Lennart Bråbäck

Atopic sensitization and respiratory symptoms among Polish and Swedish school children

Allergic sensitization and symptoms from the airways in relation to air pollution were compared in 10–12‐year‐old school children (n= 1113) from urban Konin in central Poland and both urban and rural parts of Sundsvall in northern Sweden. The measurements included parental questionnaires, skin‐prick tests and serial peak flow measurements during 2 weeks with simultaneous monitoring of outdoor air pollutants. The skin‐prick test technique was validated by IgE antibody determinations. The levels of common industrial pollutants, SO2 and smoke particles were much higher in Konin than in urban Sundsvall and the levels of NO2 were similar. Various respiratory symptoms were more often reported among school children in Konin (except for wheezing and diagnosed asthma). Multiple logistic regression analyses yielded the following increased odds ratios for children in Konin as compared with the reference group (rural Sundsvall): chest tightness and breathlessness 348 (95% confidence interval 2.08–5.82), exercise‐induced coughing attacks 3.69 (95% confidence interval 1.68–8.10), recurrent episodes of common cold 2.79 (95% confidence interval 1.53–5.09) and prolonged cough 4–89 (95% confidence interval 2.59–9.23). In contrast, as compared with rural Sundsvall, the adjusted odds ratio for a positive skin‐prick test was decreased in Konin, but increased in urban Sundsvall, 0.58 (95% confidence interval 0.37–0.91) and 1.67 (95% confidence interval 1.15–2.42) respectively. The study confirms that living in urban, as compared with rural areas, is associated with an increased prevalence of respiratory symptoms and sensitization to allergens. These differences could be explained by air pollution. Respiratory symptoms were more common in a similar urban group of Polish children who were exposed to even higher levels of air pollution. These children, however, had a much lower prevalence of sensitization to allergens, as compared with the Swedish children. This indicates that differences in lifestyle and standard of living between western Europe and a former socialist country influences the prevalence of atopy.

Risk factors for respiratory symptoms and atopic sensitisation in the Baltic area.

Recent studies have indicated that atopic sensitisation is uncommon while respiratory symptoms are common among schoolchildren in Eastern Europe. Risk factors for respiratory symptoms and atopic sensitisation were evaluated in a cross sectional study involving 2594 schoolchildren (10-12 years) from Sweden (n = 665), Poland (n = 410), and Estonia (n = 1519). The measurements included parental questionnaires and skin prick tests with eight standardised allergens. Multiple logistic analyses demonstrated that atopic heredity was a significant independent risk factor for respiratory symptoms and atopic sensitisation in all the countries. Current dampness and maternal smoking were related to respiratory symptoms whereas domestic crowding, male gender, and passive smoking during infancy were related to atopic sensitisation. Current maternal smoking had a strong dose response association with current coughing attacks (nocturnal cough > 4 weeks or exercise induced coughing attacks) but only in Eastern Europe. A strong inverse relationship was recorded between domestic crowding and sensitisation as the risk for sensitisation increased with decreasing number of persons per room in the household (odds ratio (OR) 0.58, 95% confidence interval (CI) 0.43 to 0.77). Exposure to tobacco smoke at home during infancy was a risk factor for atopic sensitisation but only to animal dander and only in Eastern Europe (OR 1.41, 95% CI 1.03 to 1.93). In conclusion, there were small differences in the pattern of risk factors between Eastern and Western Europe. The only exception was environmental tobacco smoke being a risk factor only in Eastern Europe. The study also suggests that factors related to domestic crowding protect against atopic sensitisation in Estonia and Poland. A higher standard of living with less crowding may give rise to an increasing prevalence of atopic sensitisation also in Eastern Europe.

Trends in asthma, allergic rhinitis and eczema among Swedish conscripts from farming and non-farming environments. A nationwide study over three decades

Background Asthma and allergies are less common in children who have been raised in farming environments.

Does traffic exhaust contribute to the development of asthma and allergic sensitization in children : findings from recent cohort studies.

The aim of this review was to assess the evidence from recent prospective studies that long-term traffic pollution could contribute to the development of asthma-like symptoms and allergic sensitization in children. We have reviewed cohort studies published since 2002 and found in PubMed in Oct 2008. In all, 13 papers based on data from 9 cohorts have evaluated the relationship between traffic exposure and respiratory health. All surveys reported associations with at least some of the studied respiratory symptoms. The outcome varied, however, according to the age of the child. Nevertheless, the consistency in the results indicates that traffic exhaust contributes to the development of respiratory symptoms in healthy children. Potential effects of traffic exhaust on the development of allergic sensitization were only assessed in the four European birth cohorts. Long-term exposure to outdoor air pollutants had no association with sensitization in ten-year-old schoolchildren in Norway. In contrast, German, Dutch and Swedish preschool children had an increased risk of sensitization related to traffic exhaust despite fairly similar levels of outdoor air pollution as in Norway. Traffic-related effects on sensitization could be restricted to individuals with a specific genetic polymorphism. Assessment of gene-environment interactions on sensitization has so far only been carried out in a subgroup of the Swedish birth cohort. Further genetic association studies are required and may identify individuals vulnerable to adverse effects from traffic-related pollutants. Future studies should also evaluate effects of traffic exhaust on the development and long term outcome of different phenotypes of asthma and wheezing symptoms.

Social class in asthma and allergic rhinitis: a national cohort study over three decades

The aim of this study was to assess whether the association with social class differed between allergic rhinitis and asthma and whether these associations have changed over time. The Swedish Military Service Conscription Register was linked to two other national registers for 1,247,038 male conscripts in successive cohorts born between 1952 and 1977. The percentage of asthma cases associated with allergic rhinitis was 15% in the oldest cohort and 44% in the youngest cohort. Low socio-economic status (SES) was associated with an increased risk (assessed as odds ratio) of asthma without allergic rhinitis (1.14, 95% confidence interval (CI) 1.11–1.17) but a slightly reduced risk of asthma with allergic rhinitis (0.96, 95% CI 0.93–1.00). The risk of allergic rhinitis was 0.84, 95% CI 0.82–0.85. A positive interaction between SES and year of birth occurred in all three conditions. Low SES was related to a reduced risk of asthma with allergic rhinitis in the earliest cohort (0.72, 95% CI 0.53–0.82) but a slightly increased risk in the most recent cohort (1.07, 95% CI 1.01–1.14). In conclusion, the role of social class has changed over time. The steepest increase in asthma and allergic rhinitis occurred in conscripts with a low socio-economic status.

How well do questionnaires perform compared with physical examination in detecting flexural eczema? Findings from the International Study of Asthma and Allergies in Childhood (ISAAC) Phase Two

Background  Questionnaires are widely used in epidemiological studies to measure eczema symptom prevalence, but there are concerns regarding their accuracy if used as a diagnostic tool.

Atopy among schoolchildren in northern and southern Sweden in relation to pet ownership and early life events.

Studies have suggested a higher prevalence of asthma and allergies in northern, as compared to southern, Scandinavia. The aim of this study was to evaluate regional differences in atopy in relation to pet ownership and certain early life events among schoolchildren (n = 2108) aged 10–11 years from Linköping in southern Sweden and Östersund in northern Sweden. The parents completed a questionnaire, comprising questions on home environment, heredity, socio‐economic conditions, and the core questions on symptoms from the International Study of Asthma and Allergies in Childhood. The children were skin‐prick tested to eight common inhalant allergens. Information on maternal smoking habits, gestational age, and anthropometric measures were obtained from the Swedish Medical Birth Registry. The prevalence of atopic symptoms and sensitization to pollen were similar in Östersund and in Linköping. A higher prevalence of sensitization to animal dander among children in Östersund could be linked to a higher occurrence of pets in the community. Current cat ownership was related to less sensitivity to cat allergen but only in children with an atopic heredity. Ponderal index > 30 kg/m3 was related to an increased risk of atopic sensitization, both in Linköping (adjusted odds ratio 2.1; 95% confidence interval 1.1–4.0) and in Östersund (adjusted odds ratio 2.0; 95% confidence interval 1.1–3.5). Maternal smoking during pregnancy was related to an increased risk of atopic sensitization among children in Linköping, whereas current smoking was associated with a decreased risk of sensitization in Östersund. In conclusion, we demonstrated that a high occurrence of pets in the community was associated with sensitization, whereas atopic symptoms were essentially unaffected. This study has also suggested an association between body size at birth and atopic sensitization at 10–11 years of age.

Effect of breastfeeding on asthma, lung function and bronchial hyperreactivity in ISAAC Phase II

The association between breastfeeding and wheezing, lung function and atopy was evaluated in the International Study of Asthma and Allergy in Childhood (ISAAC) Phase II. Cross-sectional studies were performed in 27 centres in 20 countries. Information on disease and exposure factors was collected by parental questionnaires. Data from 54,000 randomly selected school children (aged 8–12 yrs, 31,759 with skin prick testing) and a stratified subsample (n = 4,888) were used for testing the correlation of breastfeeding with bronchial hyperreactivity and lung function. Random effect models for meta-analysis were applied to calculate combined odds ratios (ORs). Any breastfeeding was associated with less wheeze both in affluent (adjusted OR (ORadj) 0.87, 95% confidence interval (CI) 0.78–0.97) and nonaffluent countries (ORadj 0.80, 95% CI 0.68–0.94). Further analyses revealed that this was true only for nonatopic wheeze in nonaffluent countries (ORadj 0.69, 95% CI 0.53–0.90). Breastfeeding was not associated with atopic wheeze and objective measures of allergy in both affluent and nonaffluent countries. In contrast, breastfeeding was associated with higher predicted forced expiratory volume in one second in affluent countries only (mean ratio 1.11, 95% CI 1.02–1.20). Breastfeeding is associated with protection against nonatopic wheeze, which becomes particularly evident in nonaffluent countries. Overall, breastfeeding was not related to any measure of allergy. These findings may explain some of the controversy regarding breastfeeding, since the direction of the association with breastfeeding depends on the predominating wheeze phenotype (e.g. atopic, nonatopic).

High body mass index, asthma and allergy in Swedish schoolchildren participating in the International Study of Asthma and Allergies in Childhood: Phase II

Aim: To assess the relationship between high body mass index (BMI) and asthma and atopic manifestations in 12‐y‐old children. Methods: The relationship between high BMI and asthma symptoms was studied in 457 sixth‐grade children, with (n= 161) and without (n= 296) current wheeze. High BMI was defined as ±75th percentile of gender‐specific BMI reference values for Swedish children at 12 y of age; overweight as a subgroup of high BMI was defined as ±95th percentile. Children with a BMI >75th percentile served as controls. Questionnaires were used to assess asthmatic and allergic symptoms, and bronchial hyperresponsiveness was assessed by hypertonic saline provocation tests. Results: Current wheeze was associated with high BMI after adjustment for confounding factors (adjusted OR 1.7, 95% CI 1.0–2.5) and overweight had an even more pronounced effect (adjusted OR 1.9, 95% CI 1.0–3.6). In addition, asthma severity was associated with high BMI, as evaluated by the number of wheezing episodes during the previous 12 mo among the wheezing children (adjusted OR 2.0, 95% CI 1.0–4.0). There was also an association between high BMI and the presence of eczema in wheezing children (adjusted OR 2.2, 95% CI 1.0–4.6). However, high BMI was not significantly associated with hay fever, positive skin prick tests or bronchial hyperresponsiveness.

Wheezing in relation to atopy and environmental factors in Estonian and Swedish schoolchildren.

Background The prevalence of asthma and allergic diseases is significantly lower in post socialist Eastern Europe than in Western industrialized countries. The reason for this difference is largely unknown. Different types of childhood wheezing could be related to different risk factors.