Exposure-response relationship between paternal smoking and children's pulmonary function

The association between secondhand smoke and childhood asthma: A systematic review and meta-analysis

BACKGROUND

Secondhand smoke (SHS) exposure can trigger asthma exacerbations in children. Different studies have linked increased asthma symptoms and even deaths in children with SHS, but the risk has not been quantified uniformly across studies. We aimed to investigate the role of SHS exposure as a risk factor of asthma among children.

METHODS

We performed a systematic review in PubMed, Scopus, and Google Scholar from June 1975 to 10 March 2020. We included cohort, case-control, and cross-sectional studies reporting odds ratio (OR) or relative risk estimates and confidence intervals of all types of SHS exposure and childhood asthma.

RESULTS

Of the 26 970 studies identified, we included 93 eligible studies (42 cross-sectional, 41 cohort, and 10 case-control) in the meta-analysis. There were significantly positive associations between SHS exposure and doctor-diagnosed asthma (OR = 1.24; 95% confidence interval (CI) = 1.20-1.28), wheezing (OR = 1.27; 95% CI = 1.23-1.32) and asthma-like syndrome (OR = 1.34; 95% CI = 1.34-1.64). The funnel plots of all three outcomes skewed to the right, indicating that the studies generally favor a positive association of the disease with tobacco exposure. Subgroup analysis demonstrated that younger children tended to suffer more from developing doctor-diagnosed asthma, but older children (adolescents) suffered more from wheezing. There was no evidence of significant publication or small study bias using Egger's and Begg's tests.

CONCLUSION

The results show a positive association between prenatal and postnatal secondhand smoking exposure and the occurrence of childhood asthma, asthma-like syndrome, and wheezing. These results lend support to continued efforts to reduce childhood exposure to secondhand smoke.

Impulse oscillometry, spirometry, and passive smoking in healthy children and adolescents

OBJECTIVE

To identify changes in the forced and quiet breathing parameters of lung function in healthy children and adolescents exposed to passive smoking (PS).

METHOD

Comparative cross-sectional study. Healthy schoolchildren aged 6 to 14 years. We collected anthropometric data, lung function parameters using spirometry (forced breathing), and quiet breathing parameters using impulse oscillometry. The sample was divided into two groups according to exposure to PS: passive smoking group (PSG) and non-passive smoking group (NPSG). For the statistical analysis, the Shapiro-Wilk test was used to verify data normality and the T-test or Mann-Whitney test to compare spirometric and oscillometric parameters between groups (p≤0.05).

MAIN FINDINGS

The study included 78 children and adolescents, with 14 boys and 25 girls in each group. There were differences in the mean values for peak expiratory flow (p=0.01). There were no significant differences between the groups in values for z-score and lower limit of normal. The PSG had higher mean absolute values for reactance area (X5=0.05) and significant percentage of predicted values for the following impulse oscillometry parameters: central airway resistance (R20%, p=0.03) and for the indicators of presence of airway obstruction (Fres%, p=0.01; X5%=0.01% and AX%, p=0.01).

CONCLUSION

Children and adolescents exposed to PS had lower values for the spirometric variables and higher values for the oscillometric variables, indicating changes in forced and quiet parameters of lung function compared to the NPSG.

Pulmonary effects of active smoking and secondhand smoke exposure among adolescent students in Juárez, Mexico

BACKGROUND

Youth smoking trends among Latin American countries, including Mexico, are on the rise. Notably, although the high prevalence of smoking in teens has been well documented in the literature, few studies have evaluated the impact of smoking and secondhand smoke (SHS) exposure on their respiratory system.

OBJECTIVE

To investigate the effects of smoking and SHS exposure on the respiratory health and lung function among eighth-grade students in Juárez, Mexico.

METHODS

A cross-sectional study was undertaken on a sample of convenience. The study outcomes centered on evaluating 300 students' lung function by spirometry (forced expiratory volume in 1 second [FEV1], forced expiratory volume in 1 second/forced vital capacity ratio [FEV1/FVC], and forced mid-expiratory flow rate [FEF25%-75%]) and their respiratory health (smoking behavior and SHS exposure) by their self-reported responses to a standardized respiratory questionnaire. The study outcomes were compared among three distinct groups: 1) nonsmokers/nonexposed to SHS; 2) nonsmokers/exposed to SHS; and 3) smokers.

RESULTS

The majority of the study participants were 14 years old (85%), females (54%), who attended eighth grade in a public school setting (56%). Approximately, half reported being of low socioeconomic status (49%) and nonsmokers/exposed to SHS (49%). The lung function parameters of smokers were found to be lower (FEV1 =62.88±10.25; FEV1/FVC =83.50±14.15; and FEF25%-75% =66.35±12.55) than those recorded for the nonsmokers/exposed to SHS (FEV1 =69.41±11.35; FEV1/FVC =88.75±15.75; and FEF25%-75% =78.90±14.65) and significantly reduced when compared to the nonsmokers/nonexposed to SHS (FEV1 =79.14±13.61; FEV1/FVC =94.88±21.88; and FEF25%-75% =87.36±17.02) (P<0.001). Similarly, respiratory complaints were more prevalent among smokers and those exposed to SHS when compared to nonsmokers/nonexposed to SHS.

CONCLUSION

Our findings suggest that initiation of cigarette smoking and, to a lesser extent, exposure to SHS in adolescence leads to increased respiratory symptoms and reduction of pulmonary function test values. Public health initiatives that aim to prevent smoking initiation, assist in cessation, and lessen SHS exposure of adolescents need to be school-based and employed as early as middle school.

[Perception of parents about second hand smoke on the health of their children: an ethnographic study]

OBJECTIVE

To analyze the perception of parents about secondhand smoking in their children's health.

METHODS

Ethnographic qualitative and quantitative study. We sought the point of view and understanding of the parents that were active smokers in relation to environmental tobacco smoke (ETS) and secondhand smoking. Mothers and fathers who are active smokers and that live with their children from seven different public schools in the city of Anápolis, Midwest Brazil, were interviewed in the first semester of in a reserved room in the schools. A descriptive and qualitative analysis was carried out through the ethnography.

RESULTS

58 parents with an average time of smoking of 15.3 years and an average quantity of cigarettes smoked per day of 2 were interviewed. Among them, 59% didn't know what ETS was, and 60% stated knowing what a secondhand smoker was. However, when questioned about their children as secondhand smokers, 52% didn't consider them to be. Some parents knew some of the effects of secondhand smoking in the health of their children. However, the majority (52%) of them did not believe that their children would suffer any respiratory impairment or did not know about these impairments.

CONCLUSIONS

Children were exposed to Environmental Tobacco Pollution in their residence if one considers parental duration of smoking and average of cigarettes smoked per day. There was a lack of knowledge of the parents about ETS, secondhand smoking and the evils that cigarettes could cause in the health of their children.

Heredity of chronic bronchitis: a registry-based twin study

BACKGROUND

Smoking is a major risk factor for lung diseases and lower respiratory symptoms, but since not all smokers develop chronic bronchitis and since chronic bronchitis is also diagnosed in never-smokers, it has been suggested that some individuals are more susceptible to develop chronic bronchitis due to genetics.

OBJECTIVE

To study the relative influence of genetic and environmental factors on the variation in the susceptibility to chronic bronchitis.

METHODS

In a population-based questionnaire study of 13,649 twins, 50-71 years of age, from the Danish Twin Registry, we calculated sex-specific concordance rates and heritability of chronic bronchitis. The response rate was 75%.

RESULTS

The prevalence of chronic bronchitis was 9.3% among men and 8.5% among women. The concordance rate for chronic bronchitis was higher in monozygotic twins than in dizygotic twins among women; 0.30 vs. 0.17, but not among men; 0.15 vs. 0.18. The heritability of chronic bronchitis adjusted for smoking and age was 55% (36-71%) in women, whereas the susceptibility to chronic bronchitis in men for 25% (8-41%) was ascribable to familial environment but not to genetic factors.

CONCLUSIONS

Chronic bronchitis shows a moderate familial aggregation, particularly in women. Increased susceptibility to respiratory disease among female smokers relative to male smokers may have a genetic origin.

Risk of chronic bronchitis in twin pairs discordant for smoking

BACKGROUND

It is well known that smoking is a major risk factor for lung disease and respiratory symptoms. We examined the association between smoking and the risk of chronic bronchitis in a large twin sample.

METHODS

In a population-based questionnaire study of 13,649 twins, aged 50-71 years, from the Danish Twin Registry, we identified 1,146 twin pairs, discordant for a lifetime history smoking. We performed co-twin control analysis to examine the impact of smoking on the risk of chronic bronchitis.

RESULTS

The prevalence of chronic bronchitis was 9.7 %. In the total sample, high age, living without a spouse, and smoking remained statistically significant predictors with an up to tenfold increased risk of chronic bronchitis in the heaviest smokers compared with never-smokers, after multivariate adjustment. Among twin pairs discordant for smoking, chronic bronchitis was significantly more common in the smoking twin compared with the nonsmoking co-twin. There was no differential effect of smoking on the risk of chronic bronchitis in monozygotic and dizygotic twins.

CONCLUSIONS

The risk of chronic bronchitis increases with age and increasing tobacco consumption. The results indicate a direct relationship between smoking and development of chronic bronchitis, but other environmental factors, such as exposure to household smoking in childhood and living without a spouse, also play a role.

[Environmental tobacco smoke exposure in children and its relationship with the severity of asthma]

INTRODUCTION

Environmental tobacco smoke (ETS) exposure produces serious respiratory problems in childhood. The aim of the study was to evaluate if environmental tobacco smoke affects the severity of asthma in asthmatic children.

MATERIAL AND METHODS

A prospective, multicentre study was conducted on asthmatic children and their parents in 2007-2008, using an exposure questionnaire, pulmonary function, level of cotinine in urine, and evaluation of the severity of asthma according to GEMA guide. The characteristics of the sample are summarised using the appropriate statistical tools, and the comparisons were made using the Pearson chi2 test, Mann-Whitney U test or Studentĭs t, according to the variable and number of groups compared.

RESULTS

Four hundred and eighty four households in 7 Autonomous Communities were included. The population included, 61% male children with asthma, 56% with a smoking caregiver in their home, 34% fathers, 31% mothers and 17% both. Home exposure was 37%, with 11% daily and 94% passive smokers since birth. There was 20% with exposure during whole period of pregnancy of 5±1 cigarettes/day. Children exposed to 6±1 cigarettes/day, 27%, up to 10 cigarettes/day, and 10% to more than 10. Severity of asthma during the survey was worse among those exposed (episodic-occasional 47%, episodic-frequent 35% and persistent-moderate 18% versus 59%, 25% and 16%, respectively, P=.040). Severity of asthma in the last year was worse in those exposed (episodic - occasional 22%, episodic - frequent 37% and persistent - moderate 50% versus 38%, 28% and 25% respectively, P=.037). The spirometry was abnormal in 64% of the exposed against to 36% in the non-exposed for FEV(1) (P=.003, 63% vs 38% for FVC (P=.038), and 54% vs 46% for the PEF (P=.050). The cotinine was higher in exposed: 51 (0-524) ng/ml vs 27 (0-116) ng/ml (P=.032). A relationship was observed between cotinine and level of exposure: 120 (0-590) ng/ml for >10 cigarettes/day as opposed to 44 (0-103) ng/ml ≤10 cigarettes/day (P=.035), which corroborates the consistency of the data collected.

CONCLUSIONS

The exposure of children with asthma to environmental tobacco smoke has a highly negative effect on the severity of their asthma.

Environmental tobacco smoke exposure and Chinese schoolchildren's respiratory health: a prospective cohort study

BACKGROUND

Although China is the most coveted cigarette market worldwide, few studies have examined the longitudinal effects of environmental tobacco smoke (ETS) on health.

PURPOSE

To examine the relationship between exposure to ETS and respiratory health in Chinese schoolchildren.

METHODS

The study subjects included 1718 children, who were never-smokers, aged 10.05±0.86 years and asthma-free at baseline. The children performed spirometric tests in 2006 and 18 months later. Parents reported the children's respiratory symptoms and illnesses, ETS exposure, and other related information by self-administered survey at both assessment points. The data were analyzed in 2010.

RESULTS

Significant exposure-response relationships were found between ETS exposure and coughing at night (p for trend<0.001); sneezing (p for trend=0.031); and sneezing with itchy, watery eyes (p for trend=0.006) in the first survey, and coughing at night (p for trend=0.019); phlegm without a cold (p for trend<0.001); and sneezing (p for trend=0.036) in the second survey. Compared with those who reported no ETS exposure in either survey, children who had a high ETS exposure level (>5 cigarettes/day) in either survey had lower growth rates in forced expiratory flow between 25% and 75% of forced vital capacity (FEF(25-75); β= -0.104, p=0.020) and forced expiratory flow at 25% of forced vital capacity (FEF(25); β= -0.077, p=0.027). A monotonic exposure-response effect was observed between ETS exposure and the deficits in the growth rate of FEF(25) and FEF(25-75.)

CONCLUSIONS

Exposure to ETS increased the risks of respiratory symptoms in Chinese school-aged children and was associated with impaired lung function growth. A dose-response relationship was observed for the latter effect.

Lifestyle and the Respiratory Health of Children

This article offers a review of the potential influences of personal lifestyle on respiratory health in children, looking at both healthy individuals and those with respiratory disorders. As with many aspects of health, regular physical activity, an appropriate diet, and avoidance of obesity and cigarette smoke all contribute to optimal development of the healthy child. An active lifestyle is associated with greater static and dynamic lung volumes, greater efficiency of the ventilatory process, and an optimization of breathing patterns. The risk of upper respiratory infections is also reduced in those maintaining a moderate level of physical activity. Maternal smoking during pregnancy, as well as active and passive smoking, all have an adverse influence on lung function in the child, the largest effects being on dynamic lung volumes. The risk of developing asthma seems reduced in children who maintain a normal body mass and are physically active. A program of graded physical activity is of therapeutic value in a number of established respiratory conditions, including asthma, cystic fibrosis, and ventilatory impairment from neuromuscular disorders. Exercise carries a slight risk of fatalities from asthma and anaphylactic reactions. In designing an optimal physical activity program, it is also important to guard against the hazards of deep oronasal breathing, including the precipitation of bronchospasm by the inhalation of cold, dry air and pollens; an increased exposure to atmospheric pollutants (reducing and oxidant smog, fine and ultra-fine particulates, and carbon monoxide); and possible long-term dangers from chlorine derivatives in the atmosphere of indoor swimming pools.

Association of passive exposure of pregnant women to environmental tobacco smoke with asthma symptoms in children

Environmental tobacco smoke (ETS) is a significant risk factor for the presence and increased severity of asthma- and allergy-related symptoms in children. Smoking during pregnancy has detrimental effects on asthma-associated outcomes in childhood. Whether passive exposure of pregnant women to ETS may also lead to asthma in their offspring, is not known. The aim of this study was to investigate the association of passive exposure of pregnant women to ETS and asthma- and/or allergy-related symptoms in Preschool children. Cross-sectional data were collected with questionnaires from 2374 Preschool children, recruited from public and private nurseries and day-care centers. Parental smoking was significantly associated with wheezing symptoms in their children. Mother's active smoking during pregnancy significantly increased the risk for occurrence of asthma symptoms and/or medically diagnosed asthma in Preschool children in a dose-dependent manner. Passive exposure to ETS, mainly during the third trimester of pregnancy, was significantly associated with asthma- and allergy-related symptoms after adjusting for several confounders in a multivariate analysis (current wheeze: OR = 1.42, 95% CI = 1.06-1.91, pruritic rash ever: OR= 1.45, 95% CI = 1.01-2.08). Passive exposure of pregnant women to ETS during the third trimester is positively associated with asthma- and allergy-related symptoms in their Preschool age children. Public health policies should be oriented not only towards smoking cessation, but also reinforce elimination of ETS exposure of pregnant women.

[Lung function and exposure to tobacco smoke among adolescents]

OBJECTIVE

To study lung function in adolescents in relation to smoking (active and passive smokers) and to investigate the repercussion on spirometric parameters.

PATIENTS AND METHOD

We studied 301 healthy adolescents with no history of bronchial asthma or colds in the month prior to the study. A questionnaire on tobacco exposure was administered and spirometry (Datospir-92) was performed.

RESULTS

There were 165 boys (54.5%) and 136 girls (45.5%) aged between 14 and 20 years old (16.40+/-1.32). A total of 27.2% were non-smokers and were not exposed to tobacco smoke (NS), 31.3% were passive smokers, with household exposure of 10 cigarettes per day during at least the previous year (PS), and 41.5% were current smokers who had been smoking>or=10 cigarettes/day for at least 1 year (CS). Significant differences were found between age and smoking habits (p=0.0001) and between smoking habits and female sex (girls CS: 33.9% vs boys CS: 21.8 %) (p=0.007). A significant association was found between smoking (NS, PS and CS) and spirometric parameters (ANOVA): forced vital capacity (FVC) (p=0.001), forced expiratory volume in 1 second (FEV1) (p=0.0001), FEV1/FVC (p=0.004), peak expiratory flow (PEF) (p=0.0001), midexpiratory flow at 25% of forced vital capacity (MEF25%) (p=0.01), MEF50% (p=0.0001) and MEF25-75% (p=0.0001); CS in relation to NS was as follows: FEV1, PEF, MEF50%, MEF25-50% (p=0.0001) and FVC, FEV1/FVC, MEF25% (p=0.01); CS in relation to PS: FEV1/ FVC (p=0.02), PEF (p=0.004), MEF50% and MEF25-75% (p=0.003), PS in relation to NS: FVC and FEV1 (p=0.02). Significant differences in FVC, FEV1 and MEF25-75% were found in female CS in comparison with boys.

CONCLUSIONS

The CS group showed a significant decrease in spirometric parameters in relation to the NS group. The airway was affected sooner in the female group of smokers than in the male group, even though the intensity and time of exposure were the same in both groups.

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.

Asthmatic symptoms among pupils in relation to winter indoor and outdoor air pollution in schools in Taiyuan, China

BACKGROUND

There are few studies on associations between children's respiratory heath and air pollution in schools in China. The industrial development and increased traffic may affect the indoor exposure to air pollutants in school environment. Moreover, there is a need to study respiratory effects of environmental tobacco smoke (ETS) and emissions from new building materials in homes in China.

OBJECTIVES

We studied the associations between pupils' asthmatic symptoms and indoor and outdoor air pollution in schools, as well as selected home exposures, in a coal-burning city in north China.

METHODS

A questionnaire survey was administered to pupils (11-15 years of age) in 10 schools in urban Taiyuan, collecting data on respiratory health and selected home environmental factors. Indoor and outdoor school air pollutants and climate factors were measured in winter.

RESULTS

A total of 1,993 pupils (90.2%) participated; 1.8% had cumulative asthma, 8.4% wheezing, 29.8% had daytime attacks of breathlessness. The indoor average concentrations of sulfur dioxide, nitrogen dioxide, ozone, and formaldehyde by class were 264.8, 39.4, 10.1, and 2.3 microg/m3, respectively. Outdoor levels were two to three times higher. Controlling for possible confounders, either wheeze or daytime or nocturnal attacks of breathlessness were positively associated with SO2, NO2, or formaldehyde. In addition, ETS and new furniture at home were risk factors for wheeze, daytime breathlessness, and respiratory infections.

CONCLUSIONS

Indoor chemical air pollutants of mainly outdoor origin could be risk factors for pupils' respiratory symptoms at school, and home exposure to ETS and chemical emissions from new furniture could affect pupils' respiratory health.

[The effects of tobacco on children]

INTRODUCTION

Smoking remains an important topic. It is estimated that at present half the children born in France have been, or will be, exposed to the toxic effects of passive smoking. This paper aims to review the evidence of the effects of passive smoking, both intra and extra-uterine.

STATE OF THE ART

Extra-uterine passive smoking is implicated in numerous respiratory (asthma, allergy, infections...) and non respiratory diseases (neoplastic, dental, ophthalmic, digestive, cardio-vascular and infective). Intra-uterine exposure is even more dangerous and leads to abnormalities of the pregnancy (placental abnormalities, prematurity...), of the foetus (behavioural problems, malformations) and long term problems for the unborn child. Passive smoking is responsible for pulmonary morphological abnormalities (pulmonary hypoplasia, reduction in elasticity, increased deposition of collagen and alteration of alveolar structure) and functional disorders (reduced compliance, increased airways resistance, bronchial hyperreactivity). Finally it causes a disturbance of respiratory control, promoting all the factors responsible for sudden cot death.

CONCLUSIONS

The ill effects of passive smoking fully justify efforts to inform and persuade the medical profession of its duty to fight this scourge.

[Parental smoking and lung function in healthy children and adolescents]

OBJECTIVE

The debate continues on the effect of passive smoking on nonsmokers. The effect of parental smoking on the lung function of children varies considerably according to geographic area, source of passive smoking, and sex. The objective of this study was to evaluate the effect of parental smoking on the lung function of children.

POPULATION AND METHODS

A cross-sectional study was performed on a sample of the population of healthy children and adolescents between 6 and 18 years of age in Galicia. Subjects were selected by means of 2-stage cluster sampling grouped by sex and age.

RESULTS

Approximately 56% of the children were exposed to the tobacco smoke of one of their parents. Children whose fathers were smokers presented a 40% higher risk of reduced forced expiratory flow at 75% of forced vital capacity (FEF75%) and a 30% higher risk of reduced FEF25%-75%. Children whose mothers were smokers presented a 30% higher risk of reduced forced expiratory volume in the first second and a 40% higher risk of reduced FEF50%. There was a 60% increase in risk of reduced FEF75%. The fact that both parents smoked did not appear to increase the risk of reduced lung function.

CONCLUSIONS

Parental smoking has a considerable effect on the lung function of children and adolescents. Smoking by either the mother or the father has a decisive influence. The fact that this effect is independent of the growth of the child and that the obstructive effect is located principally in the distal airways appears to confirm the hypothesis that this effect is produced after birth.

School proximity to concentrated animal feeding operations and prevalence of asthma in students

STUDY OBJECTIVES

Asthma prevalence and severity are rising in industrialized nations. Studies supporting the hygiene hypothesis suggest that being raised on a farm protects against atopy and, often, asthma. In rural United States, however, an increased rate of asthma has been found among schoolchildren. We hypothesized that the rural US environment may not be protective against airway inflammation, perhaps due to environmental effluents from a relatively high number of concentrated animal feeding operations (CAFOs). We compared the prevalence of asthma in two Iowa elementary schools, one adjacent to a CAFO, and the other distant from any large-scale farming operations.

DESIGN

Cross-sectional questionnaire-based study.

SETTING

Two rural Iowa elementary schools: the study school is located one-half mile from a CAFO, and the control school is distant from any large-scale agricultural operation.

PARTICIPANTS

Children, kindergarten through grade 5, who attended either the study school or the control school.

RESULTS

Children in the study school had a significantly increased prevalence of physician-diagnosed asthma (adjusted odds ratio, 5.71; p = 0.004). Although this group was more likely to live on a farm and have parents who smoke, these potentially confounding variables did not account for increased prevalence in a multivariate model. No difference in measures of asthma severity was found between the two populations. Because different sets of physicians are responsible for the medical care of the groups of children, it is possible that physician bias is responsible for the different prevalence of asthma diagnoses. This was not explored in the study.

CONCLUSIONS

This study supports a role for exposure to rural environmental toxicants in the etiology of asthma, and suggests a need for further study of this relationship.

Updated spirometric reference values for adult Chinese in Hong Kong and implications on clinical utilization

STUDY OBJECTIVES

The accuracy of reference values of lung function is important for assessment of severity and functional impairment of respiratory diseases. The aim of the study was to establish updated prediction formulae of spirometric parameters for Hong Kong Chinese and to compare the reference values with those derived from other studies in white and Chinese subjects.

DESIGN

Cross-sectional multicenter study.

SETTING

Lung function laboratories of eight regional hospitals in Hong Kong.

PARTICIPANTS

Subjects were recruited by random-digit dialing. One thousand one hundred seventy-six subjects who fulfilled recruitment criteria underwent spirometry.

MEASUREMENTS

Spirometry was performed according to American Thoracic Society recommendations, and the technique was standardized among the eight participating lung function laboratories.

RESULTS

Evaluable data of 1,089 (494 men and 595 women) healthy nonsmokers aged 18 to 80 years were analyzed. Age and height were found to be the major determinants of FEV1 and FVC, with a linear decline of height-adjusted values with age in both sexes. Spirometric values of this population have increased compared to Chinese populations of similar sex, age, and height two decades ago. Reference values derived from white populations were higher than our values by 5 to 19%, and the degree of overestimation varied with age, sex, and lung function parameter. We also demonstrated that the blanket application of correction factors for Asian populations may not be appropriate. In this study cohort, the distribution-free estimation of age-related centiles was more appropriate for the determination of lower limits of normal.

CONCLUSIONS

Our findings underscore the need to use reference values based on updated data derived from local populations or those matched for ethnicity and other sociodemographic characteristics.

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.

Respiratory symptoms in relation to residential coal burning and environmental tobacco smoke among early adolescents in Wuhan, China: a cross-sectional study

BACKGROUND

Cigarette smoking and coal burning are the primary sources of indoor air pollution in Chinese households. However, effects of these exposures on Chinese children's respiratory health are not well characterized.

METHODS

Seventh grade students (N = 5051) from 22 randomly selected schools in the greater metropolitan area of Wuhan, China, completed an in-class self-administered questionnaire on their respiratory health and home environment.

RESULTS

Coal burning for cooking and/or heating increased odds of wheezing with colds [odds ratio (OR) = 1.57, 95% confidence interval (CI): 1.07-2.29] and without colds (OR = 1.44, 95% CI: 1.05-1.97). For smoking in the home, the strongest associations were seen for cough (OR = 1.74, 95% CI: 1.17-2.60) and phlegm production (OR = 2.25, 95% CI: 1.36-3.72) without colds among children who lived with two or more smokers.

CONCLUSIONS

Chinese children living with smokers or in coal-burning homes are at increased risk for respiratory impairment. While economic development in China may decrease coal burning by providing cleaner fuels for household energy use, the increasing prevalence of cigarette smoking is a growing public health concern due to its effects on children. Adverse effects of tobacco smoke exposure were seen despite the low rates of maternal smoking (3.6%) in this population.

Exposure-response relationships between lifetime exposure to residential coal smoke and respiratory symptoms and illnesses in Chinese children

Data collected in a large epidemiologic study were analyzed to examine respiratory health effects of residential coal use in 7058 school children living in the four Chinese cities of Chongqing, Guangzhou, Lanzhou, and Wuhan. A Scenario Evaluation Approach was used to develop two exposure variables, heating coal smoke and cooking coal smoke. Estimated lifetime exposures to heating coal smoke and cooking coal smoke were both classified into four-level ordinal scales, as follows: no reported exposure (control); lightly exposed; moderately exposed; and heavily exposed. Zero-one dummy variables were constructed for each exposure level other than the control level (total six variables). These variables were entered into the analytical model. We tested for exposure-response relationships using logistic regression models, while controlling for other relevant covariates, including an indicator variable of ambient air pollution levels. We observed monotonic and positive exposure-response relationships of exposure to heating coal smoke with modeled odds ratios (ORs) of phlegm, cough with phlegm, and bronchitis. Other health outcomes were not associated with such exposure in a monotonic exposure-response pattern. However, ORs for cough, wheeze, and asthma were all higher in the exposed groups than in the control group. We observed no consistent associations between cooking coal smoke and the examined health outcomes. We conclude that exposure to heating coal smoke could have adverse effects on children's respiratory symptoms and illnesses in these four Chinese cities.

Maternal and personal cigarette smoking synergize to increase airflow limitation in adults

Susceptibility of the lungs to cigarette smoke is poorly understood. It is not known whether maternal smoking increases chronic obstructive pulmonary disease (COPD) risk. In 1998 we reported an inverse association between maternal smoking (prerecorded) and FEV(1) in adults. Because FEV(1) and FVC are strongly correlated, it is unclear whether the association in question reflects a link with lung volume, airflow limitation, or both. We extended our original analysis to investigate whether maternal and personal smoking synergize to increase airflow limitation. We estimated residual FEV(1) to express FEV(1) variation that was not associated with FVC. Maternal smoking was inversely associated with FVC and FEV(1) irrespective of personal smoking. It was inversely associated with FEV(1)/FVC, forced midexpiratory flow rates (FEF(25-75) [mean forced expiratory flow during the middle half of the FVC], FEF(25-75)/FVC), and residual FEV(1) in current smokers but not in never or former smokers (heterogeneity p = 0.016, 0.024, 0.021, and 0.016, respectively). We tested the clinical relevance of findings in ever smokers without asthma: 10 cigarettes/day maternal smoking increased prevalent COPD by 1.7 (95% confidence interval: 1.2-2.5) after adjustment for covariates. Maternal smoking impairs lung volume irrespective of personal smoking and appears to synergize with personal smoking to increase airflow limitation and COPD.

Indoor air pollution: a global health concern

Indoor air pollution is ubiquitous, and takes many forms, ranging from smoke emitted from solid fuel combustion, especially in households in developing countries, to complex mixtures of volatile and semi-volatile organic compounds present in modern buildings. This paper reviews sources of, and health risks associated with, various indoor chemical pollutants, from a historical and global perspective. Health effects are presented for individual compounds or pollutant mixtures based on real-world exposure situations. Health risks from indoor air pollution are likely to be greatest in cities in developing countries, especially where risks associated with solid fuel combustion coincide with risk associated with modern buildings. Everyday exposure to multiple chemicals, most of which are present indoors, may contribute to increasing prevalence of asthma, autism, childhood cancer, medically unexplained symptoms, and perhaps other illnesses. Given that tobacco consumption and synthetic chemical usage will not be declining at least in the near future, concerns about indoor air pollution may be expected to remain.