Pediatric origins of adult lung diseases. 4. Tobacco related lung diseases begin in childhood

Does lung function in preschoolers help to predict asthma in later life?

The earliest respiratory function assessments, within or close to the neonatal period, consistently show correlations with lung function and with the development of asthma into adulthood. Measurements of lung function in infancy reflect the in utero period of lung development, and if early enough, show little influence of postnatal environmental exposures. Later in the preschool and school age periods, influences of the environment are superimposed on initial levels. Fetal exposures before birth such as maternal smoking during pregnancy, lead to reduced lung function and an increased risk of asthma in females particularly those with certain glutathione S-transferase genotypes. Lung function measurements later in the preschool period are also associated with development of asthma. Although lung function in preschoolers does help predict asthma in later life and these observations have increased our understanding of the physiology underlying asthma, the findings have not led to thewidespread use of lung function measurements being in preschoolers as clinical predictors of asthma due to the practicalities of testing in this age group.

Ventilatory response to added dead space in infants exposed to second-hand smoke in pregnancy

Maternal cigarette smoking in pregnancy can adversely affect infant respiratory control. In utero nicotine exposure has been shown to blunt the infant ventilatory response to hypercapnia, which could increase the risk of sudden infant death syndrome. The potential impact of maternal second-hand smoke exposure, however, has not yet been determined. The aim of this study was to assess ventilatory response to added dead-space (inducing hypercapnia) in infants with second-hand smoke exposure during pregnancy, in infants whose mothers smoked and in controls (non-smoke exposed). Infants breathed through a face mask and specialised "tube-breathing" circuit, incorporating a dead space of 4.4 ml/kg body weight. The maximum minute ventilation (MMV) during added dead space breathing was determined and the time taken to achieve 63% of the MMV calculated (the time constant (TC) of the response). Infants were studied on the postnatal ward prior to discharge home. Thirty infants (ten in each group) were studied with a median gestational age of 39 [range 37-41] weeks, birthweight of 3.1 [2.2-4.0] kg, and postnatal age of 33 (21-62) h. The infants whose mothers had second-hand smoke exposure (median TC 42 s, p = 0.001), and the infants of cigarette smoking mothers (median TC 37 s, p = 0.002) had longer time constants than the controls (median TC 29 s). There was no significant difference between the TC of the infants whose mothers had second-hand smoke exposure and those whose mothers smoked (p = 0.112).    Conclusion: Second-hand smoke exposure during pregnancy was associated with a delayed newborn ventilatory response. What is Known: • Maternal cigarette smoking in pregnancy can adversely affect infant respiratory control. • The potential impact of maternal second-hand smoke exposure, however, has not yet been determined. What is New: • We have assessed the ventilatory response to added dead-space (inducing hypercapnia) in newborns with second-hand smoke exposure during pregnancy, in infants whose mothers smoked, and in controls (non-smoke exposed). • Maternal second-hand smoke exposure, as well as maternal smoking, during pregnancy was associated with a delayed newborn ventilatory response.

Mmp12 Is Upregulated by in utero Second-Hand Smoke Exposures and Is a Key Factor Contributing to Aggravated Lung Responses in Adult Emphysema, Asthma, and Lung Cancer Mouse Models

Matrix metalloproteinase-12 (Mmp12) is upregulated by cigarette smoke (CS) and plays a critical role in extracellular matrix remodeling, a key mechanism involved in physiological repair processes, and in the pathogenesis of emphysema, asthma, and lung cancer. While cigarette smoking is associated with the development of chronic obstructive pulmonary diseases (COPD) and lung cancer, in utero exposures to CS and second-hand smoke (SHS) are associated with asthma development in the offspring. SHS is an indoor air pollutant that causes known adverse health effects; however, the mechanisms by which in utero SHS exposures predispose to adult lung diseases, including COPD, asthma, and lung cancer, are poorly understood. In this study, we tested the hypothesis that in utero SHS exposure aggravates adult-induced emphysema, asthma, and lung cancer.

Methods: Pregnant BALB/c mice were exposed from gestational days 6–19 to either 3 or 10mg/m³ of SHS or filtered air. At 10, 11, 16, or 17weeks of age, female offspring were treated with either saline for controls, elastase to induce emphysema, house-dust mite (HDM) to initiate asthma, or urethane to promote lung cancer. At sacrifice, specific disease-related lung responses including lung function, inflammation, gene, and protein expression were assessed.

Results: In the elastase-induced emphysema model, in utero SHS-exposed mice had significantly enlarged airspaces and up-regulated expression of Mmp12 (10.3-fold compared to air-elastase controls). In the HDM-induced asthma model, in utero exposures to SHS produced eosinophilic lung inflammation and potentiated Mmp12 gene expression (5.7-fold compared to air-HDM controls). In the lung cancer model, in utero exposures to SHS significantly increased the number of intrapulmonary metastases at 58weeks of age and up-regulated Mmp12 (9.3-fold compared to air-urethane controls). In all lung disease models, Mmp12 upregulation was supported at the protein level.

Conclusion: Our findings revealed that in utero SHS exposures exacerbate lung responses to adult-induced emphysema, asthma, and lung cancer. Our data show that MMP12 is up-regulated at the gene and protein levels in three distinct adult lung disease models following in utero SHS exposures, suggesting that MMP12 is central to in utero SHS-aggravated lung responses.

Low lung function in the developing world is analogous to stunting: a review of the evidence

Background: Low vital capacity, one of the consequences of restricted lung growth, is a strong predictor of cardiovascular mortality. Vital capacity is lower in the developing world than the developed world, even after adjusting for height, weight and gender. This difference is typically dismissed as ethnic variation, adjusted for by redefining normal. Whether this is a consequence of stunted lung growth, rather than just genetically smaller lungs, has not been investigated in detail. Therefore, we sought to compare factors implicated in both stunting and lung development, particularly in the developing world.

Methods: We conducted a manual screen of articles identified through Google Scholar and assessed risk of bias. No language restrictions were applied, so long as there was an associated English abstract. We queried VizHub (Global Burden of Disease Visualization Tool) and Google Dataset search engines for disease burden and genome wide association studies.  The scope of the article and the heterogeneity of the outcome measures reported required a narrative review of available evidence. To the extent possible, the review follows PRISMA reporting guidelines.

Results: Early life influences operate in synergism with genetic, environmental and nutritional factors to influence lung growth and development in children.  Low lung function and stunting have common anthropometric, environmental and nutritional correlates originating during early development. Similar anthropometric correlates shared chronic inflammatory pathways, indicated that the two conditions were analogous.

Conclusion: The analogy between poor lung function and stunting is conspicuous in the developing world, with malnutrition at the center of non -achievement of growth potential, susceptibility to infectious diseases and intrauterine programming for metabolic syndrome. This counter the idea of redefining the normal for lung function measurements, since observed inter-ethnic variations are likely a mix of natural genetic differences as well as differences in nurture such that reduced lung function reflects early life adversities.

Low lung function in the developing world is analogous to stunting: a review of the evidence

Background: Low vital capacity, one of the consequences of restricted lung growth, is a strong predictor of cardiovascular mortality. Vital capacity is lower in the developing world than the developed world, even after adjusting for height, weight and gender. This difference is typically dismissed as ethnic variation, adjusted for by redefining normal. Whether this is a consequence of stunted lung growth, rather than genetically smaller lungs, has not been investigated in detail. Therefore, we sought to compare factors implicated in both stunting and lung development, particularly in the developing world. Methods: We conducted a manual screen of articles identified through Google Scholar and assessed risk of bias. No language restrictions were applied, so long as there was an associated English abstract. We queried VizHub (Global Burden of Disease Visualization Tool) and Google Dataset search engines for disease burden and genome wide association studies.  The scope of the article and the heterogeneity of the outcome measures reported required a narrative review of available evidence. To the extent possible, the review follows PRISMA reporting guidelines. Results: Early life influences operate in synergism with environmental and nutritional factors to influence lung growth and development in children.  Low lung function and stunting have common anthropometric, environmental and nutritional correlates originating during early development. Similar anthropometric correlates and shared chronic inflammatory pathways indicated that the two conditions were analogous. Conclusion: The analogy between poor lung function and stunting is conspicuous in the developing world, where malnutrition lies at the center of non -achievement of growth potential, susceptibility to infectious diseases and intrauterine programming for metabolic syndrome. The common pathological mechanisms governing stunting and lung function deficits counter the idea of redefining the normal for lung function measurements.

Airway function in infancy is linked to airflow measurements and respiratory symptoms from childhood into adulthood

INTRODUCTION

Increasing evidence suggests that poor lung function in adulthood is determined very early in life. Our study aims were: (1) identify factors associated with early infant lung function; (2) quantify the link between early infant lung function and early adult lung function; and (3) identify environmental and inherited factors which predict lung function throughout the post-natal growth period.

METHODS

In this longitudinal study, 253 individuals were recruited antenatally. Lung function and allergy testing occurred at 1, 6, 12 months, 6, 11, 18, and 24 years of age. The relationship between lung function at 1 month (V'maxFRC) and spirometry variables at each follow-up was evaluated. Early life predictors of spirometry were assessed longitudinally using linear mixed models.

RESULTS

V'maxFRC correlated positively with FEF25-75% at every assessment from 6 to 24 years and FEV₁ /FVC at 11 and 24 years and inversely with airway responsiveness at 6 and 18 years. Maternal asthma and smoking in pregnancy were associated with lower FEV₁ from 6 to 24 years (-99 mL, P = 0.03; -77 mL, P = 0.045 respectively). Lower V'maxFRC at 1 month was associated with asthma and wheeze through to 24 years.

CONCLUSION

Lung airflow measurements track from birth into early adulthood, suggesting a permanent and stable airway framework is laid down in the antenatal period. Lower infant airway function is associated with respiratory symptoms into adulthood, indicating the link is clinically important. Antenatal and early life exposures must be addressed in order to maximize airway growth and reduce lifelong respiratory compromise.

Outcomes of primary gastric transposition for long-gap esophageal atresia in neonates

BACKGROUND

Gastric transposition is a relatively novel method of esophageal replacement. The purpose of this retrospective study was to assess the outcomes of long-gap esophageal atresia (LGEA) treated with esophageal replacement using primary gastric transposition in neonates.

METHODS

Between March 2008 and May 2015, 14 newborns with LGEA were treated in our hospital. They were all found to have gaps of over 3 cm at the time of the surgery and were diagnosed with LGEA. Primary gastric transposition was performed. They also underwent a gastric drainage procedure by pyloromyotomy. The nasogastric tube was removed if no anastomotic fistula was present and oral feeding was initiated. After initial recovery and discharge, the patients were evaluated with outpatient follow-ups or telephone follow-ups from 1 month after the surgery.

RESULTS

The mean age of the neonates at the time of the surgery was 32 hours (range, 4-96 h). The mean birth weight was 2550 g (range, 2100-3500 g). There were 2 deaths in this series of patients due to respiratory failure or withdrawal of treatment by the parents, with a mortality rate of 14.3%. Seven of the neonates developed unilateral or bilateral severe pneumonia. Early anastomotic leak occurred in 3 cases and anastomotic strictures occurred in 4 cases. These 4 neonates were able to eat a fairly normal diet after esophageal balloon dilation. Gastroesophageal reflux occurred in 7 of 12 cases. Feeding multiple small meals and postural support for positioning and feeding were instructed for these 7 cases. Subsequently, the symptoms alleviated and they had no additional surgical therapy. None of the neonates had delayed gastric emptying or gastric retention.

CONCLUSION

Primary gastric transposition may be a rewarding reconstructive option in the treatment of LGEA.

Respiratory outcomes for the tiniest or most immature infants

Extremely low birth weight (<1000 g birth weight) or extremely preterm (<28 weeks of gestation) infants are surviving in greater numbers as neonatal care advances. Many of these survivors, especially those who develop bronchopulmonary dysplasia, have more respiratory ill health in the first years after discharge home, reduced respiratory function and impaired exercise capacity throughout childhood and into adulthood compared with term-born controls. It is important to establish the long-term respiratory outcomes for the tiniest or most immature survivors as they grow older, since they may contribute disproportionately to rates of chronic obstructive pulmonary disease and respiratory ill-health in adulthood.

Prevalence and risk factors associated with wheezing in the first year of life

OBJECTIVE

to investigate the prevalence and risk factors associated with wheezing in infants in the first year of life.

METHODS

this was a cross-sectional study, in which a validated questionnaire (Estudio Internacional de Sibilancias en Lactantes--International Study of Wheezing in Infants--EISL) was applied to parents of infants aged between 12 and 15 months treated in 26 of 85 primary health care units in the period between 2006 and 2007. The dependent variable, wheezing, was defined using the following standards: occasional (up to two episodes of wheezing) and recurrent (three or more episodes of wheezing). The independent variables were shown using frequency distribution to compare the groups. Measures of association were based on odds ratio (OR) with a confidence interval of 95% (95% CI), using bivariate analysis, followed by multivariate analysis (adjusted OR [aOR]).

RESULTS

a total of 1,029 (37.7%) infants had wheezing episodes in the first 12 months of life; of these, 16.2% had recurrent wheezing. Risk factors for wheezing were family history of asthma (OR=2.12; 95% CI: 1.76-2.54) and six or more episodes of colds (OR=2.38; 95% CI: 1.91-2.97) and pneumonia (OR=3.02; 95% CI: 2.43-3.76). For recurrent wheezing, risk factors were: familial asthma (aOR=1.73; 95% CI 1.22-2.46); early onset wheezing (aOR=1.83; 95% CI: 1.75-3.75); nocturnal symptoms (aOR=2.56; 95% CI: 1.75-3.75), and more than six colds (aOR=2.07; 95% CI 1.43- .00).

CONCLUSION

the main risk factors associated with wheezing in Fortaleza were respiratory infections and family history of asthma. Knowing the risk factors for this disease should be a priority for public health, in order to develop control and treatment strategies.

Early life influences on the development of chronic obstructive pulmonary disease

There is increasing evidence that chronic obstructive pulmonary disease (COPD) is not simply a disease of old age that is largely restricted to heavy smokers, but may be associated with insults to the developing lung during foetal life and the first few years of postnatal life, when lung growth and development are rapid. A better understanding of the long-term effects of early life factors, such as intrauterine growth restriction, prenatal and postnatal exposure to tobacco smoke and other pollutants, preterm delivery and childhood respiratory illnesses, on the subsequent development of chronic respiratory disease is imperative if appropriate preventive and management strategies to reduce the burden of COPD are to be developed. The extent to which insults to the developing lung are associated with increased risk of COPD in later life depends on the underlying cause, timing and severity of such derangements. Suboptimal conditions in utero result in aberrations of lung development such that affected individuals are born with reduced lung function, which tends to remain diminished throughout life, thereby increasing the risk both of wheezing disorders during childhood and subsequent COPD in genetically susceptible individuals. If the current trend towards the ever-increasing incidence of COPD is to be reversed, it is essential to minimize risks to the developing lung by improvements in antenatal and neonatal care, and to reduce prenatal and postnatal exposures to environmental pollutants, including passive tobacco smoke. Furthermore, adult physicians need to recognize that lung disease is potentially associated with early life insults and provide better education regarding diet, exercise and avoidance of smoking to preserve precious reserves of lung function in susceptible adults. This review focuses on factors that adversely influence lung development in utero and during the first 5 years of life, thereby predisposing to subsequent COPD.

Evidence for in vivo nicotine-induced alveolar interstitial fibroblast-to-myofibroblast transdifferentiation

Nicotine exposure alters normal homeostatic pulmonary epithelial-mesenchymal paracrine signaling pathways, resulting in alveolar interstitial fibroblast (AIF)-to-myofibroblast (MYF) transdifferentiation. Though this has been described under in vitro conditions, it is not known if the same phenomenon also takes place in vivo. A well-established rodent model of lung damage following perinatal nicotine exposure was used. By probing for the well-established markers of fibroblast differentiation (parathyroid hormone-related protein [PTHrP], peroxisome proliferator-activated receptor gamma [PPARgamma], adipocyte differentiation-related protein, alpha-smooth muscle actin, and fibronectin) at the mRNA, protein, and tissue levels, the authors provide the first in vivo evidence for nicotine-induced AIF-to-MYF transdifferentiation. In addition, these data also provide the first evidence for nicotine-induced up-regulation of Wnt signaling, accompanying the down-regulation of PTHrP/PPARgamma signaling in vivo following nicotine exposure during pregnancy. These data provide an integrated mechanism for in utero nicotine-induced lung damage and how it could permanently alter the "developmental program" of the developing lung by disrupting critically important epithelial-mesenchymal interactions. More importantly, these data are likely to provide specific interventions to augment the pulmonary mesenchymal lipogenic pathway to ameliorate nicotine-induced in utero lung injury.

Review Series: What goes around, comes around: childhood influences on later lung health?: Relationship between environmental exposures in children and adult lung disease: The case for outdoor exposures

There is a growing understanding that chronic respiratory diseases in adults have their origins in early life. Adverse environmental exposures occurring in vulnerable periods during lung growth and development in the fetal period and in early childhood that alter lung structure and limit the growth in lung function may have lifelong consequences. Evidence is increasing that exposure to the ambient environment, including air pollutants, persistent toxic substances, water pollutants and respiratory viral infections, can inhibit lung function growth and predispose to chronic non-malignant lung diseases. These exposures generally interact with a genetic predisposition, and gene—environment interactions and epigenetic phenomena are attracting considerable study. An understanding of how ambient exposures impact on normal lung growth and development will aid in understanding of how chronic respiratory diseases of adults develop and may lead to new preventative strategies.

The effects of smoking on the developing lung: insights from a biologic model for lung development, homeostasis, and repair

There is extensive epidemiologic and experimental evidence from both animal and human studies that demonstrates detrimental long-term pulmonary outcomes in the offspring of mothers who smoke during pregnancy. However, the molecular mechanisms underlying these associations are not understood. Therefore, it is not surprising that that there is no effective intervention to prevent the damaging effects of perinatal smoke exposure. Using a biologic model of lung development, homeostasis, and repair, we have determined that in utero nicotine exposure disrupts specific molecular paracrine communications between epithelium and interstitium that are driven by parathyroid hormone-related protein and peroxisome proliferator-activated receptor (PPAR)gamma, resulting in transdifferentiation of lung lipofibroblasts to myofibroblasts, i.e., the conversion of the lipofibroblast phenotype to a cell type that is not conducive to alveolar homeostasis, and is the cellular hallmark of chronic lung disease, including asthma. Furthermore, we have shown that by molecularly targeting PPAR gamma expression, nicotine-induced lung injury can not only be significantly averted, it can also be reverted. The concept outlined by us differs from the traditional paradigm of teratogenic and toxicological effects of tobacco smoke that has been proposed in the past. We have argued that since nicotine alters the normal homeostatic epithelial-mesenchymal paracrine signaling in the developing alveolus, rather than causing totally disruptive structural changes, it offers a unique opportunity to prevent, halt, and/or reverse this process through targeted molecular manipulations.

Do mental health problems in childhood predict chronic physical conditions among males in early adulthood? Evidence from a community-based prospective study

BACKGROUND

Previous studies have documented associations between mental and physical health problems in cross-sectional studies, yet little is known about these relationships over time or the specificity of these associations. The aim of the current study was to examine the relationship between mental health problems in childhood at age 8 years and physical disorders in adulthood at ages 18-23 years.

METHOD

Multiple logistic regression analyses were used to examine the relationship between childhood mental health problems, reported by child, parent and teacher, and physical disorders diagnosed by a physician in early adulthood.

RESULTS

Significant linkages emerged between childhood mental health problems and obesity, atopic eczema, epilepsy and asthma in early adulthood. Specifically, conduct problems in childhood were associated with a significantly increased likelihood of obesity and atopic eczema; emotional problems were associated with an increased likelihood of epilepsy and asthma; and depression symptoms at age 8 were associated with an increased risk of asthma in early adulthood.

CONCLUSIONS

Our findings provide the first evidence of an association between mental health problems during childhood and increased risk of specific physical health problems, mainly asthma and obesity, during early adulthood, in a representative sample of males over time. These data suggest that behavioral and emotional problems in childhood may signal vulnerability to chronic physical health problems during early adulthood.

Changes in cigarette use and nicotine dependence in the United States: evidence from the 2001-2002 wave of the national epidemiologic survey of alcoholism and related conditions

OBJECTIVES

We examined the roles of gender and poverty in cigarette use and nicotine dependence among adults in the United States.

METHODS

Our data were drawn from the 2001-2002 National Epidemiological Survey of Alcoholism and Related Conditions, a nationally representative sample of US adults 18 years and older.

RESULTS

The overall rate of cigarette use declined between 1964 and 2002. Nicotine dependence does not appear to have declined overall, and there is evidence that nicotine dependence has increased among women in recent cohorts. The odds of nicotine dependence among cigarette users appear to have increased significantly in recent cohorts.

CONCLUSIONS

Despite recent declines in cigarette use, the prevalence of nicotine dependence has increased among some groups and has remained steady overall, which may be hampering public health initiatives to reduce cigarette use. Efforts to study or curb cigarette use should therefore take nicotine dependence into account.

Respiratory effects of tobacco smoking on infants and young children

Second-hand smoke (SHS) and tobacco smoke products (TSPs) are recognised global risks for human health. The present article reviews the causal role of SHS and TSPs for respiratory disorders in infants and young children. Several studies have shown an effect of TSPs exposure during pregnancy upon lung function in the newborn infant and of SHS on symptoms and lung function after birth. From 1997 to 1999 a set of systematic reviews concerning the relationship between second-hand exposure to tobacco smoke and respiratory health in children was published in Thorax by Cook and Strachan, covering hundreds of published papers. The evidence for a causal relationship between SHS exposure and asthmatic symptoms and reduced lung function is quite strong, whereas the evidence related to the development of allergy is much weaker. There is recent evidence relating to an interaction between TSP exposure and genetic ploymorphisms, demonstrating that certain individuals are more susceptible to the effect of TSP exposure on lung health. In the present review, an overview is given for the effects of TSP exposure and SHS upon lung health in children, with a focus on infants and young children. There is a need for intervention to reduce TSP exposure in young children, by educating parents and adolescents about the health effects of TSP exposure. Recent legislation in many European countries related to smoking in the workplace is of great importance for exposure during pregnancy. Studies are needed to identify possible critical periods for TSPs to induce harmful effects upon lung health in young children and on environment-gene interactions in order to prevent harm.

Environmental tobacco smoke and the epidemic of asthma in children: the role of cigarette use

BACKGROUND

Asthma is the most common chronic disease affecting youth worldwide. The prevalence of asthma has increased at least 3-fold during the past several decades. The reason for this increase remains unknown.

OBJECTIVE

To examine one possible factor that may be affecting the increase in prevalence of asthma among youth.

METHODS

Data on the incidence of asthma among youth were aggregated using the National Health Interview Survey (sample of 4,500 children) and were compared on an ecologic level with data on cigarette consumption in the United States from 1900 to 2003 from the American Lung Association.

RESULTS

Our results suggest a parallel increase in the rates of cigarette use among adults and asthma in children. These findings show an increase in cigarette use during the past 4 birth cohorts, with subsequent leveling off at a population level with a progressively more prominent increase in cigarette use among women in the United States.

CONCLUSION

We present one possible factor that may be contributing to the epidemic of childhood asthma. We hypothesize that (1) there has been a marked increase in smoking during the past century, (2) this increase in smoking has resulted in a substantial increase in exposure to environmental tobacco smoke among children, and (3) increased exposure to environmental tobacco smoke has contributed to the increase in childhood asthma. Data on trends in cigarette use among adults and asthma prevalence among children during the past century are presented as ecological evidence in support of this hypothesis. Future studies will be needed to confirm these findings with community-level analyses in a variety of geographic regions.

Postnatal cardiopulmonary adaptations to high altitude

Postnatal cardiopulmonary adaptations to high altitude constitute a key component of any set of responses developed to face high altitude hypoxia. Such responses are required ultimately to meet the energy demands necessary for adequate functioning at cell and organism level. After a brief insight on general and cardiopulmonary comparative studies in growing and adult organisms, differences and possible explanations for varying cardiopulmonary pathology, pulmonary artery hypertension, persistent right ventricular predominance and subacute high altitude pulmonary hypertension in different populations of children living at high altitude are discussed. Potential long-term implications of early chronic hypoxic exposure on later diseases are also presented. It is hoped that this review will help the practicing physician working at high altitude to make informed decisions concerning individual pediatric patients, specifically with regard to diagnosis and management of altitude-related cardiopulmonary pathology. Finally, plausibility and the knowledge-base of public health interventions to reduce the risks posed by suboptimal or inadequate postnatal cardiopulmonary responses to high altitude are discussed.

Maternal smoking in pregnancy: do the effects on innate (toll-like receptor) function have implications for subsequent allergic disease?

Subtle increases in immaturity of immune function in early infancy have been implicated in the rising susceptibility to allergic disease, particularly relative impairment of type 1 interferon (IFN)-γ responses in the neonatal period. Although genetic predisposition is a clear risk factor, the escalating rates of allergic disease in infancy suggest that environmental factors are also implicated. We previously showed that maternal smoking in pregnancy may impair neonatal IFN-γ responses. Our more recent studies now indicate that this common avoidable toxic exposure is also associated with attenuation of innate immune function, with attenuated Toll-like receptor (TLR)-mediated microbial responses (including TLR-2, -3, -4, and -9 responses). Most notably, the effects were more marked if the mothers were also allergic. In this review, we discuss the significance of these observations in the context of the emerging hypothesis that variations in TLR function in early life may be implicated in allergic propensity. There is now growing evidence that many of the key pathways involved in subsequent T-cell programming and regulation (namely, antigen-presenting cells and regulatory T cells) rely heavily on microbe-driven TLR activation for maturation and function. Factors that influence the function and activity of these innate pathways in early life may contribute to the increasing predisposition for allergic disease. Although "cleaner" environments have been implicated, here we explore the possibility that other common environmental exposures (such as maternal smoking) could also play a role.

Cough throughout life: children, adults and the senile

We review cough from premature birth, mature neonatal life, in childhood and adult life, and in old age. There is a regrettable lack of definitive studies, but many clues in the literature. The cough reflex seems weak in premature infants, but develops with maturity. It is pronounced in childhood, but there seem to be no studies comparing its strength then with that in adulthood. In old age the cough may weaken, as indicated by the prevalence of aspiration pneumonia. These changes are presumably related to the development and degeneration of the afferent and central nervous pathways for cough, which may be reflected in the changes in laryngeal muscle function with age. There is much evidence that age influences the development of the respiratory system in general, and of the immune system which would affect the degree, frequency and clinical issues of cough. Other factors that limit our understanding of the changes in cough with age include the reporting of cough by parents in infants and carers in old age and the use of different diagnostic criteria throughout life. Age-related variation in cough sensitivity seems to be well established, but its quantitation and mechanisms require much further research.

Maternal allergen exposure as a risk factor for childhood asthma

The role of early allergen exposure has been a central focus in the effort to curtail the rising rates of allergic disease. Exposures in pregnancy have been of interest because the first signs of disease are often seen in early infancy. However, so far, strategies to avoid or reduce allergen exposure in pregnancy have had disappointing results in reducing disease. Although there is growing evidence that the fetus is exposed to allergens, this appears to be physiologic and not a risk factor for allergic disease. It is still not clear if this exposure has some role in the context of normal tolerance. Although infants who later develop allergic disease show some differences in neonatal allergen-specific responses, these are not consistent. Furthermore, the magnitude and frequency of responses do not correlate well with maternal allergen exposure, and it now seems likely that these responses do not reflect true immunologic "memory." Despite this, there is accumulating evidence that a number of other exposures in pregnancy have the capacity to significantly influence immune development and alter the risk for allergic responses to allergens. This underscores the importance of further defining the events in this early period, to determine causal pathways and better strategies for prevention.

Breastfeeding does not increase the risk of asthma at 14 years

OBJECTIVES

There are conflicting data regarding the impact of breastfeeding on the development of asthma in late childhood. Our aim with this study was to investigate the relationship between breastfeeding and the prevalence of asthma in children at 14 years.

METHODS

The Mater-University of Queensland Study of Pregnancy is a birth cohort of 7223 women and their infants recruited from a public antenatal clinic in Brisbane, Australia, between 1981 and 1984. Data regarding breastfeeding and the duration of breastfeeding were collected through the use of a questionnaire completed by the mother 6 months postdelivery, and the prevalence of asthma was determined through the use of a questionnaire completed by the mother 14 years postdelivery.

RESULTS

Data regarding both breastfeeding and asthma were available for 4964 children. The prevalence of asthma in children at 14 years was 28.4%. Breastfeeding for > or =4 months was not found to have a significant effect on the prevalence of asthma in 14-year-olds. The unadjusted odds ratio of developing asthma at 14 years if the child was breastfed for > or =4 months was 1.03. The odds ratio of developing asthma did not change appreciably when allowance was made for potential confounding factors.

CONCLUSION

Data from this study indicate that breastfeeding neither increases nor decreases the prevalence of asthma in children at 14 years.

Parental smoking and childhood asthma: clinical implications

Environmental tobacco smoke and constituents are global risks for human health. Considerable evidence shows that environmental tobacco smoke exposure contributes to, and exacerbates, respiratory disorders. This review assesses the causal role of environmental tobacco smoke exposure for childhood respiratory disorders, and in particular asthma. Tobacco smoke and environmental tobacco smoke exposure during pregnancy have an effect upon lung function in newborn infants; exposure after birth also has an effect upon lung function. An effect upon bronchial responsiveness has been suggested but the evidence is not as strong as for lung function. From 1997 to 1999 a comprehensive set of systematic reviews concerning the relationship between exposure to environmental tobacco smoke and respiratory health in children summarized the results from hundreds of published papers. The evidence for a causal relationship between environmental tobacco smoke exposure and asthmatic symptoms on the one hand, and between environmental tobacco smoke exposure and reduction in lung function on the other hand, was quite strong, whereas the evidence between environmental tobacco smoke exposure and development of allergy was much weaker. Here we present an overview of the effects of environmental tobacco smoke exposure on lung health in children. A hypothesis has been put forward regarding upregulation of pulmonary neuroendocrine cells in relationship to mechanisms of tobacco smoke products (TSP)-induced pulmonary disease. It has also been reported that genetic variation makes part of the population especially vulnerable to environmental tobacco smoke exposure during pregnancy. Furthermore, there is a need for intervention to reduce environmental tobacco smoke exposure in young children, by educating parents and adolescents about the health effects of environmental tobacco smoke exposure. Studies are needed to identify possible critical periods when environmental tobacco smoke exposure is more likely to induce harmful effects on lung health in young children in order to implement effective preventive strategies.

Cough: are children really different to adults?

Worldwide paediatricians advocate that children should be managed differently from adults. In this article, similarities and differences between children and adults related to cough are presented. Physiologically, the cough pathway is closely linked to the control of breathing (the central respiratory pattern generator). As respiratory control and associated reflexes undergo a maturation process, it is expected that the cough would likewise undergo developmental stages as well. Clinically, the 'big three' causes of chronic cough in adults (asthma, post-nasal drip and gastroesophageal reflux) are far less common causes of chronic cough in children. This has been repeatedly shown by different groups in both clinical and epidemiological studies. Therapeutically, some medications used empirically for cough in adults have little role in paediatrics. For example, anti-histamines (in particular H1 antagonists) recommended as a front-line empirical treatment of chronic cough in adults have no effect in paediatric cough. Instead it is associated with adverse reactions and toxicity. Similarly, codeine and its derivatives used widely for cough in adults are not efficacious in children and are contraindicated in young children. Corticosteroids, the other front-line empirical therapy recommended for adults, are also minimally (if at all) efficacious for treating non-specific cough in children. In summary, current data support that management guidelines for paediatric cough should be different to those in adults as the aetiological factors and treatment in children significantly differ to those in adults.

Development of lung function in early life: influence of birth weight in infants of nonsmokers

This study aimed to compare lung growth and development during the first year of life in healthy term infants of low or appropriate birth weight for gestation. Paired measurements of forced expiratory volume in 0.4 second, FVC, and forced expiratory flow when 75% of FVC has been exhaled were obtained, using the raised volume technique, at about 7 weeks and 9 months of age in 80 infants (32 low and 48 appropriate birth weight for gestation) of white, nonsmoking mothers. Forced flows and volumes increased with growth. Longitudinal trends in results were compared between the two groups, using random effects modeling and adjusted for potential confounding factors. After adjustment for sex, age, and length, forced expiratory volume was significantly reduced by an average (95% confidence interval) of 9% (2 to 16%) in low birth weight compared with appropriate birth weight for gestation infants throughout the first year of life, with a similar trend in forced expiratory flow (8% [-2 to 17%]) and FVC (4% [-3 to 11%]). These findings suggest that lung function is reduced in low birth weight for gestation infants born to nonsmoking white mothers and that this is independent of somatic growth during infancy.

The effect of parental smoking on lung function and development during infancy

While the adverse effects of parental smoking on respiratory health during childhood are well recognized, its potential impact on early lung development is less clear. This review summarizes current evidence on the effect of parental smoking on lung function during infancy. It is difficult to separate the effects of pre- and postnatal exposure, since the majority of mothers who smoke in pregnancy (currently around 30% worldwide) continue to do so thereafter. Nevertheless, measurements undertaken prior to any postnatal exposure have consistently demonstrated significant changes in tidal flow patterns in infants whose mothers smoked in pregnancy. While there is, as yet, no convincing evidence from studies in human infants that smoking during pregnancy is associated with increased airway responsiveness at birth, many studies have demonstrated a reduction in forced expiratory flows (on average by 20%) in infants exposed to parental smoking. While maternal smoking during pregnancy remains the most significant source of such exposure and is likely to be responsible for diminished airway function in early life, continuing postnatal tobacco smoke exposure will increase the risk of respiratory infections, the combination of both being responsible for the two- to fourfold increased risk of wheezing illnesses observed during the first year of life in infants whose parents smoke. These findings emphasize the need to keep infants in a smoke-free environment both before and after birth, not least because of growing awareness that airway function in later life is largely determined by that during foetal development and early infancy.

Adverse health effects of prenatal and postnatal tobacco smoke exposure on children

Parents who choose to smoke are possibly not aware of, or deny, the negative effects of passive smoking on their offspring. This review summarises a wide range of effects of passive smoking on mortality and morbidity in children. It offers paediatricians, obstetricians, specialists in preventive child health care, general practitioners, and midwives an approach to promote smoking cessation in smoking parents before, during, and after pregnancy.

Effects of childhood respiratory diseases on the anatomical and functional development of the respiratory system

The anatomical and functional development of the lung appears especially vulnerable to a whole range of insults during gestation and the first few years of life. A significant proportion of adult lung disease originates in utero or early infancy. Most publications on this topic are descriptive retrospective studies. An important limitation of these is that structural changes may precede abnormalities in lung function and development of symptoms. Little is known with certainty with respect to the long-term effects of early insults to the respiratory system. Furthermore, the reversibility of the functional and/or structural defects is hardly ever adequately investigated and it is probably not correct to extrapolate findings from adult studies to paediatric pulmonary diseases. Promoting or facilitating optimal lung growth in fetuses and infants and reducing the incidence of lower respiratory tract infection in infancy may reduce the incidence of adult chronic lung disease in generations to come.

Altered arousal response in infants exposed to cigarette smoke

AIMS

A failure of the arousal mechanism is a key feature in the apnoea theory for sudden infant death syndrome (SIDS). In infants studied at an age when the incidence of SIDS is highest, we evaluated whether in utero smoke exposed infants have altered arousal response to standardised auditory stimuli, and/or sleep pattern, as recorded on overnight complex sleep polysomnography.

METHODS

A standardised sequence of audiology stimuli was applied binaurally to 20 in utero smoke and non-smoke exposed infants aged 8-12 weeks during a rapid eye movement (REM) and NREM epoch, in a controlled (temperature, position, pacifier use, noise) sleep environment. Infants were monitored for 10-12 hours using complex sleep polysomnography.

RESULTS

Five infants exposed to in utero tobacco smoke did not have behavioural arousal response, whereas all non-smoke exposed infants aroused during NREM (p = 0.016). There was, however, no difference in REM sleep, and the groups did not differ in routine overnight complex sleep polysomnography parameters.

CONCLUSION

At the age when the incidence of SIDS is at its peak, infants of smoking mothers are less rousable than those of non-smoking mothers in NREM sleep; this may partly explain why such infants are more at risk of SIDS.