S. Lennart Nordvall

The BAMSE Project: presentation of a prospective longitudinal birth cohort study

The aims of this prospective and longitudinal project are to establish crucial risk factors for asthma and other allergic diseases in childhood, and to study factors of importance for prognosis at already established allergic disease. Socio‐economic factors, such as inequality in health, are also to be addressed. The project started in February 1994. To reach sufficient power, 4,000 children had to be included. In November 1996, this number was reached (4,093). Inclusion in the study was made at 3–4 months of age. At that time, and before induction of allergic disease/asthma of the child, a questionnaire focused on exposure, genetics and socio‐economic factors was answered. Settled dust was sampled for later analysis of furred animal and mite allergens. When the children were aged both 1 and 2 years, their parents were asked to fill in new questionnaires focusing on respiratory and allergic (skin, gastrointestinal) symptoms, but also key variables of exposure. Cases with asthma are identified and, for every case, two matched controls drawn. During the following winter, the homes of cases and controls were investigated and the temperature, indoor humidity, air change rate and NO2 measured. Two hundred cases (5%) were expected to be identified during the first 2 years of the childrens lives. Some 479 homes have now been investigated and 97.7% of the original 4,093 children still remain in the cohort. The 2‐year symptom follow‐up ended in November 1998. The 4‐year follow‐up started on 1 September 1998 and was planned to be finished in June 2000. Questionnaires (allergic and respiratory symptoms, key variables of exposure at home and day care) are sent out to all 4,093 families. All children are invited for examination, lung function tests (PEF, flow‐volume, MVV and oxygen clearance) and physical performance. Blood is taken from all children (20 ml). Allergy screening is performed and specific IgE examined. Blood cells will be frozen to allow for later DNA extraction. In subsets (children with any allergic and/or respiratory manifestation and controls), markers of inflammation in blood and urine will be examined, as well as eosinophils in nasal smear. Interviews are carried out to assess the severity of asthma, type/periodicity of health care given, asthma medication and parental sick leave when appropriate. As a separate project, financed by the EU, outdoor pollution as risk factors for asthma and allergies are to be studied within the BAMSE cohort. A follow‐up of 8–9 years is underway.

House dust mite sensitization in children and residential characteristics in a temperate region

House dust mite (Hdm) infestation used to be rare in Stockholm, but Hdm-sensitized children are now frequently observed, which probably indicates an increased infestation rate. This study was performed to elucidate determinants of Hdm sensitization in children living in the area. In a case-control study, 53 Hdm-sensitized children (cases), a group of non-Hdm-sensitized atopic children (N = 54), and a group of nonallergic neighborhood children (N = 53) were included. Mattress dust was analyzed with ELISA for content of Hdm allergens. Indoor humidity and temperature were measured, and questionnaire data were collected. Asthma was significantly more common in the Hdm-sensitized group than in the atopic control group. Hdm allergens were found in 40%, 19%, and 23% of the dust samples of the case group, atopic group, and neighborhood control groups, respectively. Only 15% of the dust samples of the Hdm-sensitized children contained Hdm allergens above the recommended threshold levels of sensitization of 2000 ng/gm of dust. Inadequate ventilation, which partly appeared to be a consequence of energy saving, appeared to be a risk factor for Hdm sensitization. This result may apply also to other temperate regions and suggests that the problem is preventable.

Influence of interaction of environmental risk factors and sensitization in young asthmatic children

BACKGROUND The increasing prevalence of asthma and allergy in many countries demands evaluation of potential risk factors to improve the possibility of prevention. OBJECTIVE We studied the association between exposure to cat and dog allergen and allergic sensitization in young children with asthma and interactions with potential environmental risk factors. METHODS One hundred eighty-nine young children with asthma were evaluated. IgE antibodies to cat and dog were analyzed. Questionnaires were filled in focusing on exposure to cats and dogs, environmental tobacco smoke (ETS), and signs of home dampness as indicated by window pane condensation (WPC) during the first years of life. House dust was analyzed for content of cat (Fel d 1) and dog (Can f 1) allergen. RESULTS There was a strong association between the degree of reported exposure to cat and dog and the concentration of the respective allergens in floor dust. A dose-response relationship was found between cat exposure, measured as either reported degree of cat exposure or cat allergen levels in dust, and sensitization both to cat and dog. No such relationship was found between exposure and sensitization to dog. WPC increased the risk for sensitization to cat (odds ratio = 2.6, 95% confidence interval 1.2-5.8), whereas ETS strongly tended to do so both to cat and dog. Interaction was found between exposure to ETS, WPC, and high levels of cat allergen (>8 microg/g dust). The presence of all 3 risk factors revealed a multiplicative interaction with a high risk of sensitization to cat (odds ratio = 42.0, 95% confidence interval 3.7-472.8). CONCLUSIONS Keeping cats indoors may be a health hazard for infants and young children at risk for development of asthma, particularly when they live in a damp house and their parents smoke.

Clinical features of atopic dermatitis at two years of age: a prospective, population-based case-control study.

While atopic dermatitis (AD) usually presents early in life, few prospective studies focus on young children with AD. The objective of this study was to characterize, phenotypically and prospectively, young children with AD. From a community birth cohort of 2,256 children, consecutive children with AD (n = 221) were followed to 2 years of age, when they were re-examined and screened for atopic sensitization (skin-prick test to foods; Phadiatop). Ninety-nine controls were also examined. AD debuted during the first year in 88% of cases. At the 2-year examination, when the children had already undergone topical treatment, 157/221 (71%) had ongoing eczema ranging among mild (45%), moderate (53%) and severe (2%). Airway problems indicating asthma had occurred in 9% of cases and 6% of controls (not significant), and allergic rhinoconjunctivitis in 5% and 0%, respectively (p<0.05). The skin-prick test to common food allergens was positive in 27% of cases and Phadiatop was positive in 15%. In 67% both tests were negative. Eczema severity did not differ between sensitized and non-sensitized children. Positive Phadiatop was more common in boys than in girls with ongoing AD (22% vs 3%, p<0.01), and more boys than girls had ongoing AD (82% vs 59%, p<0.001); otherwise, no differences attributable to gender were found.

Atopic dermatitis and concomitant disease patterns in children up to two years of age.

There are few prospective studies of atopic dermatitis and co-existing diseases such as respiratory infections in children up to 2 years of age. Using annual questionnaires, we studied the cumulative incidence of atopic dermatitis and concomitant symptoms indicating other atopic diseases and respiratory infections in 0-2-year-old children in a prospective birth cohort of 4089 children. We found associations between atopic dermatitis and asthma (ratio of proportion 1.45, 95% CI 1.16-1.80), allergic rhinoconjunctivitis (RP 2.25, CI 1.77-2.85), adverse reactions to foods (RP 3.20, CI 2.83-3.62), urticaria (RP 2.04, CI 1.80-2.31), acute otitis media (RP 1.13, CI 1.05-1.21), more than one pneumonia during the first and/or second year of life (RP 2.17, CI 1.14-4.15), and use of antibiotics at least twice yearly (RP 1.29, CI 1.07-1.56). The association between atopic dermatitis and respiratory infections persisted after stratification for asthma. There was a higher proportion of atopic disease manifestations, but not respiratory infections, in children with onset of atopic dermatitis during the first year of life than during the second. The study shows that during the first 2 years of life there is a significant association not only between atopic dermatitis and other atopic disease manifestations, but also between atopic dermatitis and respiratory infections manifested in an increased rate of acute otitis media, pneumonia and use of antibiotics.

Strategies for preventing wheezing and asthma in small children

Objective:  To assess the effects of living in agreement with allergy preventive guidelines on wheezing and asthma at 2 years of age.

Family history and risk of atopic dermatitis in children up to 4 years

Background The aetiology of atopic dermatitis (AD) is presumably multi‐factorial, with interactions between genetic and environmental factors.

Immunotherapy in children with allergic asthma : Effect on bronchial hyperreactivity and pharmacotherapy

BACKGROUND Immunotherapy has been shown to reduce allergen sensitivity to allergens such as cat and dust mite. The aim of this study was to investigate the effect of cat or dust mite immunotherapy on bronchial hyperreactivity and the need for inhaled corticosteroids in children with asthma, cat or dust mite allergy, and hay fever. SUBJECTS Twenty-nine children, 7 to 16 years old, completed the 3-year study. They were randomly allocated to receive cat/dust mite or placebo and birch/timothy immunotherapy. METHODS Before immunotherapy was begun and then once each year, bronchial histamine challenges were performed. Bronchial allergen challenge with the perennial allergen was done before and after the 3-year study. Pharmacotherapy was given according to a standardized protocol. RESULTS PC20 allergen increased significantly in both the active immunotherapy group (P <.001) and in the placebo-pollen group (P <.05). PC20 histamine increased continuously in the active immunotherapy group (P <.05 and P =.002 after 1 and 3 years, respectively) and had also increased after 3 years in the placebo-pollen group (P <.05). The difference between the 2 groups was significant for PC20 allergen (P =.001) but not for PC20 histamine. There was no significant change in the dose of inhaled budesonide needed for symptom control in either of the groups. CONCLUSION Pollen immunotherapy combined with inhaled corticosteroids results in improvement of both cat/dust mite bronchial sensitivity and hyperresponsiveness to histamine. The combination of cat or dust mite, pollen immunotherapy, and inhaled budesonide enhances this improvement. Cat immunotherapy also induces cat allergen tolerance.

Risk factors associated with allergic and non-allergic asthma in adolescents.

Introduction:  Risk factors for asthma have been investigated in a large number of studies in adults and children, with little progress in the primary and secondary prevention of asthma.