Lung function in children of low birth weight

Length at birth and effect of prenatal and postnatal factors on early wheezing phenotypes. Kraków epidemiologic cohort study

The main goal of the study was to assess the pattern of risk factors having an impact on the onset of early wheezing phenotypes in the birth cohort of 468 two-year-olds. A secondary objective was to investigate a possible association between early persistent wheezing and infant's length at birth. Approximately one third of the children in the study sample experienced wheezing in the first two years of life, and in about two third of cases (67%), the symptom developed within the first year of life. The early wheezing was easily reversible and in about 70% of the affected infants, the symptom receded in the second year of life. The adjusted relative risk ratio (RRR) of persistent wheezing increased with maternal atopy (RRR = 3.13; 95% CI: 1.35-7.27), house dampness (RRR = 3.94; 95% CI: 1.26-12.3), parity (RRR = 2.56; 95% CI: 1.51-4.32) and prenatal ETS exposure (RRR = 1.13; 95% CI: 1.05-1.22), but was inversely associated with the infant's length at birth (RRR = 0.87; 95% CI: 0.76-0.99). The data support the hypothesis that wheezing phenotypes in early childhood and possibly later in life may already be programmed in the prenatal and early postnatal period when the respiratory system is completing its growth and maturation.

Reduced exercise capacity in children born very preterm

OBJECTIVE

In the past 20 years, there has been an increase in survivors of very preterm birth, but little is known regarding their long-term respiratory and fitness outcomes. We aimed to assess the 10-year lung function and fitness outcomes for children who were born weighing <1000 g and before 32 weeks' gestation in 1992-1994.

METHODS

A cross-sectional study was conducted of 126 children (mean age: 10 years) who were born at a mean gestation of 27 weeks and 34 term-born control subjects. Extensive lung function (spirometry, lung volumes, and gas exchange) and fitness (6-minute walk and 20-m shuttle run tests) assessments were conducted at a single visit according to previously validated techniques.

RESULTS

The preterm group had significantly lower values for all measured spirometric parameters compared with the control group. In contrast to airflow, the preterm group had significantly higher percentage predicted values in all standard lung-volume parameters and transfer factor than the control group. The exercise capacity of the preterm group was approximately half that of the control group. There was no significant difference in the distance walked in the 6-minute walk test.

CONCLUSIONS

In the largest cohort of school-aged children (born very preterm in the 1990s) to undergo extensive lung function and fitness assessments, we demonstrated significant impairment in exercise capacity despite evidence of only mild small-airway obstruction and gas trapping. Additional studies are required to evaluate the cause of this exercise limitation and whether it can be improved with a training program.

Longitudinal evaluation of airway function 21 years after preterm birth

RATIONALE

There are limited longitudinal data about respiratory morbidity and lung function after preterm birth into adulthood.

OBJECTIVES

To determine the evolution of respiratory symptoms, spirometry, and airway hyperresponsiveness of ex-preterm subjects from childhood into adulthood.

METHODS

Ex-preterm subjects (median birth weight, 1,440 g; median gestation, 31.5 wk), recruited at birth (not treated with surfactant), had excess respiratory symptoms, airway obstruction, and increased airway hyperresponsiveness in mid-childhood. At a median age of 21.7 years, 60 of these subjects (the index study group) and 50 healthy term control subjects were recruited to determine respiratory morbidity and spirometry.

MEASUREMENTS AND MAIN RESULTS

Respiratory symptom questionnaire, spirometry, and methacholine challenge test. The index study group had significantly more respiratory symptoms (16 of 60) than did control subjects (4 of 50) (odds ratio, 4.2; 95% confidence interval, 1.3 to 13.5; P = 0.01), but no significant difference in measured spirometry. Specifically, in the index study group and control subjects, the mean z scores (95% confidence interval of the group difference) for the FEV(1) were -0.60 and -0.58 (-0.44 to 0.49), respectively (P = 0.92); for the forced mid-expiratory flow they were -1.02 and -0.86 (-0.33 to 0.64), respectively (P = 0.52); and for the FVC they were -0.29 and -0.33 (-0.46 to 0.38), respectively (P = 0.85). Ex-preterm adults did not show evidence of increased airway hyperresponsiveness compared with control subjects, 23 and 19%, respectively (P = 0.89).

CONCLUSIONS

There are still excess respiratory symptoms 21 years after preterm birth. Reassuringly, this longitudinal study did not show evidence of persistent airway obstruction or airway hyperresponsiveness in ex-preterm adults.

Growth rate of lung function in healthy preterm infants

RATIONALE

It remains unclear whether premature birth, in the absence of neonatal respiratory disease, results in abnormal growth and development of the lung. We previously reported that a group of healthy infants born at 32-34 weeks' gestation and without respiratory complications had decreased forced expiratory flows and normal forced vital capacities at 2 months of age.

OBJECTIVES

Our current study evaluated whether these healthy infants born prematurely exhibited improvement or "catch-up" in their lung function during the second year of life.

METHODS

Longitudinal measurements of forced expiratory flows by the raised volume rapid thoracic compression technique were obtained in the first and the second years of life for infants born prematurely at 32.7 (range, 30-34) weeks' gestation (n = 26) and infants born at full term (n = 24).

MEASUREMENTS AND MAIN RESULTS

Healthy infants born prematurely demonstrate decreased forced expiratory flows and normal forced vital capacities in the first and second years of life. In addition, the increases in lung function with growth were similar to full-term infants.

CONCLUSIONS

Persistently reduced flows in the presence of normal forced vital capacity and the absence of catch-up growth in airway function suggest that premature birth is associated with altered lung development.

Pulmonary testing using peak flow meters of very low birth weight children born in the perisurfactant era and school controls at age 10 years

We determined lung function at age 10 years in very low birthweight (VLBW, <or=1,500 g) children and controls, and compared the sensitivity to detect subgroup differences by peak expiratory flow (PEF), forced expiratory volume in one second (FEV(1)), forced vital capacity (FVC) and their diurnal variation. VLBW children were recruited across the perisurfactant era at admission to six NICUs in Wisconsin and Iowa, and controls from area classrooms. Two hundred sixty five VLBW children and 360 controls were tested by the Jaeger AM1 peak flow meter at age 10 years. Two hundred six VLBW and 79 controls had additional home monitoring. Abnormality was defined as observed/predicted ratio <0.8 for PEF, FEV(1), and FVC, and by criteria of Pelkonen for diurnal PEF variation. VLBW children were compared to controls, VLBW children with bronchopulmonary dysplasia (BPD) to those without, and those with respiratory conditions to those without. PEF and FEV(1) showed high reproducibility (intraclass correlations, ICC 0.75-0.83). Controls and VLBW children with and without BPD differed significantly on all measures. Baseline test results did not differ across birth years, but PEF variation was less after surfactant availability (P = 0.04). Observed over predicted FEV(1) was the most sensitive in detecting differences between groups (P < 0.001), with mean (s.d.) 0.97 (0.12) for controls, 0.88 (0.14) for VLBW children without BPD, and 0.78 (0.13) for those with BPD. Odds ratios for abnormality were especially high with respiratory medication use during the first 5 years of life, 4.4 (95% CI: 2.0-9.8) for FEV(1) and 5.1 (95% CI: 2.0-13.2) for diurnal PEF variation. Our results show that respiratory abnormalities persist to at least age 10 years for VLBW children born in the surfactant era.

Palivizumab prophylaxis, respiratory syncytial virus, and subsequent recurrent wheezing

OBJECTIVE

Children who experience respiratory syncytial virus (RSV) lower respiratory tract infections (LRTIs) early in life have high rates of subsequent recurrent wheezing. Palivizumab, an anti-RSV monoclonal antibody, has 78% to 80% efficacy in preventing RSV hospitalization in premature infants without chronic lung disease. We hypothesized that palivizumab, by ameliorating or preventing early RSV LRTI in preterm infants, might decrease later recurrent wheezing.

STUDY DESIGN

A cohort of preterm infants who had received palivizumab and were not hospitalized for RSV (n = 191) or who never received palivizumab (n = 230; 76 who were hospitalized for RSV and 154 who were not), were prospectively followed for 24 months beginning at a mean age of 19 months. The subjects were assessed for recurrent wheezing by caretaker or physician report.

RESULTS

The incidences of recurrent wheezing and physician-diagnosed recurrent wheezing were significantly lower in the 191 palivizumab-treated subjects (13% and 8%, respectively) compared with all 230 untreated subjects (26%, P = .001 and 16%, P = .011, respectively) and with the 154 patients in the subgroup not hospitalized for RSV LRTI (23%, P = .022 and 16%, P = .027, respectively). The effect of palivizumab treatment remained significant after adjustment for potential confounding variables.

CONCLUSIONS

Our study suggests that preventing RSV LRTI with palivizumab may reduce subsequent recurrent wheezing in premature infants.

Early growth and adult respiratory function in men and women followed from the fetal period to adulthood

BACKGROUND

While some studies suggest that poor fetal growth rate, as indicated by lower birth weight, is associated with poor respiratory function in childhood, findings among adults remain inconsistent. A study was undertaken to determine the association between early growth and adult respiratory function.

METHODS

A longitudinal birth cohort study was performed of 5390 men and women born full term and prospectively followed from the fetal period to adulthood. Weight at birth and infancy were recorded, and forced expiratory volume in 1 s (FEV(1)) and forced vital capacity (FVC) were assessed by standard spirometry at age 31 years.

RESULTS

Adult FEV(1) and FVC increased linearly with higher birth weight in both men and women with no apparent threshold. After adjustment for sex, adult height and other potential confounders operating through the life course, every 500 g higher birth weight was associated with a higher FEV(1) of 53.1 ml (95% CI 38.4 to 67.7) and higher FVC of 52.5 ml (95% CI 35.5 to 69.4). These positive associations persisted across categories of smoking, physical activity and body mass index, with the lowest respiratory function noted among those with lower birth weight who were smokers, led a sedentary lifestyle or were overweight. Weight gain in infancy was also positively associated with adult lung function.

CONCLUSION

Birth weight is continuously and independently associated with adult respiratory function. It is plausible that poor growth in early life may restrict normal lung growth and development, which could have long-term consequences on lung function later in life.

Respiratory function at age 8-9 years in extremely low birthweight/very preterm children born in Victoria in 1991-1992

Our aim was to determine respiratory function at 8 years of age in extremely low birth weight (ELBW; birth weight, < 1,000 g)/very preterm (< 28 weeks of gestation) children born in the 1990s compared with normal birth weight (NBW; birth weight, >2,499 g) controls. The ELBW/very preterm subjects comprised 298 consecutive survivors with either birth weight < 1,000 g or gestational age < 28 weeks born in the state of Victoria during 1991-1992. Controls comprised 262 randomly selected NBW survivors. Respiratory function was measured on 81% (240/298) of the ELBW/very preterm children and 79% (208/262) of the NBW controls. Respiratory function variables reflecting airflow were substantially diminished in ELBW/very preterm children compared with NBW controls. Moreover, the proportions with clinically important reductions in airflow were higher in the ELBW/very preterm group (e.g., forced expired volume in 1 sec, < 75%; ELBW/very preterm, 19.7%; NBW, 2.4%; P < 0.0001). Within the ELBW/very preterm group, children who had bronchopulmonary dysplasia (BPD) in the newborn period and those who had later asthma had significantly reduced respiratory function in variables reflecting airflow. In conclusion, the abnormalities in respiratory function in ELBW/very preterm children compared with NBW subjects described in the presurfactant era persisted in the 1990s, especially in those who had BPD in the newborn period.

Airway function measurements and the long-term follow-up of survivors of preterm birth with and without chronic lung disease

This seventh paper in a review series on different aspects of chronic lung disease following preterm birth focuses on the current knowledge of respiratory symptoms, airway function, airway hyperresponsiveness, and exercise capacity from childhood to adulthood. This paper further considers the long-term implications of these studies for both future research and clinical practice.

Reduced lung function in healthy preterm infants in the first months of life

RATIONALE

Preterm delivery has been associated with a higher incidence of respiratory morbidity even in infants that do not have significant respiratory disease during the neonatal period. Reduced flows have been reported in children and adolescents born prematurely.

OBJECTIVE

The aim of this study was to assess lung function in healthy preterm infants in the first months of life.

METHODS

Preterm infants with less than 48 h of supplemental oxygen were recruited. Lung function was assessed by the raised-volume rapid thoracic compression in the first months of life. The control group consisted of full-term infants without a history of respiratory diseases.

MEASUREMENTS AND MAIN RESULTS

Sixty-two preterm (29 male) and 27 full-term (10 male) infants were tested. Adjusting for length, age, and sex, we found a mean significant reduction of 92 ml/s (22%) in FEF(50), 73 ml/s (21%) in FEF(25-75), and 19 ml (28%) in FEV(0.5) in the preterm group. These differences in expiratory flows remained significant using another model that adjusts for lung volume (p < 0.01 for FEF(50), FEF(25-75), and FEV(0.5), and p < 0.05 for FEF(75)). In the preterm group, after adjusting for length, male sex, lower gestational age, and increased weight were significantly and independently associated with reduced flows.

CONCLUSIONS

Our findings confirm that prematurity is independently associated with reduced lung function and that this is detectable in the first months of life. Male sex, lower gestational age, and weight are important predictors for reduced expiratory flows in this group.

Respiratory Function in Adolescence in Relation to Low Birth Weight, Preterm Delivery, and Intrauterine Growth Restriction

OBJECTIVES

To study the associations between respiratory function in 18-year-old male subjects and birth weight, preterm delivery, and intrauterine growth restriction (IUGR).

METHODS

Population-based birth cohort. Subsamples of 118 male subjects with low birth weight (LBW) [< 2,500 g] and 236 male subjects with normal birth weight were examined at the age of 18 years.

RESULTS

In the crude analysis, subjects with LBW showed reductions in FEV1 and FVC of 0.166 L and 0.141 L, respectively, compared to those born weighing > or = 2,500 g. These differences were not significant after adjustment for confounding. When subjects with LBW were stratified into those with preterm delivery and those with IUGR, the latter presented a significant reduction in both FEV1 and FVC, when compared to the reference group. These differences also disappeared after adjustment for confounders. Preterm delivery per se was also not associated with poor lung function.

CONCLUSIONS

In this population, LBW was not associated with respiratory function in 18-year-old male subjects.

Characteristics of asthma and airway hyper-responsiveness after premature birth

Asthma-like symptoms and airway hyper-responsiveness (AHR) are frequently reported in children subsequent to premature birth and bronchopulmonary dysplasia (BPD). There is limited knowledge on the mechanisms underlying these respiratory manifestations. Generally, childhood asthma and AHR is described within a context of inheritance, allergy and eosinophilic airway inflammation, and often in relation to cigarette exposures. We investigated these factors in relation to current asthma and AHR in a population-based cohort of 81 young people, born with gestational age < or = 28 wk or birth weight < or = 1000 g, and in a matched term-born control population. In the pre-term population, asthma and AHR were additionally studied in relation to neonatal respiratory morbidity. At follow up, more pre-term than control subjects had asthma. Forced expiratory volume in first second (FEV1) was reduced, AHR was substantially increased, and the level of the urinary leukotriene metabolite E4 (U-LTE4) was increased in the pre-term population compared to the term-born. In control subjects, asthma and AHR was associated with a pattern consistent with inheritance, allergy, airway inflammation, and cigarette exposures. In the pre-terms, asthma and AHR was either unrelated or less related to these factors. Instead, AHR was strongly related to a neonatal history of BPD and prolonged requirement for oxygen treatment. In conclusion, asthma and AHR subsequent to extremely premature birth differed from typical childhood asthma with respect to important features, and AHR was best explained by neonatal variables. These respiratory manifestations thus seem to represent a separate clinical entity.

Effect of indoor air quality in the postnatal period on lung function in pre-adolescent children: a retrospective cohort study in Poland

The purpose of this study was to determine the association between level of lung function in pre-adolescence and indoor air quality in the postnatal period. The retrospective cohort study was carried out in a sample of 1036 pre-adolescent children (9 years of age) attending schools in two residential areas of Krakow, Poland. Measurement of health outcomes considered lung function together with height and weight. Indoor air quality was based on environmental tobacco smoke and type of household heating. In addition, the number of winter months that occurred during the first 6 months of life was included as a key independent variable. Multivariate linear regression of lung function measured by forced expiratory volume in 1s (FEV1) and forced vital capacity (FVC), and postnatal exposure to indoor pollution in the heating season (PEIP score) was adjusted for potential confounders such as maternal smoking during pregnancy and parental education as a proxy of social class. In the total study sample, the adjusted beta coefficient for FEV1 per unit of the PEIP score was -0.06 (P=0.02), while that for FVC was -0.05 (P=0.04). The analysis carried out in the more polluted area found that children living in households heated with gas or coal had a PEIP score that was strongly inversely related to lung function (adjusted beta coefficient for FEV1=-0.13; P=0.03; for FVC=-0.15, P=0.01), whereas regression coefficients were not significant in the group of children living in households with central heating. This study suggests that a lower level of lung function in pre-adolescent children can be related to postnatal exposure to indoor emissions in the winter.

Influence of socioeconomic status on lung function and prediction equations in Indian children

The present study was carried out to assess the influence of socioeconomic status on lung functions and to suggest prediction equations for Indian children. For this purpose, 2,616 normal, healthy schoolchildren aged between 5-15 years were recruited. Boys were classified into three groups, i.e., high-income (HIG), middle-income (MIG), and low-income (LIG), while girls were classified into HIG and LIG groups, based on socioeconomic status (SES). Height, weight, chest circumference, body surface area (BSA), fat-free mass (FFM), and body fat were assessed. Forced expiratory volume in 1 sec (FEV1), forced vital capacity (FVC), FEV1/FVC ratio, and peak expiratory flow rate (PEFR) were measured. The results, before and after adjustment of physical characteristics, showed that anthropometry, body composition, and lung functions were significantly higher in HIG compared to MIG and LIG children, while in girls, no differences were observed in physical characteristics after adjustments. Multiple linear regression equations were developed to predict FEV1, FVC, and PEFR, using independent variables like age, height, fat-free mass, and SES. It is opined that these equations could be used as Indian reference equations for healthy children based on the SES.

Asthma research: the real action is in children

Many adult diseases have their roots in infancy or even prenatally. If events that initiate these diseases, as opposed to those that propagate the disease state, are to be understood, then the difficult area of how ethically to research problems in infancy must be tackled. Furthermore, the predisposition to archetypally 'pure' adult problems such as chronic obstructive pulmonary disease, may lie antenatally, the effects being masked until the lung starts to age. An additional factor is that the success of paediatricians, for example in ensuring the survival of extremely premature, low birth weight infants leads to adult survivors with potentially a whole new morbidity. The first prerequisite to making progress is a sound understanding of the development of the normal lung and how adverse environmental and genetic influences, such as exposure to environmental tobacco smoke and maternal atopy, respectively, may affect growth. This paper focuses on three key areas: the implications of different pre-school wheezing phenotypes for adult disease; the importance of very early life events in cystic fibrosis; and the long term consequences of chronic lung disease of prematurity. Finally, the ethical principles that must underpin future research in pre-school children is discussed, as well as the means we might use to further our understanding of the relevant early disease processes.

Radiology of diffuse interstitial pulmonary disease in children

Diffuse interstitial lung disease (DILD) represents a heterogeneous group of disorders characterised by restrictive lung function and impaired gas exchange. As these diseases occur on a background of the developing lungs and immune system, the clinical presentation and disease progression is modified by comparison with their adult equivalents; thus, often differs markedly in presentation, clinical features and progress from ILD in adults, and it is not safe to extrapolate from adults to children. It is important to understand the normal growth and development of the lungs in children to understand the development of interstitial lung disease. As the chest radiograph is often non-specific, HRCT has been shown in adults and children to increase the accuracy at diagnosis of diffuse lung disease. The trade-off in sensitivity and specificity of HRCT over chest X-ray is related to radiation dose which is significantly higher with conventional spiral or volumetric CT; however, the use of low-dose (50 mA, 0.75 s) limited (1-mm slices every 15-20 mm) HRCT in inspiration with three expiratory supplementary scans allows accurate assessment of the presence and extent of diffuse lung disease at a dose equivalent to approximately ten chest radiographs. Images are reconstructed on a high spatial resolution algorithm and displayed with a wide window setting, at a width of 1500 Hounsfield units (HU) and at a level of -500 HU.

Some chronic obstructive pulmonary disease will originate in neonatal intensive care units

Chronic lung disease is the most common adverse outcome in survivors of prematurity. These infants experience frequent hospitalisation because of respiratory-related illness in their first year, as well as persistent cough, wheeze and oxygen dependence. Although the severity of respiratory illness decreases and supplemental oxygen is needed less as their lungs mature, childhood is still complicated by persistent wheeze, cough and reduced exercise tolerance in comparison with their peers. Although there is little longitudinal follow-up data beyond adolescence, imaging studies suggest that these infants are highly likely to suffer with respiratory problems akin to chronic obstructive pulmonary disease in later adulthood. The nature of their long-term respiratory problems, the impact of cigarette smoking and the effect on life expectancy are all unanswered questions that need addressing as these infants grow up.

COPD: can prevention be improved? Proposal for an integrated intervention strategy

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a worldwide public health problem with increasing morbidity and mortality. The aim of this proposal is to contribute to the improvement of COPD prevention by identifying groups at risk for COPD and targeting them for preventive interventions.

METHODS

Based on the existing organizational structures for COPD detection, detailed analysis of the determinants of COPD will allow to identify groups at high risk to develop COPD. The Stepwise Target Group-Oriented Prevention (STOP) model developed during this study proposes an integrated identification and intervention strategy for high-risk groups.

RESULTS

Apart from smoking, other environmental determinants and host factors contribute to further lung function's rapid decline. Combined with smoking, these factors increase the risk for COPD. Target groups for early disease detection and appropriate interventions can be identified by the presence of one or more known risk factors and by identification of high-risk groups.

CONCLUSION

The Stepwise Target Group-Oriented Prevention (STOP) strategy is a step toward improvement in COPD prevention, by shifting the focus from the group of a focus symptomatic smokers aged 45+ years to much earlier and preventable stages of the disease, that is, from disease treatment to risk management.

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.

Respiratory symptoms and lung function in relation to atopy in children born preterm

Respiratory morbidity is a major health problem among children. The aim of this study was to compare the background of respiratory problems of children born preterm with that of children born full-term, with special reference to atopy. The study comprised two cohorts of 10-year-old children: a group of 72 children born preterm with birth weights of less than 1,501 g, and a group of 65 children born full-term with birth weights of over 2,500 g. Histories of respiratory and atopic symptoms, and of risk factors for atopy, were collected with a questionnaire. Predisposition to atopy was verified by skin-prick testing and by measuring serum total and antigen-specific IgEs. Lung function was evaluated by spirometry testing. Children born preterm had significantly more wheezing. In them, the lifetime prevalence of wheezing was 43%, vs. 17% in children born full-term (P = 0.001; odds ratio, 3.71; 95% confidence interval, 1.67-8.25). In the full-term group, wheezing was associated with atopy: 64% of wheezers were atopic; in the preterm group, 23% of wheezers were atopic (difference between groups, P = 0.024). Children born preterm expired significantly lower spirometry values of forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1), FEV1/FVC ratio, forced expiratory flow after 50% of vital capacity has been exhaled (FEF50), and forced expiratory flow during middle half of FVC (FEF25-75). In the preterm group, wheezing, asthma, and low gestational age, but not atopy, were significantly associated with lower lung function values. Wheezers of the preterm group who still wheezed at age 10 were significantly more often atopic than those who no longer wheezed (62% vs. 9%, P = 0.006). In conclusion, we demonstrated a significant difference between groups in the association of atopy with respiratory problems. However, although atopy was not associated with a lifetime prevalence of respiratory symptoms in prematurely born children, an atopic predisposition in them was found to associate with persistence of wheezing.

Low birth weight for gestation and airway function in infancy: exploring the fetal origins hypothesis

BACKGROUND

Poor fetal growth has been associated with impaired airway function in adult life, but evidence linking birth weight and airway function in early childhood is sparse. We examined the hypothesis that low birth weight for gestation is associated with impaired airway function shortly after birth and that this is independent of impaired postnatal somatic growth.

METHODS

Airway function was measured using the raised volume technique in healthy white infants of low (< or =10th centile) or appropriate (> or =20th centile) birth weight for gestation and was expressed as forced expiratory volume in 0.4 s (FEV0.4), forced vital capacity (FVC), and the maximal expired flow at 25% of forced vital capacity (MEF25). Infant length and weight, maternal height and weight, maternal report of smoking prenatally and postnatally, and parental occupation were recorded.

RESULTS

Mothers of low birth weight for gestation infants (n=98) were lighter, shorter, and more likely to smoke and have partners in manual occupations. At 6 weeks their infants remained lighter and shorter than those of appropriate birth weight (n=136). FEV0.4, FVC, and MEF25 were reduced in infants of low birth weight for gestation, in those whose mothers smoked in pregnancy, or who were in manual occupations. After adjusting for relevant maternal and infant characteristics, infants in the low birth weight for gestation group experienced a mean reduction of 11 ml in FEV0.4 (95% CI 4 to 18; p=0.002), of 12 ml in FVC (95% CI 4 to 19; p=0.004), and of 28 ml/s in MEF25 (95% CI 7 to 48; p=0.03).

CONCLUSIONS

Airway function is diminished in early postnatal life as a consequence of a complex causal pathway which includes social disadvantage as indicated by maternal social class, smoking and height, birth weight as a proximal and related consequence of these factors, and genetic predisposition to asthma. Further work is needed to establish the relevance of these findings to subsequent airway growth and development in later infancy and early childhood.

Adverse effects of smoking on respiratory function in young adults born weighing less than 1000 grams

OBJECTIVE

To determine whether active smoking has an adverse impact on respiratory function of young adults of extremely low birth weight (ELBW; birth weight <1000 g).

METHODS

This was a cohort study of 60 consecutive ELBW survivors who were born during 1977-1980 at Royal Women's Hospital, Melbourne, Australia. Respiratory function was measured on 44 (73%) of the subjects at a mean age of 20.2 years (standard deviation: 1.0 year). Respiratory function had also been measured on 42 of the 44 subjects at 8 years of age. Respiratory function was compared between the 14 smokers and the 30 nonsmokers.

RESULTS

Several respiratory function variables reflecting airflow (the forced expired volume in 1 second [FEV(1)]/forced vital capacity [FVC] ratio; flow rates at 75%, 50%, and 25% of vital capacity; and mid-expiratory flow from 25% to 75% of vital capacity) were significantly diminished in smokers. The proportion with a clinically important reduction in the FEV(1)/FVC ratio (<75%) was significantly higher in smokers (64%) than in nonsmokers (20%). There was a significantly larger decrease in the FEV(1)/FVC ratio between ages 8 and 20 years in the smokers (mean change: -8.2%; 95% confidence interval: -14.1% to -2.4%)

CONCLUSIONS

Active smoking by young adult survivors of ELBW is associated with reduced respiratory function.

Lung function and respiratory health in adolescents of very low birth weight

AIMS

To determine if very low birth weight (VLBW; birth weight <1500 g) is associated with reduced lung function and respiratory health in adolescence and, if it is, whether this impairment is associated with prematurity or intrauterine growth restriction.

METHODS

A geographically defined cohort of 128 VLBW infants and an age, sex, and school matched comparison group born in 1980/81 were studied. The cohort and comparison group were assessed at 15 years of age. The birth weight ratio of the index cases (observed birth weight/expected birth weight for the gestation) was determined to assess the degree of growth restriction. Respiratory support received during the neonatal period was obtained from hospital records. Smoking habits and respiratory morbidity were obtained through questionnaires. Forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), and forced expiratory flow when 25-75% of FVC is expired (FEF(25-75%)) were measured using a portable spirometer. The values are expressed as percentage predicted for height, age, and gender using standard reference values. Adjustments were made for smoking habits of mother and children.

RESULTS

The differences in means between index and comparison groups for FEF(25-75%) (-12.42%; p < 0.001) and FEV1/FVC (-3.53%; p < 0.001) ratio were statistically significant. The differences in FVC and FEV1 were not significant. No correlation was found between the birth weight ratio and lung function among the index cohort. Chronic cough, wheezing, and asthma were more common among the index cohort than in the comparison group. Within the index group, there was no difference in lung function between those who received and those who did not receive respiratory support.

CONCLUSION

Adolescents who were VLBW compared with matched controls showed medium and small airways obstruction. This was associated with prematurity rather than intrauterine growth restriction or having received respiratory support during the neonatal period. The index VLBW cohort compared with their controls were also more prone to chronic cough, wheezing, and asthma.

Development of airway function in infancy after preterm delivery

OBJECTIVE

To assess airway function at 1 year and compare this with similar measurements made shortly after birth in preterm infants without clinical neonatal respiratory disease.

STUDY DESIGN

Infants born at </=36 weeks' gestational age were eligible if they required no neonatal ventilatory support and were otherwise healthy. Paired measurements of maximal expiratory flow at functional residual capacity (V'(maxFRC)) were obtained ~3 weeks after birth in 24 preterm infants (gestational age [mean +/- SD], 33.2 +/- 2.2 weeks) and repeated at a corrected postnatal age (mean +/- SD) of 57.0 +/- 12.2 weeks. V'(maxFRC) values were expressed as Z scores by means of sex-specific prediction equations.

RESULTS

V'(maxFRC) was within normal range for all infants shortly after birth (mean +/- SD Z score: -0.06 +/- 0.92). By 1 year, Z scores had reduced significantly [mean (95% CI) 2nd-1st test: -1.94 (-2.27, -1.60)]. V'(maxFRC )Z scores at 3 weeks were highly correlated with those at 1 year of age (Spearman correlation coefficient 0.64).

CONCLUSIONS

Airway function during the first year shows considerable tracking. Even in the absence of neonatal respiratory disease, preterm delivery is associated with altered airway development during early infancy.

Pregnancy and immunology: selected aspects

LEARNING OBJECTIVES

This article reviews current concepts of the immunology of pregnancy and of the diagnosis and management of certain allergic conditions in the pregnant woman: asthma, rhinitis, immunotherapy, and hereditary angioedema (HAE).

DATA SOURCES

Current texts, reviews, and individual studies were picked from the National Library of Medicine database.

RESULTS AND CONCLUSIONS

Knowledge concerning the immunologic paradox of pregnancy continues to evolve. Although the answer is not definitive, attention is being paid to the role of a Th-2 shift in the pregnant uterus. Extensive studies, both epidemiologic and therapeutic, are clarifying the influence of pregnancy on asthma and rhinitis (and vice versa) and the best methods for treatment of these conditions in the pregnant woman. A brief guideline to the handling of hereditary angioedema in pregnancy is presented.

Influence of intrauterine growth restriction on airway development in fetal and postnatal sheep

Epidemiologic studies suggest that intrauterine growth restriction (IUGR) can lead to impaired lung function, yet little information exists on the effects of IUGR on airway development. Our objectives were to characterize morphometrically effects of IUGR on airway structure in the fetus and to determine whether alterations persist into postnatal life. We used two groups of sheep, each with appropriate controls; a fetal group was subjected to IUGR by restriction of placental function from 120 to 140 d (term approximately 147 d), and a postnatal group, killed 8 wk after birth, was subjected to IUGR from 120 d to birth at term. In both fetuses and postnatal lambs, IUGR did not alter lung weight relative to body weight. In IUGR fetuses, the luminal areas and basement membrane perimeters of the trachea and larger bronchi (generations 0-8, trachea = 0) were smaller than in controls. Airway wall areas, relative to basement membrane perimeters, were reduced in IUGR fetuses compared with controls, largely due to reduced areas of cartilage and epithelium. At 8 wk after birth, there were no significant differences in airway dimensions between IUGR and control lambs. However, the number of profiles of bronchial submucosal glands, relative to basement membrane perimeters, was lower in IUGR lambs than in controls and the area of epithelial mucin was increased. We conclude that restriction of fetal growth during late gestation impairs the growth of bronchial walls that could affect airway compliance in the immediate postnatal period. Although airway growth deficits are reversed by 8 wk, alterations in mucus elements persist.

Risk factors for severe pneumonia in children in Basrah

A case-control study was undertaken in Basrah Maternity and Children Hospital, Iraq. We studied 148 children who were admitted to hospital with severe pneumonia according to the World Health Organization (WHO) criteria and the controls were 250 children attending the out-patient department for non-severe respiratory infections. Significant risk factors were younger age (2-6 months), low parental education, smoking at home, prematurity, weaning from breast milk at < 6 months, a negative history of diphtheria, pertussis and tetanus vaccination, anaemia and malnutrition.

Genetic/environmental determinants of adult chronic obstructive pulmonary disease and possible links with childhood wheezing

Epidemiological evidence and similarities in underlying inflammatory mechanisms suggest that childhood respiratory conditions and adult onset chronic obstructive pulmonary disease (COPD) may have a common aetiology. The prevalence of COPD in the UK has been estimated to be 10% in males and 11% in females, and like asthma, is thought to have a polygenic contribution with a complex interplay between genetic and environmental factors. The only proven genetic factor so far identified in its pathogenesis is alpha1-antitrypsin deficiency, although this accounts for less than 1% of individuals with disease. Environmental exposures are significant but the observation that only 15% of smokers develop COPD and only some young children exposed in utero develop recurrent wheezing points to as yet undefined contributory genetic factors. The similarity in response to medication also suggests some features in common and a central question must be whether those adults who develop COPD had transient viral-associated wheeze (VAW) or non-specific bronchial hyperresponsiveness (BHR) in childhood? Similarities between some of the childhood wheezing syndromes and adult onset COPD invites a re-examination of possible links between the two conditions.

Prematurity at birth reduces the long-term risk of atopy

BACKGROUND

Antigen exposure in early life has long-lasting effects on atopic sensitization. Thus the predisposition to atopy of children born preterm can be assumed to differ from that of children born at term.

OBJECTIVE

The aim of this study was to evaluate the association between premature birth and atopy.

METHODS

At an outpatient clinic, we examined 2 groups of 10-year-old children, 72 who were born preterm (birth weight < 1500 g) and 65 who were born at term (birth weight > 2500 g). The atopy data were collected with a questionnaire, by performing skin prick testing, and by measuring the serum total IgE level, 3 allergen-specific IgE levels, the eosinophil cationic protein level, and the blood eosinophil level. The data on perinatal and neonatal events affecting the preterm children were collected from the hospital records.

RESULTS

By the age of 10 years, the children born preterm had significantly less atopy than the children born at term: 15% versus 31% of children in the 2 groups were defined as having had obvious atopy (P = .03, odds ratio 0.41, 95% CI 0.18-0.93). The mean value of total IgE level was significantly higher in the term group, 74 kU/L versus 41 kU/L (P = .02). By skin prick testing, the children born at term had positive reactions 2 to 3 times more often; 37% versus 17% of children in the groups had at least 1 positive reaction (P = .007).

CONCLUSION

Our data show that prematurity at birth is linked with a decreased long-term risk of atopic sensitization.

Birth weight <1501 g and respiratory health at age 14

AIMS

To determine the respiratory health in adolescence of children of birth weight <1501 g, and to compare the results with normal birthweight controls.

METHODS

Prospective cohort study of children born in the Royal Women's Hospital, Melbourne. Two cohorts of preterm children (86 consecutive survivors 500-999 g birth weight, and 124 consecutive survivors 1000-1500 g birth weight) and a control group of 60 randomly selected children >2499 g birth weight were studied. Children were assessed at 14 years of age. A paediatrician determined the clinical respiratory status. Lung function was measured according to standard guidelines.

RESULTS

Of 180 preterm children seen at age 14, 42 (23%) had bronchopulmonary dysplasia (BPD) in the newborn period. Readmission to hospital for respiratory ill health was infrequent in all groups and the rates of asthma were similar (15% in the 500-999 g birth weight group, 21% in the 1000-1500 g birth weight group, 21% in controls; 19% BPD, 18% no BPD). Overall, lung function was mostly within the normal range for all cohorts; few children had lung function abnormalities in clinically significant ranges. However, the preterm children had significantly lower values for variables reflecting flow. Lung function in children of 500-999 g birth weight was similar to children of 1000-1500 g birth weight. Preterm children with BPD had significantly lower values for variables reflecting flow than children without BPD.

CONCLUSIONS

The respiratory health of children of birth weight <1501 g at 14 years of age is comparable to that of term controls.

The prognosis of cyclical vomiting syndrome

AIMS

The medium term prognosis of cyclical vomiting syndrome (CVS) was studied to determine the proportion of affected individuals who had gone on to develop headaches fulfilling the International Headache Society criteria for migraine.

METHODS

Twenty six (76%) of 34 CVS sufferers identified from the authors' clinical records were traced, and all agreed to participate. Each child was matched to a control, and telephone interviews were conducted using a standardised questionnaire.

RESULTS

Thirteen (50%) of the subjects had continuing CVS and/or migraine headaches while the remainder were currently asymptomatic. The prevalence of past or present migraine headaches in subjects (46%) was significantly higher than in the control population (12%).

CONCLUSION

Results support the concept that CVS is closely related to migraine.

Effects of birthweight and oxygen supplementation on lung function in late childhood in children of very low birth weight

Impaired respiratory function has been found frequently in ex-premature children, but it is unclear which specific factors influence this impairment the most. The aim of this study was to determine the importance of the contributions of birth weight, gestational age, neonatal respiratory disease, and its treatment on subsequent childhood lung function at age 11 years in a cohort of children of very low birth weight (VLBW; </=1,500 g). Detailed clinical histories were recorded, and lung function was measured in 60% (102 children) of surviving VLBW infants born 1981/1982, and compared with 82 matched control children (birth weight >2,000 g) of similar age. VLBW children were shorter and lighter than controls (P < 0.0001) at 11 years of age, and had reduced expiratory flows (P < 0.00001) and forced vital capacities (P < 0.001). The residual volume to total lung capacity ratio (RV/TLC ratio) was increased (P < 0.00001), while total lung capacity (TLC) remained unchanged. Those with bronchopulmonary dysplasia (BPD) had the lowest mean expiratory flows. Males had lower expiratory flows than females. On univariate analysis, gestational age by itself accounted for 8.8% of the explained variance in FEV(1) at 11 years of age, but birth weight accounted for 16% on its own; both together accounted for a further 0.2% (16.2%), suggesting that the latter was the dominant factor. On multivariate analysis, the contribution of birth weight and gestational age was small, and the best predictors at 11 years of age, which together explained 43.4% of the total variance in FEV(1), were log days of supplemental oxygen (9.6%) and a reported history of asthma (10.8%). For FEF(25-75), these predictors explained 7.2% and 13.4%, respectively, of the total explained variance of 40.6%. The relation between neonatal oxygen supplementation and childhood FEV(1) was such that up to 20 days of supplemental oxygen had little effect on subsequent FEV(1) at 11 years of age, but each additional week of supplemental oxygen after that time was associated with a progressive reduction in FEV(1) of 3%. These data confirm the significant role of supplemental oxygen in the neonatal period and a history of asthma on the subsequent reduction of expiratory flows in VLBW children. Birth weight was a more important prenatal factor than gestational age, but both were of lesser predictive significance than either supplemental oxygen or a reported history of asthma.

Growth and respiratory health in adolescence of the extremely low-birth weight survivor

ELBW children grow poorly in early childhood, but catch up substantially in weight and height by 14 years of age. The final adult stature for ELBW children remains to be determined. Despite the need sometimes for prolonged periods of assisted ventilation and oxygen therapy, the respiratory health and lung function of ELBW children is mostly normal in adolescence. ELBW children with BPD had similar respiratory health compared with ELBW children without BPD. The effects of cigarette smoke, both passive and active, and of newer therapies, such as exogenous surfactant and postnatal corticosteroids, on respiratory health in adulthood remain to be determined.

Childhood asthma: causes, epidemiological factors and complications

Asthma is common in children and its prevalence in this age group is increasing. While the reasons for this reported increase, and indeed the true magnitude of the increase, remain unclear, there can be no doubt that asthma is now a major health problem in children worldwide. Fortunately, our knowledge of the pathophysiology of asthma is also increasing. It is now known that asthma is a chronic inflammatory disease regulated by a variety of mediators, of which perhaps the leukotrienes are among the most important. This new understanding of the pathophysiology of the disease has spurred the development of the antileukotriene agents, which can be expected to play an increasingly important role in the management of childhood asthma.

Respiratory function in survivors of the United Kingdom Extracorporeal Membrane Oxygenation Trial

Extracorporeal membrane oxygenation (ECMO) improves survival in mature neonates with reversible lung disease. However, ECMO could result in survival of infants with severe respiratory dysfunction who would otherwise have died. Alternatively, infants receiving ECMO might be spared prolonged ventilation and consequent barotrauma, resulting in improved respiratory function. Our aim was to compare respiratory function at 1 yr of age in infants assigned to receive either ECMO or conventional management (CM). Seventy-eight surviving infants of the United Kingdom (UK) ECMO trial (51 in the ECMO group) were studied at 1 yr of age. Questionnaires provided details of respiratory symptoms, and laboratory measurements of respiratory function were made for respiratory rate, tidal volume, lung volume, airway conductance, specific airway conductance, and maximal expiratory flow at FRC (Vmax (FRC)). Data were exchanged on floppy disk for cross-analysis and to ensure that investigators were blinded to the status of the infants. There was a wide spectrum of respiratory function, from normal to markedly abnormal. There were few differences between the groups, but in the CM group lung volume was increased (95% confidence intervals [CIs] of the difference in ECMO versus CM subjects: -67; -4 ml), and inspiratory specific conductance was lower (95% CI: 0.03; 0.98 s(-)(1). kPa(-)(1)). There was a trend toward a lower V max(FRC) (95% CI: -2; 67 ml/s(-)(1) in the CM group. In addition to providing a survival advantage, ECMO did not worsen lung function in infants assigned to receive it. Indeed, their lung function appeared slightly better than that of infants treated conventionally.

High frequency ventilation trial. Nine year follow up of lung function

The high frequency ventilation (HIFI) trial for hyaline membrane disease (HMD) showed no advantage of high frequency over conventional ventilation in pulmonary outcomes after 24 months. The present study tested the hypothesis that there would be no significant difference in childhood lung function between patients who had been ventilated by either method. Thirty-two children aged 8-9 years who completed the HIFI trial were asked to return for pulmonary function tests. For purposes of analysis, the patient population was divided according to mode of ventilation, and by diagnosis of bronchopulmonary dysplasia (BPD) or HMD. Results were compared to those of 15 term-born, matched, controls. Lung function tests showed a mildly obstructive pattern in prematurely born children. More severe obstruction was seen in those children who had physician-diagnosed asthma or who had used bronchodilators in the past. The prevalence of mild obstructive pattern on pulmonary function testing in preterm infants with HMD or BPD was similar in those who received high frequency vs. conventional ventilation. Factors other than the mode of ventilation exert greater influence on pulmonary outcome in survivors of lung disease of prematurity.

Lung function outcome in children of premature birth

Since the 1960s there has been a continual improvement in the survival of premature infants of birthweight less than 1500 g. This has resulted in an increase in the prevalence of bronchopulmonary dysplasia (BPD), or its milder form, chronic lung disease (CLD) of prematurity. In children with BPD; the initial air trapping improves in the first 3-4 years of life, but small airway obstruction is often slow to improve, suggesting dysanaptic lung growth. Despite this, the majority of older children and adolescents with BPD/CLD do not have significant respiratory symptoms. Children born prematurely with or without hyaline membrane disease may also have a reduction in expiratory flows during childhood, albeit less severe. The clinical significance of this in the longer term is unclear. Although significant associations between decrements in expiratory flows, neonatal oxygen therapy and assisted ventilation have been demonstrated. Airway function has also been reported to be largely unrelated with perinatal events but strongly associated with birthweight. The latter suggests that intra-uterine factors such as under-nutrition may be more important than hitherto recognized. Because of a lack of longitudinal studies, it is unclear how lung function will track during adolescence and adult life. Bronchial hyper-responsiveness is significantly increased in children with BPD and to a lesser extent in those born prematurely with or without hyaline membrane disease. It is unclear whether this is due to a genetic predisposition, neonatal lung injury or anatomically smaller airways. Given the morbidity and fiscal cost of a premature birth, effective strategies to reduce the premature birth rate are needed.

Risk factors for early, persistent, and late-onset wheezing in young children. SIDRIA Collaborative Group

Wheezing in childhood is not a single disorder and different wheezing-associated respiratory illnesses have been recently described. We investigated the association between wheezing conditions and familial, pre-, peri-, and postnatal risk factors. We studied 16,333 children, 6 to 7 yr old, enrolled in a population-based study. Standardized questionnaires were filled in by parents. A total of 1,221 children had transient early wheezing, 671 had persistent wheezing, 918 had late-onset wheezing, and 13,523 never had wheezing or asthma (control group). Maternal asthma or chronic obstructive airway disease were significantly (p < 0.0001) more associated with persistent wheezing than with transient early and late-onset wheezing. The same pattern was observed for exposure to maternal smoke during pregnancy. Having a mother > 35 yr old was protective against transient early wheezing (odds ratio [OR]: 0.68, 95% confidence intervals [95% CI]: 0.53 to 0.86). Breast feeding >/= 6 mo was slightly protective against transient early wheezing (OR: 0.82, 95% CI: 0.68 to 0.97), whereas it was a moderate risk factor for late-onset wheezing (OR: 1.22, 95% CI: 0.99 to 1.50). On the contrary, having siblings and attending a day care center were both risk factors for transient early wheezing (OR: 1.41 [95% CI: 1.21 to 1.64] and 1.70 [95% CI: 1.48 to 1.96], respectively) and protective factors against wheezing of late onset (OR: 0.83 [95% CI: 0.70 to 0.97] and 0.72 [95% CI: 0.59 to 0.88]). There was a stronger (p < 0.0001) positive association between personal history of eczema or allergic rhinitis and persistent and late-onset wheezing than transient early wheezing. Our findings suggest a different contribution of risk factors to wheezing conditions in childhood.

Potential interventions for the prevention of childhood pneumonia in developing countries: improving nutrition

Acute respiratory infections are the leading cause of childhood death in developing countries. Current efforts at mortality control focus on case management and immunization, but other preventive strategies may have a broader and more sustainable effect. This review, commissioned by the World Health Organization, examines the relations between pneumonia and nutritional factors and estimates the potential effect of nutritional interventions. Low birth weight, malnutrition (as assessed through anthropometry), and lack of breast-feeding appear to be important risk factors for childhood pneumonia, and nutritional interventions may have a sizeable effect in reducing deaths from pneumonia. For all regions except Latin America, interventions to prevent malnutrition and low birth weight look more promising than does breast-feeding promotion. In Latin America, breast-feeding promotion would have an effect similar to that of improving birth weights, whereas interventions to prevent malnutrition are likely to have less of an effect. These findings emphasize the need for tailoring interventions to specific national and even local conditions.

Changes in lung function between age 8 and 14 years in children with birth weight of less than 1,501 g

We set out to determine whether lung function of children with a birth weight of <1,501 g changed relative to expectations between the ages of 8 and 14 years. We hypothesized that changes in lung function may differ between those of birth weight above and below 1,000 g. The subjects of this study were born in the Royal Women's Hospital, Melbourne. There were 86 consecutive survivors with birth weights <1,000 g born between January 1, 1977 and March 31, 1982, and 124 consecutive survivors with birth weights 1,000-1,500 g born between October 1, 1980 and March 31, 1982. Lung function was measured at both age 8 and 14 years, corrected for prematurity in 78% (67/86) of those with birth weight <1,000 g, and in 69% (86/124) of those with birth weight 1,000-1,500 g. Overall, lung function was similar to predicted values at both 8 and 14 years of age [e.g., (forced expired volume in 1 s, FEV1% predicted) at age 8 years mean 88.5% (SD 14.7) and at age 14 years, mean 94.9% (SD 13.8)]. There were significant changes, mostly improvements, in lung function between age 8-14 years relative to predicted values: FEV1 (% predicted) increased between 8-14 years of age by a mean of 6.4 (95% confidence interval, 4.4-8.3). The improvements in some lung function variables were significantly greater in those of birth weight <1,000 g compared with those of birth weight 1,000-1,500 g: improvement in FEV1 (% predicted) between age 8-14 years in infants with birth weight <1,000 g had a mean of 10.3 (SD 13.1), and in those with birthweight 1,000-1,500 g a mean of 3.3 (SD 10.1). We conclude that lung function improved significantly relative to predicted values in children of birth weight <1,501 g between age 8-14 years. The improvements were greatest in those of birth weight <1,000 g.

Health effects of passive smoking. 9. Parental smoking and spirometric indices in children

BACKGROUND

A systematic quantitative review was conducted of the evidence relating parental smoking to spirometric indices in children.

METHODS

An electronic search of the Embase and Medline databases was completed in April 1997 and identified 692 articles from which we included four studies in neonates, 42 cross-sectional studies in school aged children (22 were included in a meta-analysis), and six longitudinal studies of lung function development.

RESULTS

In a pooled analyses of 21 surveys of school aged children the percentage reduction in forced expiratory volume in one second (FEV1) in children exposed to parental smoking compared with those not exposed was 1.4% (95% CI 1.0 to 1.9). Effects were greater on mid expiratory flow rates (5.0% reduction, 95% CI 3.3 to 6.6) and end expiratory flow rates (4.3% reduction, 95% CI 3.1 to 5.5). Adjustment for potential confounding variables had little effect on the estimates. A number of studies reported clear evidence of exposure response. Where exposure was explicitly identified it was usually maternal smoking. Two studies in neonates have reported effects of prenatal exposure to maternal smoking. Of five cross sectional studies that compared effects of perinatal exposure (retrospectively assessed) with current exposure to maternal smoking in later childhood, the three largest concluded that the major effect was in utero or neonatal exposure. Longitudinal studies suggest a small effect of current exposure on growth in lung function, but with some heterogeneity between studies.

CONCLUSIONS

Maternal smoking is associated with small but statistically significant deficits in FEV1 and other spirometric indices in school aged children. This is almost certainly a causal relationship. Much of the effect may be due to maternal smoking during pregnancy.

Consistent effects of high socioeconomic status and low birth order, and the modifying effect of maternal smoking on the risk of allergic disease during childhood

Birth order, maternal age, gestational age, birth weight, maternal smoking, and social class have all been associated with allergic rhinitis, eczema and asthma in childhood, but the consistency of independent effects of these exposures in relation to all of these allergic conditions has not been investigated. We have compared and contrasted the independent effects of these putative risk factors on parent-reported hayfever, eczema and wheeze by age 16 years and in the past 12 months at age 16 using data from the 1970 British birth cohort. The 1970 British birth cohort comprised all children born in England, Scotland and Wales in one week of April 1970, and follow-up surveys at birth, 5, 10 and 16 years of age involved a cumulative total of 17,427 children. We have used data on over 6000 children with complete data at every stage. Social advantage was a risk factor common to each of wheeze at, and hayfever and eczema at and by age 16. Low birth order was an independent risk factor for eczema and hayfever at age 16, but not for wheeze. However, wheeze at age 16 was significantly increased in relation to maternal smoking, with a significant interaction such that the effect of smoking was greatest in those of high birth order and, in the absence of maternal smoking, low birth order was a risk factor for wheeze at age 16. Social advantage and low birth order appear to be the independently consistent determinants of atopic disease. Maternal smoking is an additional risk factor for wheeze, which applies primarily in low socioeconomic groups.

Inspiratory flow limitation in children with bronchopulmonary dysplasia

The objective of this study was to compare pulmonary function tests of children with bronchopulmonary dysplasia (BPD) and asthma, and to evaluate children with BPD for evidence of upper airway obstruction. This is a case-control retrospective study of pulmonary function tests (PFTs) of 11 children with BPD between 5 and 8 years of age who were followed by pediatric pulmonologists, and of 32 age- and height-matched children with asthma. The median forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and peak expiratory flow (PEF) were significantly lower in the BPD group (0.86 L, 0.79 L, 120 L/min) than in the asthmatic group (1.34 L, 1.21 L, 155 L/min; P = 0.002, P = 0.007, P = 0.004, respectively). Both groups were equally hyperinflated (median thoracic gas volume 155% of predicted values in the BPD compared to 152% predicted in the asthma group; P = 0.67), and both groups showed decreases in air-trapping after a bronchodilator. The ratios of forced expiratory flow at 50% of the FVC to forced inspiratory flow at 50% of the FVC (FEF50%/FIF50%) and FEV1 to PEF (FEV1/PEF) were used to assess upper airway obstruction and were higher in children with BPD than asthma (P = 0.0001 and P = 0.035, respectively). We conclude that pulmonary function of children with BPD who are still symptomatic after 5 years of age is different from age-matched children with asthma, and the children with BPD demonstrate significant inspiratory flow limitations.

Effect of preterm birth on pulmonary function at school age: a prospective controlled study

OBJECTIVE

To assess long-term pulmonary outcome of a regional cohort of children born at < 32 weeks' gestation compared with a matched term control group.

STUDY DESIGN

All 125 surviving children born at 24 to 31 weeks' gestation during a 1-year period and a sociodemographically matched term control group were evaluated at age 7 years.

RESULTS

Preterm children with previous bronchopulmonary dysplasia (BPD) were twice as likely to require rehospitalization during the first 2 years of life than were preterm children without BPD (53% vs 26%, P < .01). At 7 years of age the BPD group had more airway obstruction than did both preterm children without BPD and the term control group (significantly reduced mean forced vital capacity, forced expiratory volume in 1 second, and forced expiratory flow, 25% to 75% vital capacity, all, P < .001). Lung function among preterm children without previous BPD was similar to that of the term control group. Bronchodilator responsiveness was observed twice as often in preterm children with previous BPD (20 of 43, 47%) compared with preterm children without BPD (13 of 53, 25%) or the term control group (23 of 108, 21%, P < .001). These differences remained significant after adjustment was done for birth weight and gestational age.

CONCLUSION

Preterm children without BPD demonstrate pulmonary function at school age similar to that of children in a healthy term control group, whereas preterm children with previous BPD demonstrate abnormal pulmonary function.

Effects of intrauterine growth retardation and prematurity on spirometric flow values and lung volumes at school age in twin pairs

Lung volumes and pulmonary expiratory flow values were investigated in 67 children from multiple pregnancies (30 twins, one set of triplets, one set of quadruplets) at the age of 7-15 years. At birth, 30 of 67 children (44%) had intrauterine growth retardation (IUGR, birth weight <-2 SD or birth weight difference between twin-pairs >1.3 SD). The median gestational age was 35 weeks (range, 28-38 weeks), and the median birth weight was 2,050 g (800-3,150 g). Lung functions were measured with a heated pneumotachograph. Data were standardized using height-based reference equations. No differences were found in lung volumes between children with IUGR and those children who had normal birth weight. Gestational age did not correlate with either airway flow rates or lung volumes. Maximum mid-expiratory flow (FEF50) did not correlate with standardized birth weight or with gestational age. In discordant twin pairs, the IUGR twins had significantly lower FEF50 than their normal birth weight counterparts (p=0.03, Z=-2.13). In the whole study group (67 children), children with IUGR had significantly lower FEF50 than children with normal birth weight (p=0.04; CI, 0.3-19.9). We propose that IUGR has the most pronounced effect on the growth of airways, and no detectable influence on lung volumes. This study confirms the crucial effect of appropriate intrauterine growth on subsequent growth on pulmonary airways.