Infections in early childhood and risk of atopic disease

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.

Impact of socioeconomic and environmental factors on atopic eczema and allergic rhinitis: a cross sectional study

The prevalence of allergic rhinitis and atopic eczema is on the rise in recent decades. Many factors can be related to the development of these diseases. We aimed to investigate the association between socioeconomic status (SES), environmental risk factors and these conditions. In this study, the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire was translated and validated. Then it was used to determine the prevalence, severity and possible related factors for both diseases in 1904 schoolchildren aged 6-7 and 13-14 years from various regions of Tehran. The prevalence of rhinitis and eczema in the past year was 33.2 % and 8.2 %, respectively. The prevalence of rhinoconjunctivitis in the past year was 30 %. The risk factors such as birth order, nursery attendance, pet ownership, past allergic experiences as well as some SES factors were associated with both conditions. The prevalence of allergic rhinitis and atopic eczema was on the rise in comparison to the previous studies and SES as well as environmental factors are thought to be associated with the prevalence of these conditions.

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.

Recurrent childhood upper respiratory tract infections do not reduce the risk of adult atopic disease

BACKGROUND

Children of large families and those attending day care are at increased risk of respiratory tract infections, which in turn may protect against the development of allergic disease. Longitudinal studies investigating these associations beyond childhood are, however, scarce.

OBJECTIVE

To investigate the association between childhood recurrent upper respiratory tract infections (URTI) and asthma, allergic rhinitis (AR) and eczema in adulthood.

METHODS

A birth cohort of 1055 members followed prospectively from the ages of 2 to 21 years. Detailed information on URTI between the ages of 2 and 4 years was collected at 3 monthly intervals in a standardized interview. At the age of 8 years, a parental questionnaire regarding URTI between the ages of 4 and 8 years was used. The incidence of asthma and atopic disease at the age of 21 years was determined using a standardized questionnaire.

RESULTS

Of the original cohort, 693 (66%) members completed the questionnaire. Children who experienced recurrent URTI before the age of 2 years, between the ages of 2-4 years and between ages of 4 and 8 years were not less likely to have asthma at 21 years of age than children who did not experience recurrent URTI, relative risk (RR) 0.97 (95% confidence interval (CI) 0.65-1.46), RR 1.45 (CI 0.95-2.21) and RR 1.51 (CI 0.97-2.36), respectively. Neither were recurrent URTI associated with a decreased risk of AR, nor eczema at the age of 21 years.

CONCLUSIONS

Recurrent URTI in childhood did not reduce the risk of atopic disease in young adulthood.

Day-care attendance and increased risk for respiratory and allergic symptoms in preschool age

BACKGROUND

The reported impact of day-care attendance on respiratory and atopic symptoms has varied between studies from different countries. Regarding to the 'hygiene-hypothesis', day-care attendance may lead to less sensitization later in life, but the question still is whether day-care attendance and subsequent exposure to more frequent early infections is a risk or a protection against future allergic disease or asthma (atopic and nonatopic).

METHODS

A cross-sectional postal questionnaire was replied by parents of 10,851 children, aged 1-6 years, in the year 2000 in a Swedish region (DBH-phase 1). The questionnaire focused on respiratory and atopic symptoms, the home environment and information on day care of the children.

RESULTS

Children in day care were reported to have more symptoms than children in home care: adjusted odds ratio (AOR) for wheezing last 12 months, AOR 1.33 (CI 95%: 1.12-1.58), cough at night apart from colds last 12 months AOR 1.56 (CI: 1.17-2.07), doctor diagnosed asthma AOR 1.23 (CI: 0.88-1.71), rhinitis last 12 months AOR 1.15 (CI: 0.92-1.44), doctor diagnosed hay fever AOR 1.75 (CI: 0.94-3.23), eczema last 12 months, AOR 1.49 (CI: 1.24-1.79), allergic reactions to foods, AOR 1.27 (CI: 1.07-1.52), >6 colds last 12 months of 2.57 (CI: 2.12-3.12) and ear infection ever AOR 2.14 (CI: 1.87-2.45). The increased risks were mainly seen and reached significance in the youngest group of children, aged 1-4 years. Adjusting and stratification for the number of airway infections last year did not change the risk associated with day-care attendance for allergic diseases.

CONCLUSIONS

Attending day care was associated with an increased risk of symptoms related to airways infections as well with eczema and allergic reactions to food. No sign of protection from day-care attendance for allergic diseases was found up to 6 years of age. Multiple airway infections and day-care attendance were found to be independently associated with asthma and allergic symptoms.

Prophylactic management of children at risk for recurrent upper respiratory infections: the Preventia I Study

BACKGROUND

Given the morbidity and mortality of asthma and the recent dramatic increase in its prevalence, pharmacologic prophylaxis of this disease in children at risk would represent a major medical advance.

OBJECTIVES

The Preventia I Study was designed to evaluate the efficacy and long-term safety of loratadine in reducing the number of respiratory infections in children at 24 months. A secondary objective was to investigate the benefit of loratadine treatment in preventing the onset of respiratory exacerbations.

METHODS

Preventia I was a randomized placebo-controlled study involving 22 countries worldwide. The children were 12-30 months of age at enrollment and had experienced at least five episodes of ENT infections, and no more than two episodes of wheezing during the previous 12 months. Phase I was a 12-month double-blind period during which the children were treated with loratadine 5 mg/day (2.5 mg/day for children</=24 months of age) or placebo. Phase II was a double-blind follow-up period without study medication.

RESULTS

Of the 412 children enrolled, 342 and 310 completed Phase I and Phase II, respectively. The results showed a significant decrease in the number of infections in the whole population of children. However, no difference was observed between the loratadine and placebo group. When considering secondary end-points, loratadine was shown to reduce the number of respiratory exacerbations during the treatment phase. None of the 204 children who received loratadine discontinued the study because of drug-related events. Loratadine treatment was not more sedative than placebo and was not associated with cardiovascular events.

CONCLUSION

The strong decrease in the rate of infections in the children at risk of recurrent infections, while not being influenced by loratadine treatment, should encourage future reflection in terms of prophylactic management. This study also confirms the long-term safety of loratadine and its metabolites in young children.

Childhood infections and risk of wheezing and allergic sensitisation at age 7-8 years

BACKGROUND

Childhood atopic disease has been associated with exposure to infections early in life. There is however considerable controversy on this issue, since evidence exists for both protective and adverse effects of infections. Aim of this study was to investigate the association between childhood infections and the occurrence of wheeze and allergic sensitisation in 7-8-year-old Dutch and German children.

METHODS

A nested case-control study was conducted among German and Dutch children participating in a large longitudinal study on respiratory health. Parents of 510 7-8-year-old children with respiratory complaints and an equal number of children without respiratory complaints were asked to complete a questionnaire. Blood samples were collected for specific serum Immunoglobulin E (IgE) analysis. Data on childhood infections were collected through records of the participating Municipal Health Services.

RESULTS

No association was found between recent wheeze and any of the childhood infections investigated. For scarlet fever infection an increased risk of allergic sensitisation (OR: 2.82; 95% CI: 1.40-5.72) and sensitisation against grasses (OR: 3.00; 95% CI: 1.35-6.69) at the age of 7-8 years was found. Varicella infection tended towards increased risk of sensitisation against grasses (OR: 1.88; 95% CI: 0.99-3.58). For allergic sensitisation and sensitisation against grasses the odds ratios increased with increasing number of infections.

CONCLUSIONS

The results do not lend support to the suggestion that childhood infection protects against wheezing or allergic sensitisation at age 7-8 years. Scarlet fever or varicella infection presented an increased risk of allergic sensitisation.

T cell activation, from atopy to asthma: more a paradox than a paradigm

During the last 15 years, it was largely shown that allergic inflammation was orchestrated by activated Th2 lymphocytes, leading to IgE production and eosinophil activation. Indeed, Th2 activation was shown to be necessary to induce allergic sensitization in animal models. In humans, a Th2 skewing was shown in atopic children soon after birth. In asthma, descriptive studies showed that Th2 cells were more numerous in patients than in controls. In addition, during specific allergen stimulation, an increase of Th2 cells was described in most cases. According to this Th2 paradigm, it was proposed that early avoidance of microbial exposure could explain the increase of atopic diseases seen in the last 20 years in developed countries, as the "hygiene hypothesis". Recently, it was proposed that early exposure to lipopolysaccharide (LPS) could be protective against atopic diseases. However, it is well established that exposure to LPS can induce asthma symptoms, both in animals and humans, although it induces a Th1 inflammatory response. In addition, most infections induce asthma exacerbations and Th1 responses. Recently, some studies have showed that some Th1 cells were present in asthmatic patients, which could be related to bronchial hyperreactivity. There is therefore an "infectious paradox" in asthma, which contributes to show that the Th2 paradigm is insufficient to explain the whole inflammatory reaction of this disease. We propose that the Th2paradigm is relevant to atopy and inception of asthma albeit a Th1 activation would account at least in part for bronchial hyperreactivity and asthma symptoms.

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.

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.