Farm environment in childhood prevents the development of allergies

BACKGROUND: A protective effect of infections in early life might explain the firmly reported finding of an inverse association between atopic disorders and large sibships. OBJECTIVE: To study the effect of childhood farm, rural non-farm and urban environment, as well as family size and other factors on the occurrence of asthma, wheezing and atopic disorders up to young adulthood. METHODS: Data on lifetime prevalence of physician-diagnosed asthma, allergic rhinitis and/or allergic conjunctivitis, atopic dermatitis, as well as self-reported episodic wheezing from 10 667 Finnish first-year university students aged 18-24 years were collected by a postal questionnaire. Associations of lifetime prevalence of the diseases with living on a farm, in a rural non-farm and urban environment during childhood were estimated by logistic regression analysis. Adjustment was made for potential confounding by gender, parental atopy, parental education, number of older siblings, day care outside the home and passive smoking. RESULTS: The childhood farm environment independently reduced the risk for physician-diagnosed allergic rhinitis and/or allergic conjunctivitis (adjusted odds ratio 0.63, 95% CI 0.50-0.79, P < 0.001), and for diagnosed asthma and episodic wheezing analysed together (OR 0.71, 95% CI 0.54-0.93, P < 0.05), but not for atopic dermatitis during lifetime. Urban childhood environment did not show independent increased risk when compared with rural non-farm residence. The inverse association of sibship size with the occurrence of allergic rhinitis and/or allergic conjunctivitis was found among subjects with one (OR 0.86, 95% CI 0.77-0.96, P < 0.01) or at least four older siblings (OR 0.47, 95% CI 0.26-0.84, P < 0.05). CONCLUSION: Childhood farm environment seems to have a protective effect against allergic rhinitis and/or conjunctivitis, and more weakly against asthma and wheezing irrespective of family size. Environmental exposure to immune modulating agents, such as environmental mycobacteria and actinomycetes, favouring manifestation of a nonatopic phenotype could explain the finding.     

A retrospective study of the relationship between childhood asthma and respiratory infection during gestation

BACKGROUND: Wheeze in children has been found to be associated with prior antepartum haemorrhage and raised levels of IgE in cord blood, and acute wheezing episodes are intimately linked with respiratory viral infections. OBJECTIVE: To assess the relationship between maternal presentation with respiratory tract infections in pregnancy and childhood asthma, taking into account factors which could affect presentation. METHODS: This was a case-control study of 200 asthmatic children, 5-16-year-old, age-matched with one control, having no recorded history of wheeze. Data on respiratory tract infections, maternal wheeze, atopy and smoking was collected from primary care records. Deprivation score was assessed according to small residential areas and subjects were equally distributed between four general practices in Plymouth, UK. RESULTS: Presentation with respiratory tract infections during pregnancy was significantly associated with childhood asthma (OR 1.69, 95% confidence interval 1.05-2.77, P = 0.03). The association was marginally stronger for infections in the first trimester (OR 2.30, 95% CI 1.05-5.41, P = 0.04) and for those with cough during pregnancy (OR 2.24, 95% CI 1.23-4.22, P = 0.007). The associations remained significant after allowing for the effect of the independent variables (gender, maternal smoking, maternal wheeze, allergic rhinitis, eczema, asthma treatment in pregnancy and deprivation [Townsend] score), using multiple logistic regression analysis (ORs and 95% CIs 1.91, 1.14-3.22; 2.32, 1.01-5.34 and 2.29, 1.17-4.48, respectively). There was also an association between numbers of presentations with respiratory infections and childhood asthma (test for trend, P = 0.02). CONCLUSIONS: This study has shown an association between presentation with respiratory infection during gestation and childhood asthma. The results were not affected by the other independent variable factors studied and therefore provide some evidence to support the theory that respiratory viruses may be implicated in the aetiology of asthma.     

Asthma, allergy and atopy in southern Chinese school students

In order to determine the prevalence of asthma, allergy and atopy in southern China and the relative importance of atopy and parental history in predicting asthma and allergic diseases, we carried out a cross-sectional study on 737 secondary school students aged 12-20(492 boys, 245 girls; mean age = 16.4 years, so = 1.8 years) in the city of San Bu, Guangdong, China. Standard questionnaires on respiratory and allergic symptoms were distributed for completion by parents with an overall response of 98.6%. Skin-prick tests to common aeroallergens were performed on 647 subjects (87.8%) to determine atopic status. The prevalence (and 95% CI) of a history of hay fever, eczema, wheeze or asthma ever and wheeze in past 12 months were 1.6% (0.7-2.5), 10.4% (8.2-12.6), 1.9% (0.9-1.9) and 1.1% (0.3-1.9) respectively. Forty-nine per cent (45.2-52.9) of students had one or more positive skin tests to common aeroallergens. Amongst atopic subjects, 87.3% reacted to house dust mite (Dermatophagoides pteronyssinus) and 73.3% to cockroach. There was a close association between the degree of atopy and the prevalence of a history of wheeze (P < 0.05) but not with hay fever or eczema. After adjusting for age and sex, parental histories of hay fever, eczema and wheeze were strongly associated with the respective symptoms in the subjects (OR = 17.4 (3.2-93.9) for hay fever, 27.4 (12.7-59.0) for eczema, 79.4 (21.9-288.4) for wheeze). It is concluded that respiratory and allergic symptoms were uncommon in Chinese school students despite a high prevalence of atopy, and that parental history is more important in predicting asthma and allergy than atopy.     

Smallpox vaccination and risk of allergy and asthma

BACKGROUND: It has been proposed that childhood vaccinations may influence the development of allergy. Atopy and allergic diseases have increased after routine smallpox vaccination was stopped in the 1970s. OBJECTIVE: We examined whether administration of smallpox vaccination during childhood was associated with a decreased risk of atopy, allergic rhinitis, and asthma. METHODS: The occurrence of atopy, allergic rhinitis, and asthma was studied in nearly 2000 women participating in a national birth cohort study. Detailed information on smallpox vaccination was available from school health records. Atopic status was assessed serologically by a specific response to 11 common inhalant allergens by using serum samples obtained from the women during the period 1997 to 2001. Information on allergic rhinitis and asthma was available from telephone interviews. RESULTS: We found no association between having been vaccinated against smallpox in childhood and risk of atopy or allergic rhinitis. Smallpox vaccination was associated with a slightly decreased risk of asthma. There was no association between age at smallpox vaccination and risk of atopy, allergic rhinitis, or asthma. Adjusting for birth cohort, sibship size, age of the woman's mother at birth, and social class in childhood did not change these results. CONCLUSION: Our findings do not suggest that childhood vaccination against smallpox, even if given early in life, influences the development of atopy or allergic rhinitis. The association with asthma should be interpreted with caution and needs further study.     

Prevalence and predictors of atopy among young Danish adults

BACKGROUND: The prevalence of atopic diseases is increasing in western countries, and environmental exposures in childhood may influence development of atopic sensitization. OBJECTIVE: To investigate the prevalence and predictors of atopy among young Danish adults. METHODS: Of 940 invited subjects, aged 19-29 years, complete data were obtained from 525 (56%) subjects. All completed a questionnaire concerning asthma, rhinitis, preschool nursery care, smoking habits, family size, education and employment. A skin prick test was performed, and pulmonary function was measured using standard techniques. Atopy was defined as a positive skin prick test. RESULTS: The frequency of atopy was 32% (males 43% vs. females 23%, P < 0.001). We found a positive association between atopy and atopic dermatitis (P < 0.05), rhinitis (P < 0.001), itching when eating nuts (P < 0.001) and current asthma (P < 0.001). There was an inverse relation between atopy and having furred pets in childhood (P < 0.05), passive smoking in childhood (P < 0.01) and current passive smoking (P < 0.05). An increasing number of siblings was inversely related to atopy to grass (P < 0.05); however, only an increasing number of older siblings seemed to protect from atopy to grass (P < 0.05). Subjects who had never attended a day-care centre had significantly more atopy to grass (P < 0.05). No significant association was found between atopy and airway infections requiring hospitalization before the age of 5 years, or between atopy and bedroom sharing in childhood. CONCLUSION: Atopy is common among young Danish adults, especially in males. Participants were less likely to be atopic, especially to grass allergen, if they came from large families, had kept furred pets as children, and had been exposed to tobacco smoke.     

Clinical atopy and associated factors in primary-school pupils

To investigate potential risk factors for clinical atopy in childhood, we obtained cross-sectional data from a cohort of 1376 8-year-old pupils. Parental atopy (hay fever, asthma, eczema), gestational age, maternal smoking habits, and the child's history of asthma, hay fever, and eczema were ascertained by questionnaire. Combining the history and the result of a skin prick test using seven aeroallergens, we defined the child's atopic diseases. Of the population evaluated, 25.4% were categorized as atopic (10.2% allergic asthma, 17.3% eczema, 6.9% hay fever). As compared with the clear nonatopics (40.2%), parental atopic diseases were more prevalent in each of the atopic groups. Significant associations of the parents' and child's disease were obvious for eczema and hay fever. Low gestational age (LGA) was more frequent in children with any atopy or with an allergic asthma (odds ratio (OR) 1.7; 95% confidence interval (CI) 1.02-2.97; OR 2.8; 95% CI 1.5-5.4). Hay fever and allergic asthma occurred less frequently in girls (OR 0.5; 95% confidence interval 0.3-0.8; OR 0.6; 95% CI 0.4-0.9). In conclusion, our data underline the importance of parental atopy for the clinical outcome in the offspring. In addition, LGA appears to be a risk factor for allergic asthma and for general atopy in later life.     

Endotoxin in inner-city homes: associations with wheeze and eczema in early childhood

BACKGROUND: An inverse association between domestic exposure to endotoxin and atopy in childhood has been observed. The relevance of this aspect of the hygiene hypothesis to US inner-city communities that have disproportionately high asthma prevalence has not been determined. OBJECTIVES: To measure endotoxin in the dust from inner-city homes, evaluate associations between endotoxin and housing/lifestyle characteristics, and determine whether endotoxin exposure predicted wheeze, allergic rhinitis, and eczema over the first 3 years of life. METHODS: As part of an ongoing prospective birth cohort study, children of Dominican and African-American mothers living in New York City underwent repeated questionnaire measures. Dust samples collected from bedroom floors at age 12 or 36 months were assayed for endotoxin. RESULTS: Among the samples collected from 301 participants' homes, the geometric mean endotoxin concentration (95% CI) was 75.9 EU/mg (66-87), and load was 3892 EU/m2 (3351-4522). Lower endotoxin concentrations were associated with wet mop cleaning and certain neighborhoods. Endotoxin concentration correlated weakly with cockroach (Bla g 2: r = 0.22, P < .001) and mouse (mouse urinary protein: r = 0.28; P < .001) allergens in the dust. Children in homes with higher endotoxin concentration were less likely to have eczema at age 1 year (odds ratio, 0.70 [0.53-0.93]) and more likely to wheeze at age 2 years (odds ratio, 1.34 [1.01-1.78]). These associations were stronger among children with a maternal history of asthma. CONCLUSION: Endotoxin levels in this inner-city community are similar to those in nonfarm homes elsewhere. In this community, domestic endotoxin exposure was inversely associated with eczema at age 1 year, but positively associated with wheeze at age 2 years. CLINICAL IMPLICATIONS: Endotoxin exposure in the inner-city community may be related to wheeze in the early life; however, given the inverse association seen with eczema, the long-term development of allergic disease is still in question.     

Defining childhood atopic phenotypes to investigate the association of atopic sensitization with allergic disease

AIMS: Although atopic sensitization is common in childhood, its relationship to clinical allergic disease remains incompletely understood. We therefore sought to explore this relationship by defining sensitization based atopic phenotypes. METHODS: Children were recruited at birth (n = 1456) and reviewed at 1, 2, 4 and 10 years. Skin prick testing (SPT) to common allergens was done at 4 (n = 980) and 10 years (n = 1036) with lung function (n = 981), bronchial challenge (n = 784) and serum IgE (n = 953) testing at 10. Atopic phenotypes were defined, by sensitization pattern, for children with SPT at both 4 and 10 years (n = 823). RESULTS: Of phenotyped children, 68.0% were never atopic, 4.3% early childhood atopic (only atopic at age 4), 16.5% chronic childhood atopics (at 4 and 10 years) and 11.2% delayed childhood atopics (only at 10). Never atopics showed small but identifiable prevalence of allergic diseases such as asthma, eczema and rhinitis. Amongst allergen-sensitized subjects, aeroallergen predominated over food sensitization throughout childhood. Chronic childhood atopics showed highest prevalence of lifetime plus persistent wheeze, eczema and rhinitis, increased prevalence of aeroallergen sensitization, some evidence of persistent food sensitization, significantly greater cord IgE than never atopics (P = 0.006), plus higher total IgE (P < 0.001) and bronchial hyper-responsiveness (P < 0.001) at 10 years than other phenotypes. CONCLUSION: A proportion of childhood eczema, rhinitis and asthma is nonatopic. The commonest childhood pattern of atopy is chronic sensitization, associated with early, persisting and clinically significant allergic disease. The currently accepted childhood 'Allergic March' may oversimplify the natural history of childhood atopy and allergic disease.     

Association of allergic symptoms in children with those in their parents

This study investigated the association of asthma, allergic rhinitis, and eczema in United Arab Emirates (UAE) schoolchildren with allergic conditions in their parents. A cross-sectional, population-based study among schoolchildren aged 6–14 years was conducted in Al-Ain City, UAE. The field survey was conducted from October 1992 to May 1993. A questionnaire was distributed to 850 UAE government school students from representative, randomly selected schools with a majority of UAE nationals. The student and both or either of the parents were present during the interview. A detailed clinical history of asthma and wheezing in the target children and a history of asthma and allergic rhinitis in their parents and siblings were obtained. It was found that 13.1% of asthmatic children had mothers with asthma (relative risk (RR) = 2.67; 95% confidence intervals (CI)= 1.65–4.35), and 15.2% had fathers who were asthmatic (RR = 2.85; 95% CI = 1.81–4.49). This contrasted with 4.4% of nonasthmatic children who had fathers with asthma, and 4.1% who had mothers with asthma. A similar pattern was seen with symptoms of allergic rhinitis when it was found that 34.3% of children who had asthma had mothers with allergic rhinitis (RR: 2.74; 95% CI: 1.90–3.94). The corresponding figure for fathers was 12.7% (RR: 0.92; 95% CI: 0.5–1.7). The frequency of either parent of the asthmatic children having allergic rhinitis was 28.6%; for both parents, it was 14.5%. It was also found that asthmatic children had 12.5% of their fathers, 32.8% of their mothers, 26.4% of either of their parents, and 33.3% of both their parents suffering from allergic rhinitis. Siblings of the asthmatic children were also studied to establish the relationship between allergic conditions in the siblings and asthma in the study sample. It was found that in the asthmatic study population the frequency of siblings having asthma was 31.9%; of those having allergic rhinitis, 21.3%; and of those having eczema, 16.1%. Twenty-nine percent of either of the parents of the children with eczema had the same condition, and the corresponding figure for allergic rhinitis was 36.5%. The prevalence rate of asthma in the schoolchildren studied increased dramatically to 22% when wheeze, asthma, or nocturnal cough were grouped together. When eczema and allergic rhinitis were also considered together along with the above, the rate increased to 31%. The size of the family did not seem to affect the parent/child association of allergic symptoms. Our findings indicate that there is a strong association between respiratory allergies and eczema in parents and in their asthmatic children, thereby indicating a strong genetic basis for the occurrence of asthma in particular and atopy in general.     

Pet-keeping in childhood and adult asthma and hay fever: European community respiratory health survey

BACKGROUND: Whether pet-keeping early in life protects against or promotes allergy remains unclear. OBJECTIVE: Our aim was to examine the effects of childhood pet-keeping on adult allergic disease in a large international population-based study, including information on sensitization, adult pet-keeping, and pet prevalence in the populations. METHODS: We used information from structured interviews (n = 18,530) and specific IgE to common aeroallergens in blood samples (n = 13,932) from participants in the European Community Respiratory Health Survey (ECRHS) to analyze the associations between keeping pets and adult asthma and hay fever. RESULTS: Keeping cats in childhood was associated with asthma only among atopic subjects, an association that varied between centers (P =.002) and was stronger where cats where less common (< 40% cats: odds ratio(wheeze) [OR(wheeze)] = 1.84, 95% CI = 1.31-2.57; 40%-60% cats: OR(wheeze) = 1.33, 95% CI = 1.10-1.61; > or =60% cats: OR(wheeze) = 0.98, 95% CI = 0.73-1.33). Dogs owned in childhood or adulthood were associated with asthma among nonatopic subjects (childhood: OR(wheeze) = 1.28, 95% CI = 1.13-1.46; adulthood: OR(wheeze) = 1.31, 95% CI = 1.14-1.51; both: OR(wheeze) = 1.69, 95% CI = 1.40-2.04). In atopic subjects, those who had owned dogs in childhood had less hay fever (OR = 0.85; 95% CI = 0.73-0.98) and no increased risk of asthma (OR(wheeze) = 1.01, 95% CI = 0.87-1.17). Respiratory symptoms were more common in subjects who had owned birds during childhood (OR(wheeze) = 1.12; 95% CI = 1.02-1.23) independent of sensitization. CONCLUSIONS: The effects of pet-keeping in childhood varied according to the type of pet, the allergic sensitization of the individual, and the wider environmental exposure to allergen. Cats owned in childhood were associated with more asthma in sensitized adults who grew up in areas with a low community prevalence of cats. Dogs owned in childhood seemed to protect against adult allergic disease but promote nonallergic asthma.     

Risk factors for wheeze in the last 12 months in preschool children

Most children with asthma develop their symptoms before the age of 5 years and many preschool wheezers continue to wheeze in the early school years. It is thus important to investigate the factors that predispose young children to wheeze. The objective of this study was to investigate the relevant environmental and family influences on recent wheeze (wheeze within the last 12 months) in preschool children. A cross-sectional study was conducted in five primary health clinics in the district of Kota Bharu from April to October 1998. Nurses from these clinics distributed Bahasa Malaysia questionnaires containing questions on asthma symptoms, environmental risk factors, family's social status and family history of atopy and wheeze to preschool children aged 1-5 years during their home visits. The respondents were parent(s) or carer(s) of the children. A total of 2,524 (87.7%) complete questionnaires were available for analysis of risk factors. One hundred and fifty six (6.2%) children had current wheeze. Significant risk factors associated with current wheeze were a family history of asthma (O.R. = 6.36, 95% C.I. = 4.45-9.09), neonatal hospital admission (O.R. = 2.38, 95% C.I. = 1.51 - 3.75), and a maternal (O.R. = 2.12, 95% C.I. = 1.31-3.41) or paternal (O.R. = 1.52, 95% C.I. = 0.95-2.43) history of allergic rhinitis. Among environmental factors examined, namely, household pets, carpeting in bedroom, use of fumigation mats, mosquito coils and aerosol insect repellents, maternal and paternal smoking, and air conditioning, none were associated with an increased risk of wheeze. In conclusion, the strongest association with current wheeze was a family history of asthma. Also significant were neonatal hospital admission and a history of allergic rhinitis in either the mother or father. None of the environmental factors studied were related to current wheeze in preschool children.     

Age at bacille Calmette–Guérin vaccination and risk of allergy and asthma

BACKGROUND: It has been proposed that early age at bacille Calmette-Guérin (BCG) vaccination protects against the development of allergy. OBJECTIVE: To study whether early age at BCG vaccination was associated with a decreased risk of atopy, allergic rhinitis, and asthma compared to BCG vaccination at later ages in childhood. METHODS: The occurrence of atopy, allergic rhinitis, and asthma was studied in nearly 2000 women participating in the Danish National Birth Cohort study. Detailed information on age at BCG vaccination (age 0-15 years) was available from school health records. Atopic status was assessed serologically by a specific response to 11 common inhalant allergens using serum samples obtained from the women during the period 1997-2001. Information on allergic rhinitis and asthma was available from telephone interviews. RESULTS: Approximately 85% of the women had been BCG-vaccinated. Age at BCG vaccination was not associated with risk of atopy, allergic rhinitis, or asthma. The odds ratio of atopy, allergic rhinitis, and asthma associated with being vaccinated during the first year of life was 1.05 (95% CI 0.71-1.56), 1.42 (95% CI 0.85-2.36), and 1.71 (95% CI 0.91-3.20), respectively, compared with being vaccinated at the age of 7 years. Adjustment for birth cohort, sibship size, age of the woman's mother at birth, and social class in childhood did not affect the results. CONCLUSION: Our findings suggest that age at BCG vaccination in childhood does not influence the development of allergy or asthma.     

Lower prevalence of reported asthma in adolescents with symptoms of rhinitis that received neonatal BCG

BACKGROUND: BCG is a vaccine used against tuberculosis and leprosy and is an immunostimulant that primes T(H)1 lymphocytes to produce cytokines that antagonize atopy both in animal models and in man. Considering that atopy is the main risk factor for asthma, one can hypothesize that vaccination inducing T(H)1 responses, such as BCG, can be protective against asthma. METHODS: OBJECTIVE: To estimate the association between neonatal BCG vaccination and prevalence of asthma among adolescents. STUDY DESIGN: Cross-sectional study with schoolchildren aged 12-16 years. The presence of a scar compatible with BCG was used as a surrogate of neonatal vaccination. A self administered structured questionnaire was prepared based on that used by the International Study of Asthma and Allergies in Childhood. The prevalence of asthma was categorized according to the report of lifetime wheeze, lifetime asthma, lifetime asthma among those referring allergy and among those referring allergy and sneezing. RESULTS: Neonatal BCG vaccination was not associated with the overall prevalence of reported wheezing or asthma. However, in the subgroup reporting current allergy and sneezing, neonatal BCG was associated with a 37% reduction of prevalence of lifetime asthma. CONCLUSIONS: In the population we surveyed, neonatal BCG scar was associated with a reduction in the risk of asthma only in individuals with a past history suggestive of allergic rhinitis.     

Relevance of the hygiene hypothesis to early vs. late onset allergic rhinitis

Introduction The hygiene hypothesis proposes that reduced exposure to infections in early life increases the risk of developing allergic conditions including allergic rhinitis. We examined the association between markers of the hygiene hypothesis and allergic rhinitis that developed before 7 years of age and allergic rhinitis that developed after 7 years of age. Methods The Tasmanian Longitudinal Health Study (TAHS) is a population‐based cohort (n=8583) study of respiratory disease. Participants have been followed from 7 to 44 years of age. Information on potential risk factors, allergies and respiratory symptoms was collected longitudinally. Using multi‐nomial logistic regression, exposure to siblings, infections, tonsillectomy and farm residence during childhood were examined as risk factors for allergic rhinitis that developed before or after 7 years of age. All analyses were adjusted for gender, maternal and paternal atopy, mother's age at participant's birth, paternal socio‐economic status in 1968 and personal socio‐economic status in 2004. Results Greater cumulative exposure to siblings before the age of 2 years was strongly inversely associated with early onset allergic rhinitis (<1 year sib exposure: OR=0.6, 95% CI 0.3–1.0; 1–3 years sib exposure: OR=0.6, 95% CI 0.4–0.9; >3 years sib exposure: OR=0.4, 95% CI 0.3–0.8) less so with later onset allergic rhinitis. The risk of early onset allergic rhinitis decreased with increasing viral infections (OR=0.7, 95% CI 0.5–0.9) during childhood. Having a tonsillectomy before 7 years of age increased the risk of early onset allergic rhinitis (OR=1.7, 95% CI 1.2–2.5). None of these factors was associated with later onset allergic rhinitis. Conclusions Exposures relevant to the hygiene hypothesis were important predictors for the development of early onset but less so for later onset allergic rhinitis. The exact mechanisms by which siblings and infections protect against allergic rhinitis are unclear. The stronger findings for earlier onset allergic rhinitis suggest that family structure and infections have most impact on disease risk in early life. Further research should focus on early onset allergic rhinitis when exploring causal explanations for any sibling effect.     

The prevalence of asthmatic respiratory symptoms among adults in Estonian and Swedish university cities

The prevalence of atopy and related diseases is lower among children in Eastern European countries than in countries with a market economy. Such comparisons have not been made in adults. The European Community Respiratory Health Survey (ECRHS) postal questionnaire was mailed to random samples of 3000 inhabitants in Tartu, Estonia, and 3600 in Uppsala, Sweden, between the ages of 20 and 44 years. Asthmatic symptoms (wheeze with breathlessness occurring in the absence of colds) were less prevalent in Tartu (4.6% vs 6.8%, P<0.001), as were attacks of asthma (1.9% vs 3.3%, P<0.01), current asthma medication (0.7% vs 4.9%), and allergic rhinitis (17.8% vs 22.2%, P<0.001). Age was inversely related to allergic rhinitis in Uppsala (P<0.05), but not in Tartu. Nocturnal respiratory symptoms (wakening with chest tightness or being woken by an attack of breathlessness or an attack of cough) were more prevalent in Tartu (P<0.001), and their prevalence increased with age (P<0.05) in Tartu, but not in Uppsala. Symptoms of asthma and hay fever were less common but other respiratory problems more common in Tartu than in Uppsala. The difference in the prevalence of hay fever diminished with age, supporting the notion that the increasing prevalence of allergy among children and young adults in Western Europe is caused by a cohort effect.     

Effect of neonatal sepsis on the development of allergies and asthma in later childhood

BACKGROUND: Exposure to large amounts of endotoxins and other bacterial products in early childhood may protect against the development of allergic diseases later in childhood. The aim of this study was to investigate the effects of neonatal sepsis on subsequent development of asthma, allergic rhinitis, and atopic dermatitis in children. METHODS: We recruited 85 children (mean age 48.67 +/- 12.88 months) who had been hospitalized for sepsis in their neonatal period and their siblings (n = 85) as controls (mean age 61.81 +/- 21.34 months) to investigate the prevalences of asthma, atopic dermatitis and allergic rhinitis. After asking the questions in the International Study of Asthma and Allergies in Children (ISAAC) questionnaires to the parents, total IgE levels in sera were measured and skin prick tests were performed. RESULTS: Children with neonatal sepsis had lower total IgE levels and less sensitivity to Dermatophagoides pteronyssinus than controls (25.9 vs. 9.4%, p = 0.003). In addition, wheeze ever, wheeze in the last 12 months, physician-diagnosed asthma, and use of asthma drugs were less common in these subjects. Prevalences of allergic rhinitis and atopic dermatitis were equal in both groups. CONCLUSION: Exposure to severe infections such as sepsis in the neonatal period may decrease sensitization to environmental allergens and prevalence of asthma in later childhood.     

Allergies, infections and the hygiene hypothesis--the epidemiological evidence

The 'hygiene hypothesis' was first proposed by Strachan in 1989 suggesting that infections and unhygienic contact with older siblings or through other exposures may confer protection from the development of allergic illnesses. This hypothesis has evolved in various ways exploring the role of overt viral and bacterial infections, the significance of environmental exposure to microbial compounds, and their effect on underlying responses of innate and adaptive immunity. So far a truly unifying concept is still lacking, but various pieces of a complex interplay between a host's immune response, characteristics of the invading microorganism, the level and variety of the environmental exposure, and the interactions between a genetic background and a range of exposures become apparent. All these pieces eventually assemble to the clinical presentation of a complex syndrome namely of asthma and allergic illnesses. Even if today practical implications cannot directly be deduced from these findings, there is great potential for the development of novel preventive and therapeutic strategies in the future based on the concepts of the 'hygiene hypothesis'.     

Respiratory illnesses in early life and asthma and atopy in childhood

BACKGROUND: The relation between respiratory illnesses in early life and the development of asthma and atopy in childhood is incompletely understood. OBJECTIVE: We sought to examine the relationship between respiratory illnesses in early life and atopic diseases at school age. METHODS: We performed a prospective birth cohort study of the relationship between respiratory illnesses in the first year of life and asthma, atopy (sensitization to >or=1 allergen), and allergic rhinitis at school age in 440 children with a parental history of atopy. Logistic regression was used to examine the relationship between respiratory illnesses and asthma, atopy, and allergic rhinitis. The relationship between respiratory illnesses in early life and repeated measures of wheezing between the ages of 1 and 7 years was investigated by using a proportional hazards models. RESULTS: Physician-diagnosed croup (adjusted odds ratio [OR], 0.30; 95% CI, 0.12-0.72) and having 2 or more physician-diagnosed ear infections (adjusted OR, 0.58; 95% CI, 0.35-0.98) in the first year of life were inversely associated with atopy at school age. Physician-diagnosed bronchiolitis before age 1 year was significantly associated with asthma at age 7 years (adjusted OR, 2.77; 95% CI, 1.23-6.22). Recurrent nasal catarrh (>or=3 episodes of a runny nose) in the first year of life was associated with allergic rhinitis at age 7 years (adjusted OR, 2.99; 95% CI, 1.03-8.67). CONCLUSION: The relationship between early-life respiratory illnesses and asthma and atopy is complex and likely dependent on the type of infection and immune response it initiates. CLINICAL IMPLICATIONS: Certain respiratory illnesses in early life modify the risk of atopy and asthma at school age.     

Relationship between childhood atopy and wheeze: what mediates wheezing in atopic phenotypes?

BACKGROUND: The nature of the relationship between childhood wheeze and atopy remains uncertain. OBJECTIVE: To characterize childhood wheeze among atopic phenotypes in a longitudinal birth cohort study. METHODS: A whole population birth cohort (N = 1,456) was recruited in 1989. Children were seen at birth and at 1, 2, 4, and 10 years of age to obtain information on asthma and allergic disease development and relevant risk factors for these states. Skin prick testing at ages 4 (n = 980) and 10 (n = 1,036) years was used to define atopic phenotypes. Wheezing in these states was characterized, and logistic regression was used to identify independent risk factors for wheeze onset in different atopic phenotypes. RESULTS: Wheeze ever occurred in 37% of never atopics, 38% of early childhood atopics, 65% of chronic childhood atopics, and 52% of delayed childhood atopics. Chronic childhood atopics had significant wheezing morbidity and bronchial hyperresponsiveness. Their wheezing was associated with male sex, early eczema, family history of eczema, and early tobacco exposure. Never atopic wheeze was related to maternal asthma, parental smoking, and respiratory tract infections. Exclusive breastfeeding protected against early childhood atopic wheeze. Maternal asthma, family history of urticaria, and dog ownership increased delayed childhood atopic wheeze. CONCLUSIONS: In many respects, chronic childhood atopy is the atopic phenotype associated with the most significant forms of childhood wheezing. In such children, heritable drive, allergens, and synergy with other environmental triggers seem to be crucial determinants of wheeze onset. Where such sensitization is absent, numerous environmental factors plus genetic predisposition may assume importance for wheezing.     

Childhood allergic rhinitis predicts asthma incidence and persistence to middle age: a longitudinal study

BACKGROUND: The association between allergic rhinitis and asthma is well documented, but the temporal sequence of this association has not been closely examined. OBJECTIVE: We sought to assess the associations between childhood allergic rhinitis and (1) asthma incidence from preadolescence to middle age and (2) asthma persistence to middle age. METHODS: Data were gathered from the 1968, 1974, and 2004 surveys of the Tasmanian Asthma Study. Cox regression was used to examine the association between childhood allergic rhinitis and asthma incidence in preadolescence, adolescence, and adult life. Binomial regression was used to examine the association between childhood allergic rhinitis and asthma beginning before the age of 7 years and persisting at age 44 years. RESULTS: Childhood allergic rhinitis was associated with a significant 2- to 7-fold increased risk of incident asthma in preadolescence, adolescence, or adult life. Childhood allergic rhinitis was associated with a 3-fold increased risk of childhood asthma persisting compared with remitting by middle age. CONCLUSIONS: Childhood allergic rhinitis increased the likelihood of new-onset asthma after childhood and the likelihood of having persisting asthma from childhood into middle age. CLINICAL IMPLICATIONS: Asthma burden in later life might be reduced by more aggressive treatment of allergic rhinitis in early life.