preterm-born subjects with IUGR (n=23), defined as birth weight less than -2 SD, were compared with preterm-born subjects without IUGR (n=65).

RESULTS

In the preterm-born children exposed to IUGR, the forced expiratory volume in 1 s (FEV1) was 5.7 (95% CI -10.2 to -1.3) and DLCO 9.2 percentage points lower (95% CI -15.7 to -2.7) than in the preterm-born children with appropriate in utero growth (expressed as percentage of predicted values). The effect of IUGR in decreasing FEV1 and DLCO remained significant after adjustment for bronchopulmonary dysplasia (BPD). Further study indicated that after adjustment with IUGR and BPD, prematurity explained reduction in FEV1 but not in DLCO.

CONCLUSIONS

In children born very preterm, IUGR is an independent risk factor for a lower lung function in school age. We propose that IUGR and BPD are the major early factors predisposing the children born very preterm to lower lung function.

Respiratory effects of air pollution on children

A substantial proportion of the global burden of disease is directly or indirectly attributable to exposure to air pollution. Exposures occurring during the periods of organogenesis and rapid lung growth during fetal development and early post-natal life are especially damaging. In this State of the Art review, we discuss air toxicants impacting on children's respiratory health, routes of exposure with an emphasis on unique pathways relevant to young children, methods of exposure assessment and their limitations and the adverse health consequences of exposures. Finally, we point out gaps in knowledge and research needs in this area. A greater understanding of the adverse health consequences of exposure to air pollution in early life is required to encourage policy makers to reduce such exposures and improve human health.

Birth weight, early childhood growth and lung function in middle to early old age: 1946 British birth cohort

BACKGROUND

Findings from previous studies investigating the relationship between birth weight and adult lung function have been inconsistent, and data on birth weight and adult lung function decline are lacking. Few studies have investigated the relation between early childhood growth and adult lung function.

METHODS

FEV1 and FVC were measured at ages 43 years, 53 years and 60-64 years in the 1946 British birth cohort study. Multiple linear regression models were fitted to study associations with birth weight and weight gain at age 0-2 years. Multilevel models assessed how associations changed with age, with FEV1 and FVC as repeated outcomes.

RESULTS

3276 and 3249 participants were included in FEV1 and FVC analyses, respectively. In women, there was a decreasing association between birth weight and FVC with age. From the multilevel model, for every 1 kg higher birth weight, FVC was higher on average by 66.3 mL (95% CI 0.5 to 132) at 43 years, but significance was lost at 53 years and 60-64 years. Similar associations were seen with FEV1, but linear change (decline) from age 43 years lost statistical significance after full adjustment. In men, associations with birth weight were null in multilevel models. Higher early life weight gain was associated with higher FEV1 at age 43 years in men and women combined but not in each sex.

CONCLUSIONS

Birth weight is positively associated with adult lung function in middle age, particularly in women, but the association diminishes with age, potentially due to accumulating environmental influences over the life course.

Impact of childhood anthropometry trends on adult lung function

BACKGROUND

Poor fetal growth rate is associated with lower respiratory function; however, there is limited understanding of the impact of growth trends and BMI during childhood on adult respiratory function.

METHODS

The current study data are from the Mater-University of Queensland Study of Pregnancy birth cohort. Prospective data were available from 1,740 young adults who performed standard spirometry at 21 years of age and whose birth weight and weight, height, and BMI at 5, 14, and 21 years of age were available. Catch-up growth was defined as an increase of 0.67 Z score in weight between measurements. The impact of catch-up growth on adult lung function and the relationship between childhood BMI trends and adult lung function were assessed using regression analyses.

RESULTS

Lung function was higher at 21 years in those demonstrating catch-up growth from birth to 5 years (FVC, men: 5.33 L vs 5.54 L; women: 3.78 L vs 4.03 L; and FEV1, men: 4.52 L/s vs 4.64 L/s; women: 3.31 L/s vs 3.45 L/s). Subjects in the lowest quintile of birth (intrauterine growth retardation) also showed improved lung function if they had catch-up growth in the first 5 years of life. There was a positive correlation between increasing BMI and lung function at 5 years of age. However, in the later measurements when BMI increased into the obese category, a drop in lung function was observed.

CONCLUSIONS

These data show evidence for a positive contribution of catch-up growth in early life to adult lung function. However, if weight gain or onset of obesity occurs after 5 years of age, an adverse impact on adult lung function is noted.

Modification of the effect of ambient air pollution on pediatric asthma emergency visits: susceptible subpopulations

BACKGROUND

Children may have differing susceptibility to ambient air pollution concentrations depending on various background characteristics of the children.

METHODS

Using emergency department (ED) data linked with birth records from Atlanta, Georgia, we identified ED visits for asthma or wheeze among children 2 to 16 years of age from 1 January 2002 through 30 June 2010 (n = 109,758). We stratified by preterm delivery, term low birth weight, maternal race, Medicaid status, maternal education, maternal smoking, delivery method, and history of a bronchiolitis ED visit. Population-weighted daily average concentrations were calculated for 1-hour maximum carbon monoxide and nitrogen dioxide; 8-hour maximum ozone; and 24-hour average particulate matter less than 10 microns in diameter, particulate matter less than 2.5 microns in diameter (PM2.5), and the PM2.5 components sulfate, nitrate, ammonium, elemental carbon, and organic carbon, using measurements from stationary monitors. Poisson time-series models were used to estimate rate ratios for associations between 3-day moving average pollutant concentrations and daily ED visit counts and to investigate effect-measure modification by the stratification factors.

RESULTS

Associations between pollutant concentrations and asthma exacerbations were larger among children born preterm and among children born to African American mothers. Stratification by race and preterm status together suggested that both factors affected susceptibility. The largest estimated effect size (for an interquartile range increase in pollution) was observed for ozone among preterm births to African American mothers: rate ratio = 1.138 (95% confidence interval = 1.077-1.203). In contrast, the rate ratio for the ozone association among full-term births to mothers of other races was 1.025 (0.970-1.083).

CONCLUSIONS

Results support the hypothesis that children vary in their susceptibility to ambient air pollutants.

Respiratory consequences of late preterm birth

In developed countries most preterm births occur between 34 and 37 weeks' gestation. Deliveries during this 'late preterm' period are increasing and, since even mild prematurity is now recognised to be associated with adverse health outcomes, this presents healthcare challenges. Respiratory problems associated with late preterm birth include neonatal respiratory distress, severe RSV infection and childhood wheezing. Late preterm birth prematurely interrupts in utero lung development and is associated with maternal and early life factors which adversely affect the developing respiratory system. This review considers 1) mechanisms underlying the association between late preterm birth and impaired respiratory development, 2) respiratory morbidity associated with late preterm birth, particularly long-term outcomes, and 3) interventions which might protect respiratory development by addressing risk factors affecting the late preterm population, including maternal smoking, early life growth restriction and vulnerability to viral infection.

Disparities in pulmonary function in healthy children across the Indian urban-rural continuum

RATIONALE

Marked socioeconomic health-care disparities are recognized in India, but lung health inequalities between urban and rural children have not been studied.

OBJECTIVES

We investigated whether differences exist in spirometric pulmonary function in healthy children across the Indian urban-rural continuum and compared results with those from Indian children living in the UK.

METHODS

Indian children aged 5 to 12 years were recruited from Indian urban, semiurban, and rural schools, and as part of the Size and Lung Function in Children study, London. Anthropometric and spirometric assessments were undertaken.

MEASUREMENTS AND MAIN RESULTS

Acceptable spirometric data were obtained from 728 (58% boys) children in India and 311 (50% boys) UK-Indian children. As an entire group, the India-resident children had significantly lower z FEV1 and z FVC than UK-Indian children (P < 0.0005), when expressed using Global Lung Function Initiative-2012 equations. However, when India-resident children were categorized according to residence, there were no differences in z FEV1 and z FVC between Indian-urban and UK-Indian children. There were, however, significant reductions of ∼ 0.5 z scores and 0.9 z scores in both FEV1 and FVC (with no difference in FEV1/FVC) in Indian-semiurban and Indian-rural children, respectively, when compared with Indian-urban children (P < 0.0005). z Body mass index, socioeconomic circumstances, tobacco, and biomass exposure were individually significantly associated with z FEV1 and z FVC (P < 0.0005).

CONCLUSIONS

The presence of an urban-rural continuum of lung function within a specific ethnic group emphasizes the impact of environmental factors on lung growth in emerging nations such as India, which must be taken into account when developing ethnic-specific reference values or designing studies to optimize lung health.

Chronic obstructive pulmonary disease mortality and prevalence: the associations with smoking and poverty--a BOLD analysis

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a commonly reported cause of death and associated with smoking. However, COPD mortality is high in poor countries with low smoking rates. Spirometric restriction predicts mortality better than airflow obstruction, suggesting that the prevalence of restriction could explain mortality rates attributed to COPD. We have studied associations between mortality from COPD and low lung function, and between both lung function and death rates and cigarette consumption and gross national income per capita (GNI).

METHODS

National COPD mortality rates were regressed against the prevalence of airflow obstruction and spirometric restriction in 22 Burden of Obstructive Lung Disease (BOLD) study sites and against GNI, and national smoking prevalence. The prevalence of airflow obstruction and spirometric restriction in the BOLD sites were regressed against GNI and mean pack years smoked.

RESULTS

National COPD mortality rates were more strongly associated with spirometric restriction in the BOLD sites (<60 years: men rs=0.73, p=0.0001; women rs=0.90, p<0.0001; 60+ years: men rs=0.63, p=0.0022; women rs=0.37, p=0.1) than obstruction (<60 years: men rs=0.28, p=0.20; women rs=0.17, p<0.46; 60+ years: men rs=0.28, p=0.23; women rs=0.22, p=0.33). Obstruction increased with mean pack years smoked, but COPD mortality fell with increased cigarette consumption and rose rapidly as GNI fell below US$15 000. Prevalence of restriction was not associated with smoking but also increased rapidly as GNI fell below US$15 000.

CONCLUSIONS

Smoking remains the single most important cause of obstruction but a high prevalence of restriction associated with poverty could explain the high 'COPD' mortality in poor countries.

Small for gestational age birth weight: impact on lung structure and function

Accumulating data suggest that prenatal compromises leading to intrauterine growth restriction (IUGR) increase the risk for respiratory deficiencies after birth. In this respect, a growing body of epidemiological evidence in infants, children and adults indicates that small for gestational (SGA) birth weight can adversely affect lung function, thus questioning the widely accepted concept that IUGR accelerates lung maturation and improves outcome. Although the mechanisms responsible for the relationship between SGA and later lung dysfunction remain poorly documented, animal data indicate that intrauterine lung development can be adversely affected by factors associated with IUGR, namely reduced substrate supply, fetal hypoxemia and hypercortisolemia. Thus, it is suggested that fetal adaptations to intrauterine undernutrition result in permanent changes in lung structure, which in turn lead to chronic airflow obstruction. The purpose of this review is to describe and discuss the effects of IUGR on lung structure and function.

From Childhood Asthma to Chronic Obstructive Pulmonary Disease: Evidence Supporting a Disease Continuum

In this review, we analyze the available evidence showing a link between asthma and chronic obstructive pulmonary disease (COPD). Many features (epidemiologic, physiologic, and histologic) overlap between these two conditions. Both environmental cigarette smoke exposure and early lung development are risk factors for the development of asthma and COPD. However, recent studies suggest that up to 25% of COPD cases were nonsmokers. Asthma during early childhood, independent of smoking history, may be an independent risk factor for the later development of COPD. One explanation for this phenomenon suggests that early small airway dysfunction (including chronic airway inflammation and airway remodeling) can lead to permanent impairment in lung physiology. Several reasons why control of airway inflammation is difficult in some patients are explored. Finally, we examine the available evidence suggesting overlapping histologic features in both asthma and COPD.

Effect of two models of intrauterine growth restriction on alveolarization in rat lungs: morphometric and gene expression analysis

Intrauterine growth restriction (IUGR) in preterm infants increases the risk of bronchopulmonary dysplasia, characterized by arrested alveolarization. We evaluated the impact of two different rat models (nitric oxide synthase inhibition or protein deprivation) of IUGR on alveolarization, before, during, and at the end of this postnatal process. We studied IUGR rat pups of dams fed either a low protein (LPD) or a normal diet throughout gestation and pups of dams treated by continuous infusion of Nω-nitro-L-arginine methyl ester (L-NAME) or its diluent on the last four days of gestation. Morphometric parameters, alveolar surface (Svap), mean linear intercept (MLI) and radial alveolar count (RAC) and transcriptomic analysis were determined with special focus on genes involved in alveolarization. IUGR pups regained normal weight at day 21 in the two treated groups. In the LPD group, Svap, MLI and RAC were not different from those of controls at day 4, but were significantly decreased at day 21, indicating alveolarization arrest. In the L-NAME group, Svap and RAC were significantly decreased and MLI was increased at day 4 with complete correction at day 21. In the L-NAME model, several factors involved in alveolarization, VEGF, VEGF-R1 and –R2, MMP14, MMP16, FGFR3 and 4, FGF18 and 7, were significantly decreased at day 4 and/or day 10, while the various factors studied were not modified in the LPD group. These results demonstrate that only maternal protein deprivation leads to sustained impairment of alveolarization in rat pups, whereas L-NAME impairs lung development before alveolarization. Known growth factors involved in lung development do not seem to be involved in LPD-induced alveolarization disorders, raising the question of a possible programming of altered alveolarization.

Fetal growth and risk of childhood asthma and allergic disease

Introduction

Early genetic and environmental factors have been discussed as potential causes for the high prevalence of asthma and allergic disease in the western world, and knowledge on fetal growth and its consequence on future health and disease development is emerging.

Objective

This review article is an attempt to summarize research on fetal growth and risk of asthma and allergic disease. Current knowledge and novel findings will be reviewed and open research questions identified, to give basic scientists, immunologists and clinicians an overview of an emerging research field.

Methods

PubMed-search on pre-defined terms and cross-references.

Results

Several studies have shown a correlation between low birth weight and/or gestational age and asthma and high birth weight and/or gestational age and atopy. The exact mechanism is not yet clear but both environmental and genetic factors seem to contribute to fetal growth. Some of these factors are confounders that can be adjusted for, and twin studies have been very helpful in this context. Suggested mechanisms behind fetal growth are often linked to the feto-maternal circulation, including the development of placenta and umbilical cord. However, the causal link between fetal growth restriction and subsequent asthma and allergic disease remains unexplained. New research regarding the catch-up growth following growth restriction has posited an alternative theory that diseases later on in life result from rapid catch-up growth rather than intrauterine growth restriction per se. Several studies have found a correlation between a rapid weight gain after birth and development of asthma or wheezing in childhood.

Conclusion and clinical relevance

Asthma and allergic disease are multifactorial. Several mechanisms seem to influence their development. Additional studies are needed before we fully understand the causal links between fetal growth and development of asthma and allergic diseases.

Maternal exposure to polycyclic aromatic hydrocarbons and 5'-CpG methylation of interferon-γ in cord white blood cells

BACKGROUND

Maternal factors are implicated in the onset of childhood asthma. Differentiation of naïve CD4+ T lymphocytes into pro-allergic T-helper 2 cells induces interleukin (IL)4 expression and inhibits interferon (IFN)γ expression accompanied by concordant methylation changes in the promoters of these genes. However, it has yet to be established whether maternal exposure to polycyclic aromatic hydrocarbons (PAHs) can alter these gene promoters epigenetically during fetal development.

OBJECTIVES

In this study we sought to elucidate the relationship between maternal PAH exposure and promoter methylation status of IFNγ and IL4.

METHODS

We assessed the effects of benzo[a]pyrene (BaP), a representative airborne PAH, on the methylation status of the IFNγ and IL4 promoters in Jurkat cells and two lung adenocarcinoma cell lines, and on gene expression. In addition, we evaluated methylation status of the IFNγ promoter in cord white blood cells from 53 participants in the Columbia Center for Children's Environmental Health cohort. Maternal PAH exposure was estimated by personal air monitoring during pregnancy.

RESULTS

In vitro exposure of the cell models to low, noncytotoxic doses (0.1 and 1 nM) of BaP elicited increased promoter hypermethylation and reduced expression of IFNγ, but not IL4. IFNγ promoter methylation in cord white blood cells was associated with maternal PAH exposure in the cohort study subsample.

CONCLUSION

Consistent with the results for the cell lines, maternal exposure to PAHs was associated with hypermethylation of IFNγ in cord blood DNA from cohort children. These findings support a potential role of epigenetics in fetal reprogramming by PAH-induced environmental diseases.

Long term respiratory consequences of intrauterine growth restriction

Epidemiological studies demonstrate that in-utero growth restriction and low birth weight are associated with impaired lung function and increased respiratory morbidity from infancy, throughout childhood and into adulthood. Chronic restriction of nutrients and/or oxygen during late pregnancy causes abnormalities in the airways and lungs of offspring, including smaller numbers of enlarged alveoli with thicker septal walls and basement membranes. The structural abnormalities and impaired lung function seen soon after birth persist or even progress with age. These changes are likely to cause lung symptomology through life and hasten lung aging.

The use of ethnically specific norms for ventilatory function in African-American and white populations

BACKGROUND

In the USA, different standards are usually set for spirometric values in African-American and white populations. It is unclear to what extent the lower lung function found in African-Americans is 'normal' in the sense of having no adverse consequences.

METHODS

African-American and white participants in the Atherosclerosis Risk in Communities (ARIC) limited access data set, from four communities in the USA had spirometric testing at baseline beginning in 1986 and were followed up to assess survival to the end of 2002.

RESULTS

Forced Expiratory Volume in 1 s (FEV(1)) and Forced Vital Capacity (FVC) were lower in the African-American than the white sample both for men and women and adjustment for potential confounders had little effect on the estimated difference {difference in FVC after adjustment: men, -0.68 l [95% confidence interval (95% CI) -0.75 to -0.61]; women, -0.41 l (95%CI -0.45 to -0.36)}. The FEV(1)/FVC ratio was slightly greater among African-American than white participants [difference: men, 1.5% (95%CI 0.7-2.1); women, 1.7% (95%CI 1.1-2.2)]. After adjustment for age and height, survival was similar in each ethnic group for any given level of FVC before and after adjustment for potential confounders. The hazard ratio for African-American compared with white participants was 1.24 for men (95% CI 0.91-1.69) and 0.96 for women (95% CI 0.66-1.38).

CONCLUSIONS

A given FVC has the same prognostic significance for 'normal' African-American and white participants. It is inappropriate to use ethnic norms when assessing prognosis.

Relation of early childhood growth and wheezing phenotypes to adult lung function

RATIONALE

Several studies have reported associations between indicators of birth size and postnatal growth rates with levels of pulmonary function achieved as adults. The objective of this study was to determine if levels and/or rates of weight gain, measured in early life (birth-6 years), are associated with FVC or FEV1 levels achieved in young adulthood and if these associations differ by early childhood wheezing phenotypes.

METHODS

We used data from participants in the Tucson Children's Respiratory Study (CRS), a prospective birth cohort study. Weight was measured quarterly up to age 3 years and again at age 6 years. Pulmonary function was assessed at ages 16 and 22. Mean weight and slope of weight growth between 3 and 6 years were estimated using standardized residuals. Longitudinal models were used to determine predictors of FVC and FEV1 at ages 16 and 22 years.

RESULTS

There were 127 non-Hispanic white subjects that had at least four weight measures and one or more pulmonary function measures as young adults. After adjusting for sex, height, and age, the standardized slope of weight growth (between 3 and 6 years) was positively associated with higher levels of FVC at age 16 and 22 years (P = 0.0001) among subjects who did not have preschool wheezing. However, this association was completely absent among subjects who had wheezing lower respiratory tract illnesses in the first 3 years of life. Similar trends were found for FEV1.

CONCLUSION

The rate of weight gain between 3 and 6 years is significantly positively related to adult FVC and FEV1 and this association is modified by early wheezy phenotypes.

A strong synergism of low birth weight and prenatal smoking on asthma in schoolchildren

BACKGROUND

Prenatal smoke exposure is associated with airway inflammation and asthma in children. It also increases the risk of low birth weight (LBW). LBW is associated with decreased lung function independently of smoking.

OBJECTIVE

To study the independent and joint effects of prenatal smoking and LBW on childhood asthma.

METHODS

In 1996, all children aged 7 to 8 years in 3 cities in northern Sweden were invited to an International Study of Asthma and Allergy in Childhood questionnaire survey. This study focused on the follow-up of children aged 11 to 12 years, in which 3389 children (96%) participated. A subset of 2121 children underwent skin-prick testing. Self-reported physician-diagnosed asthma has been clinically validated.

RESULTS

Mean birth weight was 3360 g in children exposed to prenatal smoking and 3571 g in nonexposed children (P < .001). The association of prenatal smoking with physician-diagnosed asthma was stronger in LBW children (risk ratio: 8.8 [95% confidence interval: 2.1-38]) than in normal birth weight children (risk ratio: 1.3 [95% confidence interval: 1.0-1.8]). LBW alone was not an independent predictor of asthma. These associations were similar in multivariate analysis, and the interaction term LBW × smoking was highly statistically significant.

CONCLUSIONS

There was a strong interaction of LBW and prenatal-smoking on the risk of physician-diagnosed asthma, which has not been demonstrated previously. This was consistently seen with adjustment for known risk factors, including allergic sensitization. Plausibly, airway inflammation from prenatal smoke exposure induces obstructive symptoms more easily in the underdeveloped airways of LBW children.

Environmental epigenetics of asthma: an update

Asthma, a chronic inflammatory disorder of the airway, is influenced by interplay between genetic and environmental factors now known to be mediated by epigenetics. Aberrant DNA methylation, altered histone modifications, specific microRNA expression, and other chromatin alterations orchestrate a complex early-life reprogramming of immune T-cell response, dendritic cell function, macrophage activation, and a breach of airway epithelial barrier that dictates asthma risk and severity in later life. Adult-onset asthma is under analogous regulation. The sharp increase in asthma prevalence over the past 2 or 3 decades and the large variations among populations of similar racial/ethnic background but different environmental exposures favors a strong contribution of environmental factors. This review addresses the fundamental question of whether environmental influences on asthma risk, severity, and steroid resistance are partly due to differential epigenetic modulations. Current knowledge on the epigenetic effects of tobacco smoke, microbial allergens, oxidants, airborne particulate matter, diesel exhaust particles, polycyclic aromatic hydrocarbons, dietary methyl donors and other nutritional factors, and dust mites is discussed. Exciting findings have been generated by rapid technological advances and well-designed experimental and population studies. The discovery and validation of epigenetic biomarkers linked to exposure, asthma, or both might lead to better epigenotyping of risk, prognosis, treatment prediction, and development of novel therapies.