Nils Åberg

Does early exposure to cat or dog protect against later allergy development

It is unknown which factors in modern western society that have caused the current increase in prevalence of allergic diseases. Improved hygiene, smaller families, altered exposure to allergens have been suggested.

Increase of asthma, allergic rhinitis and eczema in Swedish schoolchildren between 1979 and 1991

Background: A previous study has shown a twofold increase in prevalence of asthma and allergic rhinitis (AR) in Swedish recruits during the 1970s. The increase was higher in more northerly colder regions.

Asthma and allergic rhinitis in Swedish conscripts.

The computer records of Swedish conscript examinations in 1971 and 1981 were analysed regarding the prevalence of asthma and allergic rhinitis. The material comprised ∼ 55 000 18‐year‐old males in each cohort. During the 10‐year period the prevalence of asthma increased from 1.9 to 2.8% and of allergic rhinitis from 4.4 to 8.4%. The prevalence of allergic rhinitis was already higher in the northern than in the southern part of the country in 1971. The increase in both diseases was higher in the northern parts of Sweden, giving double prevalence figures in the northern part of the country compared to the southern part in 1981. The distribution of the prevalence was similar to the temperature pattern in the country, the higher prevalence being associated with a colder outdoor climate. Both diseases were more prevalent in urban than in rural areas.

Reduced enterobacterial and increased staphylococcal colonization of the infantile bowel: an effect of hygienic lifestyle?

The modern Western lifestyle may have altered the composition of the commensal microflora. Here, we investigated the first years intestinal colonization pattern in 99 vaginally delivered Swedish infants and 17 delivered by cesarean section. Rectal swabs obtained at 3 d of age were cultured for aerobic bacteria and fecal samples obtained at 1, 2, 4, and 8 wk and at 6 and 12 mo of age were cultivated quantitatively for aerobic and anaerobic bacteria. Vaginally delivered infants more often had Escherichia coli compared with cesarean section–delivered infants, whereas the latter more frequently carried other enterobacteria, such as Klebsiella and Enterobacter. Independent of delivery mode, it took 2 mo until most infants were colonized by enterobacteria, traditionally the first colonizers. In contrast, coagulase-negative staphylococci colonized 99% of the infants from d 3 onwards. The poor adaptation of staphylococci to the gut was shown by declining population sizes after some weeks. Dominating anaerobes were initially bifidobacteria and clostridia, whereas Bacteroides initially colonized only 30% of vaginally delivered infants and increased very slowly in prevalence. Bacteroides colonization was delayed up to 1 y in cesarean section–delivered compared with vaginally delivered infants. Our results show that some “traditional” fecal bacteria are acquired late today especially in cesarean section–delivered infants, probably due to limited environmental circulation. In their absence, skin bacteria like staphylococci have become the first gut colonizers.

Escherichia coli in Infants' Intestinal Microflora: Colonization Rate, Strain Turnover, and Virulence Gene Carriage

Colonization by Escherichia. coli in infants might have decreased in the last decades, owing to changes in hospital routines and family lifestyle. In this study, the E. coli flora was characterized in 70 healthy Swedish infants followed for the first year of life. E. coli was isolated from rectal swabs obtained at 3 d of age and quantified in fecal samples collected at 1, 2, 4, and 8 wk of age and at 6 and 12 mo of age. Strains were typed using random amplified polymorphic DNA, and their virulence factor genes were identified by multiplex PCR. Colonization by E. coli occurred late; only 61% of the infants were positive by 2 mo of age. The turnover of individual strains in the microflora was slow (1.5 strains per infant during 6 mo, 2.1 during 1 y). Environmental factors, such as siblings, pets, or feeding mode, did not influence colonization kinetics or strain turnover rate. Genes encoding type 1 fimbriae, P fimbriae, and hemolysin were significantly more common in E. coli strains persisting for at least 3 wk in the microflora than in transient strains. The P-fimbrial class III adhesin gene was more common in E. coli from children who had a cat in their homes than in E. coli from children without pets (p = 0.01); this adhesin type is common in E. coli from cats. The late colonization and low E. coli strain turnover rate suggest limited exposure of Swedish infants to E. coli. Our results confirm that P fimbriae and other virulence factors facilitate persistence of E. coli in the human colonic microflora.

Allergic Diseases in Swedish School Children

ABSTRACT. The occurrence of allergic diseases in children was studied on the basis of a questionnaire sent to the parents of 20000 school children, 7, 10 and 14 years of age, in 3 parts of Sweden with different climatic conditions. The prevalence of asthma was 2.4%, allergic rhinocon‐junctivitis 7.4%, eczema 7.8% and total allergic diseases 16.9%. The prevalence of all diseases was significantly higher in the northern part of the country than in the southern parts. This geographic variation was not related to heredity, infant feeding pattern or known exposure variables other than the cold and dry climate. Parental history of allergic diseases increased the incidence in the offspring 2–9 times, with a pattern of symptom specificity and a cumulative effect of double parental history. Breast‐feeding postponed the onset of allergic disease only in children with double parental history.

Prevalence of allergic diseases in schoolchildren in relation to family history, upper respiratory infections, and residential characteristics

The prevalences of asthma, allergic rhinitis (AR), and eczema were analyzed in relation to retrospective risk factors from birth in a questionnaire study of schoolchildren in two areas covering the whole climatic span of Sweden: the Göteborg area on the southwestern coast (7‐year‐olds, n= 1649) and Kiruna, a mining town in the northernmost inland mountains (7–9‐year‐olds, n= 832). The strongest background factor, a family history of the diseases, was more common in children with another strong risk factor, particularly for asthma: high frequency of upper respiratory tract infection (URTI). Other significant risk factors related to high indoor humidity caused an increased prevalence of both allergic diseases and URTI. Active mechanical ventilation of the homes caused a slight reduction of the prevalence of allergic diseases, and repainting or new wallpaper in the bedroom of the child after birth caused a moderately increased risk of allergic disease. This study illustrates the interaction between genetic and environmental risk factors with special emphasis on factors related to an unventilated indoor climate, which may have substantially contributed to the current increase of the diseases in the country.

Neonatal Antibiotic Treatment Is a Risk Factor for Early Wheezing

OBJECTIVE. The use of antibiotics in infancy and subsequent changes in the intestinal bacterial flora have been discussed as risk factors for the development of asthma. However, it has been difficult to exclude the possibility that antibiotics have been given in early episodes of wheezing. As a result, there has been a risk of reverse causation. To minimize the risk of reverse causation, we have focused on the effect of antibiotics that are already administered on the neonatal ward. METHODS. In a cohort study of infants born in western Sweden in 2003, we studied the development of wheezing. The families of the infants were randomly selected and sent a questionnaire at child ages 6 and 12 months. The response rate was 68.5% to the 6-month questionnaire and 68.9% to the 12-month questionnaire. RESULTS. At 12 months, 20.2% of infants had had 1 or more episodes of wheezing, and 5.3% had had 3 or more episodes. Inhaled corticosteroids had been taken by 4.1% of the infants. Independent risk factors for wheezing disorder treated with inhaled corticosteroids were neonatal antibiotic treatment, male gender, gestational age of <37 weeks, having a mother with asthma, having a sibling with asthma or eczema, and breastfeeding for <5 months. CONCLUSIONS. Treatment with antibiotics in the neonatal period was an independent risk factor for wheezing that was treated with inhaled corticosteroids at 12 months of age. These results indirectly support the hypothesis that an alteration in the intestinal flora can increase the risk of subsequent wheezing.

Early introduction of fish decreases the risk of eczema in infants

Background: Atopic eczema in infants has increased in western societies. Environmental factors and the introduction of food may affect the risk of eczema. Aims: To investigate the prevalence of eczema among infants in western Sweden, describe patterns of food introduction and assess risk factors for eczema at 1 year of age. Methods: Data were obtained from a prospective, longitudinal cohort study of infants born in western Sweden in 2003; 8176 families were randomly selected and, 6 months after the infant’s birth, were invited to participate and received questionnaires. A second questionnaire was sent out when the infants were 12 months old. Both questionnaires were completed and medical birth register data were obtained for 4921 infants (60.2% of the selected population). Results: At 1 year of age, 20.9% of the infants had previous or current eczema. Median age at onset was 4 months. In multivariable analysis, familial occurrence of eczema, especially in siblings (OR 1.87; 95% confidence interval (CI) 1.50 to 2.33) or the mother (OR 1.54; 95% CI 1.30 to 1.84), remained an independent risk factor. Introducing fish before 9 months of age (OR 0.76; 95% CI 0.62 to 0.94) and having a bird in the home (OR 0.35; 95% CI 0.17 to 0.75) were beneficial. Conclusions: One in five infants suffer from eczema during the first year of life. Familial eczema increased the risk, while early fish introduction and bird keeping decreased it. Breast feeding and time of milk and egg introduction did not affect the risk.

Day care attendance and increased risk for respiratory and allergic symptoms in preschool age

Background:  The reported impact of day‐care attendance on respiratory and atopic symptoms has varied between studies from different countries. Regarding to the ‘hygiene‐hypothesis’, day‐care attendance may lead to less sensitization later in life, but the question still is whether day‐care attendance and subsequent exposure to more frequent early infections is a risk or a protection against future allergic disease or asthma (atopic and nonatopic).