Effect of parental cigarette smoking on the pulmonary function of children

Models for the propensity score that contemplate the positivity assumption and their application to missing data and causality

Generalized linear models are often assumed to fit propensity scores, which are used to compute inverse probability weighted (IPW) estimators. To derive the asymptotic properties of IPW estimators, the propensity score is supposed to be bounded away from zero. This condition is known in the literature as strict positivity (or positivity assumption), and, in practice, when it does not hold, IPW estimators are very unstable and have a large variability. Although strict positivity is often assumed, it is not upheld when some of the covariates are unbounded. In real data sets, a data-generating process that violates the positivity assumption may lead to wrong inference because of the inaccuracy in the estimations. In this work, we attempt to conciliate between the strict positivity condition and the theory of generalized linear models by incorporating an extra parameter, which results in an explicit lower bound for the propensity score. An additional parameter is added to fulfil the overlap assumption in the causal framework.

Bridging observational studies and randomized experiments by embedding the former in the latter

Consider a statistical analysis that draws causal inferences from an observational dataset, inferences that are presented as being valid in the standard frequentist senses; i.e. the analysis produces: (1) consistent point estimates, (2) valid p-values, valid in the sense of rejecting true null hypotheses at the nominal level or less often, and/or (3) confidence intervals, which are presented as having at least their nominal coverage for their estimands. For the hypothetical validity of these statements, the analysis must embed the observational study in a hypothetical randomized experiment that created the observed data, or a subset of that hypothetical randomized data set. This multistage effort with thought-provoking tasks involves: (1) a purely conceptual stage that precisely formulate the causal question in terms of a hypothetical randomized experiment where the exposure is assigned to units; (2) a design stage that approximates a randomized experiment before any outcome data are observed, (3) a statistical analysis stage comparing the outcomes of interest in the exposed and non-exposed units of the hypothetical randomized experiment, and (4) a summary stage providing conclusions about statistical evidence for the sizes of possible causal effects. Stages 2 and 3 may rely on modern computing to implement the effort, whereas Stage 1 demands careful scientific argumentation to make the embedding plausible to scientific readers of the proffered statistical analysis. Otherwise, the resulting analysis is vulnerable to criticism for being simply a presentation of scientifically meaningless arithmetic calculations. The conceptually most demanding tasks are often the most scientifically interesting to the dedicated researcher and readers of the resulting statistical analyses. This perspective is rarely implemented with any rigor, for example, completely eschewing the first stage. We illustrate our approach using an example examining the effect of parental smoking on children's lung function collected in families living in East Boston in the 1970s.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Respiratory outcomes for the tiniest or most immature infants

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

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.

Detrimental effects of tobacco smoke exposure during development on postnatal lung function and asthma

Exposure to environmental tobacco smoke (ETS) during fetal development and early postnatal life is perhaps the most ubiquitous and hazardous of children's environmental exposures. The developing lung is highly susceptible to ETS. A large body of literature links both prenatal maternal smoking and children's ETS exposure to decreased lung growth. This review summarizes the state of the knowledge, including both human epidemiology and laboratory animal experiments, linking ETS, lung development, and respiratory outcomes. Important issues discussed include lung development and lung function and asthma in relation to ETS exposure during critical windows of growth. Prenatal exposure to ETS is associated with impaired lung function and increased risk of developing asthma, whereas postnatal exposure mainly acts to trigger respiratory symptoms and asthma attacks, but it also plays an important role in the occurrence of asthma in children. This review provides evidence that avoidance of ETS exposure both before and after birth is beneficial to long-term respiratory health, because airway function in later life is believed to be largely determined by lung development occurring in utero and in early infancy.

Respiratory health effects of exposure to environmental tobacco smoke

Tobacco smoke is a major component of indoor air pollution. Exposure to environmental tobacco smoke (ETS) is prevalent worldwide despite growing awareness of its adverse health effects on non-smokers. ETS contains the same toxic substances as identified in mainstream tobacco smoke. Cotinine (a metabolite of nicotine) can be measured in urine and serum of non-smokers exposed to ETS and reflects the degree of exposure. In children, exposure to ETS leads to reduced lung function, increased risk of lower respiratory tract illnesses, acute exacerbation of asthma resulting in hospitalization, increased prevalence of non-allergic bronchial hyperresponsiveness, increased risk for sudden infant death syndrome (SIDS) and possibly increased risk for asthma. Exposure to ETS is responsible for excess cost to the family's financial resources and demands on health services. In adults, exposure to ETS is associated with increased risk of lung cancer, particularly in those with high exposure and acute and chronic respiratory symptoms that improve after the cessation of exposure. Healthcare providers should advocate for non-smokers' rights in the community and support legislation to limit tobacco exposure.

Environmental tobacco smoke exposure and nocturnal symptoms among inner-city children with asthma

BACKGROUND

Environmental tobacco smoke (ETS) is a frequent exposure and is linked to asthma among inner-city children.

OBJECTIVE

We sought to examine the relationship among ETS exposure, select asthma symptoms, and consequences among inner-city children with asthma.

METHODS

Data from interviews with primary caregivers of inner-city elementary school children with asthma were evaluated (n = 590). Caregiver reports of child asthma symptoms, exercise limitations, asthma management, health care use, and ETS exposure were examined.

RESULTS

Smoking in the home was reported by 29.4% of primary caregivers. ETS exposure (yes/no) was not related to frequency of child nocturnal symptoms or other select asthma morbidity markers. However, among children exposed to ETS, the frequency and severity of child nocturnal symptoms were highest among children exposed to moderate-to-heavy levels of ETS. After controlling for child age, anti-inflammatory medication use, asthma primary care, and caregiver's education, exposure to higher levels of ETS was associated with nearly a 3-fold increase in nocturnal symptoms in children (odds ratio, 2.83; 95% CI, 1.22-6.55).

CONCLUSION

Among elementary school inner-city children with asthma, exposure to higher levels of ETS was associated with increased frequency of nocturnal symptoms. Reducing the exposure of children with asthma to ETS should be a clear priority in developing effective asthma management plans for inner-city families.

Morbidade respiratória em crianças fumantes passivas

Objetivo: Avaliar a prevalência de morbidade respiratória entre crianças expostas ao fumo passivo e determinar os efeitos do fumo ambiental no sistema respiratório inferior e superior dessas crianças, na cidade de Fortaleza, Ceará, Brasil. Casuística e método: Este é um estudo censitário do tipo transversal em 1.104 crianças menores de cinco anos. Dados sobre os sintomas respiratórios e as doenças dessas crianças, o histórico familiar de doenças respiratórias, os hábitos tabagísticos dos membros da casa e as condições habitacionais foram avaliados através de um questionário aplicado junto aos pais. Resultados: Das 1.104 crianças, 558 eram do sexo masculino e 546 do feminino. A morbidade respiratória foi maior entre as crianças expostas ao fumo ambiental do que entre as não expostas (82% vs. 74%). Em relação ao trato respiratório inferior as queixas mais comuns foram sibilância (57,7%; OR = 1,32; IC 95%: 1,04-1,68), dispnéia (43,8%; OR = 1,56; IC 95%: 1,22-1,99), asma, bronquite ou pneumonia (29,4%; OR = 1,31; IC 95%: 1,13-1,88). Quanto ao trato respiratório superior, a queixa mais comum foi de rinite em 38,1% dos casos (OR = 1,46; IC 95%: 1,00-1,71).A análise de regressão logística mostrou que as queixas referentes ao trato respiratório inferior se associaram com tabagismo materno (OR = 2,02; IC 95% 1,12-3,66); tabagismo paterno(OR = 1,99; IC 95%: 1,16-3,40); mofo (OR = 1,55; IC 95%: 1,14-2,13) e antecedentes de doenças respiratórias (OR = 1,72; IC 95%: 1,26-2,35). As doenças do trato respiratório superior associaram-se com antecedentes de doenças respiratórias (OR = 1,44; IC 95%: 1,13-1,85) e tabagismo materno (OR = 1,54; IC 95%: 1,01-2,35). Conclusão: A exposição de crianças ao fumo ambiental é um fator de associação para a morbidade do trato respiratório superior e inferior entre menores de cinco anos.

Marginal and dynamic regression models for longitudinal data

Regression models for longitudinal data often employ random effects and serial correlation to account for residual variation between and within subjects. Most of these models are marginal models, separating the mean and covariance parameters. This paper discusses the use of dynamic models in which a lagged response serves as a predictor and compares these to marginal models. Regression parameters have a different interpretation in dynamic models as they describe changes in response levels, rather than the levels themselves. Lagged predictors are also useful with longitudinal data, explicitly quantifying the effect of previous levels of risk factors. These models are explored through analysis of data from the Childhood Respiratory Study, modelling lung function (FEV(1)) levels as a function of age, height, sex and smoking status in children measured over a five-year period.

Association of environmental tobacco smoke at work and forced expiratory lung function among never smoking asthmatics and non-asthmatics. The SAPALDIA-Team. Swiss Study on Air Pollution and Lung Disease in Adults

Inconsistencies across studies on the association of environmental tobacco smoke (ETS) and pulmonary function may be clarified addressing potentially susceptible subgroups. We determined the association of ETS exposure at work with FVC, FEV1, and FEF25-75% in life-time never smokers (N = 3534) of the SAPALDIA random population sample (age 18-60). We considered sex, bronchial reactivity, and asthma status as a priori indicators to identify susceptible riskgroups. The multivariate regression models adjusted for height, age, education, dust/aerosol exposure, region, and ETS at home. Overall, ETS was not significantly associated with FVC (0.7%; -0.4 to +1.8), FEV1 (-0.1%; 95% CI: -1.3 to +1.1) or FEF25-75% (-1.9%; -4.2 to +0.5). Effects were observed among asthmatics (n = 325), FEV1 (-4.8%; 0 to -9.2); FEF25-75% (-12.4%; -3.7 to -20.4); FVC: (-1.7%; +2.1 to -5.5), particularly in asthmatic women (n = 183): FVC -4.4% (-9.6 to +1.1); FEV1: -8.7% (-14.5 to -2.5); FEF25-75%: -20.8% (-32 to -7.6), where duration of ETS exposure at work was associated with lung function (FEV1 -6% per hour of ETS exposure at work (p = 0.01); FEF25-75%: -3.4%/h (p < 0.05). In non-asthmatic women (n = 1963) and in men no significant effect was observed. The size of the observed effect among susceptible subgroups has to be considered clinically relevant. However, due to inherent limitations of this cross-sectional analysis, selection or information biases may not be fully controlled. For example, asthmatic women reported higher ETS exposure at work than asthmatic men. Given the public health importance to identify susceptible subgroups, these results ought to be replicated.

The effect of passive smoking on pulmonary function during childhood

Passive smoking, especially of maternal origin, is known to influence adversely the development of children's pulmonary function. In this study, the effect of parental smoking on the pulmonary function of 360 primary school children aged 9-13 (mean 10.8 +/- 0.7) years was investigated. Information on parental smoking history was collected using a questionnaire, and spirometric measurements were performed on the children. All spirometric indices were lower in children who had been passively exposed to parental tobacco smoke than those not exposed. The percentage of households in which at least one parent smoked was 81.5%. This figure was significantly lower for mothers (27.5%) than for fathers (79%). Paternal smoking was associated with reduced levels of forced expiratory flow between 25-75% of vital capacity, peak expiratory flow, and flow rates after 50% and 75% of vital capacity expired (p < 0.05). Maternal smoking did not have statistically significant adverse effects on children's pulmonary function. This result might be due to the low occurrence of either pre- or post-natal smoking among mothers and confirms that, in our population, the main target group for antitobacco campaigns should be fathers.

Urinary Cotinine and Exposure to Parental Smoking in a Population of Children with Asthma

Background: Studies of the effects of tobacco smoke often rely on reported exposure to cigarette smoke, a measure that is subject to bias. We describe here the relationship between parental smoking exposure as assessed by urinary cotinine excretion and lung function in children with asthma.

Methods: We studied 90 children 4–14 years of age, who reported a confirmed diagnosis or symptoms of asthma. In each child, we assessed baseline pulmonary function (spirometry) and bronchial responsiveness to carbachol stimulation. Urinary cotinine was measured by HPLC with ultraviolet detection.

Results: Urinary cotinine concentrations in the children were significantly correlated (P &lt;0.001) with the number of cigarettes the parents, especially the mothers, smoked. Bronchial responsiveness to carbachol (but not spirometry test results) was correlated (P &lt;0.03) with urinary cotinine in the children.

Conclusion: Passive smoke exposure increases the bronchial responsiveness to carbachol in asthmatic children.

Maternal smoking and medical expenditures for childhood respiratory illness

OBJECTIVES

This study sought to assess the association between environmental tobacco smoke exposure from maternal smoking and health care expenditures for respiratory conditions among US children.

METHODS

Multivariate analysis of the 1987 National Medical Expenditure Survey was undertaken with a sample that included 2624 children 5 years of age and under.

RESULTS

After analysis that controlled for various sociodemographic factors associated with health care usage, respiratory-related health care expenditures among children whose mothers smoke were found to be significantly higher than those expenditures for children of nonsmoking mothers. Truncated regression techniques were used to estimate that maternal smoking was associated with increased health care expenditures averaging (in 1995 dollars) $120 per year for children aged 5 years and under and $175 per year for children aged 2 years and under. Our analysis indicates that passive smoking was associated with $661 million in annual medical expenditures in 1987, representing 19% of all expenditures for childhood respiratory conditions.

CONCLUSIONS

Maternal smoking is associated with significantly increased child health expenditures and contributes significantly to the overall cost of medical care.

Effects of indoor air pollution on lung function of primary school children in Jordan

Environmental exposure to tobacco smoke and contaminants from unvented cooking stoves has been linked to impaired pulmonary function and respiratory diseases. These risk factors exist to a greater extent in developing countries and, in the case of exposure to tobacco smoke, they are reported to be increasing. In this study, pulmonary function studies were performed on 1905 children in Jordan. The effect of exposure to these environmental factors on respiratory function was analyzed. A significant negative impact was found with regard to environmental exposure to both passive smoking and wood and kerosene unvented cooking stoves. The mean values of lung function in children exposed and not exposed to passive smoking were, respectively, FVC (L): 1.29-1.49; FEV1 (L): 1.2-1.4; FEF25-75 (L/S): 1.84-2.24; PEFR (L/S): 2.6-3.21, and to wood and kerosene were FVC (L): 1.02-1.32; FEV1 (L): 0.91-1.25; FEF25-75 (L/S): 1.24-1.86; PEFR (L/S): 1.67-2.64. This is a major problem in developing countries because of the increasing incidence of smoking and the high exposure to pollution risk factors.

Effect of passive smoking, asthma, and respiratory infection on lung function in Australian children

We have calculated normal standards for lung function of Australian children and have estimated the effects on lung function of passive smoking, current asthma, past asthma, and a current respiratory infection. Three cross-sectional samples of children in school years 3-5 (aged 8-11 years) were studied. The 2765 children were from two rural regions of NSW and from the city of Sydney. Details of passive smoking and respiratory illness were collected by a questionnaire sent to parents. Forced vital capacity (FVC), forced expiratory volume in 1 sec (FEV1), peak expiratory flow rate (PEFR), and forced mid-expiratory flow rate (FEF25-75%) were used as measures of lung function. Airway responsiveness was assessed by histamine inhalation test. Data from 1278 "normal" children were used in regression analysis to calculate prediction models for lung function. Passive smoking was associated with reduced FEV1, PEFR, and FEF25-75%. Children with current asthma had reduced FEV1 and FEF25-75% and children with past asthma had reduced FEF25-75%. Children with a current respiratory infection had reduced FVC, FEV1, PEFR, and FEF25-75%. The effects of these deficits on the future lung function of these children is not known but is likely to be important.

Trees and tracking

Epidemiologists have used the term 'tracking' to connote an individual's maintenance of relative rank of some longitudinally measured characteristic over a given time span. To assess the extent to which an attribute tracks we have first to summarize individual growth curves, and second to quantify the notion of maintenance of relative rank, both in the face of random error. A sequence of papers appearing in 1981 provided differing methodologies for appraising tracking. Here we take a different approach to tracking by using regression trees for longitudinal data. The above two concerns are simultaneously addressed in that the procedure identifies subgroups, defined in terms of covariates, within which the collection of growth curves is homogeneous. After reviewing the existing approaches to tracking we describe the tree-structured methodology, and present an illustrative example pertaining to lung function growth in children.

Respiratory symptoms and lung function effects of domestic exposure to tobacco smoke and cooking by gas in non-smoking women in Singapore

STUDY OBJECTIVES

To investigate the effects of passive exposure to tobacco smoke and gas cooking at home on respiratory symptoms and lung function of non-smoking women.

SETTING

Evidence on the effects of passive smoking and exposure to nitrogen dioxide from gas cooking on the respiratory health of adults is limited and variable. Over 97% of women in Singapore do not smoke, and a principal source of indoor air pollution for housewives is passive smoking and gas cooking.

DESIGN

This was a cross sectional (prevalence) study of a population based sample of 2868 adults aged 20 to 74 years in Singapore. A structured questionnaire administered by trained interviewers was used to collect data on passive smoking, gas cooking, respiratory symptoms, and other relevant variables. Passive smoking was defined as exposure to cigarette smoke from one or more members of the household who had ever smoked. Gas cooking was defined in terms of the weekly frequency of gas cooking, as well as the frequency with which the respondent's kitchen was filled with heavy cooking fumes (rarely, occasionally, often). Forced expiratory volume in one second (FEV1) was measured by using a portable Micro-spirometer. Multivariate analyses were used to estimate relative odds of association for respiratory symptoms and FEV1 effect, with adjustment for potential confounding variables.

PARTICIPANTS

Of a total of 1438 women in the sample, 1282 women who had never smoked provided questionnaire data and 1008 women provided acceptable readings of FEV1 for analysis.

MAIN RESULTS

Passive smoking was significantly associated with greater relative odds of usual or chronic cough and phlegm, wheezing, and breathlessness on exertion, as well as lower FEV1. Greater relative odds of respiratory symptoms were also associated with the weekly frequency of gas cooking, although these results were statistically insignificant. Chronic cough and phlegm and breathlessness on exertion, however, were significantly associated with the frequency with which the kitchen was filled with heavy cooking fumes. A lower FEV1 was found in women who cooked frequently (more than thrice a week).

CONCLUSION

Domestic exposure to cigarette smoke and gas cooking is associated with increased risks of respiratory symptoms and impairment of lung function in non-smoking women in Singapore.

Passive smoking and lung function in cystic fibrosis

The relationship between passive exposure to cigarette smoking and objective measures of health was examined in 340 patients with cystic fibrosis attending a large hospital-based clinic. Patients who came from households with smokers did not differ from those living in smoke-free households in terms of nutritional status, clinical scores, spirometry, or colonization with Pseudomonas. The number of cigarettes smoked in the household was not significantly related to nutritional status, clinical score, spirometry, or hospitalization. Similar results were found when children 6 to 11 yr of age were analyzed separately, except that height percentile was negatively related to the number of cigarettes smoked in the household. The effects of household exposure to cigarette smoke were further evaluated by analyzing changes in nutritional status, clinical score, and spirometry over a 15-yr period among patients whose families never, always, stopped, or started smoking during this time. Height percentile increased slightly during this interval among those whose households never smoked, whereas no change occurred among patients whose households always smoked, and a decline was seen among patients whose households quit. These differences were statistically significant. Patients whose households never smoked had consistently higher pulmonary function measurements than did patients whose families always smoked, although the differences were not statistically significant. The rates of decline were similar in these two groups. Patients whose households stopped smoking had significantly lower pulmonary functions at the end of the study than did subjects whose households never smoked.(ABSTRACT TRUNCATED AT 250 WORDS)

Exposure to environmental tobacco smoke as a risk factor for recurrent acute otitis media in children under the age of five years

Exposure to environmental tobacco smoke (ETS) has remained a controversial risk factor for otitis media in children. This study evaluates the association between exposure to ETS and recurrent acute otitis media (RAOM) in 85 cases and 85 age and gender matched controls under the age of 5 years. Cases and controls were obtained from outpatient otolaryngology and ophthalmology clinics, respectively, at the Children's Hospital of Eastern Ontario. Cases were defined as having four or more physician documented AOM episodes in the preceding 12 months and controls were otitis free in the prior 12 months. Exposure status was assessed via parental questionnaire. Controlling for other risk factors (via conditional logistic regression), such as daycare attendance, socioeconomic status, prematurity and family history of otitis media, a significant association between ETS and RAOM was evident (odds ratio = 2.68, 95% CI = 1.27-5.65). When categorized, a significant exposure response relationship between increasing level of exposure to ETS and increased risk of RAOM was evident. The population etiologic fraction indicated that up to 34% of RAOM cases may be accounted for by ETS exposure. We conclude that exposure to ETS is an important and modifiable risk factor for RAOM in children under the age of 5 years.

Parental cigarette smoking and tonsillectomy in children

The deleterious effects of parental smoking on the upper respiratory tracts of children are becoming increasingly recognized. This study examines the effect of parental smoking on the frequency of tonsillitis and incidence of tonsillectomy in children. A group of children being admitted for tonsillectomy and a control group of children from an orthoptic clinic were studied. Details recorded about the children included a history of tonsillectomy and the number of courses of antibiotics taken for sore throats in the previous 12 months. Parents were questioned about their smoking habits. A marked and statistically significant association has been found between the incidence of tonsillectomy in children and parental smoking in the home environment. There was a higher frequency of attacks of tonsillitis requiring antibiotic treatment in those children whose parents smoked. This effect may be mediated by altered oropharyngeal flora, mucociliary dysfunction, increased cross infection or a combination of these. If parents are encouraged to stop smoking there will be a reduction in tobacco smoke levels in the home environment and this should lead to a fall in both the incidence of tonsillitis and the need for tonsillectomy in their children.

Passive smoking effects on wheezy bronchitis

Previous epidemiological studies have associated parental smoking with an increased incidence of lower respiratory illness and bronchial asthma. The aim of the present study was to investigate the association between parental smoking habits and diagnosed wheezy bronchitis in schoolchildren in Saudi Arabia. In a cross-sectional study 3,041 schoolchildren ages seven to 12 years were randomly selected in Dammam, Jeddah, and Riyadh; representing three different geoclimatic regions of Saudi Arabia. Standardized questionnaires were used in our study. The results showed that paternal smoking had a significant effect on the frequency of wheezing when paternal and maternal smoking were considered separately. There was no considerable variation in the parental smoking habits in three areas. The association between passive smoking and diagnosed wheezy bronchitis and frequency of wheezing attacks was highly significant (P<0.0001). Overall, the results tend to confirm that there is a real effect of passive smoking on the respiratory health of children and that paternal smoking is a risk factor for wheezy bronchitis in children.

Age and height as predictors of peak expiratory flow rate in Indian girls

Peak expiratory flow rate (PEF) was measured on 175 healthy Indian girls in the age range 8-18 years with the help of Wright's Peak Flow Meter. PEF was recorded in the post absorptive phase at least 1 h after breakfast. The subjects rested for 0.5 h before the test procedure and tests were carried out between 1000-11000 hrs to avoid diurnal changes. The highest of three recordings was noted as the subject's PEF. PEF, age, height and body weight were correlated with each other and an intercorrelation matrix between these variables has been designed. It was observed, after performing multivariate regression analysis, that age and height are significant predictors of PEF. A multiple linear regression equation and a nomogram have been constructed for predicting PEF from age and height in young healthy Indian girls.

Lung function, respiratory illness, and passive smoking in British primary school children

BACKGROUND

Many studies have reported a significant association between parents' smoking and reduced lung function in their children, but often the association has been found to be significant only in relation to maternal smoking. There have been few epidemiological studies on this topic in Britain.

METHODS

Spirometry, in 2756 children aged 6.50-11.99 years, was carried out in a representative sample of English children, an inner city and ethnic minority sample, and a Scottish sample. Forced vital capacity (FVC), forced expiratory volume in one second (FEV1), and forced expiratory flow rates of 25-75% and 75-85% (FEF25-75 and FEF75-85) were measured and standardised scores obtained separately for the English representative sample, the Scottish sample and subgroups in the inner city sample, white and Afro-Caribbean children and those originating from the Indian subcontinent. Multiple regression analyses were used to assess associations of FVC, FEV1, FEF25-75 and FEF75-85 with the passive smoking and respiratory illness, with adjustment for a large number of potential confounders. Passive smoking was defined in terms of reported number of cigarettes smoked at home by each parent. The respiratory symptoms and illnesses assessed were wheeze, asthma and bronchitis attacks, cough in the morning, and cough at any other time as reported by parents.

RESULTS

Maternal smoking, but not paternal smoking, was associated with reduced FEF25-75 and FEF75-85 in boys. No association was found between passive smoking and lung function in girls, but in an analysis including both sexes the interaction of sex and parental smoking on lung function was not significant. With few exceptions, FEV1, FEF25-75 and FEF75-85 were reduced in children with wheeze and asthma attacks.

CONCLUSIONS

The effect of passive smoking may depend on the close contact of a parent with a susceptible child as only maternal smoking in boys was significantly associated with impaired lung function. However, this explanation remains unsubstantiated. A parent's report of wheeze and asthma attacks in the child is reflected in reduced lung function.

Relation of passive smoking as assessed by salivary cotinine concentration and questionnaire to spirometric indices in children

BACKGROUND

Previous studies of the effects of passive exposure to smoke on spirometric indices in children have largely relied on questionnaire measures of exposure. This may have resulted in underestimation of the true effect of passive smoking. Biochemical measures offer the opportunity to estimate recent exposure directly.

METHODS

The relation between spirometric indices and passive exposure to tobacco smoke was examined in a large population sample of 5-7 year old children from 10 towns in England and Wales. The effects of passive exposure to smoke on lung function were assessed by means of both salivary cotinine concentration and questionnaire measurements of exposure. Analyses of the relation between spirometric values and cotinine concentrations were based on 2511 children and of the relation between spirometric values and questionnaire measures on 2000 children.

RESULTS

Cotinine concentration was negatively associated with all spirometric indices after adjustment for confounding variables, which included age, sex, body size, and social class. The strongest association was with mid expiratory flow rate (FEF50), the fall between the bottom and top fifths of the cotinine distribution being 6%, equivalent to a reduction of 14.3 (95% confidence limits (CL) 8.6, 20.0) ml/s per ng/ml cotinine. Salivary cotinine concentrations were strongly related to exposure to cigarette smoke at home but 88% of children who were from non-smoking households and not looked after by a smoker had detectable cotinine concentrations, 5% being in the top two fifths of the cotinine distribution. A composite questionnaire score based on the number of regular sources of exposure was as strongly related to mid and end expiratory flow rates as the single cotinine measure. The fall in FEF50 per smoker to whom the child was exposed was 51.0 (26.5, 75.5) ml/s. The relationships between the questionnaire score and forced vital capacity (FVC) or forced expiratory volume in one second (FEV1) were not statistically significant.

CONCLUSIONS

These effects of passive smoking on respiratory function are consistent with the results of previous studies and, although small in absolute magnitude, may be important if the effects of exposure are cumulative. In children aged 5-7 years the use of a single salivary cotinine concentration as a marker of passive exposure to smoke resulted in clear relationships between exposure and FVC and FEV1, whereas the associations were much weaker and not significant when based on the questionnaire score. The associations between exposure and mid or end expiratory flow rates were of similar magnitude for cotinine concentration and the questionnaire score. The use of salivary cotinine concentration in longitudinal studies may help to determine the extent to which these effects are cumulative or reversible.

The relationship of nasal disorders to lower respiratory tract symptoms and illness in a random sample of children

We examined the relationship of nasal disorders, defined as frequent colds and sinus trouble, to lower respiratory tract symptoms in a random population of 718 children aged 4 to 11 years in East Boston, Massachusetts. Frequent colds were significantly associated with maternal smoking (odds ratio (OR) = 3.00; 95% confidence interval (CI) = 1.97, 4.58), and so was sinus trouble (OR = 4.73; 95% CI = 1.78, 12.51). After adjustment for maternal smoking, age and sex, frequent colds (OR = 2.88; 95% CI = 1.87, 4.42) and sinus trouble (OR = 4.95, 95% CI = 1.83, 13.39) remained significant predictors of lower respiratory tract symptoms in separate logistic regressions. If one restricted the cohort to the 513 children who also had personal smoking information and adjusted for this variable as well, the results for colds were unchanged (OR = 2.94; 95% CI = 1.78, 4.84) but the results for sinus trouble were now not statistically significant (OR = 2.30, 95% CI = 0.67, 7.94). We conclude that nasal disorders are associated with lower respiratory tract symptoms in children.

Multivariate methods for binary longitudinal data with heterogeneous correlation over time

Clustered binary data occur frequently in biostatistical work. One particular application is in binary longitudinal data, where several visits are available for the same individual. Several approaches have been proposed for the analysis of clustered binary data. In Rosner, a polychotomous logistic regression model was proposed which is a generalization of the beta-binomial distribution and allows for person- and visit-specific covariates, while controlling for clustering effects. One assumption of this model is that all pairs of visits within an individual are equally correlated, which may be inappropriate if several visits are available over a long follow-up period. In this paper, this approach is extended to allow for heterogeneous correlation over time. The total time period is divided into subintervals and a beta-binomial mixture model is introduced to estimate odds ratios relating outcomes for pairs of visits both within a subinterval as well as in different subintervals. To include covariates, an extension of the polychotomous logistic regression model is proposed, which allows one to estimate effects of person-, subinterval-, and visit-specific covariates, while controlling for clustering using the beta-binomial mixture model. This model is applied to the analysis of respiratory symptom data in children collected over a 14-year period in East Boston, MA, in relation to maternal and child smoking, where the unit is the child and symptom history is divided into early-adolescent and late-adolescent symptom experience.

Smoking and pulmonary function in five Solomon Island populations

The relationship between smoking and lung function was examined in a large sample of healthy Solomon Island Melanesians and Polynesians as part of a multidisciplinary study carried out in 1985 and 1986. Comparisons are made between samples of smokers and non-smokers to determine if smoking is associated with a reduction in pulmonary function among males and females between 25 and 75 years of age. The results of this study indicate that cigarette smoking causes significant reductions in the pulmonary function of these populations. In addition, a clear difference in pulmonary function between males and females, as well as a general reduction in female FEV1 values, suggests that cooking smoke inhalation may be operating as a possible risk factor to the pulmonary health of women. Further research is needed to quantify exposure to smoke of both males and females and relate this measure to declines in pulmonary function.

Smoking prohibition in the workplace and smoking cessation in the Federal Republic of Germany

BACKGROUND

The relationship between prohibition of smoking at the workplace and smoking cessation was assessed in a national sample survey conducted in the Federal Republic of Germany in 1987.

METHODS

Four hundred thirty-nine men and women ages 21 to 65, who were actively engaged in the workforce for at least 20 hr per week and were either current or former smokers, were included in the study.

RESULTS

Quit ratios were substantially higher among women who worked at worksites designated as smokefree compared with women who were allowed to smoke at their workplace. Among men, there were only minor differences between both types of worksites. After simultaneously controlling for age, marital status, and level of education by multiple logistic regression, the odds ratio of being a current smoker (vs former smoker) was 0.80 (95% confidence interval, 0.44-1.45) for men and 0.22 (95% confidence interval, 0.09-0.50) for women working at places where smoking was prohibited (compared with men and women who were allowed to smoke at the workplace).

CONCLUSION

These results suggest that prohibition of smoking at the workplace may help a substantial proportion of smokers, particularly female smokers, to quit. Prohibition of smoking at the workplace might therefore be a particularly cost-effective public health measure.

Controlling allergies by controlling environment. A big help for your patients

Control of the environment is a cost-effective method of limiting allergic reactions in susceptible people. For physicians working with allergic patients, this approach involves guiding the patient and family in ridding their home and surroundings of allergens and irritants. Dr. Klein discusses the environmental-control protocol, particularly in regard to dust mites, mold, pollen, and pets.

Respiratory irritation from environmental tobacco smoke

Acute physiological and chronic pathological responses of the respiratory tract to environmental tobacco smoke (ETS) are reviewed briefly. This study excludes discussion of the possible risk of lung cancer and the known impact of carbon monoxide on the fetus and adult. In some environments, the dose of particulate matter and the concentrations of irritant vapors absorbed on the ETS particles reach a level for which a physiological response may be expected, not only in the nose but also the bronchi. However, direct measurements indicate only small increases of nasal and bronchial resistance if normal subjects are exposed to maximal, likely concentrations of ETS. ETS is readily detected by the nonsmoker, but there is no strong evidence that pulmonary reactions have a psychogenic basis. The condition of approximately 20% of asthmatic patients is exacerbated by ETS exposure. Further study is needed to clarify the likelihood that adults will progress from a minor physiological response to pathological reactions, e.g., chronic obstructive lung disease. In young children (who are less able to escape from ETS), the association between exposure and an increase in respiratory disease is stronger than in adults. Exacerbation of asthma and an increase of respiratory disease are further arguments for legislation to guarantee smoke-free air to the nonsmoking public.

A profile of respiratory symptoms in urban and rural South Australian school children

This report describes the cross-sectional analyses of data from the first year of a longitudinal study using questionnaire and respiratory function data over a 5 year period from a sample of rural South Australian school children. The cumulative or lifetime prevalences of respiratory symptoms were estimated in 825 rural and 1261 urban school children aged between 5 and 15 years in order to determine if the prevalence rates differed between rural and urban school children. The study found the overall cumulative prevalence of asthma and/or wheezy breathing (AWB) to be 24.1% in the rural school children compared to 27.6% in the urban school children. Most children developed AWB symptoms before the age of 7 years, with 20% reporting moderately severe symptoms and 10% having more than one attack per fortnight. The cumulative prevalence of bronchitis, loose/rattly cough (BLRC) differed significantly between the rural school children (34.1%) and urban school children (47.9%). The BLRC symptoms preceded the development of AWB in many cases. Urban school children also reported a higher prevalence of atopic conditions.

Environmental tobacco smoke: current assessment and future directions

Scientific information on environmental tobacco smoke (ETS) is critically reviewed. Key areas addressed are: differences in chemical composition between mainstream smoke, sidestream smoke, and ETS; techniques for measurement of ETS; epidemiology; in vitro and in vivo toxicology; and chamber and field studies of perceptual or physiological effects. Questions concerning estimation of ETS exposure, suitability of various biomarkers, calculation of lifetime dose, control of confounding variables, use of meta-analysis, and the relationship between ETS concentrations and human responses all emphasize the need for additional research in order to assess potential effects of ETS on health or comfort.

Impact of a hospital smoking ban: changes in tobacco use and employee attitudes

The authors investigated the impact of a complete smoking ban on 349 employees of a cancer treatment center. A questionnaire administered approximately 4 months after the ban was initiated queried smokers on the impact of the ban on their smoking habits, their experience of withdrawal symptoms during the workday, and changes in work habits. A separate questionnaire asked nonsmokers about changes in the work environment. Results showed that few smokers quit while a majority decreased their consumption. Withdrawal symptoms were a problem in less than half the smokers, but those reporting signs of physical dependency on nicotine tended to smoke more before and after work and reported negative changes in work performance. Nonsmokers in general reported positive effects on the work environment.

Parental smoking and the risk of childhood asthma

In order to explore the correlation between parents' smoking habits and bronchial asthma in children, we undertook a cross-sectional study of 3300 (54% males, 46% females) school children aged 7-12 years old. A survey of smoking habits and attitudes conducted in Saudi Arabia showed a positive correlation between parental smoking and asthma. This study showed a significant link between parental smoking and chest wheeze or whistling, cough, and family history of rhinitis. Evidence is accumulating that there is a relationship between parental smoking and respiratory symptoms in Saudi children. The present study results are clear evidence of a definite association between smoking in the home and bronchial asthma in young children, which not only may present immediate problems, but may also be a cause of illness in the future.

The relationship of salivary cotinine to respiratory symptoms, spirometry, and exercise-induced bronchospasm in seven-year-old children

The effects of passive tobacco smoke exposure upon respiratory symptoms and lung function were assessed in a cross-sectional survey of 770 children 7 yr of age, using cotinine as a quantitative biochemical marker of exposure. Salivary cotinine levels were strongly related to the number of smokers in the home, but three-quarters of children from nonsmoking households had detectable salivary cotinine, and 10% of this group were in the upper two-fifths of the distribution of measured tobacco smoke exposure. Smoking by persons other than members of the household may deserve greater attention in future studies of young children. After adjustment for housing tenure, most respiratory symptoms were unrelated to salivary cotinine, but a "tendency for colds to go to the chest" was twice as prevalent in the upper two-fifths as in the lower two-fifths of the cotinine distribution. No association was found between salivary cotinine and reports of wheeze or measured reduction in FEV1 after 6 min of free running. After adjustment for sex, height, test conditions, and housing tenure, all baseline spirometric indices except FVC were inversely associated with salivary cotinine. Only FEF75-85 and FEF75 were significantly reduced, the difference for each index between the top and bottom quintiles of the cotinine distribution being about 7%, equivalent to a reduction of 1.1% (95% CL, 0.1 to 2.1%) per doubling of cotinine concentration. These changes may be evidence of small airways damage, which could later progress to more severe respiratory impairment.

Lipoprotein and oxygen transport alterations in passive smoking preadolescent children. The MCV Twin Study

We investigated the cardiovascular effects of lifelong passive cigarette smoke exposure in preadolescent children and examined the following questions: 1) Is systemic oxygen transport altered? 2) Are coronary heart disease risk factors adversely affected? We recruited 216 families from the MCV Twin Study; 105 had at least one smoking parent. Serum thiocyanate and cotinine levels were used as measures of smoke exposure in the children and thiocyanate was proportional to the number of parental cigarettes smoked each day (p = 0.0001). Paternal smoking had no effect on these measures. Whole blood 2,3-diphosphoglycerate was higher in smoke-exposed than unexposed children (p less than 0.01) and was related to the thiocyanate level (p less than 0.02). High density lipoprotein (HDL) cholesterol was lower in passive smoking children (p less than 0.05); the HDL2 subfraction was reduced in passive smoking boys, while the HDL3 subfraction was reduced in passive smoking girls. Significant adverse alterations in systemic oxygen transport and lipoprotein profiles are already present in preadolescent children exposed to long-term passive cigarette smoke, primarily from maternal smoke. Children with long-term exposure to passive smoke may be at elevated risk for the development of premature coronary heart disease.

Effects of passive smoking on the pulmonary function of adults

The effects of exposure to environmental tobacco smoke (passive smoking) on pulmonary function of non-smoking, healthy Iranian men (n = 167) and women (n = 108) were investigated. There were significant reductions in % predicted FEV1 (5.7%), forced vital capacity (FVC, 4.6%) and forced expiratory flow 25-75% (FEF25-75, 9.9%) among men exposed to cigarette smoke (n = 78). The adverse effect of passive smoking was greatest among men exposed at the workplace (reduction in % predicted FEV1 9.4%, FVC 7.6%, and FEF25-75 15.3%). No significant difference in pulmonary function was found among the 54 women exposed to passive smoke, but only eight women had smoke exposure at work. It is concluded that exposure to environmental tobacco smoke, particularly at the workplace, adversely affects the pulmonary function of adults.