Atopic babies with wheezy bronchitis. Follow-up study relating prognosis to sequential IgE values, type of early infant feeding, exposure to parental smoking and incidence of lower respiratory tract infections

History of pollutant adjuvants in respiratory allergy

Combined exposures to allergens and air pollutants emerged as a topic of concern in scientific circles by the 1980's, when it became clear that parallel increases in respiratory allergies and traffic-related air pollution had been occurring during the 20th century. Although historically there has been a tendency to treat exposure-related symptoms as either allergic or toxicologic in nature, cross-interactions have since been established between the two modalities. For example, exposure to selected air pollutants in concert with a given allergen can increase the likelihood that an individual will become sensitized to that allergen, strongly suggesting that the pollutant acted as an adjuvant. Although not a review of underlying mechanisms, the purpose of this mini-review is to highlight the potential significance of co-exposure to adjuvant chemicals in predicting allergic sensitization in the respiratory tract. The current discussion emphasizes the upper airway as a model for respiratory challenge studies, the results of which may be applicable-not only to allergic rhinitis-but also to conjunctivitis and asthma.

Breastfeeding and allergic disease: a multidisciplinary review of the literature (1966-2001) on the mode of early feeding in infancy and its impact on later atopic manifestations

BACKGROUND

Strategies to prevent children from developing allergy have been elaborated on the basis of state-of-the-art reviews of the scientific literature regarding pets and allergies, building dampness and health, and building ventilation and health. A similar multidisciplinary review of infant feeding mode in relation to allergy has not been published previously. Here, the objective is to review the scientific literature regarding the impact of early feeding (breast milk and/or cow's milk and/or formula) on development of atopic disease. The work was performed by a multidisciplinary group of Scandinavian researchers.

METHODS

The search in the literature identified 4323 articles that contained at least one of the exposure and health effect terms. A total of 4191 articles were excluded mainly because they did not contain information on both exposure and health effects. Consequently, 132 studies have been scrutinized by this review group.

RESULTS

Of the 132 studies selected, 56 were regarded as conclusive. Several factors contributed to the exclusions. The studies considered conclusive by the review group were categorized according to population and study design.

CONCLUSIONS

The review group concluded that breastfeeding seems to protect from the development of atopic disease. The effect appears even stronger in children with atopic heredity. If breast milk is unavailable or insufficient, extensively hydrolysed formulas are preferable to unhydrolysed or partially hydrolysed formulas in terms of the risk of some atopic manifestations.

Reversing the trend: reducing the prevalence of asthma

BACKGROUND

We urgently need to take steps towards reducing the prevalence of asthma in countries where the prevalence has become unacceptably high in recent years. Because we do not have any good information about causes of the increased prevalence, we cannot act directly to reverse the trend. Therefore we need to take an indirect approach and use known information of etiologic factors to try to reduce asthma in the next generation, while acknowledging that we may be dealing with different factors from those responsible for the increased prevalence. Any successful strategies will also help to ensure that developing countries do not attain such high rates of asthma in their children in coming years.

OBJECTIVE

This article summarizes the roles of the risk factors that identify "high-risk" children, that provide insights into mechanisms, or that have potential for primary prevention. The factors with the most potential for primary prevention are allergen exposure, parental smoking, breast-feeding, and dietary fatty acids.

CONCLUSION

In other health models, information about risk factors has been used in successful public health interventions. It is disappointing that the important risk factors for asthma are well documented but that there have been few trials of primary prevention and no changes in public health policies.

Health effects of passive smoking. 6. Parental smoking and childhood asthma: longitudinal and case-control studies

BACKGROUND

The relation of parental smoking to wheezing and asthma occurring after the first year of life was assessed by a systematic quantitative review of case-control and longitudinal studies, complementing earlier reviews of cross sectional surveys and wheezing in early childhood.

METHODS

Fifty one relevant publications were identified after consideration of 1593 abstracts selected by electronic search of the Embase and Medline databases using keywords relevant to passive smoking in children. The search was completed in April 1997 and identified six studies of asthma incidence, seven of prognosis, 22 case-control studies, and 10 case series addressing disease severity.

RESULTS

Maternal smoking was associated with an increased incidence of wheezing illness up to age 6 (pooled odds ratio 1.31, 95% CI 1.22 to 1.41), but less strongly thereafter (1.13, 95% CI 1.04 to 1.22). The long term prognosis of early wheezing illness was better if the mother smoked. The pooled odds ratio for asthma prevalence from 14 case-control studies was 1.37 (95% CI 1.15 to 1.64) if either parent smoked. Four studies suggest that parental smoking is more strongly associated with wheezing among non-atopic children. Indicators of disease severity including symptom scores, attack frequency, medication use, hospital attendance, and life threatening bronchospasm were in general positively related to household smoke exposure.

CONCLUSIONS

The excess incidence of wheezing in smoking households appears to be largely non-atopic "wheezy bronchitis" with a relatively benign prognosis, but among children with established asthma, parental smoking is associated with more severe disease. This apparent paradox may be reconciled if environmental tobacco smoke is considered a co-factor provoking wheezing attacks, rather than a cause of the underlying asthmatic tendency.

Health effects of passive smoking .5. Parental smoking and allergic sensitisation in children

BACKGROUND

A systematic review was conducted of the effects of parental smoking on immunoglobulin (IgE) levels, skin prick positivity, and allergic rhinitis or eczema in children. Asthma was excluded in order to distinguish more clearly the effect of passive smoke exposure on allergic sensitisation.

METHODS

Thirty six relevant publications were identified after consideration of 692 articles selected by electronic search of the Embase and Medline databases using keywords relevant to passive smoking in children. The search was completed in April 1997 and identified nine studies of IgE in neonates, eight of IgE in older children, 12 which included skin prick tests, and 10 describing symptoms of allergic disease other than asthma or wheezing. A quantitative meta-analysis was possible only for the studies reporting skin prick tests.

RESULTS

Several large studies failed to confirm early reports of a substantial or statistically significant association of maternal smoking with concentrations of total serum IgE in neonates or in older children. No consistent association emerged between parental smoking and allergic rhinitis or eczema. Few of these studies adjusted for potential confounding variables. The quantity and quality of evidence was greatest for skin prick tests, and studies of parental smoking during pregnancy or infancy were broadly consistent in showing no adverse effect on prick positivity (pooled odds ratio 0.87, 95% confidence interval 0.62 to 1.24). There was much greater and statistically significant (p = 0.002) heterogeneity of odds ratios relating current parental smoking to skin prick positivity.

CONCLUSIONS

Parental smoking, either before or immediately after birth, is unlikely to increase the risk of allergic sensitisation in children.

Eczema, asthma and allergy

The literature in relation to the development of atopic and allergic disorders has been reviewed, in order to assess the claim that prolonged and exclusive breast feeding protects against the development of such disorders. The data in the literature show little consistent evidence to identify any protective association between breast feeding and either eczema, wheezing/asthma or other types of atopy or allergic response.

Immuno-allergologic aspects of childhood asthma

Asthma has a major impact on the health of children. Airway inflammation and bronchial hyperresponsiveness of variable severity have presently come to be considered underlying the pathogenesis and pathophysiology of the condition. Atopy in infancy seems to predict the severity of bronchial hyperresponsiveness in later childhood. Genetic predisposition, allergen exposure and contributory factors combine to set the clinical picture. Early sensitization to ingested or inhaled allergens accelerates development of allergic asthma. In children, the activity of inflammation can be assessed by estimation of indirect markers.

Effect of an allergy prevention programme on incidence of atopic symptoms in infancy. A prospective study of 159 "high-risk" infants

A total of 105 "high-risk" infants born in 1988 were studied prospectively from birth to 18 months of age. The infants were recommended breastfeeding and/or hypoallergenic formula (Nutramigen or Profylac) combined with avoidance of solid foods during the first 6 months of life. All mothers had unrestricted diet. Avoidance of daily exposure to tobacco smoke, furred pets and dust-collecting materials in the bedroom were advised. This prevention group was compared with a control group consisting of 54 identically defined "high-risk" infants born in 1985 in the same area. All infants had either severe single atopic predisposition combined with cord blood IgE > or = 0.5 KU/l or biparental atopic predisposition. The control group had unrestricted diet and was not advised about environmental factors. Apart from the prevention programme and year of birth the prevention group and the control group were comparable. The parents were highly motivated and compliance was good. The rate of participation was 97%, and 85% followed the dietary measures strictly. The cumulative prevalence of atopic symptoms was significantly lower at 18 months in the prevention group (32%), as compared with the control group (74%) (p < 0.01), due to reduced prevalence of recurrent wheezing (13% versus 37%; p < 0.01), atopic dermatitis (14% versus 31%; p < 0.01), vomiting/diarrhoea (5% versus 20%; p < 0.01) and infantile colic (9% versus 24%; p < 0.01). The cumulative prevalence of food allergy was significantly lower in the prevention group (6% versus 17%; p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Recurrent wheezing in relation to environmental risk factors in infancy. A prospective study of 276 infants

Clinical course and environmental factors were recorded in a prospective study of 276 unselected infants followed from birth to the age of 18 months. The study was performed with a questionnaire at the age of 6 and 12 months and a physical examination at 18 months. Fifty-nine (21%) of the children had greater than or equal to 2 episodes of wheezing before they were 18 months old. A total of 58 (21%) of the children belonged to the lowest social class V, 182 (66%) were daily exposed to passive tobacco smoking at home and/or in daycare, 164 (59%) were breastfed greater than or equal to 3 months, 192 (70%) were in daycare, 62 (22%) lived in flats and 167 (61%) were in daily contact with furred pets at home and/or in daycare. In social class V a preponderance of children were exposed to passive tobacco smoking, a majority were living in flats and a minority were breastfed greater than or equal to 3 months. Linear logistic regression analysis was used for the purpose of assessing the causal effect of environmental risk factors on the risk of recurrent episodes of wheezing before the age of 18 months. The study demonstrated that male sex and daily exposure to passive tobacco smoking were significant risk factors with estimated odds ratios 1.9 and 2.4, respectively. Maternal tobacco smoking seemed to be associated with the highest risk. There was a tendency--though not significant--indicating that breastfeeding greater than or equal to 3 months had a protective effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Passive smoking and childhood asthma. Urinary cotinine levels in children with asthma and in referents

Passive exposure to tobacco smoke was assessed in children with asthma (age 3-15) and in referents. There was statistically significantly (P less than 0.0005) higher excretion of the nicotine metabolite, cotinine, in the urine of 49 children with asthma (geometric mean 10 ng/ml) compared with 77 referents (4.8 ng/ml). Maternal smoking was statistically significantly more prevalent among the asthmatics than among the referents (relative risk = RR = 2.6, 95% C1 = 1.2-5.3). In conclusion, the exposure to environmental tobacco smoke in asthmatic children was higher than among healthy children, indicating that passive smoking may be a predisposing and/or aggravating factor for childhood asthma.

The influence of a family history of asthma and parental smoking on airway responsiveness in early infancy

BACKGROUND

Airway responsiveness to inhaled nonspecific bronchoconstrictive agents has been demonstrated in normal, healthy infants. However, it is unknown whether airway responsiveness is present from birth or if it develops as a result of subsequent insults to the respiratory tract. To investigate this question, we assessed airway responsiveness in 63 normal infants at a mean age of 4 1/2 weeks.

METHODS

Respiratory function was measured with use of the partial forced expiratory flow-volume technique to determine the maximal flow at functional residual capacity (VmaxFRC). The infants inhaled nebulized histamine at sequentially doubled concentrations (0.125 to 8.0 g per liter), until a concentration was reached at which the VmaxFRC fell by 40 percent from the base-line value (PC40) or until a concentration of 8.0 g per liter was reached. We also assessed maternal serum levels of IgE, cord-serum levels of IgE, the infants' skin reactivity to several allergens, and the parents' responsiveness to histamine and obtained family histories of asthma and smoking.

RESULTS

Airway responsiveness was increased in infants with a family history of asthma (n = 19; median PC40, 0.78 g per liter; 95 percent confidence interval, 0.44 to 1.15; P less than 0.01), parental smoking (n = 13; median PC40, 0.52 g per liter; 95 percent confidence interval, 0.43 to 5.40; P less than 0.05), or both (n = 20; median PC40, 0.69 g per liter; 95 percent confidence interval, 0.37 to 2.10; P less than 0.05), as compared with the infants with no family history of asthma or smoking. The infants with no family history of asthma or smoking had a median PC40 of 2.75 g per liter (95 percent confidence interval, 1.48 to 4.00). No significant relations were detected between the immunologic variables and the PC40 in the infants.

CONCLUSIONS

This study indicates that airway responsiveness can be present early in life and suggests that a family history of asthma or parental smoking contributes to elevated levels of airway responsiveness at an early age.

Environmental factors and symptoms in infants at high risk of allergy

STUDY OBJECTIVE

To identify environmental determinants of six symptoms associated with allergic disease in infancy.

DESIGN

Infants were participants in a prospective randomised controlled trial of feeding practices in families with a history of atopy.

SETTING

Infants were recruited in two maternity hospitals in S Wales and followed up in the community for 1 year.

PARTICIPANTS

Mothers of 519 infants agreed to participate, but 36 were excluded (mainly for moving home or failing to attend for follow-up), leaving 483 in the study (253 male, 230 female). Infants were followed up and examined for evidence of allergic disease at 3, 6, and 12 months.

MEASUREMENTS AND MAIN RESULTS

At each examination, mothers were questioned about episodes of illness in the infant, and the data presented relate to (reported and observed) eczema and nasal discharge, and (reported) wheeze, prolonged colds, diarrhoea and vomiting. Mothers kept a diary with details of feeding for the first 6 months. All homes were visited by a nurse who took samples of dust for dust mite antigen analysis. Extensive socio-demographic data were collected. None of the factors studied showed a convincing relationship with eczema. In a multiple logistic regression analysis breast feeding appeared to protect against wheeze, nasal discharge, colds, vomiting and diarrhoea. Having more siblings increased the likelihood of prolonged colds, and (together with overcrowding) of wheeze and nasal discharge. Maternal smoking and low social class were associated with wheeze, and house dust antigen with prolonged colds. Respiratory symptoms were associated with some aspects of housing but these could not be distinguished clearly from other social factors. Babies born in Autumn were at increased risk of wheeze, vomiting and diarrhoea.

CONCLUSIONS

Environmental factors play an important part in determining risk of symptoms in potentially atopic babies. These factors are in principle open to manipulation.