Syed Hasan Arshad

The prevalence of and risk factors for atopy in early childhood : A whole population birth cohort study

OBJECTIVES A birth cohort was followed-up to age 4 years to record the development of allergic disorders and to study the influence of genetic and environmental factors. METHODS Information on family history and environmental factors was obtained at birth, and serum cord IgE was measured. At age 4 years, 1218 children were reviewed. RESULTS By age 4 years, 27% of the children had symptoms of allergic disease. Period prevalence of asthma increased from 8.7% in infancy to 14.9% at 4 years. Family history of atopy was the single most important risk factor for atopy in children. Sibling atopy was a stronger predictor of clinical disease than maternal or paternal atopy, whereas paternal atopy, male sex, and high cord IgE were significant for the development of allergen sensitization. Children of asthmatic mothers were three times more likely to have asthma (odds ratio [OR]: 3.0, 95% confidence interval [CI]: 1.6-5.8) and rhinitis (OR: 2.9, CI: 1.1-7.4). Formula feeding before 3 months of age predisposed to asthma at age 4 years (OR: 1.8, CI: 1.2-2.6). The effect of maternal smoking on childhood wheeze seen at 1 and 2 years was lost by age 4, except for a subgroup with negative skin test responses (nonatopic asthma). Less than half (46%) of the infantile wheezers were still wheezing at 4 years of age. CONCLUSION Family history of atopy remains the most important risk factor for atopy in children, but other markers can be identified with a potential for intervention at an early age.

Allergen avoidance in infancy and allergy at 4 years of age.

In an attempt to prevent or reduce the manifestations of atopic disease, a group of infants considered to be genetically at high risk of atopy was entered in a prenatally randomized, controlled study. A prophylactic group (n= 58) was either breast‐fed with their mothers excluding foods regarded as highly antigenic from their diets, or given an extensively hydrolysed formula. In addition, strenuous efforts were made to reduce exposure to the house‐dust mite by application of acaricide to the bedroom and living room carpets and upholstered furniture. A control group (n= 62) was fed conventionally by breast or on formula, and no specific environmental measures were taken. The results (previously reported) after 1 year showed significantly less total allergy, asthma, and eczema in the prophylactic group. Similar results were obtained at 2 years although the reduction in asthma no longer achieved statistical significance. However, there was significantly less sensitization, as shown by a battery of skin prick tests (SPTs), to both dietary allergens and aeroallergens in the prophylactic group. A11 the children have now been reviewed at the age of 4 years, and SPTs to a wide range of dietary allergens and aeroallergens have been performed. The control group continues to show more total allergy (odds ratio [OR] 2.73, 95% confidence interval [CI] 1.21–6.13, P<0.02), definite allergy (allergic symptoms plus positive SPT) (OR 5.6, CI 1.8–17.9, P<0.005), and eczema (OR 3.4, CI 1.2–10.1, P<0.05). More control children have positive SPTs (OR 3.7, CI 1.3–10.0, P<0.02). A dual approach to the prevention of allergic disease, avoiding as far as possible sensitization to food and aeroallergens, significantly reduces the risk of atopic disease. This should be reserved for infants considered at very high risk of atopy, and close medical and dietetic supervision must be available.

Dietary prevention of allergic diseases in infants and small children.

Because of scientific fraud four trials have been excluded from the original Cochrane meta‐analysis on formulas containing hydrolyzed protein for prevention of allergy and food intolerance in infants. Unlike the conclusions of the revised Cochrane review the export group set up by the Section on Paediatrics, European Academy of Allergology and Clinical Immunology (SP‐EAACI) do not find that the exclusion of the four trials demands a change of the previous recommendations regarding primary dietary prevention of allergic diseases. Ideally, recommendations on primary dietary prevention should be based only on the results of randomized and quasi‐randomized trials (selection criteria in the Cochrane review). However, regarding breastfeeding randomization is unethical, Therefore, in the development of recommendations on dietary primary prevention, high‐quality systematic reviews of high‐quality cohort studies should be included in the evidence base. The study type combined with assessment of the methodological quality determines the level of evidence. In view of some methodological concerns in the Cochrane meta‐analysis, particularly regarding definitions and diagnostic criteria for outcome measures and inclusion of non peer‐reviewed studies/reports, a revision of the Cochrane analysis may seem warranted. Based on analysis of published peer‐reviewed observational and interventional studies the results still indicate that breastfeeding is highly recommended for all infants irrespective of atopic heredity. A dietary regimen is effective in the prevention of allergic diseases in high‐risk infants, particularly in early infancy regarding food allergy and eczema. The most effective dietary regimen is exclusively breastfeeding for at least 4–6 months or, in absence of breast milk, formulas with documented reduced allergenicity for at least the first 4 months, combined with avoidance of solid food and cows milk for the first 4 months.The role of primary prevention of allergic diseases has been a matter of debate for the last 40 years. In order to shed some light on this issue, a group of experts of the Section of Pediatrics EAACI reviewed critically the existing literature on the subject. An analysis of published peer-reviewed observational and interventional studies was performed following the statements of evidence as defined by WHO. The results of the analysis indicate that breastfeeding is highly recommended for all infants irrespective of atopic heredity. A dietary regimen is unequivocally effective in the prevention of allergic diseases in high-risk children. In these patients breastfeeding combined with avoidance of solid food and cows milk for at least 4-6 months is the most effective preventive regimen. In the absence of breast milk, formulas with documented reduced allergenicity for at least 4-6 months should be used.

The effect of genetic and environmental factors on the prevalence of allergic disorders at the age of two years

The effect of genetic and environmental factors on the prevalence of allergic disorders in early childhood was determined in a prospective follow‐up study. Information was available on 1174 children at the age of 2 years. Two‐hundred and seventy‐five were considered to have an allergic disorder. The prevalence varied from 3.2% for rhinitis to 10.9%, for asthma. At 2 years 60 children reacted positively on skin‐prick test (SPT). Multivariate logistic regression analysis was used to obtain adjusted odds ratios (95% confidence interval) for each factor. For asthma, positive family history, male sex, low birth‐weight, maternal smoking and season of birth were significant risk factors. For eczema, positive family history was the only significant risk factor. For rhinitis, lower socio‐economic group and autumn birth were significant. Maie sex and low birth‐weight were significant for skin test positivity. Positive family history and low birth‐weight were significant risk factors for any allergy. Low birth‐weight was also a significant risk for skin test reactivity to house dust mite. Genetic and environmental factors have a profound effect on the development of allergic disorders in the first two years of life.

Dietary prevention of allergic diseases in infants and small children. Part III: Critical review of published peer-reviewed observational and interventional studies and final recommendations

The role of primary prevention of allergic diseases has been a matter of debate for the last 40 years. In order to shed some light on this issue, a group of experts of the Section of Pediatrics EAACI reviewed critically the existing literature on the subject. An analysis of published peer‐reviewed observational and interventional studies was performed following the statements of evidence as defined by WHO. The results of the analysis indicate that breastfeeding is highly recommended for all infants irrespective of atopic heredity. A dietary regimen is unequivocally effective in the prevention of allergic diseases in high‐risk children. In these patients breastfeeding combined with avoidance of solid food and cows milk for at least 4–6 months is the most effective preventive regimen. In the absence of breast milk, formulas with documented reduced allergenicity for at least 4–6 months should be used.

Effect of environmental factors on the development of allergic disorders in infancy.

A total of 1167 infants were followed for 1 year in a population-based prospective study to assess the effect of environmental factors on the development of allergic disorders. Some of these environmental factors are interdependent. Mothers who formula fed their infants smoked more often (p less than 0.001) and tended to belong to lower social classes (p less than 0.01). Logistic regression analysis was performed to adjust for these confounding variables. Maternal smoking adversely affected the prevalence of asthma (p = 0.003) defined as three or more separate episodes of wheezing and total allergy (p = 0.02). Infants in lower socioeconomic groups developed asthma significantly more often (p = 0.03) than infants born in higher socioeconomic groups. There was a nonsignificant trend for infants born in summer to develop asthma more than infants born in winter (p = 0.08). No effect of these factors was observed on eczema, food intolerance, or on the subgroup of infants with definite allergy (clinical disorder with positive skin prick test [SPT]). Exposure to animal dander did not influence the prevalence of clinical disorder, but positive SPT reaction to cat dander was more prevalent in infants who were exposed to cats and/or dogs (p = 0.04). Positive SPT to house dust mite occurred significantly more often in infants who were formula fed (p = 0.05). The environmental factors had a profound effect on the prevalence of asthma but not on other allergic disorders.

Prevalence and cumulative incidence of food hypersensitivity in the first 3 years of life

Background:  Prevalence and incidence of food hypersensitivity (FHS) and its trends in early childhood are unclear.

Effect of allergen avoidance in infancy on allergic manifestations at age two years

BACKGROUND One hundred twenty children, identified before birth as being at high risk for atopy, were prenatally assigned to prophylactic or control groups. METHODS The infants in the prophylactic group either received breast milk from mothers on an exclusion diet or an extensively hydrolyzed formula. Their bedrooms and living rooms were treated repeatedly with an acaricide, and they used polyvinyl-covered mattresses with vented head areas. The infants in the control group were fed conventionally, and no environmental control was recommended. RESULTS A significant advantage, first demonstrated at 1 year of age, persists for children in the prophylactic group. They have less of any allergy or eczema, but the reduced prevalence of asthma is no longer significant. Only three children in the prophylactic group had positive skin prick test results compared with 16 in the control group, suggesting a significant reduction in sensitization. CONCLUSION A dual approach to allergen avoidance, focusing on foods and aeroallergens, appears to be beneficial in selected high-risk infants. Avoidance of potent allergens in early life increases the threshold for sensitization in these high-risk infants. Whether sensitization has been avoided or merely deferred has yet to be proved.

EAACI Food Allergy and Anaphylaxis Guidelines. Primary prevention of food allergy

Food allergy can have significant effects on morbidity and quality of life and can be costly in terms of medical visits and treatments. There is therefore considerable interest in generating efficient approaches that may reduce the risk of developing food allergy. This guideline has been prepared by the European Academy of Allergy and Clinical Immunologys (EAACI) Taskforce on Prevention and is part of the EAACI Guidelines for Food Allergy and Anaphylaxis. It aims to provide evidence‐based recommendations for primary prevention of food allergy. A wide range of antenatal, perinatal, neonatal, and childhood strategies were identified and their effectiveness assessed and synthesized in a systematic review.

Primary prevention of asthma and atopy during childhood by allergen avoidance in infancy: a randomised controlled study

Background: Recent increases in the prevalence of asthma and atopy emphasise the need for devising effective methods for primary prevention in children at high risk of atopy. Method: A birth cohort of genetically at risk infants was recruited in 1990 to a randomised controlled study. Allergen avoidance measures were instituted from birth in the prophylactic group (n=58). Infants were either breast fed with mother on a low allergen diet or given an extensively hydrolysed formula. Exposure to house dust mite was reduced by the use of an acaricide and mattress covers. The control group (n=62) followed standard advice as normally given by the health visitors. At age 8, all 120 children completed a questionnaire and 110 (92%) had all assessments (skin prick test, spirometry, and bronchial challenges). Results: In the prophylactic group eight children (13.8%) had current wheeze compared with 17 (27.4%) in the control group (p=0.08). Respective figures were eight (13.8%) and 20 (32.3%) for nocturnal cough (p=0.02) and 11 of 55 (20.0%) and 29 of 62 (46.8%) for atopy (p=0.003). After adjusting for confounding variables, the prophylactic group was found to be at a significantly reduced risk for current wheeze (odds ratio (OR) 0.26 (95% confidence interval (CI) 0.07 to 0.96)), nocturnal cough (OR 0.22 (95% CI 0.06 to 0.83)), asthma as defined by wheeze and bronchial hyperresponsiveness (OR 0.11 (95% CI 0.01 to 1.02)), and atopy (OR 0.21 (95% CI 0.07 to 0.62)). Conclusion: Strict allergen avoidance in infancy in high risk children reduces the development of allergic sensitisation to house dust mite. Our results suggest that this may prevent some cases of childhood asthma.