Cross sectional study of the relation between sibling number and asthma, hay fever, and eczema

Early-life and health behaviour influences on lung function in early adulthood

RATIONALE

Early-life exposures may influence lung function at different stages of the life course. However, the relative importance of characteristics at different stages of infancy and childhood are unclear.

OBJECTIVES

To examine the associations and relative importance of early-life events on lung function at age 24 years.

METHODS

We followed 7545 children from the Avon Longitudinal Study of Parents and Children from birth to 24 years. Using previous knowledge, we classified an extensive list of putative risk factors for low lung function, covering sociodemographic, environmental, lifestyle and physiological characteristics, according to timing of exposure: 1) demographic, maternal and child; 2) perinatal; 3) postnatal; 4) early childhood; and 5) adolescence characteristics. Lung function measurements (forced vital capacity (FVC), forced expiratory volume in 1 s (FEV₁), FEV₁/FVC and forced expiratory flow at 25-75% of FVC) were standardised for sex, age and height. The proportion of the remaining variance explained by each characteristic was calculated. The association and relative importance (RI) of each characteristic for each lung function measure was estimated using linear regression, adjusted for other characteristics in the same and previous categories.

RESULTS

Lower maternal perinatal body mass index (BMI), lower birthweight, lower lean mass and higher fat mass in childhood had the largest RI (0.5-7.7%) for decreased FVC. Having no siblings, lower birthweight, lower lean mass and higher fat mass were associated with decreased FEV₁ (RI 0.5-4.6%). Higher lean mass and childhood asthma were associated with decreased FEV₁/FVC (RI 0.6-0.8%).

CONCLUSIONS

Maternal perinatal BMI, birthweight, childhood lean and fat mass and early-onset asthma are the factors in infancy and childhood that have the greatest influence on early-adult lung function.

Factors associated with asthma expression in adolescents

Objective:

To evaluate risk factors associated with asthma symptoms in adolescents in the 13- to 14-year age bracket.

Methods:

This was a cross-sectional study involving adolescents enrolled in randomly selected public schools in the city of Belo Horizonte, Brazil, and conducted with the use of the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire and its supplementary module for risk factor assessment. The ISAAC questionnaire was completed by the students themselves, whereas the supplementary questionnaire was completed by their parents or legal guardians. Variables showing p ≤ 0.25 in the univariate analysis were included in the multivariate analysis. Stepwise regression with backward elimination was used for variable selection.

Results:

We evaluated 375 adolescents, 124 (33.1%) of whom had asthma symptoms. The final multivariate analysis model revealed that asthma symptoms were associated with birth weight < 2,500 g (p < 0.001), day care center or nursery attendance (p < 0.002), maternal history of asthma (p < 0.001), contact with animals during the first year of life (p < 0.027), current contact with animals outside the home (dogs, cats, or farm animals; p < 0.005), and more than 20 cigarettes per day smoked by parents or other household members (p < 0.02).

Conclusions:

Exposure to animals in and outside the home is associated with asthma symptoms, as is environmental tobacco smoke exposure. Families, health professionals, and administrators of health care facilities should take that into account in order to prevent asthma and reduce asthma morbidity.

Prevention of food and airway allergy: consensus of the Italian Society of Preventive and Social Paediatrics, the Italian Society of Paediatric Allergy and Immunology, and Italian Society of Pediatrics

BACKGROUND

Allergic sensitization in children and allergic diseases arising therefrom are increasing for decades. Several interventions, functional foods, pro- and prebiotics, vitamins are proposed for the prevention of allergies and they can't be uncritically adopted.

OBJECTIVE

This Consensus document was developed by the Italian Society of Preventive and Social Paediatrics and the Italian Society of Paediatric Allergy and Immunology. The aim is to provide updated recommendations regarding allergy prevention in children.

METHODS

The document has been issued by a multidisciplinary expert panel and it is intended to be mainly directed to primary care paediatricians. It includes 19 questions which have been preliminarily considered relevant by the panel. Relatively to each question, a literature search has been performed, according to the Italian National Guideline Program. Methodology, and a brief summary of the available literature data, has been provided. Many topics have been analyzed including the role of mother's diet restriction, use of breast/formula/hydrolyzed milk; timing of introduction of complementary foods, role (if any) of probiotics, prebiotics, vitamins, exposure to dust mites, animals and to tobacco smoke.

RESULTS

Some preventive interventions have a strong level of recommendation. (e.g., the dehumidifier to reduce exposure to mite allergens). With regard to other types of intervention, such as the use of partially and extensively hydrolyzed formulas, the document underlines the lack of evidence of effectiveness. No preventive effect of dietary supplementation with polyunsaturated fatty acids, vitamins or minerals has been demonstrated. There is no preventive effect of probiotics on asthma, rhinitis and allergic diseases. It has demonstrated a modest effect, but steady, in the prevention of atopic dermatitis.

CONCLUSIONS

The recommendations of the Consensus are based on a careful analysis of the evidence available. The lack of evidence of efficacy does not necessarily imply that some interventions may not be effective, but currently they can't be recommended.

Siblings, asthma, rhinoconjunctivitis and eczema: a worldwide perspective from the International Study of Asthma and Allergies in Childhood

Background

Associations of larger families with lower prevalences of hay fever, eczema and objective markers of allergic sensitization have been found fairly consistently in affluent countries, but little is known about these relationships in less affluent countries.

Methods

Questionnaire data for 210 200 children aged 6–7 years from 31 countries, and 337 226 children aged 13–14 years from 52 countries, were collected by Phase Three of the International Study of Asthma and Allergies in Childhood (ISAAC). Associations of disease symptoms and labels of asthma, rhinoconjunctivitis and eczema were analysed by numbers of total, older and younger siblings, using mixed (multi-level) logistic regression models to adjust for individual covariates and at the centre level for region, language and national affluence.

Results

In both age groups, inverse trends (P < 0.0001) were observed for reported ‘hay fever ever’ and ‘eczema ever’ with increasing numbers of total siblings, and more specifically older siblings. These inverse associations were significantly (P < 0.005) stronger in more affluent countries. In contrast, symptoms of severe asthma and severe eczema were positively associated (P < 0.0001) with total sibship size in both age groups. These associations with disease severity were largely independent of position within the sibship and national GNI per capita.

Conclusions

These global findings on sibship size and childhood asthma, rhinoconjunctivitis and eczema suggest at least two distinct trends. Inverse associations with older siblings (observations which prompted the ‘hygiene hypothesis’ for allergic disease) are mainly a phenomenon of more affluent countries, whereas greater severity of symptoms in larger families is globally more widespread.

Factors associated with atopy in toddlers: a case-control study

In this case-control study the association between the approaches used to feed infants, together with known family and environmental factors, and the occurrence of atopic illness in toddlers between the ages of 4 months to 3 years in Hong Kong was examined. A total of 206 subjects were recruited from April to June of 2014. The results obtained by binary logistic regression indicated that atopy is associated with boys (OR 2.072, CI 1.089-3.941), the maternal use of antibiotics in utero or while breast feeding (OR 2.276, CI 1.151-4.504), the later commencement of mixed feeding (OR 2.497, CI 1.025-6.082), breast feeding exclusively for 3 months (OR 1.972, CI 1.009-3.857), and having a mother who was diagnosed with eczema (OR 4.510, CI 1.764-11.530). Although an exclusive reliance on breast feeding has been shown to be predictive of atopy among toddlers, the positive qualities of breast milk cannot be ignored. A further study of the contents and nutritional values of breast milk is warranted.

Active or passive exposure to tobacco smoking and allergic rhinitis, allergic dermatitis, and food allergy in adults and children: a systematic review and meta-analysis

BACKGROUND

Allergic rhinitis, allergic dermatitis, and food allergy are extremely common diseases, especially among children, and are frequently associated to each other and to asthma. Smoking is a potential risk factor for these conditions, but so far, results from individual studies have been conflicting. The objective of this study was to examine the evidence for an association between active smoking (AS) or passive exposure to secondhand smoke and allergic conditions.

METHODS AND FINDINGS

We retrieved studies published in any language up to June 30th, 2013 by systematically searching Medline, Embase, the five regional bibliographic databases of the World Health Organization, and ISI-Proceedings databases, by manually examining the references of the original articles and reviews retrieved, and by establishing personal contact with clinical researchers. We included cohort, case-control, and cross-sectional studies reporting odds ratio (OR) or relative risk (RR) estimates and confidence intervals of smoking and allergic conditions, first among the general population and then among children. We retrieved 97 studies on allergic rhinitis, 91 on allergic dermatitis, and eight on food allergy published in 139 different articles. When all studies were analyzed together (showing random effects model results and pooled ORs expressed as RR), allergic rhinitis was not associated with active smoking (pooled RR, 1.02 [95% CI 0.92-1.15]), but was associated with passive smoking (pooled RR 1.10 [95% CI 1.06-1.15]). Allergic dermatitis was associated with both active (pooled RR, 1.21 [95% CI 1.14-1.29]) and passive smoking (pooled RR, 1.07 [95% CI 1.03-1.12]). In children and adolescent, allergic rhinitis was associated with active (pooled RR, 1.40 (95% CI 1.24-1.59) and passive smoking (pooled RR, 1.09 [95% CI 1.04-1.14]). Allergic dermatitis was associated with active (pooled RR, 1.36 [95% CI 1.17-1.46]) and passive smoking (pooled RR, 1.06 [95% CI 1.01-1.11]). Food allergy was associated with SHS (1.43 [1.12-1.83]) when cohort studies only were examined, but not when all studies were combined. The findings are limited by the potential for confounding and bias given that most of the individual studies used a cross-sectional design. Furthermore, the studies showed a high degree of heterogeneity and the exposure and outcome measures were assessed by self-report, which may increase the potential for misclassification.

CONCLUSIONS

We observed very modest associations between smoking and some allergic diseases among adults. Among children and adolescents, both active and passive exposure to SHS were associated with a modest increased risk for allergic diseases, and passive smoking was associated with an increased risk for food allergy. Additional studies with detailed measurement of exposure and better case definition are needed to further explore the role of smoking in allergic diseases.

Daycaritis

Healthy infants and toddlers who attend day care centers are at increased risk for contracting common childhood illnesses such as viral upper and lower respiratory illnesses, viral gastrointestinal infections, and acute and chronic otitis media. The author proposes that this high frequency of common infections be termed daycaritis. Daycaritis imposes significant social and economic burdens on both the family and the health care system. This review describes the most common infections seen in day care attendees, preventative measures to decrease the rates of illness, and a practical approach to diagnosis and management in the emergency department.

Prevalence and factors linked to atopic eczema in 10- and 11-year-old schoolchildren. Isaac 2 in Almeria, Spain

BACKGROUND

Atopic eczema affects 5-10% of the Spanish paediatric population, and has increased in frequency over the last few decades, probably due to changes in the environment and lifestyle. Phase II of the ISAAC (International Study of Asthma and Allergies in Childhood) uses a standardised methodology to establish the prevalence of allergic disorders and factors linked to them in each centre.

OBJECTIVES

To assess the prevalence and severity of atopic eczema, and to establish factors linked to atopic eczema in 10-11 year-old school children in the city of Almeria (South-East coast of Spain).

MATERIAL AND METHODS

An ecological study was carried out as part of ISAAC II, using homologated questionnaires and allergic tests in 1143 schoolchildren. Statistic association was assessed by means of chi(2) test, and then logistic regression analysis was performed with the most significant variables from the univariant analysis.

RESULTS

The prevalence of atopic eczema was 11.4%. The risk factors found in the multiple logistic regression analysis were: personal antecedents of severe asthma (OR 19 CI 95% 1.35-266) and severe rhinitis (OR 7.7 CI 95% 1.79-33), fungi in bedroom during the first year of life (OR 4.2 CI 95% 1.17-15.1) and atopic eczema in one parent (OR 5.2 CI 95% 2.69-10.1).

CONCLUSIONS

The prevalence of atopic eczema is similar to that found in other studies within ISAAC Phase I. The most important risk factors for atopic eczema are family and personal history of other atopic diseases and the presence of fungi in the home.

Prevalence and factors linked to atopy in 10-and 11-year-old children in Almería, Spain

BACKGROUND

During the last decades there has been an increase in both allergic diseases and allergic sensitisation, probably due to changes in the environment and living habits. ISAAC Phase II was designed to establish the prevalence and associated factors to asthma and allergic disorders in childhood.

AIM

To assess the prevalence and factors linked to atopy in 10-11 year-old children from Almería (Spain).

METHODS

As a part of ISAAC II, a survey was conducted among a sample of 1143 schoolchildren using standardised questionnaires and skin-prick testing.

RESULTS

The overall prevalence of atopy was 42.5%. Most common sensitisations were to Dermatophagoides pteronyssinus (36.2%), D. farinae (32.3%), cat (10.8%), Alternaria (7%), grass (6%), and tree pollen (1.7%). 34.9% of these sensitisations could be regarded as subclinical sensitisations. The fractions of asthma, rhinitis and eczema attributable to atopy were 49.2%, 40.4% y 18.6%, respectively. After multivariate analysis, the risk of atopy was significantly lower among females (OR 0.62, CI 95% 0.45-0.86); children with older siblings (OR 0.67; CI 95% 0.49-0.92); intestinal parasites (OR 0.68; CI 95% 0.48-0.97); contact with farm animals in the past (OR 0.48 CI 95% 0.23-0.99); or other animals at present (OR 0.53 CI 95% 0.30-0.95). To have an allergic father (OR 2.96 CI 95% 1.77-4.94) was the only significant risk factor.

CONCLUSIONS

We found several independent factors which significantly protect against atopic sensitisation. These protective factors were not the same for asthma, rhinitis or eczema, suggesting that other factors could interact to influence atopy and act against such protective factors.

Risk of childhood asthma in relation to the timing of early child care exposures

OBJECTIVE

To examine whether early child care exposure influences the risk for development of asthma.

STUDY DESIGN

Longitudinal data from 939 children and their families from the National Institute of Child Health and Development Study of Early Child Care and Youth Development were analyzed. Exposure to other children in the primary child care setting as an infant (before 15 months) and as a toddler (16-36 months) were assessed as risk factors for persistent or late-onset asthma by age 15 via logistic regression.

RESULTS

The number of children in the child-care environment when the child was a toddler was significantly associated with odds of asthma, even after adjusting for respiratory illnesses and other risk factors (P < .05). The fewer the children exposed to as toddlers, the higher the probability of persistent or late-onset asthma by age 15.

CONCLUSIONS

This study supports the theory of a protective effect of exposure to other children at an early age, especially as a toddler, on the risk of asthma. This effect appears to be independent of the number of reported respiratory tract illnesses, suggesting that other protective mechanisms related to the number of children in the child care environment may be involved.

Sibship size and prevalence of allergic disorders in Japan: the Ryukyus Child Health Study

A number of epidemiological studies have reported an inverse association between increasing sibship size and allergic disorders. The present cross-sectional study assessed the association between the number of siblings and the prevalence of allergic disorders during the past 12 months in Japanese schoolchildren. Study subjects were 22,750 children aged 6-15 yr in Okinawa. The outcomes were based on diagnostic criteria from the International Study of Asthma and Allergies in Childhood. Adjustment was made for age, gender, maternal age at childbirth, duration of breastfeeding, region of residence, smoking in the household, paternal and maternal history of asthma, atopic eczema, and allergic rhinitis, and paternal and maternal educational level. Significant exposure-response associations were observed between increasing total sibship size and all outcomes under investigation. Having two or more older siblings was significantly inversely related to the prevalence of atopic eczema and allergic rhinoconjunctivitis, but not wheeze or asthma. Having two or more younger siblings was independently associated with a decreased prevalence of atopic eczema, but not wheeze, asthma, or allergic rhinoconjunctivitis. The inverse relationships between sibship size and the prevalence of allergic disorders under study were weakened with advancing age, although the interactions between age groups were not statistically significant. No significant interactions were found in the association of having three or more siblings with allergic disorders between children with a positive or negative parental allergic history. These results are likely to support the in utero programming hypothesis because it is probable that the in utero environment would change with parity, although our observations could not refute the hygiene hypothesis.

Maternal employment in child-care institutions and the risk of infant wheeze and atopic dermatitis in the offspring

It has been proposed that exposure to infections and microbes protects against atopic diseases, but epidemiological data has so far been conflicting. We hypothesized that maternal exposure to infections and microbes before or during pregnancy would be of particular importance. To test this hypothesis, we studied the incidence of wheezing and atopic dermatitis (AD) in infants of mothers employed in child-care institutions - and thus presumably being highly exposed to infections and microbes - compared with infants of mothers not so employed. A total of 31471 mother-child pairs enrolled in the Danish National Birth Cohort were followed prospectively. Information on wheezing episodes, AD, maternal employment, and other variables were collected by interview at 12 and 30 wk of gestation, and 6 and 18 months of age, and by linkage to the Danish Medical Birth Register and the Child-care Database. The relative risk was estimated in Cox proportional hazard models. Analyses were stratified by sibling status (first born or not), as older siblings are likely to be a significant source of infectious agents. The adjusted relative risks of wheeze, recurrent wheeze and AD was 1.14 (95% CI: 0.96-1.37), 1.37 (95% CI: 1.05-1.77), and 1.03 (95% CI: 0.81-1.31), respectively, for first-born infants of mothers employed in child-care institutions compared with infants of mothers not so employed. There was no effect of maternal employment in child-care institutions among infants with older siblings. In conclusion, the results did not support the hypothesis that maternal microbial exposure before or during pregnancy as reflected by maternal employment in child-care institutions protects the offspring against infant wheeze and AD.

Helicobacter pylori colonisation and eczema

The hygiene hypothesis postulates that the increase in atopic diseases may in part be due to diminished exposure to microorganisms. But it is unknown which type of infection does render protection. An epidemiological study was conducted in Leipzig, Germany, and its rural county, involving 3347 school starters. Two types of infection were considered: (1) gastrointestinal colonisation (Helicobacter pylori detection using in vivo [(13)C] urea breath test) and (2) respiratory infections (physician-diagnosed lower (bronchitis) and upper (common cold) respiratory infections). H pylori colonisation was selected because it is very common and plays an important role in gastrointestinal disorders. Atopic eczema was selected as the (allergic) target variable because of its high frequency in the age of the study participants. The results, adjusted for relevant confounders, showed a significant inverse association between H pylori infection and eczema (adjusted odds ratio (aOR) = 0.31, p = 0.006) in children not predisposed to atopy. In contrast, bronchitis increased the risk of eczema (aOR = 1.98, p<0.001). Bacterial digestive tract colonisation (infection) seems to protect against eczema in comparison with the effect of respiratory tract infections. The hygiene hypothesis may be better explained when gastrointestinal and respiratory infections are subtly differentiated.

Helicobacter pylori colonisation and eczema

The hygiene hypothesis postulates that the increase in atopic diseases may in part be due to diminished exposure to microorganisms. But it is unknown which type of infection does render protection. An epidemiological study was conducted in Leipzig, Germany, and its rural county, involving 3347 school starters. Two types of infection were considered: (1) gastrointestinal colonisation (Helicobacter pylori detection using in vivo [(13)C] urea breath test) and (2) respiratory infections (physician-diagnosed lower (bronchitis) and upper (common cold) respiratory infections). H pylori colonisation was selected because it is very common and plays an important role in gastrointestinal disorders. Atopic eczema was selected as the (allergic) target variable because of its high frequency in the age of the study participants. The results, adjusted for relevant confounders, showed a significant inverse association between H pylori infection and eczema (adjusted odds ratio (aOR) = 0.31, p = 0.006) in children not predisposed to atopy. In contrast, bronchitis increased the risk of eczema (aOR = 1.98, p<0.001). Bacterial digestive tract colonisation (infection) seems to protect against eczema in comparison with the effect of respiratory tract infections. The hygiene hypothesis may be better explained when gastrointestinal and respiratory infections are subtly differentiated.

Risk factors for asthma at 3.5 and 7 years of age

BACKGROUND

It has been suggested that factors in early life including exposure to allergens and microbes may influence the development of asthma.

OBJECTIVE

To identify risk factors for asthma in early childhood. Methods Eight-hundred and seventy-one children of European mothers were enrolled at birth, of whom 385 (44.2%) were born small for gestational age (SGA) and 486 were appropriate for gestational age (AGA). Data were collected at birth, 12 months, 3.5 years of age (y) and 7 y. The outcome of interest (current wheeze) was defined as a positive response to the question: 'Has your child had wheezing or whistling in the chest in the last 12 months?'

RESULTS

Participation rate was 85.4% at 1 y, 63.1% at 3.5 y and 68.0% at 7 y. The prevalence of asthma was 23.8% at 3.5 y and 18.1% at 7 y. Antibiotic use in the first year of life and day care in the first year of life were associated with increased risk of wheeze at 7 y [odds ratio (OR)=4.3 95% confidence interval (CI) (1.8-10.1) and OR=2.8 95% CI (1.2-6.5), respectively], but not at 3.5 y. Exposure to dogs was a risk factor for asthma at both ages [OR=2.1 95% CI (1.1-3.8)] as was sleeping on a used cot mattress in the first year of life [OR=1.8 95% CI (1.0-3.2)].

CONCLUSIONS

There was a significant association between antibiotic use and day care in the first year of life and wheezing at 7 y but not at 3.5 y. This strengthens the argument that these factors increase the risk of asthma. We have also made the novel observation that sleeping on a used mattress in the first year of life is a risk factor for wheezing at 3.5 and 7 y. Capsule summary This prospective study of 871 children made the novel observation that sleeping on a used mattress in the first year of life was a risk factor for wheezing at 3.5 and 7 y.

Birth order, allergies and lymphoma risk: results of the European collaborative research project Epilymph

Lymphomas are a heterogeneous group of malignancies of the immune system. Recent studies suggest that immunological conditions which are modulated by lifestyle-dependent environmental determinants might affect lymphoma risk. We used data from Epilymph, a European multi-centric case-control study with 2,480 cases and 2,540 controls, to analyse the relationship between lifestyle-dependent immunological determinants and risk of lymphomas. We found an inverse relationship between risk of lymphoma and allergies, mainly respiratory (OR=0.86, CI=0.89-1.01) and food allergies (OR=0.67, CI=0.52-0.85), a slightly elevated lymphoma risk for first-born children (OR=1.17, CI=0.99-1.39) and only children (OR=1.10, CI=0.86-1.39). The inverse relationship between atopic disorders and risk of lymphomas is consistent with earlier observations. Our findings on birth order and lymphoma increase the inconsistency of findings across studies and suggest a critical reappraisal of potential underlying mechanisms.

Allergic rhinoconjunctivitis: epidemiology

Allergic rhinoconjunctivitis has been studied much less frequently than asthma using epidemiologic approaches. Population-based studies are difficult to conduct because of misclassification arising from the reliance on self-reported questionnaires that use terms such as allergic rhinitis or hay fever to establish the diagnosis. In addition, many epidemiologic studies focus on diagnostic skin testing or allergen-specific IgE antibodies (RASTs) as an objective outcome to assess for hay fever. These techniques are helpful but not perfect measures for predicting hay fever outcomes in epidemiologic studies. It is generally accepted, however, that allergic rhinoconjunctivitis is one of the most common of chronic diseases and is the most common atopic disorder. This article reviews the definition of allergic rhinoconjunctivitis, the epidemiology of this disorder from infancy into adulthood, and environmental risk factors for development of sensitization to certain allergens.

Sibship characteristics and risk of allergic rhinitis and asthma

Studying associations between sibship characteristics and allergic diseases in detail may contribute clues to their etiology. The authors studied associations between sibship characteristics and risk of self-reported allergic rhinitis and asthma among 31,145 pregnant women participating in a nationwide study in Denmark during 1997-2000. Increasing sibship size was associated with a decreased risk of allergic rhinitis and asthma with allergic rhinitis but not with asthma without allergic rhinitis. The protective effect of having older siblings was stronger than the protective effect of having younger siblings for both allergic rhinitis and asthma with allergic rhinitis. There was no association between interval to closest older or younger sibling and risk of allergic rhinitis or asthma with allergic rhinitis, while the risk of asthma without allergic rhinitis increased with intervals of 2 or more years compared with less than 2 years to the nearest older sibling. The protective effect of having siblings on the risk of asthma with allergic rhinitis could be explained by a protective effect of siblings on the risk of allergic rhinitis alone. In conclusion, our findings suggest that different etiologic mechanisms are involved for allergic rhinitis and asthma with respect to the effect of sibship characteristics. Furthermore, the findings that allergic rhinitis was associated with the number of younger siblings but not with the age interval to younger siblings support the hypothesis of an influence of postnatal mechanisms and suggest that these mechanisms may not necessarily be operating only in early life.

Risk factors for atopic dermatitis in New Zealand children at 3.5 years of age

BACKGROUND

The prevalence of atopic dermatitis (AD) is increasing in Western societies. The hygiene hypothesis proposes that this is due to reduced exposure to environmental allergens and infections during early life.

OBJECTIVES

To examine factors associated with a diagnosis of AD at 3.5 years of age, especially those factors implicated by the hygiene hypothesis.

METHODS

The Auckland Birthweight Collaborative study is a case-control study of risk factors for small for gestational age babies. Cases were born at term with birthweight < or = 10th centile; controls were appropriate for gestational age, with birthweight > 10th centile. The infants were assessed at birth, 1 year and 3.5 years of age. Data were collected by parental interview and examination of the child. AD was defined as the presence of an itchy rash in the past 12 months with three or more of the following: history of flexural involvement; history of generally dry skin; history of atopic disease in parents or siblings; and visible flexural dermatitis as per photographic protocol. Statistical analyses took into account the disproportionate sampling of the study population.

RESULTS

Analysis was restricted to European subjects. Eight hundred and seventy-one children were enrolled at birth, 744 (85.4%) participated at 1 year, and 550 (63.2%) at 3.5 years. AD was diagnosed in 87 (15.8%) children seen at 3.5 years. The prevalence of AD did not differ by birthweight. AD at 3.5 years was associated with raised serum IgE > 200 kU L(-1), and wheezing, asthma, rash or eczema at 1 year. In multivariate analysis, adjusted for parental atopy and breastfeeding, AD at 3.5 years was associated with atopic disease in the parents: maternal atopy only, adjusted odds ratio (OR) 3.83, 95% confidence interval (CI) 1.20-12.23; paternal atopy only, adjusted OR 3.59, 95% CI 1.09-11.75; both parents atopic, adjusted OR 6.12, 95% CI 2.02-18.50. There was a higher risk of AD with longer duration of breastfeeding: < 6 months, adjusted OR 6.13, 95% CI 1.45-25.86; > or = 6 months, adjusted OR 9.70, 95% CI 2.47-38.15 compared with never breastfed. These findings remained significant after adjusting for environmental factors and a personal history of atopy. AD at 3.5 years was associated with owning a cat at 3.5 years (adjusted OR 0.45, 95% CI 0.21-0.97) but not with owning a dog at 3.5 years, pets at 1 year, nor with older siblings. Furthermore, AD at 3.5 years was not associated with gender, socioeconomic status, maternal smoking, parity, damp, mould, immunizations, body mass index or antibiotic use in first year of life.

CONCLUSIONS

A personal and a parental history of atopic disease are risk factors for AD at 3.5 years. Duration of breastfeeding was associated with an increased risk of AD. No association was found with those factors implicated by the hygiene hypothesis. This study suggests that breastfeeding should not be recommended for the prevention of AD.

Towards improving the accuracy of diagnosing asthma in early childhood

OBJECTIVES

Early and correct diagnosis of asthma in wheezing children is essential for early treatment and prevention of under- or over-treatment. The aim was to study whether combining frequency and age of onset of wheezing illness with respiratory and atopic morbidity at age 0-6 years and sociodemographic parameters for asthma might be helpful for the general practitioner to diagnose asthma early and accurately.

METHODS

Birth cohort, mean follow-up 20 years (SD 4.8) in general practice. The outcome, adolescent asthma, was analysed in relation to wheezing and non-wheezing respiratory and personal and familial atopic morbidity. All diagnoses were from the Continuous Morbidity Registration of the Department of General Practice of the University of Nijmegen, the Netherlands.

RESULTS

1586 (64%) of the children could be followed. Adolescent asthma occurred in 6.4%. There were indications for under- and over-diagnosis of asthma at age 0-6 years. Non-recurrent wheezing (only one episode) and recurrent wheezing (>or =2 episodes) in the first three years of life, and recurrent wheezing at age 4-6 increased the risk with odds ratios (95% confidence interval) of 3.3 (1.9-5.6), 4.7 (2.8-8.2) and 15.4 (7.1-33.7), respectively. The risk additionally increased independently with a family history for asthma, (2.0 [1.1-3.6]), atopic dermatitis (1.7 [1.1-2.7]) and sinusitis (2.9 [1.3-6.4]) and decreased for > or =2nd born children (0.38 [0.19-0.47]) and those with a low social-economic status (0.61 [0.39-0.94]).

CONCLUSION

Easily available history and clinical data may facilitate the early diagnosis of asthma in children with wheezing illness.

Childhood asthma

The prevalence of asthma and wheezing illness in children has increased substantially over recent decades and places a large burden on health care resources. Despite increasing evidence that both genetic and environmental factors have significant effects on airway development and function in early life, our understanding of the natural history of the disease is limited. Several phenotypes of wheeze have been described and many risk factors identified for the development of asthma. A thorough knowledge of early life lung physiology will enable us to identify children at risk for developing persistent disease. The development of objective outcome measures that can be applied in early life will aid in distinguishing between children with transient early wheeze and those who will progress to persistent disease, enabling effective, targeted therapy.

A prospective association between cocoon use in infancy and childhood asthma

There is increasing evidence for a role for bedding items in the development of asthma. The use of some forms of synthetic bedding, such as foam mattresses and pillows, is associated with a significantly increased risk of childhood wheeze. Our aim was to examine prospectively whether the use of synthetic cocoon/baby nests in infancy is associated with the subsequent development of wheeze in childhood. Data collected in 1988 as part of the Tasmanian Infant Health Survey were linked to the cross-sectional Childhood Asthma Survey conducted in 1995 in Tasmania, Australia. We were able to match 863 records out of the 1111 in the 1988 survey. Information including parental, child-care, and the infant's sleeping environment was collected at home interview in 1988 when the infant was 1 month of age. Data including sleep environment and asthma symptoms were available for each child at age 7 years. A generalised linear model was used to calculate the adjusted relative risk (RR) estimates for symptoms of wheeze and infant cocoon use. For children who were placed in a cocoon in infancy, there was an increased risk of recent wheeze (adjusted RR = 4.33 [95% CI 2.08, 9.02]) and night wheeze (adjusted RR = 3.35 [95% CI 1.52, 7.39]) at age 7 years. In view of the increasing prevalence of childhood asthma, the identification of potentially modifiable environmental factors which might operate in infancy is of importance. The present findings implicate infant bedding choice as a significant factor and further studies on the infant sleeping environment are indicated.

Birth order and sibship size as independent risk factors for asthma, allergy, and eczema

This study was carried out to disentangle the independent relations of birth order and sibship size with the presence of asthma, allergy and eczema. In a retrospective study, 700 families in the Netherlands were selected with index children born in 1988-90. Data were extracted from reports of health examinations at the age of 6 years of these children and their siblings. Birth order, and not sibship size, appeared to be a strong risk factor for allergy (excluding eczema). Children with higher birth order had a lower risk of allergy compared with first-borns (adjusted odds ratios: 0.43, 0.26 and 0.05 for second-, third- and fourth- or higher borns, respectively; p < 0.0001). Allergy including eczema also had a significant relation with birth order (p = 0.01). For asthma there appeared no clear relation with birth order. For asthma a non-significant relationship with sibship size (adjusted for birth order) was found (p = 0.06): first-born children in small sibships were more at risk than those in larger sibships. For allergy and eczema no such trend was observed. In conclusion, birth order is inversely related to the risk of allergy, independent of the size of the sibship.

Different sensitization profile for asthma, rhinitis, and eczema among 7-8-year-old children: report from the Obstructive Lung Disease in Northern Sweden studies

Sensitization to different airborne allergens in relation to asthma, rhinitis, and eczema has been studied. A cross-sectional study was performed among 7-8-year-old children living in northern Sweden. The ISAAC-questionnaire with additional questions were sent to the parents, and 3431 (97%) participated. Two-thirds of the children were invited to undergo a skin test with 10 common airborne allergens, and 2148 (88%) participated. The prevalence rates of all three diseases were significantly higher among the children who were sensitized to any of the tested allergens. Among asthmatics, 40% were sensitized to cat, 34% to dog, 28% to horse, 23% to birch and 16% to timothy. The corresponding figures for rhinitis were: cat 49%, dog 33%, horse 37%, birch 46%, timothy 32%; and for eczema: cat 29%, dog 21%, horse 15%, birch 20%, and timothy 11%. Only a few children were sensitized to mites or moulds. The main risk factors for all three diseases were type-1 allergy and a family history of the disease. Independently from other risk factors, sensitization to dog (OR 2.4) and horse (OR 2.2) were significant risk factors for asthma. Sensitization to birch (OR 6.0), horse (OR 4.1), and timothy (OR 2.8) were significant risk factors for rhinitis, while birch (OR 2.4), dog (OR 2.0) and cat (OR 1.6) were significant risk factors for eczema. Despite a large over-lapping of the diseases the pattern of sensitization was different for asthma, rhinitis and eczema. Sensitization to cat was most common among all children, but sensitization to dog and horse was associated with the highest risk for asthma, and sensitization to birch showed the highest risk for rhinitis and eczema. The different risk factor pattern for the often coexisting diseases; asthma, rhinitis, and eczema, may indicate differences in the etiology.

Revisiting the "hygiene hypothesis" in gastrointestinal allergy

The "hygiene hypothesis" in its original form hypothesized that infection in early childhood acquired through unhygienic contact with siblings or the mother may prevent the development of allergic disease. Several recent epidemiologic surveys showing an inverse relationship between the frequency of infectious disease and the incidence of allergic diseases lend support to this hypothesis. Allergen sensitization of the immune system can occur early in utero against a background of neonatal commitment to a Th2 immune response involving the production of Th2 cytokines (eg, interleukin (IL)-4, IL-5, IL-13) that are the principal mediators of allergic inflammation. Continued allergen exposure is associated with predominantly CD4+ Th2 cell proliferation but does not exclude a minor Th1 allergen-specific subpopulation that can be further expanded nonspecifically and polyclonally by microbial superantigens or as bystanders, by interferon-gamma (IFN-gamma) and IL-2 released from Th1 effectors responding to antigens associated with infectious pathogens. Th1 cytokines can also subvert allergen-specific Th2 lymphocytes to become allergen-specific Th1 cells-a process reminiscent of the increased tendency of the maturing immune system of growing adults to mount a Th1 response to some environmental and dietary antigens. Unlike Th2 cytokines, IFN-gamma and IL-2 inhibit B-cell production of IgE and, hence, delimit the capacity of mast cells to degranulate and release allergenic mediators. The ability of infectious agents through their danger signals to initiate a Th1 response that deviates the Th2 allergenic bias is the basis of the hygiene hypothesis.

Differences in the prevalence of asthma and current wheeze between Jews and Arabs: results from a national survey of schoolchildren in Israel

BACKGROUND

There is evidence that the prevalence of asthma is higher in Jewish schoolchildren than in Arab schoolchildren. It is not clear to what extent other risk factors explain these differences.

OBJECTIVE

To evaluate whether the population group differences in the prevalence of asthma and current wheeze remain after adjustment for several potential risk factors.

METHODS

A national survey of 10,057 13- to 14-year-old schoolchildren was carried out in Israel in 1997. There were 7,436 Jewish children and 2,621 Arab children. Differences in the two population groups were examined while controlling for demographic and environmental factors such as: sex, parental education, parental smoking and asthma, crowding, and presence of older siblings.

RESULTS

The prevalence of asthma and current wheeze was significantly higher in Jewish children compared with Arab children. The asthma prevalence was 7.8% for Jewish children and 4.9% for Arab children (P = 0.001), and prevalence of current wheeze was 20.7 and 10.1%, respectively (P = 0.001). After adjustment for demographic and environmental factors, the prevalence of asthma and current wheeze was still increased in the Jewish population (odds ratios: 1.51; 95% confidence interval [CI] = 1.06 to 2.15; 2.15 95% CI = 1.70 to 2.73, respectively). History of asthma in parents and residence in a rural area were significant risk factors for asthma and current wheeze. In addition, the presence of less than three older siblings was a significant risk factor for asthma, and female sex, ever having pets, and maternal smoking were significantly associated with current wheeze.

CONCLUSIONS

The differences between Jewish and Arab children were not explained by the studied factors. Genetic factors, different environmental exposure, and nutritional habits should be studied to further explain the differences between these populations.

The incidence of atopic dermatitis in school entrants is associated with individual life-style factors but not with local environmental factors in Hannover, Germany

BACKGROUND

Atopic dermatitis (AD) is a common skin disease in childhood. Micro- and macro-environmental factors have not yet been studied simultaneously in a large cohort of the same area in detail.

OBJECTIVES

The incidence of AD was investigated in 97% of all school entrants (n = 4219) in the city of Hannover, Germany, with regard to the influence of individual and environmental factors.

METHODS

A standardized questionnaire based on the criteria of Hanifin and Rajka that has the sensitivity and specificity of 97% compared with the clinical diagnosis of a dermatologist and a logistic regression model were used. Multiple local-based environmental factors were analysed for all 49 city quarters.

RESULTS

Of all children studied, 10.5% suffered from AD at some time in their lives. The frequency of AD was significantly increasing with more privileged socio-economic status (P < 0.01). Independent factors that were associated with a higher frequency of AD were German nationality (12.4% AD compared with 2.1% in non-German), higher paternal socio-economic status (i.e. father's profession), higher daily duration of the fathers' professional work and the lack of paternal shift work. In contrast, there was no significant association between the frequency of AD and local environmental factors such as the biological effective level of air pollution and urbanization.

CONCLUSIONS

In conclusion, we confirm an association between a privileged life-style and a higher incidence of AD in a large number of investigated children between 5 and 9 years of age (97.6% of children were 6 or 7 years old) for the German city of Hannover. We propose the socio-economic status as a marker for different life-styles and social micro-environments in further studies as there were multiple significant correlations between individual social and environmental factors. The macro-environment seems to be less important for the disease outcome in this context.

Does a higher number of siblings protect against the development of allergy and asthma? A review

STUDY OBJECTIVE

To review the "protective" effects of having a higher number of siblings for the risk of atopic eczema, asthma wheezing, hay fever, and allergic sensitisation.

METHOD

Review of the literature (Medline since 1965 and references).

MAIN RESULTS

53 different studies were identified. For eczema, 9 of 11 studies reported an inverse relation with number of siblings; for asthma and wheezing, 21 of 31 reported the inverse association; for hay fever, all 17 studies showed the effect; for allergic sensitisation or immunoglobulin E reactivity 14 of 16 studies supported the "protective" effect of a higher number of siblings. The studies emphasise a "theory" that is based exclusively on epidemiological associations.

CONCLUSIONS

Research has not yet answered the question of which causal factors explain the sibling effect. Causal factors must meet two criteria; they must vary with sibship size and they must protect against atopic manifestations. The prevailing "hygiene hypothesis" failed to explain the findings adequately. Alternative explanations include in utero programming or endocrine explanatory models. The epidemiology research into siblings and atopic disorders has entered an intellectually challenging phase. Possessing sufficient knowledge about the causal factors might prevent at least 30% of all cases of asthma, eczema, and hay fever.

February asthma outbreaks in NSW: a case control study

OBJECTIVES

To investigate individual factors associated with an asthma outbreak among children aged one to 14 years in Sydney in February 1999.

METHODS

A case control study was undertaken with cases (n=92) defined as all children admitted to Sydney Children's Hospital for asthma in February 1999. Unmatched controls (n=76) were all children admitted for asthma in the previous three months. We obtained information by a structured telephone survey of parents. Logistic regression analyses were used to determine odds ratios for risk factors for hospital admission.

RESULTS

Mean age for hospital admission of 4.7 years for cases and 4.4 years for controls. The presence of one or more siblings reduced the risk of admission during an asthma outbreak (OR=0.59, 95% CI 0.37 to 0.93). Children with older siblings aged 10 to 14 years were also less likely to be admitted (OR=0.3, 95% CI 0.12 to 0.74). An age effect was observed. Other demographic, clinical and environmental characteristics, including smoking, were not associated with admission during the outbreak.

CONCLUSIONS

The main findings of this study are the protective effect of siblings and an age-dependent effect in risk of hospital admission during an asthma outbreak. These findings are consistent with an infective cause of the outbreak.

IMPLICATIONS

Children without siblings, particularly older siblings, appear to be at highest risk of hospital admission during an asthma outbreak. Environmental and other factors need to be examined to further explain the episodicity of such outbreaks and to determine means of predicting and preventing future episodes.

Siblings, multiple births, and the incidence of allergic disease: a birth cohort study using the West Midlands general practice research database

BACKGROUND

The presence of older siblings reduces the risk of developing hay fever, eczema and atopy, but findings for asthma have been inconsistent. Whether twins have a reduced risk of allergic disease is also unclear. We have investigated these questions in a birth cohort analysis of the West Midlands General Practice Research Database (GPRD).

METHODS

Our birth cohort included 29,238 children. The incidence of allergic disease was examined according to the number of siblings, multiple births, and parental allergic disease and smoking habit using Cox regression.

RESULTS

There was a dose related decrease in the incidence of eczema and hay fever with increasing number of older siblings (hazard ratio for children with three or more older siblings compared with none 0.70 (95% CI 0.64 to 0.76) for eczema and 0.67 (95% CI 0.52 to 0.86) for hay fever). In contrast, the presence of older siblings increased the incidence of asthma (HR 1.17, 95% CI 1.06 to 1.29), although this effect was strongly dependent on age of diagnosis. For children diagnosed over the age of 2 years the presence of older siblings was protective (HR 0.66, 95% CI 0.52 to 0.82), while below this age the reverse was true (HR 1.38, 95% CI 1.24 to 1.54). Members of a multiple birth had a reduced incidence of all three allergic diseases. Birth order and multiple birth effects were independent of sex, maternal age, consulting behaviour, and parental allergy and smoking habit.

CONCLUSIONS

The presence of older siblings and being a member of a multiple birth appears to protect against the development of eczema, hay fever, and asthma diagnosed after the age of 2. In contrast, the presence of older siblings increases the incidence of early asthma.

Asthma in preschool children: prevalence and risk factors

BACKGROUND

The prevalence of asthma in children has increased in many countries over recent years. To plan effective interventions to reverse this trend we need a better understanding of the risk factors for asthma in early life. This study was undertaken to measure the prevalence of, and risk factors for, asthma in preschool children.

METHODS

Parents of children aged 3-5 years living in two cities (Lismore, n=383; Wagga Wagga, n=591) in New South Wales, Australia were surveyed by questionnaire to ascertain the presence of asthma and various proposed risk factors for asthma in their children. Recent asthma was defined as ever having been diagnosed with asthma and having cough or wheeze in the last 12 months and having used an asthma medication in the last 12 months. Atopy was measured by skin prick tests to six common allergens.

RESULTS

The prevalence of recent asthma was 22% in Lismore and 18% in Wagga Wagga. Factors which increased the risk of recent asthma were: atopy (odds ratio (OR) 2.35, 95% CI 1.49 to 3.72), having a parent with a history of asthma (OR 2.05, 95% CI 1.34 to 3.16), having had a serious respiratory infection in the first 2 years of life (OR 1.93, 95% CI 1.25 to 2.99), and a high dietary intake of polyunsaturated fats (OR 2.03, 95% CI 1.15 to 3.60). Breast feeding (OR 0.41, 95% CI 0.22 to 0.74) and having three or more older siblings (OR 0.16, 95% CI 0.04 to 0.71) decreased the risk of recent asthma.

CONCLUSIONS

Of the factors tested, those that have the greatest potential to be modified to reduce the risk of asthma are breast feeding and consumption of polyunsaturated fats.

Asthma in preschool children: prevalence and risk factors

BACKGROUND

The prevalence of asthma in children has increased in many countries over recent years. To plan effective interventions to reverse this trend we need a better understanding of the risk factors for asthma in early life. This study was undertaken to measure the prevalence of, and risk factors for, asthma in preschool children.

METHODS

Parents of children aged 3–5 years living in two cities (Lismore, n=383; Wagga Wagga, n=591) in New South Wales, Australia were surveyed by questionnaire to ascertain the presence of asthma and various proposed risk factors for asthma in their children. Recent asthma was defined as ever having been diagnosed with asthma andhaving cough or wheeze in the last 12 monthsand having used an asthma medication in the last 12 months. Atopy was measured by skin prick tests to six common allergens.

RESULTS

The prevalence of recent asthma was 22% in Lismore and 18% in Wagga Wagga. Factors which increased the risk of recent asthma were: atopy (odds ratio (OR) 2.35, 95% CI 1.49 to 3.72), having a parent with a history of asthma (OR 2.05, 95% CI 1.34 to 3.16), having had a serious respiratory infection in the first 2 years of life (OR 1.93, 95% CI 1.25 to 2.99), and a high dietary intake of polyunsaturated fats (OR 2.03, 95% CI 1.15 to 3.60). Breast feeding (OR 0.41, 95% CI 0.22 to 0.74) and having three or more older siblings (OR 0.16, 95% CI 0.04 to 0.71) decreased the risk of recent asthma.

CONCLUSIONS

Of the factors tested, those that have the greatest potential to be modified to reduce the risk of asthma are breast feeding and consumption of polyunsaturated fats.

Family size, day-care attendance, and breastfeeding in relation to the incidence of childhood asthma

A hypothesis has been suggested stating that children exposed early to infections are less likely to develop atopy or asthma. The authors investigated the relation between risk of childhood asthma and number of siblings as well as day-care attendance, as factors possibly increasing the likelihood of early infections, and breastfeeding as a factor reducing them. A case-control study was carried out in Montréal, Canada, between 1988 and 1995 that included 457 children diagnosed with asthma at 3--4 years of age and 457 healthy controls. Cases followed for 6 years were later classified as persistent or transient by the symptoms and use of medication after diagnosis. Among cases diagnosed at 3--4 years of age, the adjusted odds ratio for asthma was 0.54 (95% confidence interval (CI): 0.36, 0.80) for one sibling and 0.49 (95% CI: 0.30, 0.81) for two or more. The adjusted odds ratio for day-care attendance before 1 year of age was 0.59 (95% CI: 0.40, 0.87). Results were similar with persistent cases. Among transient cases (who possibly had an infection with wheezing at 3--4 years of age), day-care attendance and a short duration of breastfeeding resulted in increased risk. The results support the hypothesis that opportunity for early infections reduces the risk of asthma.

Asthma, inhaled corticosteroid use, and bone mass in prepubertal children

The aim of this cross-sectional study was to describe the role of asthma, asthma severity, and medication usage in bone mineralization of prepubertal children. Asthma severity, medication usage, and physical activity were assessed by questionnaire and objective measures in 330 children. Bone densitometry and body composition were measured by dual-energy x-ray absorptiometry. Asthma ever was reported by 110 subjects (33%). A diagnosis of asthma was not associated with any deficit in bone mass, whereas usage of inhaled corticosteroids (ICS) in the last year (but not past use) was associated with deficits in bone in the total body (only after adjustment for confounders), particularly for doses of > or =400 microg/day. These observations support current recommendations with regard to ICS usage in children, but require confirmation in longitudinal studies.

Seasonal allergic rhinoconjunctivitis and fatty acid intake: a cross-sectional study in Japan

PURPOSE

To investigate the associations of fatty acid intake with seasonal allergic rhinoconjunctivitis.

METHODS

The study subjects consisted of 1012 women aged 22 to 57 years (mean age +/- SD: 36.5+/-7.7 years), who had graduated from the Aichi Prefectural Junior College of Nursing, Nagoya, Japan. They completed a self-administered questionnaire on symptoms of the disease in August 1998. Symptoms of seasonal allergic rhinoconjunctivitis in spring were determined by response to the questionnaire, and fatty acid intake was estimated using a food frequency questionnaire. Odds ratios (ORs) were computed using unconditional logistic models to assess the strength of associations between the symptoms and fatty acid intake.

RESULTS

An increasing trend in the ORs was observed with increasing dietary intake of n-6 polyunsaturated fatty acids. After adjustment for potential confounders, the ORs for the second, third, and highest quartiles of intake relative to the lowest were 1.28 [95% confidence interval (CI), 0.78-2.10], 1.55 (0.96-2.50), and 1.74 (1.09-2.77), respectively (trend p = 0.015). Consumption of saturated, monounsaturated, and n-3 polyunsaturated fatty acids was not significantly related to the symptoms.

CONCLUSIONS

Dietary intake of n-6 polyunsaturated fatty acids was positively associated with seasonal allergic rhinoconjunctivitis in spring.

Parent-reported infant health and illness in a whole year birth cohort

OBJECTIVE

To describe parent-reported infant health and illness experience at 8 weeks.

SETTING

Coventry.

STUDY DESIGN

Prospective whole year birth cohort.

OUTCOME MEASURES

Period prevalences (birth to 8 weeks) and incidences, unadjusted and adjusted for differential cohort attrition, of parent-reported infant health outcomes.

METHODS

Of 3891 live births in 1996, 2572 (66%) were recruited into the study. Data were collected by health visitors as part of routine child health surveillance, at 8 weeks using the Warwick Child Health and Morbidity Profile (WCHMP) incorporated into the Parent Held Record. Period prevalences and incidences of parent-reported health outcomes in the first 8 weeks of life were calculated with and without adjustment for the effects of different rates of cohort attrition by sociodemographic group.

RESULTS

Data were collected on 2572 infants at recruitment. Health outcome data were available on 2072 (53% of all 1996 live births) infants at 8 weeks. There was differential attrition by social group between enrollment and 8 weeks. Nineteen (95% confidence intervals (CIs) 14,24)/1000 infants were reported as not very healthy/unhealthy, 12 (95% CIs 8,16)/1000 as having impaired health-related quality of life and 11 (95% CIs 7,15)/1000 impaired functional health. Chronic illness had a period prevalence rate of 19 (95% CIs 14,24)/1000. Sixty-six (95% CIs 55,77)/1000 had acute illnesses requiring medical attention and 43 (95% CIs 34,52)/1000 were admitted to hospital at least once. More minor illness than expected was reported in 87 (95% CIs 75,99)/1000. The incidence rate of accidents requiring medical attention was 16 (95% CIs 9,21)/1000. Behavioural problems had a prevalence rate of 78 (95% CIs 66,90)/1000.

CONCLUSIONS

Infant health status data have traditionally been based on mortality, hospital admissions and specific diagnoses. This is the first report of health and illness experience during infancy in a whole year birth cohort based on a validated measure of parent-reported health status incorporated into the Parent Held Record and administered by the family health visitor as part of routine child health surveillance. These data give a more comprehensive picture of infant health and illness experience than traditional measures and provide the basis for infant health needs assessment.

Daycare attendance, asthma and atopy

The objective of this article is to review studies that have examined the relation of daycare to asthma and atopy. In order to identify studies for inclusion, abstracts of all studies referenced in Medline from January 1966 to January 2000 and in BIBSYS were searched and extracted if they included 'asthma' or 'atopy' combined with words such as 'daycare', 'nursery' or 'kindergarten'. Eight studies fulfilled the criteria of inclusion. The outcomes were asthma, skin prick test (SPT) reactivity, a positive radioallergosorbent test (RAST), hay fever, and eczema. Daycare attendance was positively associated with asthma in five of six studies including asthma. In three of these studies there was no statistically significant association between daycare and asthma. Early start in daycare protected against later asthma in one study. There was a weak, but not a statistically significant positive relation between daycare and atopy in two of three studies when SPT reactivity was used as the outcome. In children of small families early start in daycare protected against atopy. The quality of the studies varies, and they are not directly comparable. The relation between daycare attendance and asthma and atopy is unclear, and further studies designed to answer this specific research question are needed.

Siblings, day-care attendance, and the risk of asthma and wheezing during childhood

BACKGROUND

Young children with older siblings and those who attend day care are at increased risk for infections, which in turn may protect against the development of allergic diseases, including asthma. However, the results of studies examining the relation between exposure to other children and the subsequent development of asthma have been conflicting.

METHODS

In a study involving 1035 children followed since birth as part of the Tucson Children's Respiratory Study, we determined the incidence of asthma (defined as at least one episode of asthma diagnosed by a physician when the child was 6 to 13 years old) and the prevalence of frequent wheezing (more than three wheezing episodes during the preceding year) in relation to the number of siblings at home and in relation to attendance at day care during infancy.

RESULTS

The presence of one or more older siblings at home protected against the development of asthma (adjusted relative risk for each additional older sibling, 0.8; 95 percent confidence interval, 0.7 to 1.0; P=0.04), as did attendance at day care during the first six months of life (adjusted relative risk, 0.4; 95 percent confidence interval, 0.2 to 1.0; P=0.04). Children with more exposure to other children at home or at day care were more likely to have frequent wheezing at the age of 2 years than children with little or no exposure (adjusted relative risk, 1.4; 95 percent confidence interval, 1.1 to 1.8; P=0.01) but were less likely to have frequent wheezing from the age of 6 (adjusted relative risk, 0.8; 95 percent confidence interval, 0.6 to 1.0; P=0.03) through the age of 13 (adjusted relative risk, 0.3; 95 percent confidence interval, 0.2 to 0.5; P<0.001).

CONCLUSIONS

Exposure of young children to older children at home or to other children at day care protects against the development of asthma and frequent wheezing later in childhood.

Relationship between early life respiratory illness, family size over time, and the development of asthma and hay fever: a seven year follow up study

BACKGROUND

The timing and mechanism of the inverse association between increasing sibling number and atopic disease are not yet understood. A study was undertaken to examine how family size at birth predicts early respiratory illness, to report the association between infant respiratory illness and childhood atopic disease, and to determine whether the protective effect of large family size operates during infancy or later childhood.

METHODS

A prospective follow up study was carried out on 863 children (78%) of 1111 participants in the Tasmanian Infant Health Survey performed in 1988. In 1988 household size and history of respiratory illness were obtained by parental interview at home (median age 35 days) and later by telephone (median age 85 days). In 1995 asthma, hay fever, and household size were assessed by parental questionnaire in a large cross sectional survey.

RESULTS

In 1988 increasing resident number (per resident) (adjusted odds ratio (AOR) 1.17 (95% CI 1.05 to 1.31)) and resident density (AOR 1.77 (95% CI 1.07 to 2.94)) were related to parental report of an upper respiratory tract infection (URTI) by one month of age. Children with a reported URTI by home interview were more likely to have subsequent asthma (adjusted relative risk (ARR) 1.27 (95% CI 1.05 to 1.53)). The association between lower respiratory tract infection (LRTI) at telephone interview (relative risk (RR) 1.34 (95% CI 1.02 to 1.75) and asthma was reduced after adjustment for family history of asthma (ARR 1.27 (95% CI 0.98 to 1.66)). Antibiotic use by home interview was not associated with subsequent asthma or hay fever. Indicators of family size in 1988 were associated with hay fever but not asthma but, in contrast, resident number in 1995 was inversely associated with asthma (AOR 0.82 (95% CI 0.72 to 0.92) per resident) and hay fever (AOR 0.82 (95% CI 0.71 to 0.96) per resident). Children with no siblings were at risk for current asthma, particularly if symptoms began after the age of four (RR 2.81 (95% CI 1.36 to 5.84)).

CONCLUSIONS

The apparent protective effect of large household size and asthma could not be explained by an increase in reported early respiratory illness. The first year of life may not be the most critical time for the protective effect of large household size to be mediated in relation to asthma, but this effect occurred by the seventh year of life.