Prenatal paracetamol exposure and risk of asthma and elevated immunoglobulin E in childhood

Prenatal paracetamol exposure and asthma: further evidence against confounding

BACKGROUND

Observational studies have reported an association between maternal use of paracetamol in pregnancy and childhood asthma, which was not explained by measured confounding factors. However, it is possible that this relation might be confounded by unmeasured behavioural factors linked to paracetamol usage; if that were the case, effects of similar magnitude of partner's paracetamol use and/or postnatal maternal use would be expected.

METHODS

In the Avon Longitudinal Study of Parents and Children (ALSPAC), a population-based birth cohort, we compared the univariate effects of maternal use of paracetamol in pregnancy on risk of doctor-diagnosed asthma, wheeze and elevated immunoglobulin E (IgE) in the offspring at 7 years of age, with the univariate effects of partner's use and postnatal maternal use on these phenotypes.

RESULTS

Maternal use of paracetamol in pregnancy was strongly associated with all outcomes. Partner's use was very weakly associated with asthma but not associated with wheezing or IgE. Postnatal maternal use was associated with asthma and wheezing, though less strongly than was prenatal use, and was not associated with IgE. On mutual adjustment, the effects of maternal use in pregnancy on all outcomes were not substantially attenuated, whereas the effects of partner's use on asthma, and of postnatal maternal use on asthma and wheezing, were reduced.

CONCLUSIONS

These findings suggest that the relation between maternal use of paracetamol in pregnancy and childhood asthma is unlikely to be confounded by unmeasured behavioural factors linked to paracetamol use.

Developments in the field of allergy in 2008 through the eyes of Clinical & Experimental Allergy

In 2008, many thousands of articles were published on the subject of allergic disease with over 200 reviews, editorials and original papers in Clinical & Experimental Allergy alone. These represent a considerable amount of data and even the most avid reader could only hope to assimilate a small fraction of this knowledge. There is therefore a pressing need for the key messages that emerge from a journal such as Clinical & Experimental Allergy to be summarized by experts in the field in a form that highlights the significance of the developments and sets them in the context of important findings in the field published in other journals. This also has the advantage of making connections between new data in conditions such as asthma, where articles often appear in different sections of the journal. As can be seen from this review, the body of work is diverse both in terms of the disease of interest and the discipline that has been used to investigate it. However, taken as a whole, we hope that the reader will gain a flavour of where the field is mature, where there remain controversies and where the cutting edge is leading.

Similarities in features of autism and asthma and a possible link to acetaminophen use

Autism and autism spectrum disorders are enigmatic conditions that have their origins in the interaction of genes and environmental factors. In this hypothesis, genes statistically associated with autism are emphasized to be important in inflammation and in innate immune pathways, including pathways for susceptibility to asthma. The role of acetaminophen (paracetamol) in an increased risk for asthma is described and a possible similar link to an increased risk for autism is suggested.

Prenatal exposure to acetaminophen and asthma in children

OBJECTIVE

To estimate whether prenatal exposure to acetaminophen is associated with risk of diagnosed asthma and asthma symptoms in children.

METHODS

The authors prospectively followed 1,505 pregnant women and their children until 6 years (+/-3 months) of life. Acetaminophen use in the first and third trimesters of pregnancy was assessed before 24 weeks of gestation and within 1 month of delivery, and asthma in children was assessed when the child was 6 years old. Adjusted odds ratios (aORs) were derived from logistic regression models controlling for potential confounders.

RESULTS

Acetaminophen was used by 69% of women during pregnancy. Use of acetaminophen did not significantly increase the risk of asthma (aOR 0.76, 95% confidence interval [CI] 0.53-1.10). Acetaminophen use during both the first and the third trimester was associated with a significantly reduced risk of asthma (aOR 0.59, 95% CI 0.36-0.98). There was no evidence of a dose response, and consumption greater than 10,400 mg (32 tablets) a month did not increase risk (aOR 0.99, 95% CI 0.19-5.30).

CONCLUSION

Our results suggest that acetaminophen use during pregnancy does not increase risk of asthma in children.

LEVEL OF EVIDENCE

II.

New developments in the assessment of developmental immunotoxicology

Recent progress has been made in directly comparing the risk of immunotoxicity following exposure to various drugs and environmental chemicals during different stages of life. With the availability of an increased developmental immunotoxicology database, new concepts of effective immunotoxicological risk assessment have emerged. From the standpoint of risk assessment, recent results suggest that there is greater value obtained from exposure-assessment of non-adults than can be derived solely from adult-exposure-outcome data. This is hardly surprising given the fact that, for the vast majority of known immunotoxicants compared across age groups, the non-adult stages are more sensitive than adults for risk of clinically important immunomodulation. Therefore, if immunotoxicity testing is to identify risk for the more susceptible subpopulations, the adult is not the informative model. This brief review, based on the Immuntoxicology III conference presentation, describes the data supporting age-based differences in sensitivity to immunotoxicants, differences in immunotoxic outcomes, and the potential benefits of utilizing non-adult exposures and life-stage-relevant immune assessment. In essence, the issue is whether historic adult immunotoxicity testing strategies can continue to ensure adequate protection of the most vulnerable subpopulations in the face of recent developmental immunotoxicological data. The review describes the possible benefits of substituting non-adult exposures for adult exposures in future assessment protocols.

Prenatal acetaminophen exposure and risk of wheeze at age 5 years in an urban low-income cohort

BACKGROUND

Acetaminophen has been associated with asthma and is in part metabolised via the glutathione pathway. Inner-city minority children have high asthma morbidity and a relatively high frequency of a minor allele variant in the glutathione S transferase Pi gene (GSTP1). We hypothesised that prenatal acetaminophen exposure would predict wheeze at age 5 years in an inner-city minority cohort and examined whether this association was modified by common polymorphisms in genes related to the glutathione pathway.

METHODS

An ongoing population-based birth cohort study of Dominican Republic and African-American children in New York prospectively assessed the use of analgesics during pregnancy and current wheeze at age 5 years in 301 children. Genotyping was conducted for GST polymorphisms. Binomial regression was used to adjust for potential confounders including postnatal acetaminophen use.

RESULTS

34% of mothers reported acetaminophen use during pregnancy and 27% of children had current wheeze at 5 years. Prenatal exposure to acetaminophen predicted current wheeze (multivariate relative risk 1.71; 95% CI 1.20 to 2.42; p=0.003), and the risk increased monotonically with increasing number of days of prenatal acetaminophen exposure (p trend <0.001). 68% of children had at least one copy of the GSTP1 minor allele (Val). The risk of wheeze was modified by GSTP1 (additive interaction p=0.009) and was observed only among children with the GSTP1 minor allele.

CONCLUSIONS

Prenatal exposure to acetaminophen predicted wheeze at age 5 years in an inner-city minority cohort. The risk was modified by a functional polymorphism in GSTP1, suggesting a mechanism involving the glutathione pathway.

Prenatal acetaminophen exposure and risk of wheeze at age 5 years in an urban low-income cohort

BACKGROUND

Acetaminophen has been associated with asthma and is in part metabolised via the glutathione pathway. Inner-city minority children have high asthma morbidity and a relatively high frequency of a minor allele variant in the glutathione S transferase Pi gene (GSTP1). We hypothesised that prenatal acetaminophen exposure would predict wheeze at age 5 years in an inner-city minority cohort and examined whether this association was modified by common polymorphisms in genes related to the glutathione pathway.

METHODS

An ongoing population-based birth cohort study of Dominican Republic and African-American children in New York prospectively assessed the use of analgesics during pregnancy and current wheeze at age 5 years in 301 children. Genotyping was conducted for GST polymorphisms. Binomial regression was used to adjust for potential confounders including postnatal acetaminophen use.

RESULTS

34% of mothers reported acetaminophen use during pregnancy and 27% of children had current wheeze at 5 years. Prenatal exposure to acetaminophen predicted current wheeze (multivariate relative risk 1.71; 95% CI 1.20 to 2.42; p=0.003), and the risk increased monotonically with increasing number of days of prenatal acetaminophen exposure (p trend <0.001). 68% of children had at least one copy of the GSTP1 minor allele (Val). The risk of wheeze was modified by GSTP1 (additive interaction p=0.009) and was observed only among children with the GSTP1 minor allele.

CONCLUSIONS

Prenatal exposure to acetaminophen predicted wheeze at age 5 years in an inner-city minority cohort. The risk was modified by a functional polymorphism in GSTP1, suggesting a mechanism involving the glutathione pathway.

Acetaminophen use and the risk of asthma in children and adults: a systematic review and metaanalysis

BACKGROUND

Epidemiologic studies have identified an increased risk of asthma with acetaminophen use, but the results have been conflicting. We sought to quantify the association between acetaminophen use and the risk of asthma in children and adults.

METHODS

We searched all the major medical databases, including MEDLINE (from 1966 to 2008) and EMBASE (from 1980 to 2008) to identify pertinent articles. All clinical trials and observational studies were considered. For observational studies, we selected those that clearly defined acetaminophen use and asthma diagnosis. Study quality was assessed by two reviewers, and data were extracted into a spreadsheet. A random-effects model was used to combine studies with asthma and wheezing among both children and adults.

RESULTS

Thirteen cross-sectional studies, four cohort studies, and two case-control studies comprising 425,140 subjects were included in the review. The pooled odds ratio (OR) for asthma among subjects using acetaminophen was 1.63 (95% CI, 1.46 to 1.77). The risk of asthma in children among users of acetaminophen in the year prior to asthma diagnosis and within the first year of life was elevated (OR: 1.60 [95% CI, 1.48 to 1.74] and 1.47 [95% CI, 1.36 to 1.56], respectively). Only one study reported the association between high acetaminophen dose and asthma in children (OR, 3.23; 95% CI, 2.9 to 3.6). There was an increase in the risk of asthma and wheezing with prenatal use of acetaminophen (OR: 1.28 [95% CI, 1.16 to 41] and 1.50 [95% CI, 1.10 to 2.05], respectively).

CONCLUSIONS

The results of our review are consistent with an increase in the risk of asthma and wheezing in both children and adults exposed to acetaminophen. Future studies are needed to confirm these results.

[Asthma and pregnancy. Review of the current literature and management according to the GINA 2006-2007 guidelines]

INTRODUCTION

Many pregnant women are asthmatics and maternal asthma is a source of questions and complications concerning both the progress of the pregnancy itself and the impact on the foetus. In this situation good asthma control is essential as the disease can deteriorate with acute exacerbations, possibly precipitated by reduction or even withdrawal of treatment on account of fear of teratogenicity.

BACKGROUND

Even though asthma treatments are not totally harmless during pregnancy, their use has been validated by several studies and guidelines. To help clinicians, we undertake here a review of the complications induced by maternal asthma and its medications, and then suggest management guidelines according to the most recent publications.

CONCLUSIONS

The risks and benefits of asthma treatments should be explained in a real partnership between the patient and her general practitioner and specialists (obstetrician, chest physician or allergist). In order to reduce complications to both mother and child, perfect control of asthma is required and inhaled steroids remain the treatment of choice for partially or uncontrolled asthma in the pregnant woman.

A novel study design to investigate the early-life origins of asthma in children (SAGE study)

This is a description of the Study of Asthma, Genes and the Environment (SAGE), a novel birth cohort created from provincial healthcare administrative records. It is a general population-based cohort, composed of children at high and low risk for asthma, living in urban and rural environments in Manitoba, Canada. The SAGE study captures the complete longitudinal healthcare records of children born in 1995 and contains detailed information on early-life exposures, such as antibiotic utilization and immunization, in relationship to the development of asthma. Nested within the birth cohort is a case-control study, which was created to collect information on home environmental exposures from detailed surveys and home dust sampling, to confirm asthma status in children and use this data to validate healthcare database measures of asthma, to determine differences in immune system responsiveness to innate and adaptive immune stimuli in asthma, to genotype children for genes likely associated with the development of asthma and to study the epigenetic regulation of pre-established protective vs allergic immune responses. The SAGE study is a multidisciplinary collaboration of researchers from pediatric allergy, population health, immunology, and genetic and environmental epidemiology. As such, it serves as a fertile, interdisciplinary training ground for graduate students, and postdoctoral and clinician fellows.

Why carry out a longitudinal birth survey?

In spite of technological progress throughout the world, ill health, both physical and mental, is widespread - but much of this is preventable. With rapid globalization, populations in both industrialised and developing countries are being exposed to various stresses and to new environmental factors, such as those related to climate change and to an increasing range of chemicals of unknown effect. There is substantial evidence that exposures to environmental risk factors in pregnancy and childhood have a major influence on health and development even into adulthood and future generations. In this paper we discuss the importance of longitudinal studies in identifying the processes underlying health and developmental problems and thus, by using the strengths of birth cohort studies, identifying preventative and other strategies which will protect public health from adverse environmental influences.

Choice of environmental components for a longitudinal birth cohort study

Various aspects of the environment of the mother and child may have major influences on the health and development of the child. Long-term influences can even affect chronic diseases of adulthood. Here we describe the major psychosocial and physical environmental factors that should be measured in longitudinal birth cohort studies.

The case for a coordinating centre for birth cohort studies

Designing, piloting and proceeding with a longitudinal birth cohort is a major exercise. Here we outline ways in which a resource centre could be initiated to provide advice and training, a library of appropriate instruments and publications, provision for cross-cohort comparisons and a biobanking facility. The resource should be available for cohorts planned in the developed and developing world, as well as those countries in transition. We discuss possible strategies for funding such a centre.

Acetaminophen use: a risk for asthma?

A growing number of studies show that regular use of acetaminophen (paracetamol) carries a dose-dependent risk of developing allergies in general and asthma in particular and of worsening other respiratory diseases and lung function. The most disturbing finding has come from the population-based Avon Longitudinal Study of Parents and Children, in which use of paracetamol-but not aspirin-in late pregnancy was positively associated with asthma when comparing children whose mothers took paracetamol "sometimes" and "most days/daily" with those whose mothers never took it. Assuming a causal relationship, the percentage of asthma attributable to paracetamol use in late pregnancy was 7%. In this review, we present data from the most important studies published since 2000. Although the pathophysiology remains unclear, the available data justify a warning to the general public that the uncritical use of over-the-counter acetaminophen can lead to the development of allergies and asthma, even in utero.

Acetaminophen use: a risk for asthma?

A growing number of studies show that regular use of acetaminophen (paracetamol) carries a dose-dependent risk of developing allergies in general and asthma in particular and of worsening other respiratory diseases and lung function. The most disturbing finding has come from the population-based Avon Longitudinal Study of Parents and Children, in which use of paracetamol-but not aspirin-in late pregnancy was positively associated with asthma when comparing children whose mothers took paracetamol "sometimes" and "most days/daily" with those whose mothers never took it. Assuming a causal relationship, the percentage of asthma attributable to paracetamol use in late pregnancy was 7%. In this review, we present data from the most important studies published since 2000. Although the pathophysiology remains unclear, the available data justify a warning to the general public that the uncritical use of over-the-counter acetaminophen can lead to the development of allergies and asthma, even in utero.

Developmental immunotoxicology: focus on health risks

Developmental immunotoxicity (DIT) has gained attention with the recognition that many chronic diseases of increasing incidence feature immune dysfunction as a component of the disease. The maturing immune system represents a vulnerable target for toxicants as it progresses through a series of novel prenatal and perinatal events that are critical for later-life host defense against a wide array of diseases. These critical maturational windows display a particular sensitivity to chemical disruption with the outcome usually taking the form of persistent immune dysfunction and/or misregulation. For this reason, health risks are significantly increased following early life vs adult immunotoxic exposure. Additionally, DIT-associated health risks are not readily predicted when based on adult-exposure safety data or via the evaluation of an unchallenged immune system in developmental toxicity testing. The same toxicant [e.g., heavy metals, 2,3,7,8-tetraclorodibenzo-p-dioxin (TCDD)] may disrupt different immune maturational processes depending upon the specific developmental timing of exposure and the target organ dose at a given stage of development. Therefore, a single toxicant may promote different immune-associated diseases that are dependent upon the specific window of early life exposure, the gender of the exposed offspring, and the genetic background of the offspring. This perspective considers the linkage between early life chemical exposure, DIT, and the postnatal immune dysfunctions associated with a variety of childhood and adult diseases. Because DIT is linked to a majority of the most significant childhood chronic diseases, safety testing for DIT is a pivotal issue in the protection of children's health.

Prenatal determinants of neonatal lung function in high-risk newborns

BACKGROUND

Neonatal lung function is suspected to be associated with wheezy disorders, but little is known about risk factors for the early lung function.

OBJECTIVES

To study prenatal determinants of neonatal lung function.

METHODS

This is a clinical, prospective birth cohort study of 411 newborns, the Copenhagen Prospective Study on Asthma in Childhood, in a single-center research clinic dedicated solely to this longitudinal birth cohort study. Lung function was determined at 1 month of age by infant spirometry (the raised volume rapid thoraco-abdominal compression technique) and bronchial responsiveness to methacholine by transcutaneous oxygen measurements. Risk factor analyses included anthropometrics; demographics; socioeconomic factors; parental atopic history; previous deliveries; exposures during the third trimester to the mother's smoking, alcohol, and medicines; third trimester pregnancy complications including mother's asthma status; and mode of delivery.

RESULTS

Lung function was determined in 404 neonates, age 6 weeks. Neonates with body mass index in the upper quartile had 14% lower baseline forced expiratory volume at 0.5 second, and neonates of mothers smoking during the third trimester had 7% lower baseline forced expiratory volume at 0.5 second. Sex or parental atopic disease did not affect the neonatal lung function and bronchial responsiveness. Maternal intake of paracetamol during the third trimester was associated with doubling of the bronchial responsiveness in the neonates, but the statistical significance may have been driven by outliers. Bronchial responsiveness exhibited a parabola development with tripling of bronchial responsiveness reaching the nadir at 3 months of age, but this needs replication in a study with repetitive measurements within individuals.

CONCLUSION

High body mass index in newborns and mothers smoking is associated with reduced neonatal lung function. This suggests that the association between body proportion and wheezing disorders may be a result of shared genes or prenatal nutrition.

Intake of paracetamol and risk of asthma in adults

Intake of paracetamol has been associated with development of asthma. The aim of this study was to address a possible association between intake of paracetamol and risk of adult-onset asthma. Using a multidisciplinary postal questionnaire survey concerning health and lifestyle we prospectively studied 19,349 adult twins enrolled in the nationwide Danish Twin Registry. There was a higher prevalence of new-onset asthma in subjects who reported frequent intake of paracetamol at baseline compared with subjects without this determinant (12.0% vs. 4.3%), OR = 3.03 (1.51-6.11), p = 0.005. The result remained significant after adjusting for sex, age, smoking, BMI, hay fever, eczema, and intake of medications other than paracetamol, OR = 2.16 (1.03-4.53), p = 0.041. Frequent intake of paracetamol is an independent risk factor for adult-onset asthma.

Association between paracetamol use in infancy and childhood, and risk of asthma, rhinoconjunctivitis, and eczema in children aged 6-7 years: analysis from Phase Three of the ISAAC programme

BACKGROUND

Exposure to paracetamol during intrauterine life, childhood, and adult life may increase the risk of developing asthma. We studied 6-7-year-old children from Phase Three of the International Study of Asthma and Allergies in Childhood (ISAAC) programme to investigate the association between paracetamol consumption and asthma.

METHODS

As part of Phase Three of ISAAC, parents or guardians of children aged 6-7 years completed written questionnaires about symptoms of asthma, rhinoconjunctivitis, and eczema, and several risk factors, including the use of paracetamol for fever in the child's first year of life and the frequency of paracetamol use in the past 12 months. The primary outcome variable was the odds ratio (OR) of asthma symptoms in these children associated with the use of paracetamol for fever in the first year of life, as calculated by logistic regression.

FINDINGS

205 487 children aged 6-7 years from 73 centres in 31 countries were included in the analysis. In the multivariate analyses, use of paracetamol for fever in the first year of life was associated with an increased risk of asthma symptoms when aged 6-7 years (OR 1.46 [95% CI 1.36-1.56]). Current use of paracetamol was associated with a dose-dependent increased risk of asthma symptoms (1.61 [1.46-1.77] and 3.23 [2.91-3.60] for medium and high use vs no use, respectively). Use of paracetamol was similarly associated with the risk of severe asthma symptoms, with population-attributable risks between 22% and 38%. Paracetamol use, both in the first year of life and in children aged 6-7 years, was also associated with an increased risk of symptoms of rhinoconjunctivitis and eczema.

INTERPRETATION

Use of paracetamol in the first year of life and in later childhood, is associated with risk of asthma, rhinoconjunctivitis, and eczema at age 6 to 7 years. We suggest that exposure to paracetamol might be a risk factor for the development of asthma in childhood.

Prenatal exposure to acetaminophen and respiratory symptoms in the first year of life

BACKGROUND

Prevalence of asthma in developed countries increased between the 1970s and the 1990s. One factor that might contribute to the trends in asthma is the increased use of acetaminophen vs aspirin in children and pregnant women.

OBJECTIVE

To examine relationships between in utero exposure to acetaminophen and incidence of respiratory symptoms in the first year of life.

METHODS

A total of 345 women were recruited in the first trimester of pregnancy and followed up with their children through the first year of life. Use of acetaminophen in pregnancy was determined by questionnaire and related to incidence of respiratory symptoms.

RESULTS

Use of acetaminophen in middle to late but not early pregnancy was significantly related to wheezing (odd ratio, 1.8; 95% confidence interval, 1.1-3.0) and to wheezing that disturbed sleep (odds ratio, 2.1; 95% confidence interval, 1.1-3.8) in the first year of life after control for potential confounders.

CONCLUSION

This study suggests that use of acetaminophen in middle to late but not early pregnancy may be related to respiratory symptoms in the first year of life. Additional follow-up will examine relationships of maternal and early childhood use of acetaminophen with incidence of asthma at ages 3 to 5 years, when asthma diagnosis is more firmly established.

Pre-natal exposure to paracetamol and risk of wheezing and asthma in children: a birth cohort study

BACKGROUND

Paracetamol use has been associated with increased prevalence of asthma in children and adults, and one study reported an association between pre-natal exposure to paracetamol and asthma in early childhood.

METHODS

To examine if pre-natal exposure to paracetamol is associated with the risk of asthma or wheezing in early childhood, we selected 66 445 women from the Danish National Birth Cohort for whom we had information on paracetamol use during pregnancy and who participated in an interview when their children were 18-months-old and 12 733 women whose children had reached the age of 7 and estimated the prevalence of physician-diagnosed asthma and wheezing at the ages of 18 months and 7 years. We also linked our population to the Danish National Hospital Registry to record all hospitalizations due to asthma up to age of 18 months.

RESULTS

Paracetamol use during any time of pregnancy was associated with a small but statistically significant increased risk of physician-diagnosed asthma or bronchitis among children at 18 months [relative risk (RR) = 1.17, 1.13-1.23)], hospitalizations due to asthma up to 18 months (hazard ratio = 1.24, 1.11-1.38) and physician-diagnosed asthma at 7 years (RR = 1.15, 1.02-1.29). The highest risks were observed for paracetamol use during the first trimester of pregnancy and persistent wheezing (wheezing at both 18 months and 7 years) (RR = 1.45, 1.13-1.85).

CONCLUSION

Paracetamol use during pregnancy was associated with an increased risk of asthma and wheezing in childhood. If this association is causal, we may need to revisit the clinical practice on use of paracetamol during pregnancy.

Non-Obstetric Pain in Pregnancy

The hormonal and mechanical changes which result from pregnancy have the capacity to exacerbate existing chronic pain conditions as well as produce pain unique to this physiological and anatomical state.Pain in pregnancy is very common and can impact negatively on maternal satisfaction with the pregnancy.Management of pain requires a multidisciplinary, biopsychosocial approach. The possible presence of co-existing pathology and obstetric conditions must be borne in mind when assessing pain in pregnancy.Treatment of pain in pregnancy should focus on non-pharmacological interventions in the first instance with due consideration of the risk of medications to the mother, fetus and the course of the pregnancy.

Prevalence and associated factors of allergic rhinitis and atopic dermatitis in children

Allergic disorders are the chronic diseases of greatest pediatric morbidity, affecting over 25 % of the pediatric population. Indeed, this situation has been referred to as an "allergic epidemic". In comparison with asthma, atopic dermatitis and allergic rhinitis have been less extensively investigated, although this does not mean that they should be regarded as minor disorders but rather as alterations that affect the quality of life of the patients and their families, which generate considerable direct and indirect costs. Despite an important research effort, the reason for this allergic epidemic is not well known. These are multifactor disorders without a single causal agent, in which the most important component is the genetic predisposition of the patient (atopy), modulated by environmental factors, exposure to allergens, infections and irritants, among others. A confounding element is the fact that the concept of allergic diseases encompasses phenotypes of rhinitis, atopic dermatitis or asthma in which no IgE-mediated atopic mechanism is demonstrated, and which can manifest in a way similar to true allergic phenotypes. Differentiation between the two is difficult to establish on the basis of self-administered questionnaires alone, in the absence of a precise etiological diagnosis. The present article reviews the numerous factors suggested to be responsible for the increase in allergic diseases recorded in the last few decades, and for the differences in prevalence observed among centres. For most of these factors the results published in the literature are contradictory, in some cases due to a lack of control of the associated interacting or confounding factors. Consensus exists for only some of these causal factors, such as the established parallelism between the increase in allergic diseases and the reduction in infectious processes on one hand, and the increase in particles generated by diesel fuel combustion on the other. In addition, the implicated factors could act differently (and in some cases even antagonically) upon atopy and on the different disease phenotypes, thereby complicating the study of these interactions even further.

The genetic and environmental basis of atopic diseases

The prevalence of atopic diseases has increased abruptly in recent years in most Westernized societies, making the question why this happened the topic of a heated debate. The best paradigm available to date to explain this steep rise, the 'hygiene hypothesis', supports that it is the excess 'cleanliness' of our environments that has led to the decline in the number of infectious stimuli that are necessary for the proper development of our immune system. Recent findings support that it is the combined effect that not only pathogenic, but also non-pathogenic microorganisms, and even their structural components,can exert on the immune system that deters from the development of atopic responses. Adding to these results are intriguing new findings on the effect different gene polymorphisms can have on an individual's predisposition to allergic diseases. The most important linkages produced, to date, include those among the genes for IL-4, IL-13, HLA-DRB, TNF, LTA,FCER1B, IL-4RA, ADAM33, TCR alpha/delta, PHF11, GPRA, TIM, p40, CD14, DPP10, T-bet, GATA-3, and FOXP3 and allergic disorders. The two parallel research efforts, epidemiologic and genetic, are only recently starting to converge,producing fascinating results on the effect particular gene-environment interactions might have in the development of atopy.The most important lesson learned through this tremendous research effort is that not only a small number but thousands and millions of separate risk factors act in concordance in the production of the allergic phenotype.

Symptoms of asthma and atopic disorders in preschool children: prevalence and risk factors

BACKGROUND

Published epidemiological data suggested that asthma and allergies may be increasing in preschool children. Identification of the risk factors is important for planning possible early intervention to prevent asthma. This study was designed to measure the prevalence of, and risk factors for, asthma and atopic disorders in preschool children from Hong Kong.

METHODS

Children aged 2-6 years living in Hong Kong were recruited through the local nurseries and kindergartens for this study to ascertain the presence of symptoms of asthma and various possible risk factors. The parental questionnaire was developed based on the International Study of Asthma and Allergies in Childhood questionnaire.

RESULTS

A total of 3089 children (1506 boys) from 14 nurseries and kindergartens participated in this study. The prevalence of wheeze ever and current wheeze were 16.7% and 9.3%. Two hundred and thirty-four subjects were born in mainland China and migrated to Hong Kong subsequently. When compared with children born and raised in Hong Kong, children born in mainland China had significantly lower prevalence of current wheeze (3.4% vs. 9.6%, P<0.01). Two environmental factors in the first year of life were associated with wheezing attacks within the last 12 months. They were the use of foam pillow (Odds ratio: 1.45; 95% Confidence interval: 1.04-2.00) and the use of gas as cooking fuel (1.68; 1.03-2.75). Frequent use of paracetamol was also associated with wheezing attack in the past 12 months.

CONCLUSIONS

This study confirms the high prevalence of symptoms of atopic disorders in preschool children from Hong Kong. Early environmental exposure factors are important determinants of subsequent development of asthma symptoms in the preschool years. Further studies are needed to evaluate the possible pathogenetic role of the identified risk factors.

[Systemic analgesia adapted to the children's condition]

A concept of balanced analgesia using nonsteroidal anti-inflammatory drugs (NSAIDs), paracetamol (acetaminophen), opioids, and corticosteroids can also be used in patients with pre-existing illnesses. NSAIDs are the most effective treatment for acute pain of moderate intensity in children; however, these drugs should be avoided in patients at increased risk for serious side effects, e.g. patients with renal impairment, bleeding tendency, or extreme prematurity. NSAIDs can be given with minimal risks to the younger child with mild to moderate asthma, and, in these patients, the use of steroids can be encouraged; in addition to their antiemetic and analgesic action, a beneficial effect on asthma symptoms can be expected. In the non-intubated child with cerebral trauma, exaggerated sedation caused by opioids and increased bleeding tendency caused by NSAIDs must be avoided. In neonates and small infants, the oral administration of sucrose or glucose is helpful to minimize pain reaction during short uncomfortable interventions.

A matched patient-sibling study on the usage of paracetamol and the subsequent development of allergy and asthma

A number of studies have suggested that intake of paracetamol during pregnancy and during the first months of life is associated with an increased risk of childhood asthma. We aimed to determine the association between paracetamol usage during pregnancy and the first 6 months of life, and childhood allergy (i.e. positive skin prick tests), allergic asthma, and asthma, using a matched patient-sibling study comparing patients with allergic asthma with their healthy siblings without any symptoms of allergic diseases. Allergy in patients and their siblings was determined by skin prick tests. Children having at least one positive skin prick test were considered to be allergic. Intake of paracetamol was assessed by standardized, interviewer-administered, questionnaire. Nineteen pairs of allergic asthma patients vs. non-allergic siblings were compared to determine the risk factors for allergic asthma, while 15 pairs of allergic asthma patients vs. allergic siblings were compared to determine the risk factors for asthma. Moreover, 33 pairs of allergic asthma patients vs. non-asthmatic siblings (with and without allergy) were compared to determine the risk factors for asthma. In addition, 17 allergic siblings (without asthma) were compared with 19 non-allergic siblings (without asthma) to determine the risk factors for allergy. Usage of paracetamol during pregnancy was associated with allergic asthma (p = 0.03). Furthermore, usage of paracetamol between birth and 6 months of age, and between 4 and 6 months of age, was also found to be associated with non-allergic asthma (p = 0.008 and p = 0.03 respectively). Usage of paracetamol during pregnancy and during the early months of life may play a role in the development of allergic and non-allergic asthma in children. However, due to obvious ethical reasons, direct evidence for this association (i.e. a double-blind, prospective study) is not available.

Asthma in Africa

A new survey shows a recent increase in the prevalence of asthma and allergic diseases in children in Ghana. Wjst and Boakye put this survey into context through a discussion of the epidemiology of asthma in Africa.

Maternal testosterone in pregnancy and atopic outcomes in childhood

BACKGROUND

In mice, androgens downregulate Th2 cytokine responses, but whether androgen levels during pregnancy might influence the development of allergy in the offspring has not been studied.

METHODS

In the Avon Longitudinal Study of Parents and Children (ALSPAC), a population-based birth cohort of 14 541 pregnancies, we related maternal blood total testosterone during pregnancy, measured in a subset of the cohort, to allergic outcomes in the offspring, including asthma, hayfever, eczema (n=543) and wheezing (n=532) at 69-81 months, and atopy (positive skin prick test to Dermatophagoides pteronyssinus, cat or grass, n=386) and blood total immunoglobulin E (IgE; n=314) at 7 years. We used logistic and linear regression to analyse binary outcomes and log-transformed IgE, respectively, controlling for potential confounders.

RESULTS

Maternal testosterone was negatively associated with total IgE in boys [adjusted geometric mean ratio (GMR), per doubling of testosterone, 0.33 (0.20-0.55), P=0.000038 (n=168)], but not in girls [GMR 1.04 (0.53-2.06), P=0.91 (n=146)], P-value interaction 0.0086. The effect in boys was even stronger in the absence of maternal atopic disease. Testosterone was not associated with skin test positivity or atopic disease in either sex.

CONCLUSIONS

Higher testosterone levels in pregnancy are associated with lower IgE production in boys.

Perinatal immunotoxicity: why adult exposure assessment fails to predict risk

Recent research has pointed to the developing immune system as a remarkably sensitive toxicologic target for environmental chemicals and drugs. In fact, the perinatal period before and just after birth is replete with dynamic immune changes, many of which do not occur in adults. These include not only the basic maturation and distribution of immune cell types and selection against autoreactive lymphocytes but also changes designed specifically to protect the pregnancy against immune-mediated miscarriage. The newborn is then faced with critical immune maturational adjustments to achieve an immune balance necessary to combat myriad childhood and later-life diseases. All these processes set the fetus and neonate completely apart from the adult regarding immunotoxicologic risk. Yet for decades, safety evaluation has relied almost exclusively upon exposure of the adult immune system to predict perinatal immune risk. Recent workshops and forums have suggested a benefit in employing alternative exposures that include exposure throughout early life stages. However, issues remain concerning when and where such applications might be required. In this review we discuss the reasons why immunotoxic assessment is important for current childhood diseases and why adult exposure assessment cannot predict the effect of xenobiotics on the developing immune system. It also provides examples of developmental immunotoxicants where age-based risk appears to differ. Finally, it stresses the need to replace adult exposure assessment for immune evaluation with protocols that can protect the developing immune system.

A brief targeted review of susceptibility factors, environmental exposures, asthma incidence, and recommendations for future asthma incidence research

Relative to research on effects of environmental exposures on exacerbation of existing asthma, little research on incident asthma and environmental exposures has been conducted. However, this research is needed to better devise strategies for the prevention of asthma. The U.S. Environmental Protection Agency (EPA) and National Institute of Environmental Health Sciences held a conference in October 2004 to collaboratively discuss a future research agenda in this area. The first three articles in this mini-monograph summarize the discussion on potential putative environmental exposure; they include an overview of asthma and conclusions of the workshop participants with respect to public health actions that could currently be applied to the problem and research needs to better understand and control the induction and incidence of asthma, the potential role of indoor/outdoor air pollutants in the induction of asthma), and biologics in the induction of asthma. Susceptibility is a key concept in the U.S. EPA "Asthma Research Strategy" document and is associated with the U.S. EPA framework of protecting vulnerable populations from potentially harmful environmental exposures. Genetics, age, and lifestyle (obesity, diet) are major susceptibility factors in the induction of asthma and can interact with environmental exposures either synergistically or antagonistically. Therefore, in this fourth and last article we consider a number of "susceptibility factors" that potentially influence the asthmatic response to environmental exposures and propose a framework for developing research hypotheses regarding the effects of environmental exposures on asthma incidence and induction.

Use of acetaminophen and the risk of self-reported allergic symptoms and skin sensitization in Butajira, Ethiopia

BACKGROUND

Studies in developed countries suggest that acetaminophen use is associated with increased risk of asthma, but it is unclear whether this association is causal.

OBJECTIVE

To determine the relation among acetaminophen use, asthma, and allergy, and to explore potential biases in acetaminophen use, in a developing country population.

METHODS

We surveyed 7649 adults and children from Butajira, Ethiopia, collecting data on self-reported symptoms of allergic disease, skin sensitization to Dermatophagoides pteronyssinus and cockroach, acetaminophen use, and potential confounders. We then collected detailed data on indications for acetaminophen use and reasons for aspirin avoidance in a nested follow-up study.

RESULTS

Allergic symptoms increased significantly with frequency of acetaminophen use, with odds ratios in those using >3 tablets in the past month relative to none 1.89 (95% CI, 1.51-2.36) for wheeze, 2.14 (1.72-2.67) for nocturnal shortness of breath, 2.52 (1.99-3.20) for rhinitis, and 1.90 (1.39-2.61) for eczema. Cockroach sensitization was also more common in the highest acetaminophen category (odds ratio, 1.40; 95% CI, 1.10-1.79), but D pteronyssinus sensitization was not. Less than 1% of participants with asthma or wheeze in our nested study reported avoidance of aspirin because of asthma symptoms. None volunteered using acetaminophen to treat allergic symptoms.

CONCLUSION

There is a dose-related association between acetaminophen use and self-reported allergic symptoms in this population that is not a result of aspirin avoidance, reverse causation, or other bias. Acetaminophen may therefore be involved in the etiology of asthma and allergic disease.