Prevention of asthma in genetically predisposed children in primary care--from clinical efficacy to a feasible intervention programme

Dust mite avoidance for the primary prevention of atopic dermatitis: A systematic review and meta-analysis

BACKGROUND

Dust mite sensitization plays a controversial role in the development of atopic dermatitis. Despite a lack of evidence for its efficacy, dust mite avoidance is commonly recommended for the prevention and treatment of atopic dermatitis. We aimed to evaluate whether dust mite avoidance strategies reduce the risk of developing atopic dermatitis in high-risk infants compared to randomized controls.

METHODS

Studies were obtained by searching MEDLINE, PubMed, Scopus, The Cochrane Library, and The Global Resource of Eczema Trials databases. We included randomized, controlled trials of high-risk infants treated with a dust mite avoidance intervention and assessed for atopic dermatitis. Data were extracted independently by two reviewers using predefined criteria.

RESULTS

Seven randomized controlled trials met our inclusion criteria (total n = 3040). Studies were largely unblinded but otherwise of reasonable quality. Three trials utilizing a dust mite avoidance approach but not additional interventions were combined in a meta-analysis. Dust mite avoidance provided no benefit in the prevention of atopic dermatitis (relative risk (RR) = 1.08, 95% confidence interval (CI) = 0.78-1.49, I(2) = 73%).

CONCLUSIONS

Dust mite avoidance strategies alone or in combination with additional allergen avoidance modalities do not decrease the risk of developing atopic dermatitis and, given the current state of the evidence, should not be recommended for this purpose. The utility of dust mite avoidance for the treatment of atopic dermatitis or for the prevention and treatment of asthma or seasonal rhinoconjunctivitis are outside the scope of this review.

Cost-effectiveness of primary prevention of paediatric asthma: a decision-analytic model

BACKGROUND

Many children stand to benefit from being asthma-free for life with primary (i.e., prenatally started) prevention addressing one environmental exposure in a unifaceted (UF) approach or at least two in a multifaceted (MF) approach. We assessed the cost-effectiveness of primary prevention programmes for Dutch children in a decision-analytic framework.

METHODS

A decision-analytic tree model analysing healthcare costs and asthma cases prevented was developed to compare usual care (UC) with two UF and three MF programmes on the primary prevention of asthma amongst children. Programmes were evaluated through incremental cost-effectiveness ratios and net monetary benefits. Decision and parameter uncertainty were subjected to value-of-information analyses.

RESULTS

The current UC and one of three MF programmes dominated the other alternatives. The MF programme was more costly but also more effective than UC at an incremental cost-effectiveness ratio of <euro>8,209.20/additional asthma case prevented. The value of perfect information to reduce uncertainty was <euro>291.6M at its lowest. Most of the uncertainty in the cost-effectiveness threshold was attributable to the probability and cost estimates for low-risk children.

CONCLUSION

This study supports the feasibility of a structured programme that simultaneously addresses exposure to house dust mites, pet dander, environmental tobacco, and breast-feeding as a cost-effective alternative to UC in the primary prevention of asthma amongst children.

The 8-year follow-up of the PIAMA intervention study assessing the effect of mite-impermeable mattress covers

BACKGROUND

Exposure to high levels of house dust mite (HDM) allergens is associated with the development of allergic sensitization to HDM, a risk factor for the development of asthma, rhinitis, and allergic dermatitis. We studied the effect of an early intervention with mite-impermeable mattress covers on HDM allergen levels and the development of asthma and mite allergy throughout the first 8 years of life.

METHODS

High-risk children (allergic mother) were prenatally recruited and randomly allocated to two groups receiving mite allergen-impermeable (n = 416) and placebo mattress covers (n = 394) or no intervention (n = 472). Asthma and allergies were assessed yearly by questionnaire. Specific immunoglobulin E and bronchial hyper-responsiveness were measured at the age of 8 years. Mattress dust samples collected at different time points were analyzed for HDM allergens.

RESULTS

At the age of 8 years, levels of HDM allergen Der f1 but not Der p1 were lower in the active than the placebo mattress cover group. In repeated measures analyses, we found a temporary decreased risk of asthma symptoms at the age of 2 years in the intervention group compared to the placebo group and a temporary association between higher HDM allergen exposure at the age of 3 months and more asthma symptoms.

CONCLUSION

Early intervention with mite-impermeable mattress covers is successful in reducing exposure to Der f1; it only temporarily reduces the risk of asthma symptoms and does not reduce the risk of hay fever, eczema, and allergic sensitization.

Prevention of asthma in genetically susceptible children: a multifaceted intervention trial focussed on feasibility in general practice

BACKGROUND

Although the effectiveness of the multifaceted allergen-reducing interventions for the prevention of asthma in susceptible children was showed to be proven, the feasibility was not clear.

METHODS

The research question of the PREVention of asthma in susceptible children (PREVASC) trial was focused on the assessment of the effectiveness and feasibility of a multifaceted intervention on the prevention of allergic asthma in general practice. The effectiveness and feasibility of an intervention aimed at the simultaneous reduction in the environmental exposures to inhalant- and food allergens in susceptible children was investigated. A total of 476 children susceptible for developing asthma were initially included during pregnancy and were randomly divided over an intervention group of n = 222 children whose parents were offered a multifaceted environmental exposure-reducing intervention. Controls (n = 221) received usual care. The main outcome was 'diagnosis of allergic asthma at age 6'.

RESULTS

A significant reduction in inhalant allergen exposure levels of house dust mite [(Der p1), p = 0.043], cat [(Fel d1), p = 0.037], and dog [(Can f1), p = 0.012] was reached. Significantly more intervention group children started using cow's milk and solids after the age of 6 months (p ≤ 0.001). No statistical difference, however, was reached between groups on the duration of breast-feeding (p = 0.635) and the reduction in smoke exposure (p = 0829). At age 6, the intervention had no influence on the development of main outcome allergic asthma (OR = 1.010 (CI 0.580-1.758).

CONCLUSION

Other primary preventive asthma-reducing interventions were shown to be effective in reducing the occurrence of asthma for at least the first 7-8 yr of life. The multifaceted PREVASC allergic asthma primary preventive intervention was effective in reducing the exposure to inhalant and food allergens, but was not feasible for the parents. A lack of sufficient room for improvement focus on stimulating adherence seemed to be involved. It is suggested that a multifaceted environmental exposure-reducing intervention may have to be adapted to the personal circumstances of patients at baseline.

Structuring and validating a cost-effectiveness model of primary asthma prevention amongst children

BACKGROUND

Given the rising number of asthma cases and the increasing costs of health care, prevention may be the best cure. Decisions regarding the implementation of prevention programmes in general and choosing between unifaceted and multifaceted strategies in particular are urgently needed. Existing trials on the primary prevention of asthma are, however, insufficient on their own to inform the decision of stakeholders regarding the cost-effectiveness of such prevention strategies. Decision analytic modelling synthesises available data for the cost-effectiveness evaluation of strategies in an explicit manner. Published reports on model development should provide the detail and transparency required to increase the acceptability of cost-effectiveness modelling. But, detail on the explicit steps and the involvement of experts in structuring a model is often unevenly reported. In this paper, we describe a procedure to structure and validate a model for the primary prevention of asthma in children.

METHODS

An expert panel was convened for round-table discussions to frame the cost-effectiveness research question and to select and structure a model. The model's structural validity, which indicates how well a model reflects the reality, was determined through descriptive and parallel validation. Descriptive validation was performed with the experts. Parallel validation qualitatively compared similarity between other published models with different decision problems.

RESULTS

The multidisciplinary input of experts helped to develop a decision-tree structure which compares the current situation with screening and prevention. The prevention was further divided between multifaceted and unifaceted approaches to analyse the differences. The clinical outcome was diagnosis of asthma. No similar model was found in the literature discussing the same decision problem. Structural validity in terms of descriptive validity was achieved with the experts and was supported by parallel validation.

CONCLUSIONS

A decision-tree model developed with experts in round-table discussions benefits from a systematic and transparent approach and the multidisciplinary contributions of the experts. Parallel validation provides a feasible alternative to validating novel models. The process of structuring and validating a model presented in this paper could be a useful guide to increase transparency, credibility, and acceptability of (future, novel) models when experts are involved.

Interactive effect of family history and environmental factors on respiratory tract-related morbidity in infancy

BACKGROUND

Family and environmental factors affect the development of respiratory morbidity. How these factors interact is unclear.

OBJECTIVE

We sought to clarify the interactive effect of family history of asthma and environmental factors on the occurrence of respiratory morbidity.

METHODS

Two hundred twenty-one infants with a positive family history of asthma (PFH) and 308 with a negative family history of asthma (NFH) were prenatally selected and followed until the age of 2 years. Exposure to environmental factors and the occurrence of respiratory morbidity were recorded. By using multiple logistic regression analysis, increased risk was expressed in odds ratios (ORs) adjusted for relevant covariables.

RESULTS

Infants with a PFH had more respiratory morbidity than infants with an NFH. Adjusted ORs ranged from 1.7 (95% CI, 1.0-2.8) for expiratory wheezing to 4.9 (95% CI, 1.7-13.6) for croup. Parental smoking increased the OR of a PFH for wheezing ever (OR, 5.8 [95% CI, 2.5-13.8]) and attacks of wheezing (OR, 6.8 [95% CI, 2.7-16.9]), as did Der p 1 (OR, 10.2 [95% CI, 2.8-36.3] and OR, 7.1 [95% CI, 7.1-21.0], respectively). Exposure to both parental smoking and Der p 1 further increased this OR (OR, 30.8 [95%, CI, 6.9-137.2] and OR, 26.2 [95% CI, 5.9-115.6], respectively). Breast-feeding decreased the ORs of PFH for tonsillitis and acute otitis media: the increased ORs for these diagnoses in formula-fed infants with PFHs versus those with NFHs (OR, 9.2 [95% CI, 2.1-39.7] and OR, 2.9 [95% CI, 1.1-7.2], respectively) was attenuated in breast-fed infants (OR, 1.8 [95% CI, 0.8-3.8] and OR, 0.7 [95% CI, 0.4-1.3]).

CONCLUSION

Parental smoking and Der p 1 increase the effect of a PFH on respiratory morbidity. Breast-feeding reduces this effect.

CLINICAL IMPLICATIONS

Extra attention should be given to stimulate mothers to breast-feed their children in case they cannot stop smoking or taking sanitation measures.

Gender-specific differences in the prevention of asthma-like symptoms in high-risk infants

The prevalence of asthma in children has increased in the last decades, and gender-specific differences in asthma development have recently been suggested. The present study investigates whether gender differences are present in a population of young children (0-2 yr) with a high risk for the development of asthma on the basis of the presence of asthma in first-degree relative(s). The study was performed on 222 children (118 boys, 104 girls) with a familial predisposition of asthma, which received standardized recommendations to reduce exposure to allergens (dust mite, pets and food allergens) and to passive smoking. Health outcome (wheezing episodes and shortness of breath) and compliance with allergen-reducing measures were studied by means of multiple regression analyses. Boys suffered more from asthma-like complaints than girls, as diagnosed by the general practitioner (32% vs. 18%, respectively, p = 0.023). Compliance with intervention measures was similar for boys and girls for most allergens, but food allergen reduction was better applied for girls: duration of exclusive breastfeeding was longer in girls (median 9 wk vs. 4 wk, p = 0.009). Further analysis showed that 4 wk of longer breastfeeding reduced the number of wheezing episodes and shortness of breath in boys by 19% and 15%, respectively, but not in girls, suggesting sex as an effect modifier in the relationship between breastfeeding and asthma-like symptoms. The present findings indicate that application and effects of prevention strategies for children with a high risk for developing asthma might be gender-specific and suggest a special importance of breastfeeding boys.

Factors influencing breastfeeding practices and postponement of solid food to prevent allergic disease in high-risk children: results from an explorative study

This paper presents results of seven focus group interviews conducted to gain insight into the feelings, opinions and perceived barriers of parents with a history of asthma who have recently delivered a child. The parents participated in an educational program regarding breastfeeding and postponement of solid food to prevent their child from developing allergic symptoms. Breastfeeding exclusively for 6 months seemed an advice difficult to follow. The most important influencing factors regarding initiation and continuation of breastfeeding were health advantages for the baby, bonding, social support, modelling, knowledge about all the aspects of breastfeeding and breastfeeding confidence. In general, parents adhered to the advice to postpone solid food until the child had reached the age of 6 years. The few obstacles revealed were social pressure, hungry babies and eagerness of parents to give solid food.

Prenatal exposure to mite and pet allergens and total serum IgE at birth in high-risk children

To examine the relationship between prenatal exposure to mite, cat and dog allergens and total serum IgE at birth in newborns at high risk of asthma. In the homes of 221 newborns with at least one first-degree relative with asthma, concentrations (ng/g dust) of allergens of house dust mite (mite), cat and dog were measured at the fourth to sixth month of pregnancy in dust samples from the maternal mattress and living room. At day 3-5 after birth, total IgE was measured in capillary heel blood. A total number of 174 blood samples were available (11 mothers refused newborn's blood sampling, and in 36 cases the blood sample was too small for analysis). In 24% of the newborns, total IgE was elevated (cut-off value 0.5 IU/ml). A significant dose response relationship was found between increasing mite allergen levels [divided in quartiles ng/g dust (qrt)] and the percentage of elevated IgE: first qrt (0-85 ng/g) 13%; second qrt (86-381) 19%; third qrt (382-2371) 26%; fourth qrt (> or =2372) 42%, respectively, p=0.01. This relationship remained significant after adjusting for passive smoking, maternal and paternal mite allergy, socio-demographic factors, birth characteristics and (breast) feeding practice in the first week of life. In high-risk newborns, prenatal exposure to mite allergens, but not to cat and dog allergens from dust of the living room and of the maternal mattress was associated with total serum IgE at birth.

Compliance of asthmatic families with a primary prevention programme of asthma and effectiveness of measures to reduce inhalant allergens--a randomized trial

BACKGROUND

Compliance to and the effect of pre- and post-natal exposure reduction measures to prevent asthma in high-risk children from asthmatic families were studied.

METHOD

Families were randomized to a special care group (n=222) and a control group (n=221). Educational advice on measures to reduce their newborn's exposure to allergens and smoke was provided to the special care group during three visits (two pre-natal and one post-natal). The control group (n=221) received usual care.

RESULT

After the intervention, the special care group differed significantly (P<0.01) from the usual care group in: use of anti-mite encasings (parental: 88% vs. 14%; baby: 98% vs. 10%); keeping pets outside (51% vs. 19%); combined breast- and hypoallergenic formula feeding (55% vs. 22%); first solids postponement until after the sixth month (71% vs. 28%); maternal post-natal smoking (52% vs. 28%). Little or no compliance was found for other sanitary measures (cleaning habits, providing a smooth floor covering, ventilation/airing, pet removal), exclusive breastfeeding, pre-natal smoking and partner smoking. In spite of pre-existent low allergen levels in both groups, there was a significant reduction of mite, cat, and dog allergens on the mattresses and mite and cat allergens in the living room in the special care group and were significantly lower compared with the usual care group after 1 year.

CONCLUSION

High compliance was found for the use of anti-mite encasings; substantial compliance for using hypoallergenic formula, solid food postponement, keeping pets outside and reported post-natal maternal smoking. There was no compliance for sanitary measures and the reduction of maternal pre-natal passive smoking. Mite and pet allergens on mattresses were strongly reduced by anti-mite encasings.

Allergen avoidance in the primary prevention of asthma

PURPOSE OF REVIEW

Six primary prevention studies trialing environmental modifications to reduce asthma in children have published results of clinical outcomes. All are still in progress.

RECENT FINDINGS

In the Isle of Wight study, mite and food avoidance were evaluated to age 9 months. At 8 years, children in the active group had less current wheeze, wheeze with bronchial hyperresponsiveness and atopy (P < or = 0.05). The Canadian Primary Prevention Study examined avoidance of inhalant and food allergens. At 1 year there was a reduction in probable asthma and rhinitis in the active group. The Study on the Prevention of Allergy in Children in Europe tested avoidance of inhalant and food allergens. At 1 year there was less atopy and sensitization to mites in the active group. In the Childhood Asthma Prevention Study both mite avoidance and a dietary supplement of omega 3 fatty acids were analysed in a factorial design. At age 18 months, children in the dietary intervention group had significantly less wheeze. Eczema was more common amongst children using the mite avoidance measures. The Prevention and Incidence of Asthma and Mite Allergy Study is a placebo-controlled study of mite avoidance. At 2 years, there was a small reduction in nocturnal cough without a cold in the active group. The Manchester Asthma and Allergy Study included stringent environmental control. At 1 year prescribed medication for wheeze and wheeze with shortness of breath were significantly less common in the active group than the control group.

SUMMARY

Although initial results look promising, further follow up of the ongoing cohorts is required before any recommendations can be made within the public health context.

Environmental exposure reduction in high-risk newborns: where do we start?

BACKGROUND

When analyzing the effect of environmental exposure reduction measures on asthma in high-risk children, one must know how far asthmatic families already have applied such measures, because this would affect the effectiveness and efficiency of interventions aimed at reducing environmental exposure.

OBJECTIVE

To describe the room for improvement by asthmatic families in mite, pet, and food allergen reducing measures and in parental passive smoking and to determine the resulting levels of mite and pet allergens by the applied sanitation measures.

METHODS

Data were sampled by observation, weekly diary entries, and questionnaire when the infant was 6 months old and 1 year old. Dust samples were collected by vacuuming the living room floor and the parental and infant mattresses. Multiple logistic regression analyses were applied with the use of mattress encasing, having a smooth floor covering, having pets, exclusive breast-feeding and/or hypoallergenic formula during the infant's first 6 months, and passive smoking as the dependent variables.

RESULTS

Frequencies of applied measures were as follows: having a smooth floor covering, 36%; daily house cleaning, 27%; use of parental and infant antimite mattress encasings, 13% and 9%, respectively; keeping no pets, 66%; no cow's milk-based regular formula, 13%; no solid foods in the first 6 months of life, 28%; and abstinence of smoking by the mother prenatally, 89%; by the mother postnatally, 85%; and by her partner, 76%. Having a smooth floor covering and daily cleaning but not use of antimite mattress encasings resulted in significantly lower mite and pet allergen levels.

CONCLUSIONS

There is (still) enough room for improvement to reduce exposure to inhalant and food allergens, especially by application of mattress encasings, exclusive breast-feeding and/or hypoallergenic formula feeding, and postponing the time until first solids are given.

Permethrin-impregnated mattress liners: a novel and effective intervention against house dust mites (Acari: Pyroglyphididae)

This study tested the efficacy of permethrin-impregnated mattress liners in reducing house dust mites in the homes of volunteers with no previous recorded history of asthma, atopic eczema, or perennial rhinitis. The field trial using permethrin-impregnated (450 mg/m2 of pure permethrin in polyester netting weighing 35 g/m2) mattress liners (n = 9) was conducted for 27 mo. The permethrin-impregnated bedding significantly reduced house dust mites in mattresses for at least 27 mo. Allergen concentrations were significantly lowered at 15-mo postintervention. No adverse side-effects were reported. This is a promising development in house dust mite control.

Long-term cetirizine treatment reduces allergic symptoms and drug prescriptions in children with mite allergy

BACKGROUND

Experimental data demonstrate that mite allergy is characterized by persistent chronic inflammation, even during asymptomatic periods. This suggests that long-term continuous treatment be included in the global strategy of allergy treatment.

OBJECTIVE

We conducted a study to evaluate whether regularly administered cetirizine reduces allergic symptoms and drug prescriptions in children with mite allergy.

METHODS

In this double-blind, randomized, placebo-controlled study, two parallel groups of 10 children with mite allergy (mean age: 6.5 years) received either cetirizine or placebo daily for 6 months. Participants were allowed to take rescue medications for rhinitis and/or mild asthma. The symptoms (nasal itching, sneezing, obstruction, rhinorrhea, conjunctival itching, lacrimation, conjunctival hyperemia, cough, wheezing, and chest tightness) were recorded on a diary card. The intake of cetirizine (as additional symptomatic treatment), antibiotics, acetaminophen, beta2-agonists, inhaled and systemic corticosteroids was also recorded.

RESULTS

Symptom scores and drug consumption were significantly lower (P < 0.05) in the cetrizine-treated group versus the placebo group. The greatest reductions were in cetirizine itself, inhaled corticosteroids, beta2-agonists, and antibiotics. No side effects were reported in either group.

CONCLUSIONS

In mite-allergic children, cetirizine administered daily for prolonged periods decreases symptoms of and drug prescriptions for allergic rhinitis and asthma compared with symptomatic treatment.

Involuntary smoking and asthma

Involuntary smoking is the third leading preventable cause of death, and among children it causes lower respiratory infections, middle ear disease, sudden infant death syndrome, and asthma. Half the world's children may be exposed to environmental tobacco smoke (ETS), exacerbating symptoms in 20% of children with asthma. Recent studies have reinforced previous conclusions that ETS exposure causes onset of childhood asthma and exacerbation of symptoms throughout life. The exact mechanisms by which this is accomplished are still unclear, as are the relative contributions of prenatal versus postnatal exposure. However, favorable health outcomes can be attained with reduced exposure. Among the few studies of ETS exposure reduction interventions, low-intensity advice methods appeared ineffective, and counseling parent smokers appeared successful. Direct counseling of school-aged children to avoid ETS has yet to be tested. Community norms may need to shift further in favor of protecting children and others from ETS before minimal interventions can be successful. This will require combined and ongoing efforts of the medical and public health establishments, in concert with legislation mandating tobacco-free public places and with ETS-related media campaigns.

Effects of house dust mite avoidance measures on Der p 1 concentrations and clinical condition of mild adult house dust mite-allergic asthmatic patients, using no inhaled steroids

BACKGROUND

Exposure to house dust mite (HDM) allergens often results in worsening of asthma. Therefore, avoidance of exposure to HDM allergens is often proposed. Unfortunately, the most effective and feasible avoidance strategy is still not completely assessed. Consequently, we investigated the effects of a combined HDM avoidance strategy on HDM allergen concentrations and clinical condition of allergic, mild asthmatic, patients using no inhaled steroids.

METHODS

Asthmatic patients, allergic to HDM, using no inhaled corticosteroids, were randomly allocated to an active (n = 76) or a placebo allergen-avoidance group (n = 81). Avoidance measures consisted of applying Acarosan(R) (placebo: water) to the living room and bedroom floors, and the use of HDM-impermeable covers for mattresses and bedding (placebo: cotton covers for mattresses only). Effects on allergen concentrations (Der p 1), FEV1, bronchial hyperresponsiveness, peak flow parameters and asthma symptom scores were studied during 20 weeks and controlled for the allergic status of the patients.

RESULTS

The active covers reduced Der p 1 concentrations to 9.4% (P = 0.0001), and were always significant lower than in the placebo group (P = 0.0002). Acarosan(R) resulted in slight but significant decreases (twofold, P = 0.0001), both on living room and bedroom floors, but concentrations were never significantly lower than the placebo group. Although the combined avoidance strategy resulted in a considerable reduction in allergen load in the active group, no differences were seen between the two groups in any of the clinical parameters during the follow-up period in this group of allergic asthmatics, using no inhaled corticosteroids. Corrections for the allergic status did not alter these results.

CONCLUSIONS

The combined avoidance strategy was effective in reducing HDM allergen concentration. This was especially achieved by the allergen-impermeable covers, while the effects of Acarosan(R) were only marginal. However, this allergen reduction was not reflected in a convincing improvement in clinical condition in this group of mild allergic asthmatics, using no inhaled steroids. Perhaps, a longer follow-up period would have resulted in more pronounced effects.