Prevalence of asthma and atopy in two areas of West and East Germany

Soluble cytokine receptor CD30 in atopic disorders: a case-control study

BACKGROUND

The cytokine receptor CD30 is an activation marker of T cells which preferentially associates with the production of the TH2 cytokine IL-4. Therefore, it may potentially be a candidate marker for atopic disorders and a target molecule for new therapeutic approaches.

OBJECTIVE

To test the hypothesis that elevated levels of soluble CD30 (sCD30) are significantly associated with atopic disorders after adjustment for other predictors of atopy.

METHODS

The presence of elevated sCD30 (> or = 20 U/mL) in atopic disorders was evaluated in a nested case-control study. Cases (n = 60) were blood donors with specific IgE antibodies, total serum levels of IgE > or = 100kU/L and presence or history of allergic symptoms. Controls (n = 59) were blood donors without presence or history of allergic symptoms and serum levels of IgE < 50 kU/L. sCD30 was determined from serum samples by an enzyme-linked immunosorbent assay. Odds ratios (OR) and confidence intervals (CI) were calculated from logistic regression coefficients.

RESULTS

Mean sCD30 levels for cases were 75 U/mL (SD 110U/mL) as compared with 35 U/mL (SD 59 U/mL) for controls. Serum levels of sCD30 were elevated in 65% of cases and 32% of controls (OR 3.9, 95% CI 1.8-8.4). The odds ratio for elevated sCD30 as a predictor of atopic disorders slightly decreased to 3.7 after controlling for smoking, age and gender. Blood eosinophilia which was a strong predictor of atopy (OR 11.7) was a weak confounder of the association between sCD30 levels and atopic disorders. Family history of allergy, another strong predictor of atopy (OR 8.6), did not confound the association.

CONCLUSIONS

The results are consistent with the hypothesis that CD30 is involved in the pathogenesis of atopic disorders independent of eosinophilia and family history of allergy.

Epidemiological analyses of the relationship between environmental pollution and asthma

Epidemiological studies performed on children and young adults indicate that the prevalence of asthma has increased over the past decades in a number of countries. Since genetic determinants alone are unlikely to explain these findings, environmental factors are expected to have an important impact on the prevalence of this disease. Environmental pollution, among many other factors, may play a role in the initiation and manifestation of asthma. However, there is little epidemiological evidence for a causal association between the classical major outdoor air pollutants, such as SO2 or particulate matter, and asthma. Evidence for an association between air pollution from motor vehicles and asthma is still controversial. Thus the indoor environment and other environmental determinants--including lifestyle factors--are likely to be more important as causes of asthma. Epidemiological studies are able to evaluate the effects of environmental factors on the health of human populations in their usual environments. In addition, they can measure associations between long-term environmental exposures and health outcomes. By using refined techniques for exposure and disease assessment, as well as time and cost-effective study designs, environmental epidemiology will increase the knowledge about the role of pollution as a possible cause of asthma.

Effect of dampness at home in childhood on bronchial hyperreactivity in adolescence

BACKGROUND

Relatively little is known about risk factors for the persistence of asthma and respiratory symptoms from childhood into adolescence, and few studies have included objective measurements to assess outcomes and exposure.

METHODS

From a large cross sectional study of all 4th grade school children in Munich (mean age 10.2 years), 234 children (5%) with active asthma were identified. Of these, 155 (66%) were reinvestigated with lung function measurements and bronchial provocation three years later (mean age 13.5 years).

RESULTS

At follow up 35.5% still had active asthma. Risk factors for persisting asthma symptoms in adolescence were more severe asthma (OR 4.94; CI 1.65 to 14.76; p = 0.004) or allergic triggers (OR 3.54; CI 1.41 to 8.92; p = 0.007) in childhood. Dampness was associated with increased night time wheeze and shortness of breath but not with persisting asthma. Risk factors for bronchial hyperreactivity in adolescence were bronchial hyperreactivity in childhood (p = 0.004), symptoms triggered by allergen exposure (OR 5.47; CI 1.91 to 25.20; p = 0.029), and damp housing conditions (OR 16.14; CI 3.53 to 73.73; p < 0.001). In a subgroup in whom house dust mite antigen levels in the bed were measured (70% of the sample), higher mite antigen levels were associated with bronchial hyperreactivity (OR per quartile of mite antigen 2.30; CI 1.03 to 5.12; p = 0.042). Mite antigen levels were also significantly correlated with dampness (p = 0.05). However, the effect of dampness on bronchial hyperreactivity remained significant when adjusting for mite allergen levels (OR 5.77; CI 1.17 to 28.44; p = 0.031).

CONCLUSION

Dampness at home is a significant risk factor for the persistence of bronchial hyperreactivity and respiratory symptoms in children with asthma. This risk is only partly explained by exposure to house dust mite antigen.

The prevalence of allergic rhinitis and nasal symptoms in Nottingham

From 1200 households selected at random, 2114 questionnaires were returned from individuals over 14 years old. They reported that in the previous year the prevalence of 'symptoms of nasal obstruction every day for more than 14 consecutive days' was 16.9%; 19.8% had had a 'runny nose'; 7.1% reported sneezing bouts; and 19.6% had hay fever during the same period. Also, 13.7% had had rhinosinusitis in the previous year using the criterion of 'two out of three symptoms of congestion, rhinorrhoea and sneezing for more than 1 h per day for a period in excess of 2 weeks'. The prevalence of perennial symptoms in individuals who did not have hay fever was 8.6%. Over the previous 2 years 18.2% of all respondents had visited their General Practitioner and 0.2% had visited a hospital as a result of their hay fever. Individuals who responded as having hay fever were significantly more likely to have worked in an environment with a lot of dust in the last 2 years than asymptomatic respondents (chi 2, P = 0.002), although fume exposure was not found to be a significant risk factor (P = 0.0681). Individuals with perennial symptoms were no more likely to have been working in a dusty or smoky environment. In those with either seasonal or perennial symptoms there was no significant effect of either social class or manual/non-manual occupation.

Indoor versus outdoor allergens in allergic respiratory disease

Immediate hypersensitivity to indoor or outdoor allergens is strongly associated with asthma or hay fever, respectively. Recent progress has defined the sequences, tertiary structures and enzymatic functions of many of the proteins involved; furthermore, the immune responses to these proteins have been examined; however, the mechanisms responsible for the dichotomous response remain elusive. The resolution of such mechanisms may explain the large increase in the prevalence of eosinophil-rich inflammation of the lower respiratory tract.

The prevalence of allergic rhinosinusitis: a review

A review of the literature indicates that there is an increase in the prevalence of self-reported symptoms suggestive of seasonal allergic rhinitis over the last 70 years. The reason for this remains unclear. Epidemiological studies which relate to the effect of pollution suggest that while pollution can exacerbate respiratory tract symptoms, there is no consistent evidence that high levels result in an increase in the prevalence of allergic rhinitis. The increased prevalence of house-dust mite, an alteration in immunity--possibly related to the number of childhood respiratory tract infections, and increased disease awareness, are all factors which may influence the reported prevalence of allergic rhinitis. At present the inconsistencies which exist in the literature mean that it is possible to 'pick' publications which support one view and ignore the rest, so that a variety of views may be held, each with apparently well referenced endorsement. The criteria defined by Bradford Hill (1965) to establish causation and not mere association between any of these factors and allergic rhinitis have, as yet, not been met (see Table V).

The rising trends in asthma and allergic disease

Considerable variation in the prevalence of childhood asthma and allergic conditions has been shown in previous studies. These differences may in part be attributable to methodological problems in defining childhood asthma and wheezing illnesses. However, the results of recent surveys using identical study instruments suggest that the variation in the distribution of the disease is real. In western societies serial prevalence studies have furthermore shown an increasing trend in the prevalence of childhood asthma and airway hyperresponsiveness. A concomitant increase in the prevalence of hay fever and atopic eczema has been reported by others. Moreover, hospitalization rates for childhood wheezing illnesses have increased in affluent countries suggesting that indeed the morbidity from these causes has increased in the last decades. Interestingly, areas of low prevalence of asthma and atopic conditions have recently been identified in developing countries and in Eastern Europe. In Eastern Germany where drastic changes towards westernization of living conditions have occurred after reunification an increase in the prevalence of hay fever and atopic sensitization has been documented over the last 4-5 years in children aged between 9 and 10 years of age. The prevalence of asthma and airway hyperresponsiveness, however, remained virtually unchanged in this age group. These children spent their first 3 years of life under socialist living conditions and were exposed to a western lifestyle only after their third birthday. Therefore, environmental factors may affect an individual's inherited susceptibility for the development of asthma and hay fever at different ages inducing changes in the prevalence of atopic diseases in populations in a time- and age-dependent way.

Early childhood infection and atopic disorder

BACKGROUND

Atopy is of complex origins but the recent rise in atopic diseases in westernized communities points to the action of important environmental effects. One candidate mechanism is the changing pattern of microbial exposure in childhood. This epidemiological study investigated the relationship between childhood infections and subsequent atopic disease, taking into account a range of social and medical variables.

METHODS

A total of 1934 subjects representing a retrospective 1975-84 birth group at a family doctor practice in Oxfordshire were studied. Public health and practice records were reviewed; temporal records were made of all diagnoses of infections and their treatments, all immunisations, and diagnoses of asthma, hay fever and eczema; maternal atopy and a number of other variables were documented.

RESULTS

Logistic regression analysis identified three statistically significant predictors of subsequent atopic disease: maternal atopy (1.97, 95% CI 1.46 to 2.66, p < 0.0001), immunisation with whole-cell pertussis vaccine (1.76, 95% CI 1.39 to 2.23, p < 0.0001), and treatment with oral antibiotics in the first two years of life (2.07, 95% CI 1.64 to 2.60, p < 0.0001). There was no significant association found for maternal smoking, bottle feeding, sibship size, or social class.

CONCLUSIONS

The prediction of atopic disease by maternal atopy mainly reflects the effect of acknowledged genetic factors. Interpretation of the prediction of atopic disorders by immunisation with wholecell pertussis vaccine and treatment with oral antibiotics needs to be very cautious because of the possibilities of confounding effects and reverse causation. However, plausible immune mechanisms are identifiable for the promotion of atopic disorders by both factors and further investigation of these association is warranted.

Gene by environment interactions in the development of asthma

Present knowledge suggests that asthma is a heterogeneous condition. Different genetic backgrounds may or may not express themselves as asthma-like symptoms, depending on both the nature and the timing of exposures in the individual. Although particular attention has been paid to environmental factors that may increase the risk of asthma, it is equally important to understand 'protective' exposures that may have decreased during the last decades and may thus explain the reported increases in asthma prevalence. Among these 'protective' factors are certain infections and the role they may have in the inception of allergics and asthma, particularly when they occur at critical times in the development of the immune system.

Factors determining the severity of asthma

Asthma typically can range from a disease of very mild and intermittent symptoms to one of debilitating and life-threatening disease. However, the factors that control these differences remain poorly understood. It is likely that the factors controlling the severity of asthma are many and dependent on each other. Potential factors include: (i) inflammatory; (ii) structural; (iii) hereditary/congenital; (iv) environmental; and (v) psychological/emotional; each potentially interacting and influencing the other. Finally, the question remains as to whether all asthmatics, no matter what their initial severity, potentially can develop severe disease, or whether only a certain subgroup will become severe.

Hypothesis: decreased use of pediatric aspirin has contributed to the increasing prevalence of childhood asthma

BACKGROUND

The prevalence of asthma, atopic eczema, and allergic rhinitis has increased over the last three decades in Western countries. Speculation on the causes of this trend have focused on changes in environmental factors. We hypothesize that the decreased use of aspirin in favor of acetaminophen, due to the association of aspirin with Reye's syndrome during febrile respiratory infections, may be contributing to these trends in the United States.

DATA SOURCES

A detailed literature search was conducted utilizing Medline. Studies considered relevant and important involving both humans and animals in English language were used.

HYPOTHESIS

In the United States, the documented prevalence of childhood asthma has increased since 1970, but the rate of this increase accelerated upward beginning in the early 1980s when the use of pediatric aspirin decreased. During the resolution of common respiratory viral infections, prostaglandin E2 (PGE2) is produced through the actions of cyclooxygenase-2 (COX-2). Aspirin, but not acetaminophen, inhibits COX-2 activity. As PGE2 promotes TH2 and inhibits THI type cytokine generation, we hypothesize that the decreased use of aspirin may be a factor in facilitating allergic sensitization and asthma by augmenting the relative TH1/TH2 cytokine imbalance in genetically predisposed children.

CONCLUSION

We have presented an hypothesis based upon epidemiologic trends, known biologic effects of cytokines and PGE2 on allergic sensitization, and a potentially relevant pharmacologic effect of aspirin to explain a component of the increasing prevalence of childhood asthma in the United States. We suggest this theory be examined further in animal models as well as in other countries where the prevalence of childhood asthma is increasing.

Atopy in children and parental social class

OBJECTIVES

This analysis was conducted to determine whether atopic disorders were related to social class in a pediatric population of a former socialist country.

METHODS

A cross-sectional study of 2471 schoolchildren was carried out in 1992 and 1993 in 3 towns in the former East Germany. Parents completed a standardized questionnaire regarding health events and lifestyle factors. In addition, skin-prick tests were performed and total serum immunoglobulin (IgE) was determined.

RESULTS

Lifetime prevalence rates for atopic disease and rates of allergic sensitization were highest in children from social class III (in which parents had more than 10 years of formal education) and lowest in social class I (less than 10 years of parental education), while rates in social class II (10 years of parental education) were constant at an intermediate level.

CONCLUSIONS

The data confirmed the assumption that in formerly socialist countries social inequalities existed under the socialist system, which were reflected by a social gradient in health outcomes. The findings support the hypothesis that increased access to modern lifestyle could be one reason for the increasing rates of atopic disorders during the last 3 decades.

Atopy and allergic disorders among adults in Tartu, Estonia compared with Uppsala, Sweden

BACKGROUND

Recent studies in children and adults indicate that the prevalence of atopy and allergic disorders is lower in previously socialist countries in Eastern Europe compared with countries with a market economy while revealed risk factors are similar.

OBJECTIVES

To estimate the prevalence of atopy among adults in Tartu, Estonia and to compare the prevalence of risk factors for atopy and allergic respiratory diseases in Estonia and Sweden.

METHODS

As a part of cross-sectional study-European Community Respiratory Health Survey-random samples of 20-44 year olds (n = 351 in Tartu and n = 470 in Uppsala) and persons of the same age with asthma like symptoms or on current asthma medication according to a postal questionnaire (n = 95 in Tartu and n = 201 in Uppsala) were interviewed and circulating IgE antibodies were measured.

RESULTS

The prevalence of atopy was 19% in Tartu and 32% in Uppsala (P < 0.001). The prevalence of sensitization to pollen was twice lower (11.5 vs 23.2; P<0.001) and the prevalence of pollen associated asthma symptoms was four times lower (1.7 vs 6.8; P<0.001) in Tartu than in Uppsala while sensitization to pollen was an equally large risk factor for asthma in both centres. Age was inversely related to cat and pollen associated symptoms of rhinoconjunctivitis in Uppsala (OR 0.6 and 0.7, respectively, P < 0.05) but not in Tartu.

CONCLUSIONS

The prevalence of atopy was lower in Tartu, Estonia than in Uppsala Sweden. Perception of allergic disorders seemed to be lower in Tartu than in Uppsala. Age did not influence the prevalence of atopy nor allergic disorders in Tartu, while in Uppsala age was inversely related to clinical allergy. This could suggest a cohort effect underlying the increasing prevalence of allergy in Western Europe.

Ascaris-specific IgE and allergic sensitization in a cohort of school children in the former East Germany

BACKGROUND

Helminthic infections induce an IL-4-dependent polyclonal stimulation of IgE synthetization. It is still unclear, however, what role helminths play in allergic sensitization.

OBJECTIVE

We sought to determine the relationship between Ascaris-specific IgE and allergic sensitization in a nontropical country.

METHODS

In 2 consecutive cross-sectional surveys in 1992-1993 and 1995-1996, data from school entrants (age range, 5 to 7 years), third graders (age range, 8 to 10 years), and sixth graders (age range, 11 to 14 years) were collected. The 2 younger groups were reexamined in the second survey. Data for about 2300 children, including a cohort of 700 subjects, were analyzed. Ascaris IgE and total and specific IgE to inhalant allergens were measured, and skin prick tests were performed. Information about asthma and allergic rhinitis was collected by a questionnaire.

RESULTS

Children who were Ascaris-IgE seropositive (>0.35 IU/mL) in both surveys had 10-fold higher levels of total IgE (451 IU/mL vs 45 IU/mL, P < .001) and higher prevalence rates of allergen-specific IgE seropositivity (56.3% vs 26.6%, P < .001). They also had a higher prevalence of allergic rhinitis (12.6% vs 3.7%, P < .001) and asthma (5.7% vs 1.6%, P < .05). In subjects who were Ascaris-seronegative in the first survey but seropositive in the second survey, total and specific IgE increased markedly. Sensitization to Dermatophagoides pteronyssinus increased nearly 3-fold in this group. In contrast, in children who became Ascaris-seronegative, total and specific IgE decreased.

CONCLUSIONS

Contact with low doses of helminthic antigen is associated with an increase of total and specific IgE production. Helminthic infections in East German children are not the cause for a low prevalence of allergies in the former East Germany.

Prevalence and determinants of house dust mite allergen in East German homes

BACKGROUND

In 1990/91, allergic sensitization to house dust mites (HDM) and other allergens was more prevalent in children from West Germany than from East Germany.

OBJECTIVE

To test the hypothesis that low indoor exposure to HDM allergen in East Germany has contributed to this difference.

METHODS

HDM allergen concentrations were determined in 634 East German dwellings shortly after the German reunification.

RESULTS

HDM group I allergen (Der p 1 + Der f 1) levels in mattresses (median 2.16, geometric mean 2.07, maximum 278.9 microg/g dust) and carpets (median 0.41, geometric mean 0.48, maximum 96.3 microg/g dust) were within the range of levels determined in West Germany in other studies. One particular East German type of dwelling (light concrete buildings) was associated with lower mite allergen exposure, but only a minority of the population lived there. Coal heating, installed in the majority of dwellings before 1989, was associated with higher allergen exposure. Higher relative humidity (RH) was a main risk factor for higher Der p 1 exposure (odds ratio [OR] for exposure to > 0.05 microg/g dust on carpets: 1.4 [95% confidence interval (CI) 1.2-1.8] for + 10% RH) but not for higher Der f 1 exposure. Higher temperature was associated with a lower risk for elevated Der p 1 levels (> 0.05 microg/g dust on carpets): OR 0.6 (95% CI 0.5-0.8) for + 2 degrees C.

CONCLUSION

Mite allergen exposure is not lower in East Germany than in West Germany. The data does not support the hypothesis, that low HDM allergen exposure in East Germany is a cause for the lower prevalence of HDM sensitization in East German children.

Characterization of obstructive airway disease in family members of probands with asthma. An algorithm for the diagnosis of asthma

To investigate the genetic susceptibility to asthma, we developed an algorithm to classify the phenotype of each family member enrolled in a family study on the genetics of asthma. This algorithm was applied to 92, two- and three-generation families, identified through a subject (proband) with asthma first diagnosed 25 yr previously. The algorithm consisted of five classes based on the presence or absence of bronchial hyperresponsiveness (BHR), respiratory symptoms, smoking, airways obstruction, and bronchodilator reversibility. All family members were classified as: (1) definite asthma; (2) probable asthma; (3) unclassifiable airway disease; (4) chronic obstructive pulmonary disease (COPD); (5) unaffected (without clinical evidence of asthma and COPD). Thirteen of the 92 probands (14%) could not be classified as asthmatic when retested 25 yr later because of loss of BHR, loss of bronchodilator reversibility, or a current history of cigarette smoking. Of the 265 first-degree offspring, 49 (18%) were classified as having definite asthma (Class 1), and 22 (8%) as probable asthma (Class 2). A large number of offspring with clinical evidence of asthma did not have a prior physician's diagnosis of asthma, and offspring in Class 1 (definite asthma), with and without a physician's diagnosis, had similar clinical and physiologic characteristics. These results support the usefulness of this approach to classify subjects with asthma for genetic epidemiologic studies and show that reliance on a prior physician's diagnosis may result in misclassification or underdiagnosis. Characterization of the offspring in this family study showed that there is familial clustering, which supports the presence of a hereditary component in asthma.

Cord blood-IgE as risk factor and predictor for atopic diseases

BACKGROUND

Cord blood-IgE as risk factor or predictor for atopic diseases in infants has been discussed in a large number of papers with contradictory results. Our aim was to evaluate cord blood-IgE as risk factor and predictor for atopic dermatitis, recurrent wheezing and sensitization with emphasis on a clear-cut distinction between risk factor and predictor.

METHODS

A cohort of 1314 newborns was recruited in six German obstetric departments and followed-up for 5 years. Four hundred and ninety-nine infants (38%) were considered to be at high risk with at least two atopic family members and/or a cord blood-IgE value above the threshold of 0.9 kU/L. At follow-up visits, parents filled in a questionnaire, the infants were clinically examined, and blood samples were taken.

RESULTS

With regard to early onset atopic dermatitis up to 12 months we found that the odds ratios at the cord blood-IgE cut-off points of 0.70 kU/L and 1.25 kU/L with values of 0.53 and 0.32, respectively, were smaller than one (i.e. protective factors) and highly statistically significant. No significant association was found between elevated cord blood-IgE and recurrent wheezing. There was a strong positive association between elevated cord blood-IgE levels and sensitization at 12 months, but even in this case the predictive performance was rather poor: a maximum positive predictive value of 42% was attained with a cut-off point of 3.0 kU/L, but the sensitivity was only 10%.

CONCLUSION

We conclude that even when elevated cord blood-IgE levels are identified as a strong risk factor for sensitization, their poor predictive performance may make them useless as a basis for preventive measures.

Regulation of immune responses at mucosal surfaces: allergic respiratory disease as a paradigm

The epithelial surfaces of the respiratory tract represent a fragile interface between the immune system and the outside environment. In order to maintain local homeostasis, the adaptive immune system must continuously discriminate between innocuous antigens which are ubiquitous in the atmosphere, and antigens associated with microbial pathogens. Any breakdown in this discrimination process can potentially lead to chronic inflammatory disease. The mechanisms employed by the mucosal immune system to maintain this delicate balance are many and varied, and a comprehensive understanding of how they collectively operate would provide novel insight into a wide variety of diseases. This discussion reviews recent progress in this area, focusing on allergic respiratory disease as a model for the study of immune regulation at mucosal surfaces.

Sibship size, birth order, and atopy in 11,371 Italian young men

BACKGROUND

Having a low number of siblings and a low birth order has been reported to be a relevant risk factor for development of atopic diseases and skin sensitization to common inhalants. Although the inverse association of atopy with sibship size has been confirmed repeatedly, the association with birth order has provided conflicting results. This possibly is due to the relatively small size of the population sample examined.

OBJECTIVE

The objective of this study was to investigate the relation between sibship size, birth order, and atopy in a very large population sample, highly homogeneous for age and sex.

METHODS

This was a retrospective survey of 11,371 Italian young men, 18 to 24 years old, all candidates for enrollment in the Italian Air Force. Demographic data had been collected by a standard questionnaire. Specific IgE for locally relevant airborne allergens had been tested by a multi-RAST assay (CAP-Phadiatop).

RESULTS

The prevalence of atopy (defined as a high level of specific IgE against inhalants [cut-point >1.2 log RU]) was inversely related to the total number of siblings (25% in those with no siblings and 9% in those with five or more siblings), with a mean of a 3% decrease in prevalence for each added sibling. This relation persisted after adjustment for relevant variables such as father's education and rural and southern residence. An independent association between birth order and atopy was also observed because the decrease in atopy prevalence with increasing numbers of older siblings was significantly steeper than that found with the number of younger siblings (chi2 = 179, df = 1, p < 0.0001).

CONCLUSIONS

In a very large and homogeneous population sample of a Mediterranean country, not only sibship size but also birth order was significantly associated with atopy. This observation further highlights the role of family structure in the development of atopy and supports the hypothesis that cross-infections acquired early in infancy or in later childhood might prevent development of atopy later in life.

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.

Is the prevalence of atopic diseases in East and West Germany already converging?

Studies comparing respiratory health of residents in the areas of former East and West Germany have shown higher rates of asthma and allergies in children and young adults in former West Germany. It has been speculated that some factors associated with western lifestyle may be related to higher rates of atopic diseases among residents of former West Germany. We examined if the prevalence rates of self-reported asthma and nasal allergies in adults converged between the areas of former East and West Germany five years after re-unification. During the years 1990-1992 and 1994-1995 two independently drawn random samples of more than 3,000 subjects between the ages of 20 to 44 years answered a screening questionnaire of the European Community Respiratory Health Survey in Erfurt (East Germany) and in Hamburg (West Germany). The prevalence rates of asthma attacks, asthma medication use, allergic rhinitis, and wheezing remained stable in Hamburg but increased significantly in Erfurt approaching those of Hamburg. The data indicate that there is a tendency for the prevalence rates of self-reported allergic rhinitis and asthma-related respiratory symptoms in the eastern part of Germany to increase to West-German levels. It is not yet clear if this is due to a true increase in morbidity or only to a higher awareness for these diseases among doctors and the public.

Increasing risk of asthma without other atopic diseases in school children: a repeated cross-sectional study after 13 years

Some children develop asthma and other atopic diseases, others asthma without atopic diseases. To better understand secular trends, we estimated the relative increase in asthma in children with (atopy related asthma) and without (non-atopy related asthma) other atopic diseases (eczema or hay fever) in two samples of school children born, 1965-1975 (n = 1674) and 1978-1988 (n = 2188). By analysing the samples as historical cohorts, age-specific prevalence rates were estimated and incidence rates were calculated (number of new cases by 1000 person years under risk). Cox regression was used to estimate the relative risk (RR) of asthma by year of birth. The point prevalence of asthma was 1.9% (95% CI: 1.4-2.4) in the 1965-1975 cohort and 4.6% (95% CI: 3.8-5.4) in the 1978-1988 cohort for three-year old children, and remained fairly constant throughout childhood. The age-specific prevalence of non-atopy related asthma increased relatively more from 1965-1975 to 1978-1988 compared to atopy related asthma. The age-specific incidence rates of asthma showed that the RRs comparing the two cohorts tended at all ages to be highest for non-atopy related asthma. The relative risks of non-atopy related asthma by gender and birth cohort, showed that the effect of cohort was higher for non-atopy related asthma, aRR: 4.0 (95 % CI: 2.5-6.5), than for atopy-related asthma aRR: 2.0 (95% CI: 1.3-3.2). Children without other atopic diseases have a higher relative risk of being diagnosed with asthma than children with other atopic diseases across all ages comparing two samples of school children born 1965-1975 and 1978-1988.

Increasing prevalence of hay fever and atopy among children in Leipzig, East Germany

BACKGROUND

Several surveys in children and adults have shown significantly lower prevalences of asthma and allergic diseases in eastern Europe than in western countries. In the former East Germany tremendous changes towards western lifestyle have occurred since unification. The aim of this survey was to investigate time trends in the prevalence of asthma and allergic diseases among children living in the eastern part of Germany.

METHODS

In 1995-96, 2334 (87.5%) schoolchildren in Leipzig participated in a cross-sectional study that used the same methods as a previous survey done shortly after the fall of communism in 1991-92. A self-administered questionnaire was distributed to the parents. Children underwent cold-air challenge and allergy skinprick tests to six common aeroallergens.

FINDINGS

The prevalence of hay fever (2.3% [34/1454] vs 5.1% [115/2252], p<0.0001) and atopic sensitisation (19.3% [252/1303] vs 26.7% [434/1624], p<0.0001) increased significantly between 1991-92 and 1995-96. However, there was no significant change in the prevalence of asthma, asthma-related symptoms, or bronchial hyper-responsiveness.

INTERPRETATION

These findings suggest important differences in the development of atopic disorders. The children were born about 3 years before unification and were therefore exposed to western living conditions only after the third birthday. Thus, factors operating very early in life may be particularly important for the acquisition of childhood asthma, whereas the development of atopic sensitisation and hay fever may also be affected by environmental factors occurring beyond infancy.

Prevalence of allergy in children in relation to prior BCG vaccination and infection with atypical mycobacteria

By influence on the Th1/Th2 cell balance, infectious agents may affect the development of atopic allergy. In this study, we investigated whether previous BCG vaccination or infection with atypical mycobacteria might be related to the development of atopic disease. The study, which involved skin testing with mycobacteria and answers to a questionnaire for more than 6000 children in Sweden, revealed a low prevalence of allergy among BCG-vaccinated children who were immigrants or adopted from other countries. Vaccinated children born in Sweden, however, did not have significantly lower allergy prevalence than age-matched, unvaccinated children. Furthermore, the overall frequencies of skin-test reactivity to the atypical mycobacteria M. avium and M. scrofulaceum were higher rather than lower in allergic than in nonallergic children. By contrast, there was a tendency toward a lower frequency of more strongly positive skin reactions (> or = 10 mm) to mycobacteria in allergic than in nonallergic children. These findings do not support the hypothesis that early mycobacterial infections have a suppressive effect on the development of atopic disease. Earlier findings of an apparent association between atopy and lack of previous mycobacterial infection may possibly be explained by a relatively decreased ability of atopic patients to mount strong Th1 cell-mediated immune responses.

Asthma, type-1 allergy and related conditions in 7- and 8-year-old children in northern Sweden: prevalence rates and risk factor pattern

As a first step in an intervention study of asthma and allergic diseases among school children, a cross-sectional study was performed during Winter 1996 in three towns (Kiruna, Luleå and Piteå) in the northernmost province of Sweden, Norrbotten. The cross-sectional study aimed to measure the prevalence of asthma, type-1 allergy and allergic diseases in order to make it possible to measure the incidence of the diseases, conditions and symptoms related to the diseases. Another aim was to perform a screening for possible risk factors. All children enrolled in the first and second classes at school, 7 and 8 years old, were invited to take part in this study. The ISAAC questionnaire with added questions about symptoms, morbidity, heredity and environment was distributed by the schools to the parents. The response rate was 97%, and 3431 completed questionnaires were returned. The children in two of the municipalities were also invited to skin test, and 2149 (88%) were tested with 10 common airborne allergens. The results showed that 7% of the children were currently using or had used asthma medicines during the last 12 months. Six percent had asthma diagnosed by a physician, and 4% were using inhaled corticosteroids. The prevalence of wheezing during the last 12 months was 12%, rhinitis without colds 14%, and eczema 27%, while 21% had a positive skin test. The respiratory symptoms and conditions were significantly greater in boys and, further, they were most prevalent in Kiruna in the very north, though not significantly. Type-1 allergy and asthma had different risk factor patterns. The main risk factors for asthma were a family history of asthma (OR = 3.2) followed by past or present house dampness (OR = 1.9), male sex (OR = 1.7) and a smoking mother (OR = 1.6). In Kiruna, when none of these three risk factors were present, none of the children had asthma, but when all three were present, 38% of these children were using asthma medicines.

Age-dependent differences in the prevalence of allergic rhinitis and atopic sensitization between an eastern and a western German city

Recent studies have found a higher prevalence of allergic rhinitis and atopic sensitization among adults living in eastern than those living in western Germany. We hypothesize that prevalence rates were similar before Germany was divided and diverged after the division. Because there are no historical data comparing atopic status between the two parts of Germany, we tested this hypothesis by comparing the prevalence of atopy among persons who were born during different decades. As part of the EC Respiratory Health Survey, a respiratory health questionnaire was mailed to a population-based sample of 8363 subjects aged 20-44 years from a city in the former West Germany (Hamburg) and a city in the former East Germany (Erfurt). Of the target population, 6428 (77%) subjects responded. Subsamples of 731 subjects from Erfurt and 1159 subjects from Hamburg participated in medical examinations, including skin prick tests and specific IgE measurements. Prevalence rates of allergic sensitization were similar in Hamburg and Erfurt for those born in the periods 1946-51 and 1952-61, respectively, but differed between Hamburg and Erfurt subjects born in the period 1962-71. After adjustment for several potential predictors, the younger subjects from Hamburg had a higher odds ratio (OR) of sensitization than those Hamburg subjects born before 1952 (skin prick test reactivity: OR 2.06, any specific IgE > 0.35 kU/l: OR 1.61). The younger subjects from Erfurt were not more frequently sensitized than the older subjects (skin prick test reactivity: OR 1.05, any specific IgE > 0.35 kU/l: OR 0.79). No single allergen could be identified as responsible for the observed difference. We conclude that factors related to a "Western lifestyle", which were prevalent in the West German city during the 1960s and 1970s, may be responsible for the higher prevalence of allergic sensitization observed in Hamburg.

Worldwide variations in prevalence of symptoms of allergic rhinoconjunctivitis in children: the International Study of Asthma and Allergies in Childhood (ISAAC)

BACKGROUND

As part of the International Study of Asthma and Allergies in Childhood (ISAAC), prevalence surveys were conducted among representative samples of school children from locations in Europe, Asia, Africa, Australia, North and South America.

SUBJECTS

257,800 children aged 6-7 years from 91 centres in 38 countries, and 463,801 children aged 13-14 years from 155 centres in 56 countries.

METHODS

Written symptom questionnaires were translated from English into the local language for self-completion by the 13-14-year-olds and completion by the parents of the 6-7-year-olds. Rhinitis was described as a problem with sneezing, or a runny, or blocked nose when you (your child) DID NOT have a cold or the flu. Additional questions were asked about rhinitis associated with itchy-watery eyes, interference with activities and a history of hay fever ever.

RESULTS

The prevalence of rhinitis with itchy-watery eyes ("rhinoconjunctivitis") in the past year varied across centres from 0.8% to 14.9% in the 6-7-year-olds and from 1.4% to 39.7% in the 13-14-year-olds. Within each age group, the global pattern was broadly consistent across each of the symptom categories. In centres of higher prevalence there was great variability in the proportion of rhinoconjunctivitis labelled as hay fever. The lowest prevalences of rhinoconjunctivitis were found in parts of eastern Europe, south and central Asia. High prevalences were reported from centres in several regions.

CONCLUSION

These results suggest substantial worldwide variations in the prevalence and labelling of symptoms of allergic rhinoconjunctivitis which require further study. These differences, if real, may offer important clues to environmental influences on allergy.

Food allergy and intolerance: an international chemical safety perspective

Chemical safety is concerned with the assessment of human health (and environmental) risks and their management. The safety of chemicals in food, present as normal constituents, intentional additives, contaminants or residues is part of chemical safety. Morbidity and mortality due to allergenic chemicals and allergic hypersensitization are being addressed on a global basis. As part of this, international efforts are being made to establish the prevalence of respiratory and dermal allergies in all countries and it is timely to extend this to food allergies. A number of international organizations are involved in the assessment of chemical risk and risk management. Information exchange is a vital part of these processes. The International Programme on Chemical Safety is an example of a cooperative programme of three organizations with close links and coordination with other bodies and organizations concerned with safe and sustainable use of chemicals.

The development of atopic sensitization in Estonian infants

In a prospective study, 251 infants were followed from birth up to 12 months of age, recording manifestations of allergy by questionnaires at 3, 6, 9 and 12 months and by clinical examinations at 6 and/or 12 months. Blood samples were obtained at birth and at 6 and 12 months and analysed for serum IgE levels. The children were skin-prick tested with foods at 6 and 12 months of age and with inhalant allergens at 12 months. Blood samples from SPT-positive individuals and controls were analysed for the presence of IgE antibodies to common inhalant allergens and their cord sera for the presence of IgE antibodies to cow's milk and egg. Twelve infants (7%) were sensitized against foods [3 to cow's milk (CM) and 9 to egg white (EW)] at 6 months and 11 (5%) (2 to CM and 9 to EW) at 12 months. Seventeen infants (7%) had IgE antibodies against inhalant allergens at 6 and/or 12 months, as determined by either SPT and/or the demonstration of circulating IgE antibodies. Out of 30 children with positive SPT and/or circulating IgE antibodies against foods and inhalant allergens at any age, 6 had atopic dermatitis, 4 gastrointestinal food allergy, 1 urticaria and 4 probable allergy, while 15 had no clinical manifestation of allergy. Immunoglobulin E antibodies against Ascaris were detected in 17% of the infants with S-IgE levels > 20 kU/l. The study indicates that the incidence of sensitization and manifestations of allergic disease is similar among Estonian and Scandinavian infants during the first year of life. Given earlier findings indicating a significantly higher prevalence of atopic disease in Scandinavian school-children relative to their counterparts in Eastern Europe, the present study suggests that the key events which determine disease expression do not occur exclusively during the first year of life.

Correlation between Epstein Barr virus antibodies, serum IgE and atopic disease

It is currently accepted that viral infections may influence the development of atopy. In the present study we evaluated serum IgE levels as well as the prevalence of symptoms indicative of atopic disease and EBV antibodies in 353 children aged from 1 month to 19 years. Antibodies against EBV were detected by immunofluorescence. IgE levels in serum were measured by enzyme immunoassay. Dividing the study population according to EBV seropositivity and age, we noted that the prevalence of high IgE levels (> 2 s.d.) was, in total, more frequent in the EBV negative (32.9%) than in the positive subjects (27.6%). Interestingly, this higher prevalence was found only in the groups aged under six, especially in the 7 to 29 month group, where it was statistically significant (p=0.037), whereas in the 6-19 year group the situation was reversed. Furthermore, selecting only the atopic children younger than 3 years of age with high IgE levels and clinical symptoms of atopy (wheezing and/or dermatitis) it was possible to demonstrate lower EBV seropositivity compared with the normal IgE controls for each group, even though these differences were not statistically significant. In conclusion, the results of our study suggest that, in our selected population, EBV infection in the first years of life is associated with a lower prevalence of high IgE levels.

Childhood antecedents of adult respiratory disease

This review examines the relations between early childhood lower respiratory symptoms and adult respiratory disease. The problems associated with investigating potential associations between respiratory disease in children and adults are discussed. Some studies have limitations because they are retrospective and early childhood respiratory symptoms have not been accurately diagnosed. Therefore, in this review, particular attention is paid to longitudinal studies (some from birth) that have used strict diagnostic criteria for respiratory episodes. These studies provide unique insights into the risk factors for the development of childhood respiratory problems and for persistence of symptoms into adulthood. Although cross-sectional studies have indicated that early childhood respiratory disease is more frequent in adults with respiratory disease, evidence from longitudinal studies suggests that respiratory symptoms such as wheezing, are transient in the majority of infants and result from developmentally small airways. These longitudinal investigations have also indicated that persistence of symptoms into later childhood is associated with atopy. The important role of cigarette-smoke exposure as a risk factor for abnormal pulmonary development, persistence of respiratory disease and reduction in lung function is discussed. The discovery of genetic markers associated with respiratory syndromes such as asthma, should facilitate studies that investigate the childhood antecedents of adult respiratory disease. Future longitudinal studies using genetic markers, will allow relations between specific genotypes and phenotypic outcomes to be examined.

Evidence for the increase in asthma worldwide

This chapter reviews the evidence that asthma is increasing and that changes in exposure to environmental risk factors may explain the increase. Although asthma is difficult to define for epidemiological studies, the prevalence of asthma as measured by the questionnaire definitions 'asthma ever diagnosed' and 'wheeze ever' is large and increasing. In all countries where serial studies using the same methods have been undertaken over the last 20 years, an increase in wheezing illness in children and adolescents has been recorded but there are insufficient data to determine whether the disease is increasing in adults. Despite the recorded increases, there remains a large difference in the prevalence of asthma between populations, with high rates of wheezing illness in Australasia and low rates in villages in poor countries. The male to female ratio for the occurrence of asthma remains at about 1.5 in children, 1.0 in late adolescence and less than 1.0 in adults, when more females than males have symptoms. The risk factors for childhood asthma are atopy (positive skin tests), parental asthma, allergen load, respiratory infections, some aspects of diet and an 'affluence' factor. There is some evidence for an increase in the prevalence of atopy in children but this may be due to earlier acquisition of atopy. Changes in the other risk factors have not been documented. The evidence for changes in indoor allergen loads, in diet, in the severity and nature of respiratory infections, and in 'affluence' is indirect and comes from a number of small studies rather than from serial epidemiological studies. It seems unlikely that a single, environmental risk factor has changed dramatically worldwide. Rather, a number of lifestyle changes may have combined to cause the disease to be expressed in children who, in previous times, were immunologically protected from developing asthma, perhaps by their T helper cell phenotype, or were not exposed to high allergen levels.

Epidemiology of pollution-induced airway disease: urban/rural differences in East and West Germany

The prevalence of asthma and allergic disorders was assessed in 9-11 year-old children in Leipzig and Halle in East Germany, as well as in Munich, West Germany. Both East German cities are heavily polluted due to private burning of coal and industrial emissions, while Munich has low smoke emissions but heavy road traffic. All fourth grade pupils in Munich were compared with those in Leipzig and Halle. Non-specific airway disease (bronchitis), cough, and autumn/winter nasal symptoms were most prevalent in Leipzig and Halle. Hay fever and skin test reactivity to aeroallergens were higher in West Germany compared with East Germany. Furthermore, the prevalence of asthma was also higher in the West German study area. Increased skin prick test reactivity in the West explained the increased prevalence of asthma. Longitudinal analysis showed increased respiratory symptoms on days with high mean levels of sulphur dioxide and oxides of nitrogen, as well as on days with a high peak level of 10 mu respirable particles (PM10) in East Germany. The effects of these pollutants were additive. Exposure to heavy road traffic in Munich was related to decreased pulmonary function and non-specific airway symptoms, but not to allergic sensitization and asthma.