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

Evaluation of the wheezy infant

BACKGROUND

The infant with persistent or recurrent wheezing during the first 2 years of life poses a diagnostic dilemma, which can be a source of anxiety to both physicians and parents. A suggested diagnostic approach to the causes of infantile wheezing is outlined.

OBJECTIVES

1. To review the physiologic considerations of the infant's airways that predispose to wheezing. 2. To discuss the key physical findings, family history, and risk factors associated with wheezing in infants. 3. To develop a rational approach to the differential diagnosis and management of infantile wheezing.

DATA SOURCES

The MEDLINE database as well as our clinical experience pertaining to infantile wheezing.

CONCLUSIONS

This review discusses the diagnostic evaluation and treatment of the wheezing infant. We suggest that infant pulmonary function testing may be used as one diagnostic aid in the workup of the wheezing infant.

Influence of smoking on asthmatic symptoms and allergen sensitisation in early childhood

BACKGROUND

Apart from heredity, several early life environmental factors are implicated in the development of childhood asthma. Maternal smoking is believed to increase asthmatic symptoms but its influence on the development of allergen sensitisation is debatable.

STUDY DESIGN

A whole population birth cohort was reviewed at ages 1, 2, and 4 years. Of 1218 children seen at 4 years, 981 (80.5%) were skin prick tested with a battery of common food and aeroallergens. Smoking history was recorded at birth and updated at each follow up and its impact on the development of asthma and allergen sensitisation in the children was assessed.

RESULTS

Two hundred and fifty mothers smoked during pregnancy (20.5%) and 307 (25.2%) after childbirth. Maternal smoking in pregnancy was associated with low birth weight (mean (SD): 3.3 (0.5) v. 3.5 (0.5) kg; p<0.001). Smoking mothers were more often from lower social classes (31.8% v. 16%, p<0. 001) and they breast fed their babies for a shorter duration (8.5 (11.4) v. 16.6 (15.2) weeks; p<0.001). The difference in breast feeding duration was partly due to a higher proportion of smoking mothers who never breast fed their babies. Although at age 2 years asthmatic symptoms were associated with exposure to maternal tobacco smoke (odds ratio 2.2, 95% confidence interval 1.5 to 3.4; p<0.001), this association was lost by 4 years. However, maternal smoking was a significant risk factor in a subgroup of children with asthmatic symptoms but negative skin prick test. Maternal smoking did not increase allergen sensitisation at age 4 years. No effect of paternal smoking on asthma was observed in the children.

The excess of atopic eczema in East Germany is related to the intrinsic type

BACKGROUND

Prevalence data for atopic eczema based on a dermatological examination have not so far been available for East and West Germany. Possible differences in the proportions of extrinsic and intrinsic types of eczema, and how far these could explain differences in the prevalence of eczema, need to be clarified.

OBJECTIVES

To compare the prevalence of atopic eczema in pre-school children between different locations in East and West Germany, and over a period of 7 years, at three time points. Additionally, to determine the proportions of intrinsic and extrinsic types of eczema by taking skin prick test reactivity into account.

METHODS

Repeated cross-sectional studies in 1991, 1994 and 1997 in 5-6-year-old pre-school children at five different locations in West Germany (n = 2075) and six in East Germany (n = 1926) were carried out. Individuals with eczema were identified by an examination performed by physicians of the Department of Dermatology. In addition, a skin prick test and a standardized questionnaire were used.

RESULTS

The overall prevalence of atopic eczema in these children was 10.4%. At all three times of investigation (1991, 17.5% vs. 11.2%; 1994, 12.6% vs. 8.7%; 1997, 11.2% vs. 4.5%) and in the total group (12.9% vs. 8.2%), the prevalence was significantly higher in East than in West Germany. After controlling for influences of sex, parental history of atopic diseases, observer and socio-economic status in multiple logistic regression analyses, these differences remained significant for 1991, 1994 and for the overall group (odds ratio, OR 1.78, 95% confidence interval, CI 1. 43-2.21). Girls (OR 1.56, 95% CI 1.27-1.92) and children whose parents had a higher level of school education (OR 1.17, 95% CI 1. 00-1.37) were affected more frequently. Of all children, 26.6%, and of those with eczema, 41.9% exhibited at least one reaction in the prick test (OR 2.21, 95% CI 1.75-2.80; sensitization in eczema vs. no eczema). Whereas 50.4% of the children with eczema in West Germany were sensitized, only 36.5% of the diseased children in East Germany reacted positively in the prick test (OR 1.77, 95% CI 1.12-2. 79).

CONCLUSIONS

These results are in accordance with findings regarding allergic sensitization and hay fever and might indicate that factors other than allergy are responsible for the higher prevalence of atopic eczema in East Germany.

The association of atopic dermatitis in infancy with immunoglobulin E food sensitization

OBJECTIVE

To prospectively investigate the association of high levels of immunoglobulin E (IgE) sensitization to foods and the presence of atopic dermatitis (judged by reported topical steroid use during the first 16 months of life) in a birth cohort of 620 Australian children "at risk" of allergic disease because of family history.

RESULTS

A total of 559 of the children in the cohort were fully evaluated, and the cumulative prevalence of atopic dermatitis was 24%. More children in the cohort who had atopic dermatitis had strongly positive skin test results (> or = 4+, histamine equivalent units, > or = approximately 6-mm wheal), consistent with IgE food sensitization to either cow's milk, egg, or peanut at 6 months (22% vs 5%, chi(2) = 35; P < 10(-6)) and at 12 months (36% vs 11%, chi(2) = 41; P < 10(-6)) than those without atopic dermatitis. The calculated attributable risk percent for IgE food sensitization as a cause of atopic dermatitis was 65% and 64% at these times. In a separate group of infants with severe atopic dermatitis, the equivalent rates of IgE food sensitization at 6 months was 83% and at 12 months, 65%.

CONCLUSION

IgE food sensitization is a major risk factor for the presence of atopic dermatitis in infancy.

Egg allergy in infancy predicts respiratory allergic disease by 4 years of age

Sensitization to hen's egg early in life has been proposed as a predictor for respiratory allergic disease during childhood. However, symptomatic egg allergy in infancy has not been studied in this context. In 1989, a cohort of consecutive births was recruited. Data on family history of atopy and environmental factors were collected. At 4 years of age, 1,218 children were seen of whom 981 were skin-prick tested with a range of food and aero-allergens. Of the 1,218 children, 29 (2.4%) had suffered symptomatic egg allergy (20 during infancy). Egg allergy in infancy was associated with increased respiratory (asthma, rhinitis) allergic disease (odds ratio [OR] 5.0, 95% confidence intervals [CI] 1.1-22.3; p < 0.05) at 4 years of age, with a positive predictive value (PPV) of 55.0%. The addition of infantile eczema to egg allergy increased the PPV to 80% whereas the addition of family history of atopy had no effect. Egg allergy also increased aero-allergen sensitization (OR 6.1, CI 1.1-37.5; PPV 61.1%; p < 0.05). As a predictor for respiratory allergic disease and aeroallergen sensitization, it carried a high specificity but poor sensitivity. Hence, egg allergy in infancy, especially when coexisting with eczema, increases respiratory allergic symptoms and aero-allergen sensitization in early childhood.

Superior clinical outcomes of inner city asthma patients treated in an allergy clinic

BACKGROUND

Asthma morbidity and mortality continue to increase especially in the inner cities despite medical advances in disease management.

OBJECTIVE

To investigate the clinical outcomes of inner city asthma patients treated in an allergy clinic.

METHODS

Phase 1 involved random review of medical records of 100 asthma patients treated in an allergy clinic for 2 consecutive years, assessing the frequency of hospitalizations, emergency room visits (ERV) and asthma severity during three periods; 1 year prior to initial visit (year 0) and during the first (year 1) and second (year 2) years of intervention. Phase 2 involved administration of quality of life (QOL) survey to 23 patients volunteered from allergy clinic (group I), and 21 patients volunteered from emergency room (group II), treated by primary care or emergency room physicians during the previous year.

RESULTS

The frequency of hospitalizations and ERV significantly declined over time (P < .001) with greatest declines during year 1. Disease severity of all patients significantly declined over time (P < .001); good compliers had significant improvement over poor compliers (P < .023). Quality of life scores were significantly lower for both groups than for the general population; and although the scores were higher in the allergy clinic group than in the non-allergy clinic group, significant differences were achieved only in mental health and social functioning domains.

CONCLUSIONS

Patients treated in an allergy clinic demonstrate superior clinical outcomes.

A guide to the pediatric patient with "difficult" asthma

Patients whose asthma symptoms are poorly controlled with the therapies usually recommended for this disease are considered to have "difficult" asthma. Although such patients represent a small proportion of patients with asthma, children who have difficult asthma are at increased risk for morbidity and mortality. Once the diagnosis of asthma is established, caregivers must appropriately categorize and treat the asthma according to the patient's level of symptom severity. The purpose of this article is to present an approach to the management of patients with difficult asthma by (a) searching for alternative diagnoses or conditions that are often associated with asthma, (b) investigating environmental issues, (c) reviewing inhalation techniques, and (d) determining the patient's level of compliance with the prescribed treatment plan and simplifying it whenever possible.

Can we predict which wheezy infants will continue to wheeze?

Early intervention strategies in infant wheezing will be dependent on the ability to predict persistence of disease. We undertook a prospective longitudinal study to determine which factors might be predictive for the persistence of wheeze. We examined a group of 107 children 3 to 36 mo of age with at least one atopic parent. Children were recruited within 12 wk of first wheeze. Factors assessed included: personal atopy (IgE > 1 SD above age-related normal and/or eczema and/or positive skin tests); parental atopy; number of siblings; age at first wheeze; sex; serum-soluble IL-2R; proliferation of peripheral blood mononuclear cells (PBMC) to beta-lactoglobulin and to D. pteronyssinus; production of IFN-gamma on stimulation of PBMC with beta-lactoglobulin and with D. pteronyssinus. A positive clinical outcome (child requiring prophylactic antiasthma treatment after 1 yr) was observed in 53 (49.5%) children. Predictor variables were assessed by univariate and multivariate logistic regression. Wheeze was more likely to be persistent in older, atopic children with biparental atopy. The model offering best prediction of persistent wheeze with least risk of including asymptomatic subjects was age at presentation + sIL-2R. Trials of early intervention strategies using a logistic regression equation based on this model for patient recruitment can now be designed.

Age-dependent tendency to become sensitized to other classes of aeroallergens in atopic asthmatic children

BACKGROUND

Several longitudinal studies report that allergic sensitization increases with age from childhood to adulthood.

OBJECTIVE

To evaluate whether an age-dependent tendency to become sensitized to new classes of allergens is present in atopic children, we studied retrospectively the changes in allergic sensitization in 165 asthmatic patients, monosensitized (ie, sensitized to only one class of allergens) in the first survey.

METHODS

All the children (18 months to 8 years at enrollment), attended our outpatient clinics twice, at time intervals ranging from 2 to 10 years. On each visit, sensitization to house dust mites, pollens, animal danders, and molds was determined by skin prick test.

RESULTS

We found that 43.6% (n = 72) of the patients became polysensitized on the second survey. According to age on first survey, the patients were further divided into two age groups: (1) group 1 = 18 months to < 5 years old (n = 98) and (2) group 2 = 5 to 8 years (n = 67). The transition from monosensitization to polysensitization observed in the entire population was present in both groups: 47 (47.9%) of the 98 children in group 1 and 25 (37.3%) of the 67 children in group 2 showed to be sensitized to more classes of allergens, as compared with first survey. Both in the whole population and in the two age subgroups, the changes in the frequency of monosensitization between the two evaluations were time-dependent (P < .05, each Chi(2)). Finally, to investigate whether monosensitization to a specific class of allergens could favor the development of polysensitization, we evaluated the frequency of polysensitization in the second survey in patients originally monosensitized to house dust mites or to pollens. We found that of the 130 patients originally monosensitized to house dust mites, 59 became polysensitized (45.4%), while of the 28 patients originally monosensitized to pollens, 9 became polysensitized (32.1%) (P > . 1). Similar results were obtained when patients were divided into age groups.

CONCLUSION

These data demonstrate that (1) monosensitized children are likely to become polysensitized and (2) house dust mite sensitization and, at a lower degree, pollen sensitization, apparently seem to play a "triggering" role in the development of polysensitization, since a high proportion of children originally monosensitized to house dust mites or to pollens became polysensitized.

Elevated cord serum IgE increases the risk of aeroallergen sensitization without increasing respiratory allergic symptoms in early childhood

BACKGROUND

Increasing prevalence of allergic disorders has focused attention on primary prevention. There is a need to improve the accuracy of early-life predictors of atopy so that the at-risk population can be accurately defined and preventive measures instituted.

OBJECTIVE

The predictive capacity of elevated cord IgE, with or without family history of atopy, to allergic symptoms and skin prick test (SPT) sensitization is evaluated in a birth cohort followed up prospectively for 4 years.

METHODS

A birth cohort of 1456 consecutively born children was recruited in 1989. Data were collected on family history of atopy and cord serum total IgE (cord IgE) was measured. Of these, 1218 children were seen in the clinic at 4 years to determine the development of symptoms and signs of allergic disease and 981 were skin tested to a range of common food and aeroallergens.

RESULTS

Of 1218 children reviewed at age 4 years, 218 (17.8%) had symptoms of respiratory allergy and, of those skin tested (n = 981), 192 (19.6%) reacted positively. Twice as many children with elevated cord IgE (>/= 0.5 kU/L) at birth became sensitized to aeroallergens by age 4 years (34.8% vs 17.3%, P < 0. 001). Positive predictive value (PPV) of elevated cord IgE for the development of aeroallergen sensitization was better than that of family history of atopy (34.8 vs 22.6%). Combining paternal atopy with elevated cord IgE substantially increased the predictive capacity (PPV 77.8%). Cord IgE levels did not correlate with clinical asthma or rhinitis at age 4 years and PPV for allergic respiratory symptoms remained poor at all cutoffs.

CONCLUSION

Cord IgE is better than family history for predicting atopy as defined by allergen sensitization and this predictive value can be further increased by combining cord IgE with paternal atopy.

Comparison of lung function in infants exposed to maternal smoking and in infants with a family history of asthma

STUDY OBJECTIVE

To compare lung function in infants exposed to maternal smoking with lung function in infants with a family history of asthma. There are no published studies comparing lung function in both groups.

DESIGN

Cross-sectional study.

SETTING

A tertiary pulmonary care center at a children's hospital.

PATIENTS

One hundred five infants with daily wheezing. Thirty-five infants had persistent exposure to maternal smoking, and 70 had a family history of asthma in parents or siblings.

MEASUREMENTS

Infant pulmonary function tests were compared between the two groups. The ratio of terminal to peak expiratory flow at tidal breathing at 25% of the previous expiration remaining and the ratio of terminal to peak expiratory flow with forced expiration at 25% of the previous expiration remaining (FEF25/PFEF) were used to evaluate peripheral airflow. A > 25% improvement in FEF25/PFEF after a bronchodilator challenge test was considered a positive response.

RESULTS

Most infants in both groups had evidence of peripheral airflow obstruction with forced expiration. In infants exposed to maternal smoking, only 4 of 35 (11.4%) responded to a bronchodilator, compared to 51 of 70 (72.9%) in the group with a family history of asthma (p < 0.0005). There was no statistically significant difference in total respiratory system compliance, total respiratory system resistance, tidal volume, and degree of peripheral airflow obstruction at tidal breathing or after forced expiration in both groups.

CONCLUSION

Infants with exposure to maternal smoking and infants with a family history of asthma have altered lung function, and a positive response to a bronchodilator is one variable that seems to differentiate the two groups.

Natural course of sensitization to food and inhalant allergens during the first 6 years of life

BACKGROUND

Specific IgE antibody responses to alimentary and environmental allergens are one of the hallmarks of atopic diseases. The knowledge of the time course of allergic sensitization during early life may facilitate measures for preventive interventions.

OBJECTIVE

In a prospective birth cohort study (the Multicenter Allergy Study [MAS]) we investigated annual incidence and prevalence rates of sensitization to food and inhalant allergens during the first 6 years of life.

METHODS

For 216 children of a prospective birth cohort (MAS), a complete follow-up of specific IgE measurements to 9 food and inhalant allergens was available at 1, 2, 3, 5, and 6 years of age. On the basis of these measurements, sensitization rates were estimated for the reference population of 4082 children by weighted analysis.

RESULTS

Annual incidence rates of sensitization to food allergens decreased from 10% at 1 year of age to 3% at the 6 years of age. Incidences of sensitization to inhalant allergen, however, increased with age (from 1.5% at 1 year to 8% at 6 years). Point prevalences of allergic sensitization to at least 1 of the 9 tested allergens increased from 11% at 1 year up to 30% at 6 years. This increase was due to markedly increasing sensitization rates to inhalant allergens (1.5% to at least 1 inhalant allergen at 1 year and 26% at 6 years of age), whereas sensitization rates to food allergens remained stable during the first 6 years of life (10%).

CONCLUSION

The earliest serologic marker for atopic immunoreactivity in infancy is the presence of IgE antibodies to egg, followed by milk. The development of sensitization to inhalant allergens occurs mostly after infancy. Beyond the third birthday annual incidence and prevalence increase markedly with age. Rates for outdoor allergens are twice those for indoor allergens.

Mite sensitization in the Scandinavian countries and factors influencing exposure levels

Mites are the common sources of indoor allergen and play a major role in sensitization and elicitation of allergic disease. In the Scandinavian countries, mite infestations in the home were not common in the past decades. Recent studies show that sensitization to mites among children, particularly in Sweden, is increasing. Similar trends have also been reported in Norway. Poor indoor climate, e.g., high humidity and poor ventilation as a consequence of energy-saving measures, are cited as a possible explanation of this increase. Modern furnishings, e.g., carpets and various kinds of upholstery, may also serve as reservoirs of indoor allergens. At least 2 microg of mite allergen per g of dust is considered to be a risk level for sensitization and symptoms of asthma. As compared to experience from other parts of the world, mite-allergen levels are generally low in the northern Scandinavian regions. Recent studies from Sweden and other European countries show that mite sensitization may occur below 2 microg/g dust. Various environmental adjuvant factors may affect the threshold levels of allergen. In this review, the importance of the indoor environment for the accumulation of mite allergens, sensitization to mites in the Scandinavian countries, and various environmental factors that could influence exposure levels will be discussed.

Risk levels for mite allergen: are they meaningful, where should samples be collected, and how should they be analyzed?

Indoor allergen exposure plays a major role in the development of sensitization and triggering of asthma in children. All over the world, mites are common sources of indoor allergens. Risk levels for mite-allergen exposure have been recommended. A mite-allergen level of >/=2 microg/g dust is considered a risk level for sensitization and symptoms of asthma. Data from several ongoing prospective studies of children show that mite sensitization may occur below the suggested threshold level. However, from these studies, it seems that high mite-allergen exposure increases the risk of early sensitization, whereas low exposure levels probably take a longer time to induce sensitization. Assessment of allergen exposure and consideration of allergen-elimination strategies should not be limited only to the home environment. High levels of mite allergens are also found in day-care centers, schools, and various other public places, such as bars. Thus, in addition to homes, these environments should also be considered when allergen-avoidance measures are taken. Allergen content in dust can be expressed in several units, e.g., ng/g, ng/m2, and ng/sampling, and as the total amount of allergen. At present, there is no consensus on the best way to measure and express mite-allergen levels. In this paper, aspects of threshold levels for mite sensitization, various exposure environments, and sampling, determination, and expression units of mite exposure will be discussed in brief.

Prediction of early-onset asthma in genetically at-risk children

The W.T. Grant Foundation Asthma Risk Study was designed to prospectively examine children who were considered at a genetically increased risk for the development of asthma. The respective contributions of 11 potential risk factors, both environmental and biological, were assessed in order to determine their relative roles in affecting the early onset of asthma. This is a report of an inception cohort of children born to asthmatic mothers and followed for a 3-year period. All 150 families were recruited from the general community and living within 2 h of the National Jewish Center for Immunology and Respiratory Medicine (Denver, CO). Mothers in the index risk sample had been previously diagnosed with asthma and were recruited during their pregnancy through physician referrals and media solicitation. The index sample of 150 families was 92% Caucasian and predominantly middle class. The mean age of mothers was 29.3 years, and of fathers, 31.1 years. The main outcome was the determination of the early onset of asthma and its association with quantified risk factors. By age 3 years, 14 of the 150 children had developed asthma. Frequent illness, IgE levels at age 6 months, parenting difficulties, and early eczema were significantly associated with the onset of asthma (P = 0.003, P = 0.006, P = 0.01, and P = 0.03, respectively). Only frequent illness, elevated serum IgE levels, and parenting difficulties entered a predictive model where they were independently related to the development of asthma.

The role of cigarette smoke in the pathogenesis of asthma and as a trigger for acute symptoms

Although it has been long believed that cigarette smoke is injurious to the lower respiratory tract, the exact early mechanisms and early events responsible for this injury remain unclear. Maternal smoking, particularly in utero, is clearly associated with an increased risk for the later development of childhood atopy and asthma. Smoking is known to increase the inflammatory burden of the lower respiratory tract through a number of related but separate mechanisms. These include the recruitment of increased numbers of inflammatory cells, alteration in cell subtypes, enhancement of some cellular functions, and proinflammatory mediator release. In addition, cigarette smoking in vitro and in animal models appears to promote neurogenic inflammation, increase oxidative stress and lead to the elevation of cysteinyl leukotrienes, all of which could potentially lead to an amplification of the airway inflammation already present in asthmatics. Greater and more consistent effort must be given to encourage the young asthmatic not to smoke. In addition, greater effort must be spent on smoking cessation, especially in pregnant women and young asthmatics.

Mapping susceptibility genes for asthma and allergy

Using family data, linkage analysis has been performed to determine the location in the genome of susceptibility genes for allergy and asthma. It has now become clear that there are multiple regions of the genome that contain susceptibility genes for allergy and asthma. The results from two genome screen studies will be reviewed and compared with results from candidate gene approaches. Results from several studies show evidence for linkage to chromosomes 5, 6, 11, 12, 13 and 14 for atopy, asthma or a related phenotype such as total serum IgE levels. Many of these regions contain candidate genes involved in regulating processes that may be involved in the development or progression of allergy and asthma. Some susceptibility genes may affect the expression of these disorders while others may affect response to therapy. Susceptibility to developing allergy or asthma appears to be due to the interaction of multiple genes with the environment.

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.

Indoor allergen levels and other environmental risk factors for sensitization in Estonian homes

The prevalence of allergic disease is low in Eastern Europe for reasons that are poorly understood. Our study aimed to investigate the levels of exposure to indoor allergens and living conditions among Estonian infants in relation to sensitization. Dust samples were collected during four winter months in 1993/94 from the homes of 197 infants participating in a prospective study of sensitization. Information about living conditions was collected through a home visit and interviewing the mothers when the children were 6 weeks old. Three dust samples were collected from each home; i.e., from the infant's mattress, bedroom floor, and living-room carpet. The levels of allergens were determined by ELISA with monoclonal antibodies. The highest allergen level in a home was regarded as the peak value. The peak geometric mean values (+/-SD) of Der p 1 and Der f 1 were 0.3 (0.07-1.4) microg/g dust, of Can f 1, 0.86 (0.23-3.12) microg/g dust, and of Fel d 1, 0.1 (0.01-0.9) microg/g dust. In 12 homes (9%), the peak value of house-dust mite (HDM) allergens exceeded 2 microg/g dust, with Der p 1 as the dominating allergen. Multivariate analyses indicated that high levels of HDM allergens were more common in apartments that were on the ground floor or first floor, that were heated with stoves, and/or that had a dampness problem. The mean allergen levels at home were similar in children sensitized to HDM (n=17, 0.29 vs 0.3 microg/ g dust), dog (n=5, 0.55 vs 1.06 microg/g dust, and cat (n=18, 0.21 vs 0.09 microg/g dust) and in children who were not sensitized to these allergens. Most of the sensitized children were exposed to relatively low allergen levels at home; i.e., below 1 microg/g dust. This level was exceeded in the homes of 4/17 mite-, 5/18 cat-, and 0/5 dog-sensitized children. The similar levels of the major indoor allergens in Estonia and in Scandinavia indicate that the large differences in atopy prevalence among children and young adults in the two regions are not due to differences in allergen exposure. No allergen threshold level for sensitization was identified.

Health effects of passive smoking .5. Parental smoking and allergic sensitisation in children

BACKGROUND

A systematic review was conducted of the effects of parental smoking on immunoglobulin (IgE) levels, skin prick positivity, and allergic rhinitis or eczema in children. Asthma was excluded in order to distinguish more clearly the effect of passive smoke exposure on allergic sensitisation.

METHODS

Thirty six relevant publications were identified after consideration of 692 articles selected by electronic search of the Embase and Medline databases using keywords relevant to passive smoking in children. The search was completed in April 1997 and identified nine studies of IgE in neonates, eight of IgE in older children, 12 which included skin prick tests, and 10 describing symptoms of allergic disease other than asthma or wheezing. A quantitative meta-analysis was possible only for the studies reporting skin prick tests.

RESULTS

Several large studies failed to confirm early reports of a substantial or statistically significant association of maternal smoking with concentrations of total serum IgE in neonates or in older children. No consistent association emerged between parental smoking and allergic rhinitis or eczema. Few of these studies adjusted for potential confounding variables. The quantity and quality of evidence was greatest for skin prick tests, and studies of parental smoking during pregnancy or infancy were broadly consistent in showing no adverse effect on prick positivity (pooled odds ratio 0.87, 95% confidence interval 0.62 to 1.24). There was much greater and statistically significant (p = 0.002) heterogeneity of odds ratios relating current parental smoking to skin prick positivity.

CONCLUSIONS

Parental smoking, either before or immediately after birth, is unlikely to increase the risk of allergic sensitisation in children.

Acquired risk factors and susceptibility to environmental toxicants

Susceptibility to illness after exposure to environmental toxicants is determined by the interaction of numerous factors involving both constitutive and acquired traits. Constitutive susceptibility (risk) factors are the intrinsic traits determined by developmental stage, gender, and genetic makeup. Within a population, changes in constitutive risk factors tend to occur slowly, through aging, alterations in the birth or death rate, or by migration in or out of the population. Often overlooked is the effect of acquired susceptibility factors on susceptibility to environmental toxicants. Acquired susceptibility factors, which are related to the effects of living conditions, psychosocial factors, diet, behavior and access to medical care, may modify the effect of constitutive factors. Three examples demonstrate the interaction of acquired susceptibility factors with exposure and constitutive factors. The increased prevalence of asthma in children is suspected of having a strong environmental component but the underlying acquired susceptibility factors, if any, are difficult to identify because of the multifactorial nature of asthma and the use of surrogate risk factors such as parent's education. β-Carotene is a dietary component which may modify acquired susceptibility. While numerous observational studies find that dietary β-carotene reduces the risk of lung cancer in cigarette smokers, intervention studies do not support this role. Hepatitis B is an example of an infectious agent functioning as an acquired susceptibility factor. Hepatitis B synergistically increases the risk of hepatocellular carcinoma when accompanied by exposure to aflatoxin, a relationship that may be modified by constitutive risk factors, such as epoxide hydrolase capabilities. Acquired risk factors have the potential to greatly influence risk and their impact should be included in future studies of the health effects of environmental toxicants.

Factors predicting food allergy

Prediction of food allergies has not been addressed systematically and to date studies have concentrated on prediction of allergic disorders in a general fashion. The current available data suggests that possibly the best predictor is the combined approach of taking into account the family history together with elevated cord blood IgE. Other indicators, such as cord blood lymphocyte responses and γ-interferon production at birth, are also discussed. Although preliminary studies seem to be promising, only studies of an unselected population with long term follow-ups will be able to show whether or not these possible predictors are of value.

Health effects of passive smoking. 1. Parental smoking and lower respiratory illness in infancy and early childhood

BACKGROUND

A systematic quantitative review was conducted of evidence relating parental smoking to acute lower respiratory illness in the first three years of life.

METHODS

Fifty relevant publications were identified after consideration of 692 articles selected by electronic search of the Embase and Medline databases using keywords relevant to passive smoking in children. The search, completed in April 1997, identified 24 studies ascertaining illnesses in a community setting, including five surveys of schoolchildren with retrospective ascertainment of early chest illness, and 17 studies of admissions to hospital for lower respiratory illness in early life. Thirty eight studies were included in a quantitative overview using random effects modelling to derive pooled odds ratios.

RESULTS

The results of community and hospital studies are broadly consistent, with only one publication reporting a reduced risk among children of smokers. The pooled odds ratios were 1.57 (95% CI 1.42 to 1.74) for smoking by either parent and 1.72 (95% CI 1.55 to 1.91) for maternal smoking. There is a significantly increased risk of early chest illness associated with smoking by other household members in families where the mother does not smoke (1.29, 95% CI 1.16 to 1.44). The associations with parental smoking are robust to adjustment for confounding factors, and show evidence of a dose-response relationship in most studies in which this has been investigated.

CONCLUSIONS

The relationship between parental smoking and acute lower respiratory illness in infancy is very likely to be causal. Although it is impossible to distinguish the independent contributions of prenatal and postnatal maternal smoking, the increased risk associated with smoking by other household members suggests that exposure to environmental tobacco smoke after birth is a cause of acute chest illness in young children.

Genetic susceptibility to asthma in a changing environment

There is a major interest in investigating the genetic components of allergy and asthma. Four different areas are involved in the study of complex genetic diseases: family studies, assessment of phenotype, segregation analysis and gene mapping. Initial assessment of phenotype must be practical, reproducible and relatively independent of compounding variables. Phenotypes important in allergy and asthma include atopic parameters such as total serum IgE, bronchial hyper-responsiveness and the presence/ absence of clinical asthma. Numerous family and twin studies have suggested the presence of a heritable component for allergy, bronchial hyper-responsiveness and asthma. The number of genes involved in these complex genetic disorders and their mode of inheritance have not been fully determined. Our group has been involved in a collaborative US-Dutch study in which 92 families with over 500 individuals have been phenotyped and DNA has been obtained for genotyping. Initial results of the classification of family members show that approximately 26% of the offspring of families ascertained through a parent with asthma have an asthmatic phenotype. A large number of these offspring with clinical evidence of asthma do not have a prior physician diagnosis of asthma, suggesting that there is a spectrum which ranges from preclinical to symptomatic asthma. The familial aggregation of asthma and other obstructive airway diseases in these families is consistent with a significant genetic component. Initial linkage studies have been performed on two characteristics of the allergic and asthmatic phenotype. Total serum IgE was analysed because this measure correlates with the clinical expression of allergy, bronchial hyper-responsiveness and asthma. Segregation analysis of total serum IgE provided evidence for a recessive mode of inheritance. Sib pair analyses and maximum likelihood scores suggest that a gene regulating IgE production maps to chromosome 5q. Bronchial hyper-responsiveness and total serum IgE are related to asthma in population-based studies. Sib pair analyses for bronchial responsiveness showed significant linkage to markers on chromosome 5q.

Cohort study of peanut and tree nut sensitisation by age of 4 years

OBJECTIVE

To determine the prevalence of sensitisation to peanuts and tree nuts in all children born during one year in one geographical area.

DESIGN

Birth cohort study with structured review at ages 1, 2, and 4 years.

SETTING

All children born on the Isle of Wight between January 1989 and February 1990.

SUBJECTS

Of 1456 children originally included, 1218 were reviewed at age 4 years. Of these, 1981 had skin prick tests.

MAIN OUTCOME MEASURES

Positive skin test results, clinical atopic disease, and risk factors for the development of atopy.

RESULTS

15 of 1218 (1.2%) children were sensitised to peanuts or tree nuts (13 to peanuts). Six had had allergic reactions to peanuts (0.5% of the population), one to hazelnuts, and one to cashew nuts; three had had anaphylactic reactions. Seven children had positive skin test results or detectable IgE to peanuts without clinical symptoms. Two children who reacted to peanut in infancy had lost their sensitivity by 4 years. Family history of atopy, allergy to egg (odds ratio 9.9, 95% confidence interval 2.1 to 47.9, and eczema (7.3, 2.1 to 26.1) were important predictors for peanut allergy.

CONCLUSIONS

IgE mediated allergy to peanuts is common in early childhood. In many the allergy persists but a minority may develop tolerance.

Study of the aetiology of wheezing illness at age 16 in two national British birth cohorts

BACKGROUND

Data from two national British birth cohorts were used to measure the increase in prevalence of wheezing illness at age 16 between 1974 and 1986, and to investigate the role of several potential risk factors in the increase.

METHODS

The occurrence of self-reported asthma or wheezy bronchitis within the past year, and the frequency of attacks of wheezing illness at age 16, were compared in 11,262 and 9266 children born in one week of 1958 and 1970, respectively. The effects of several putative risk factors for asthma--including birth weight, maternal age, birth order, breast feeding, maternal smoking in pregnancy, child's personal smoking, and father's social class--on the change in occurrence of wheezing illness at age 16 were assessed by multiple logistic regression.

RESULTS

The annual period prevalence of asthma or wheezy bronchitis at age 16 increased from 3.8% in 1974 to 6.5% in 1986 (prevalence ratio (PR) = 1.71, 95% CI 1.52 to 1.93). The proportion of children experiencing attacks more than once a week increased from 0.2% to 0.7% (PR = 3.77, 95% CI 2.28 to 6.23). The prevalence of self-reported eczema and hayfever within the past year doubled between 1974 and 1986, suggesting that the increase in asthma was part of a general increase in the prevalence of atopic disease. However, in the complete dataset, after adjustment for the effects of the risk factors studied, the prevalence odds ratio for asthma or wheezy bronchitis in 1986 compared with 1974 was virtually unchanged from the unadjusted value at 1.77 (95% CI 1.46 to 2.15).

CONCLUSION

The prevalence of wheezing illness in British teenagers increased by approximately 70% between 1974 and 1986. This increase appears to have occurred in the context of a general increase in atopic disease and was largely unexplained by changes in the distribution of maternal age, birth order, birth weight, infant feeding, maternal smoking, active smoking by the child, or father's social class.

Early detection of specific IgE antibody against house dust mite in children at risk of allergic disease

OBJECTIVES

House dust mite (HDM) is a representative inhalant allergen that triggers allergic disease in childhood. The aim of this study is early detection of HDM-specific IgE antibody and prediction of the risk of a positive reaction to this antibody by in vitro parameters in infants with allergic manifestations.

STUDY DESIGN

Levels of HDM IgE in a range below the standard cutoff point of 0.35 U/ml, serum concentrations of IgE, and specific IgE antibodies against egg white, cow milk, and soybeans were determined in 108 infants with allergic manifestations at 6 months of age, and these infants were monitored for conversion of HDM IgE to positive levels greater than 0.35 U/ml up to 5 years of age. The presence of active allergic disease at 5 years of age in relation to HDM-specific IgE was also examined.

RESULTS

We were able to determine reliably the HDM IgE values between 0.23 and 0.35 U/ml, using a fluorescent enzyme immunoassay that measured the intensity of fluorescence. The HDM IgE levels increased, resulting in positive values, in 54 of 108 subjects during the first 5 years of life. In multiple regression analysis, an HDM IgE value between 0.23 and 0.35 U/ml, a high serum IgE level, and a positive reaction to specific IgE antibody against egg white in infants at 6 months of age proved to be significant predictors of the future positive reaction to HDM IgE (p = 0.0006, 0.0043, and 0.0001). In particular, the sensitivity and specificity of specific IgE antibody against egg white for the conversion of HDM IgE to positive values were the best among these indicators. Moreover, active allergic diseases were observed significantly more often in children with positive HDM IgE values than in children with negative HDM IgE values at 5 years of age (p < 0.001 for each).

CONCLUSIONS

A determination of these predictors in infants at 6 months of age can be used for early detection of HDM IgE and would be valuable in a screening test for later allergic disease among infants with allergic manifestations.

Sensitization to airborne allergens in children with respiratory symptoms

BACKGROUND

Allergy is one of the most common causes of respiratory symptoms in children and youth.

OBJECTIVE

Evaluate the presence and the type of allergic sensitization in a paediatric population with respiratory symptoms.

METHODS

We studied 564 consecutive children, 5 months to 17 years of age, with a male to female ratio (M/F) = 1.4, referred to our outpatient clinic in a 12-month period retrospectively. Patients were arbitrarily divided into four groups (grs) according to their age: gr1 = 5 months to 4 years old (181 patients), gr2 = 4 to 7 years (201 patients), gr3 = 7 to 10 years (96 patients), and gr4 = 10 to 17 years (86 patients). Sensitization to house dust mites, pollens, animal dander, and molds was determined by skin prick testing.

RESULTS

Sensitization to at least one class of allergen occurred in 304 of the 564 patients (53.9%, M/F ratio = 2.0); the percentage of allergic patients increased with age as follows: 29.8% (54 patients) of the patients in gr1, 55.2% (111 patients) in gr2, 68.8% (66 patients) in gr3 and 84.9% (73 patients) in gr4 (chi(2) = 84.1, P < .01). In the entire allergic population and in gr1 to gr3, the most common positive allergic reaction was to house dust mites (P < .01, chi(2) test each comparison). In contrast, gr4 patients showed a nearly equal percentage of sensitization to pollens and to house dust mites (79.5% and 78.1% respectively) (chi(2) = 0.0, P = >.1). Sensitization to only one class of allergen occurred in 51.3% of the allergic patients and the percentage of these monosensitized patients tended to decrease from gr1 to gr4 (chi(2) = 15.2, P < .1). In the monosensitized group, sensitization to house dust mites was the most frequent in gr1 to gr3 (age <10 years) as in the whole sample. In gr4, the frequency of sensitization to house dust mites was similar to that of sensitization to pollens. On the contrary, within the patient group sensitized to two or more allergens (polysensitized patients), sensitization to house dust mites was as frequent as sensitization to pollens already in gr2 as compared with monosensitized patients.

CONCLUSIONS

In children with respiratory symptoms, the percentage of allergic individuals was high and increased with the age of the patients. This phenomenon was associated with an age-related enhancement in the ratio of polysensitized to monosensitized patients and with an age-related increase in the frequency of sensitization to seasonal allergens (ie, pollens).

A major house dust mite allergen disrupts the immunoglobulin E network by selectively cleaving CD23: innate protection by antiproteases

Asthma is a chronic life-threatening disease of worldwide importance. Although allergic asthma and related atopic conditions correlate strongly with immune sensitization to house dust mites, it is unclear why antigens from mites provoke such powerful allergic immune responses. We have characterized the protease activity of Der p I, the group I protease allergen of the house dust mite Dermatophagoides pteronyssinus, and here report that it cleaves the low-affinity immunoglobulin (Ig) E Fc receptor (CD23) from the surface of human B lymphocytes. Der p I selectively cleaves CD23 and has no effect on the expression of any other B cell surface molecules tested. We speculate that this loss of cell surface CD23 from IgE-secreting B cells may promote and enhance IgE immune responses by ablating an important feedback inhibitory mechanism that normally limits IgE synthesis. Furthermore, since soluble CD23 is reported to promote IgE production, fragments of CD23 released by Der p I may directly enhance the synthesis of IgE. alpha 1-Antiprotease, a pulmonary antiprotease, is also shown to inhibit the cleavage of CD23 by Der p I. This may be significant in the etiopathogenesis of asthma, because other indoor pollutants associated with asthma are known to potently inhibit this antiprotease. These data suggest that the proteolytic activity of Der p I, the group I allergen of the house dust mite D. pteronyssinus, is mechanistically linked to the potent allergenicity of house dust mites. Furthermore, inhibition of Der p I by alpha 1-antiprotease suggests a mechanism by which confounding factors, such as tobacco smoke, may act as a risk factor for allergic asthma.

[Respiratory symptoms in a pediatric population]

With the aim of determining the prevalence of respiratory symptoms and rhinitis among adolescents in Spain, we sent a brief questionnaire about respiratory symptoms to all school children (9,644) in the sixth, seventh and eight grades in our city. We identified a symptomatic group (SG) consisting of adolescents who reported having had one or more of the following three signs within the past 12 months: a) waking with a feeling of stuffiness; b) experiencing an asthma attack, or c) taking medication for asthma. Returned questionnaires accounted for 74.4% of those distributed. The following symptoms were reported: wheezing by 13.4%, nighttime oppression by 8.4%, stuffiness at night by 7.3%, nighttime coughing by 24.8%, asthma attack by 4.5%, taking asthma medication by 6.1% and seasonal rhinitis by 15.4%. The proportion of symptomatic children was 11.6% (833). All symptoms studied that were not required for inclusion in SG correlated highly with that group (p < 0.0001). Neither age nor sex were related to inclusion.

Germ-line therapy to cure mitochondrial disease: protocol and ethics of in vitro ovum nuclear transplantation

The combination of genuine ethical concerns and fear of learning to use germ-line therapy for human disease must now be confronted. Until now, no established techniques were available to perform this treatment on a human. Through an integration of several fields of science and medicine, we have developed a nine step protocol at the germ-line level for the curative treatment of a genetic disease. Our purpose in this paper is to provide the first method to apply germ-line therapy to treat those not yet born, who are destined to have a life threatening, or a severely debilitating genetic disease. We hope this proposal will initiate the process of a thorough analysis from both the scientific and ethical communities. As such, this proposal can be useful for official groups studying the advantages and disadvantages of germ-line therapy.

Sensitization to inhalant allergens in wheezing infants is predictive of the development of infantile asthma

Early recognition of infantile asthma in wheezing infants is a major problem for physicians. We investigated whether detection of early sensitization to inhalant allergens would be useful to identify those wheezing infants who are likely to develop asthma. A total of 67 infants (aged 1-25 months) hospitalized for a wheezing episode were initially tested for reactivity to inhalant allergens by both skin prick test and in vitro measurement of specific IgE antibodies (Phadiatop). Thirty-seven of the infants were already considered to have infantile asthma, and 30 presented only their first or second wheezing episode when included in the study. All infants were followed for a mean period of 18 months. Seventeen (25%) infants, including seven infants initially not asthmatic, had positive prick test to Dermatophagoides pteronyssinus or to cat fur. All of these children were diagnosed as suffering from infantile asthma at the end of the follow-up. Thus, skin test positivity to inhalant allergens was significantly associated with the diagnosis of infantile asthma (P < 0.05) and could be considered to be predictive of the development of infantile asthma (P < 0.03). In contrast, Phadiatop was less sensitive than skin prick tests, and only five children had positive in vitro test results, suggesting that specific IgE may primarily bind to tissue mast cells before being detectable in serum. We concluded that sensitization to inhalant allergens may distinguish wheezing infants who develop asthma from those who do not, and that skin testing may assist the early diagnosis of asthma in wheezing infants.

Childhood eczema: disease of the advantaged?

OBJECTIVE

To determine whether the increased prevalence of childhood eczema in advantaged socioeconomic groups is due to increased parental reporting.

DESIGN

Comparison of parental reports of eczema with visible eczema recorded by medical officers during a detailed physical examination.

SETTING

National birth cohort study.

SUBJECTS

8279 children from England, Wales, and Scotland born during 3-9 March 1958 and followed up at the ages of 7, 11, and 16.

MAIN OUTCOME MEASURES

Prevalence of eczema according to parental report compared with medical officer's examination at the ages of 7, 11, and 16.

RESULTS

Prevalence of both reported and examined eczema increased with rising social class at the ages of 7, 11, and 16 years. The point prevalence of examined eczema at age 7 was 4.8%, 3.6%, 3.6%, 2.4%, 2.2%, and 2.4% in social classes I, II, III non-manual, III manual, IV, and V respectively (chi 2 value for linear trend 12.6, P < 0.001). This trend persisted after adjustment for potential confounders such as region and family size and was not present for examined psoriasis or acne.

CONCLUSIONS

Eczema is more prevalent among British schoolchildren in social classes I and II than those in lower classes. Exposures associated with social class are probably at least as important as genetic factors in the expression of childhood eczema.