High birth weight, asthma and atopy at the age of 16 yr

The association between high birth weight and asthma has been suggested. The Northern Finland Birth Cohort 1986, a longitudinal cohort originally including 9479 participants, has been followed up since birth until the age of 16 yr. Using the data of this study, we analyzed the association of high birth weight with asthma and atopic sensitization at the age of 16 yr. The analysis included the 5995 subjects with complete skin prick test data and the 5500 subjects with data on doctor-diagnosed asthma (written questionnaire) at the age of 16 yr. Atopy was defined as at least one positive skin prick test reaction, which definition was also used to separate atopic and non-atopic asthma. There was a significant association between high birth weight (>4510 g) and asthma among the atopic subjects (OR 2.40, 95% CI 1.33-4.32). When looking at atopy, the highest risk was observed among the subjects with highest birth weight category (>4510 g) (OR 1.44, 95% CI 1.05-1.97) and the adjacent (4200-4500 g) birth weight category (OR 1.24, 95% CI 1.01-1.53), when compared with the reference category (2500-3340 g). Our results support the notion that high birth weight is associated with an increased risk of asthma and suggest that the association is mostly explained by an increased risk of atopy. The biological mechanisms behind the associations are unknown, but they could be related to obesity.

Effect of farming environment on sensitisation to allergens continues after childhood

AIMS

The farming environment in childhood has been reported to decrease the risk of sensitisation to allergens. The purpose of the present study was to explore whether later exposure to a farming environment also could affect this sensitisation.

METHODS

A population based sample of 202 women who did not live on a farm and 231 who did. The subjects filled in a questionnaire and underwent skin prick tests for several common and farming related allergens.

RESULTS

The prevalence of sensitisation to any of the allergens was similar in the two groups (37.1 v 34.6% (p = NS). However, compared with women who did not live on a farm, the women who lived on a dairy farm showed a low prevalence of sensitisation to pollens (4.4 v 17.3%, p = 0.01) and cats (3.5 v 10.4%, p = 0.047). The risk of sensitisation to pollens and pets was lowest among women with both a childhood and adulthood farming environment and was dose dependently associated with current contact with farm animals. However, this contact increased the risk of sensitisation to bovine dander.

CONCLUSION

The farming environment may reduce sensitisation to common allergens also after early childhood. However, it may also increase sensitisation to farm allergens.

Allergen-specific sensitization in asthma and allergic diseases in children: the study on farmers' and non-farmers' children

BACKGROUND

Farmers' children are less frequently sensitized to common allergens than the non-farmers' children, but less is known about their sensitization to other allergens and its association with clinical diseases.

OBJECTIVE

To examine the association of farm environment with atopic sensitization, allergic diseases, expression of allergen-induced symptoms, and the importance of specific sensitization against 'common' (timothy, dog, cat, birch, Dermatophagoides pteronyssimus, mugwort) and 'other' (cockroach, horse, Lepidoglyphus destructor, cow) allergens for asthma and allergic diseases in children.

METHODS

A cross-sectional study including 344 farmers' and 366 non-farmers' children aged 6-13 years in eastern Finland, using a self-administered written questionnaire and skin prick tests against the above-mentioned allergens.

RESULTS

Farmers' children had less asthma and allergic diseases and were less often sensitized against common allergens than the non-farmers' children. However, little difference was observed in sensitization against the other allergens between the farmers' (17.2%) and non-farmers (14.5%) children [adjusted odds ratios (aOR) 1.11 (0.71-1.72)]. Being sensitized against only other allergens, without sensitization against common allergens, was unrelated to asthma or allergic diseases. Among the single allergens, sensitization against pets or pollen, or against horse or cow, had the strongest association with asthma, hayfever, and atopic eczema; no such association was seen in D. pteronyssimus, mugwort, cockroach, or L. destructor. Farmers' children had significantly less often symptoms of allergic rhinitis in contact with dog (aOR 0.32%, 95% confidence interval (CI) 0.15-0.67), cat (aOR 0.45, 0.22-0.88), or pollen (aOR 0.58%, 95% CI 0.37-0.90) than the non-farmers' children.

CONCLUSION

Farm environment reduces the occurrence of asthma, allergic diseases, and atopic sensitization in children, and also the occurrence of allergen-induced rhinitis. Remarkable differences were observed between single allergens in their association with allergic disease, stressing the importance of allergen selection when defining atopy in epidemiological studies.

Pet- and pollen-induced upper airway symptoms in farmers and in nonfarmers

The effect of farming on the risk of upper airway symptoms is not clear. In this cross-sectional, population-based study, 198 female farmers, 50 nonfarmers living on a farm, and 218 nonfarmers not living on a farm, filled in a symptom questionnaire and underwent skin-prick testing with common and agricultural allergens. In the logistic regression analysis, the latter group served as a control. Several adjustments were made, including childhood farming environment. Current farming was found to decrease the risks of pet- and pollen-induced upper airway symptoms, dose-dependently with the intensity and duration of animal husbandry. Including skin-test positivity to pets in the regression models did not affect the negative association between farming and pet-induced symptoms. In contrast, animal husbandry increased the risk of farm work-induced upper airway symptoms. Animal husbandry often induces work-related upper airway symptoms. However, the present study among female adults suggests that it may also decrease the risk of pet- and pollen-induced upper airway symptoms.

Which factors explain the lower prevalence of atopy amongst farmers' children?

BACKGROUND

The inverse association between farming and atopy in children has been attributed to microbial exposure, especially through livestock. Very little is known about other potential explanatory factors.

OBJECTIVE

To explore potential differences in lifestyle and environmental factors between farmer and non-farmer families, and whether these factors could explain the association between farming and childhood atopy.

METHODS

A cross-sectional study, including 366 farmers' and 344 non-farmers' children in eastern Finland. Information regarding exposure and background characteristics was gathered by a written questionnaire. Atopy was defined as having one or more positive skin prick test reactions (> 3 mm) against the six common aeroallergens.

RESULTS

Regardless of the current farming type, atopy was less frequent among the farmers' children than the non-farmers' children (aOR 0.56, 95% CI 0.40-0.78). Remarkable differences were seen in many lifestyle factors (including diet) between the farmer and non-farmer families, but only a few of the explored factors were associated with atopy. The frequency of current livestock contacts seemed to have an inverse, dose-dependent association with atopy (aOR 0.46, 95% CI 0.22-0.97 for daily vs. no contact). Having lived on a dairy farm in infancy (aOR 0.51, 95% CI 0.28-0.93), or having had cats or dogs in infancy (aOR 0.60, 95% CI 0.42-0.85), decreased the risk of atopy at school age. The inverse association between farming and atopy was not explained by the sociodemographic factors, or by differences in conventional risk factors of atopy. Animal contacts explained partially, but not completely, the association.

CONCLUSION

Higher frequency of animal contacts is one factor, but probably not the only one, explaining the inverse association of farming and atopy in children. The importance of early life exposures may have recently been over-emphasized, and current exposures discounted, when studying the risk factors of childhood atopy.

Does heredity modify the association between farming and allergy in children?

AIM

It has been suggested that living on a farm decreases the risk of childhood allergy, especially if farming involves livestock. The aim of this study was to examine the association between farming and allergy in children, and the influence of atopic heredity in this association.

METHODS

The cross-sectional data of the 7981 children aged 13-14 y who participated in the Finnish ISAAC study between the years 1994 and 1995 were used to evaluate the association between farming and allergy.

RESULTS

Living on a farm was associated with a decreased risk of current symptoms of allergic rhinoconjunctivitis among all children (aOR 0.79; 95% CI 0.63, 0.99), and with a decreased risk of hay fever, especially among those children with a parental history of hayfever (aOR 0.60; 95% CI 0.40-0.89, p = 0.072 for interaction). The children of farmers with a history of hay fever also had a decreased risk of current wheeze (aOR 0.38; 95% CI 0.12-1.24, p = 0.040 for interaction). No significant association was found between farming and either asthma or eczema. Children living on a farm with livestock had the lowest risk of allergic rhinoconjunctivitis (aOR 0.69), followed by those living on a farm without livestock (aOR 0.89) compared with the non-farming children (p-value for trend 0.024).

CONCLUSION

Our results support the recent findings on a decreased risk of allergy among the children living on farms. A possible differential effect of parental history of hay fever on the relation of farming environment and the risk of allergic symptoms warrant further investigation.

In search of childhood asthma: questionnaire, tests of bronchial hyperresponsiveness, and clinical evaluation

BACKGROUND

The definition or diagnosis of asthma is a challenge for both clinicians and epidemiologists. Symptom history is usually supplemented with tests of bronchial hyperresponsiveness (BHR) in spite of their uncertainty in improving diagnostic accuracy.

METHODS

To assess the interrelationship between respiratory symptoms, BHR, and clinical diagnosis of asthma, the respiratory symptoms of 1633 schoolchildren were screened using a questionnaire (response rate 81.2%) and a clinical study was conducted in a subsample of 247 children. Data from a free running test and a methacholine inhalation challenge test were available in 218 children. The diagnosis of asthma was confirmed by a paediatric allergist.

RESULTS

Despite their high specificity (>0.97), BHR tests did not significantly improve the diagnostic accuracy after the symptom history: area under the receiver operator characteristic (ROC) curve was 0.90 for a logistic regression model with four symptoms and 0.94 for the symptoms with free running test and methacholine inhalation challenge results. On the other hand, BHR tests had low sensitivity (0.35-0.47), whereas several symptoms had both high specificity (>0.97) and sensitivity (>0.7) in relation to clinical asthma, which makes them a better tool for asthma epidemiology than BHR.

CONCLUSIONS

Symptom history still forms the basis for defining asthma in both clinical and epidemiological settings. BHR tests only marginally increased the diagnostic accuracy after symptom history had been taken into account. The diagnosis of childhood asthma should not therefore be overlooked in symptomatic cases with no objective evidence of BHR. Moreover, BHR should not be required for defining asthma in epidemiological studies.

The association between persistent eosinophilia and asthma in childhood is independent of atopic status

BACKGROUND

Although peripheral blood eosinophilia is associated with risk of asthma, the relation with atopy has not been established.

OBJECTIVE

To assess the relationship between eosinophils and chronic asthma in childhood, and to determine the factors associated with eosinophil levels over time.

METHODS

Percent eosinophils/300 white blood cell (WBC) count ('eos') was measured at 9 months, 6 years and 11 years in subjects participating in the prospective Tucson Children's Respiratory Study. Children were classified based on the number of measurements in which they had low (< or = 2%) or high (>5%) eosinophils, as follows: (1) Persistently low eos (n = 130); (2) Low eos (intermittently low or consistently moderate, but never high, n = 317); (3) Intermittently high eos (n = 192); and (4) Persistently high eos (n = 17). Only children with > or = 2 eos measurements were included in the analysis. Chronic asthma was defined as medical doctor (MD)-diagnosed asthma with reports of wheezing during the previous year, on > or = 3 questionnaires completed between 2 and 13 years of age. Children with at least one positive skin prick test (SPT; > or = 3 mm) at age 6 or 11 were considered 'atopic'.

RESULTS

Chronic asthma was linearly related to longitudinally ascertained eosinophils (trend chi2 P<0.001) with prevalence ranging from 5.8% among children with persistently low eos to 37.5% among children with persistently high eos. This relation was independent of atopy. Parental history of asthma was associated with both chronic asthma (P <0.001) and with longitudinal eosinophil status (P < 0.001). After adjusting for atopy and gender, there was a 70% increase in asthma risk with each increase in longitudinal eosinophil level. This stepwise increase was reduced to 48% when parental asthma was added to the model.

CONCLUSION

Longitudinal eosinophil levels are linearly associated with chronic asthma in childhood, independent of atopy. The strong association between parental asthma and eosinophil status suggests that genetic background may be an important determinant of eosinophilic response.

Dog exposure in infancy decreases the subsequent risk of frequent wheeze but not of atopy

BACKGROUND

Influence of household pets in the development of childhood asthma or atopy has been controversial.

OBJECTIVE

The purpose of this study was to investigate whether pet exposure in early life decreases the subsequent risk of frequent wheezing and/or allergic sensitization.

METHODS

This was a prospective observational birth cohort study. The setting was a large health maintenance organization in Tucson, Ariz; the subjects were a population sample of 1246 newborns enrolled at birth and followed prospectively to age 13 years. The main outcome measures were as follows: time to first report of frequent wheezing (>3 episodes in the past year), skin prick test reactivity at 6 years and 11 years of age, and total serum IgE at 9 months, 6 years, and 11 years of age.

RESULTS

Children living in households with > or =1 indoor dogs at birth were less likely to develop frequent wheeze than those not having indoor dogs (P =.004). This inverse association was confined to children without parental asthma (hazard ratio = 0.47; P <.001 [Cox regression]) and was not evident for children with parental asthma (hazard ratio = 0.96; P =.87). Adjustment by potential confounders did not change the results. Indoor cat exposure was not significantly associated with the risk of frequent wheezing. Neither cat exposure in early life nor dog exposure in early life was associated with skin prick test reactivity or total serum IgE at any age.

CONCLUSION

Dog exposure in early life might prevent the development of asthma-like symptoms, at least in low-risk children with no family history of asthma. Nevertheless, early pet exposure does not seem to significantly influence the development of allergic sensitization.

Lung function in school-aged asthmatic children with inhaled cromoglycate, nedocromil and corticosteroid therapy

Two-thirds of the children with asthma in our area use cromones and only one-third steroids as the maintenance therapy. This study aimed to evaluate our treatment policy based on the international consensus. Peak expiratory flow (PEF), dynamic spirometry and bronchodilation test results were therefore collected in 195 school-aged patients who visited our outpatient clinic in 1995. Sixty-four children (33%) used cromoglycate, 86 (44%) nedocromil and 45 (23%) inhaled steroids. Twenty-five (12%) needed combination therapy, mainly with salmeterol. Lung function results were good, and there were no significant differences between the therapeutic groups irrespective of whether pre- or postbronchodilator values were considered. PEF was decreased in eight (4%), forced expiratory volume in one second (FEVI) in four (2%) and maximum mid-expiratory flow (MMEF) in 33 (17%) patients. At least one result was decreased in 39 (20%) cases, in most cases (77%) MMEF alone. Significant rises after salbutamol inhalations were observed in 17 (9%) in PEF, in two (1%) in FEV1 and 20 (10%) in MMEF values. Thus, the bronchodilation test was positive in 33 (17%) cases, and in 22 (11%) cases it was the only sign of bronchial obstruction. Over 70% of the children with asthma can be treated with cromones by a stepwise treatment modality. Inhaled steroids can be restricted to those not controllable by cromones. Lung function tests, including postbronchodilator values, should be part of the follow-up of continuous maintenance medication for asthma.

Prevalence of allergic rhinitis and atopic dermatitis among children in four regions of Finland

The primary aim of the study was to evaluate the prevalences of allergic rhinitis and atopic dermatitis and their regional differences among Finnish children. The secondary objective was to determine whether the responses to the questions used are affected by the pollen season if asked during such a season. In 1994-5, the self-reported prevalence of allergic symptoms in four regions of Finland was studied among 11,607 schoolchildren aged 13-14 years, as part of the International Study of Asthma and Allergies in Childhood (ISAAC). The prevalence of rhinoconjunctivitis during the preceding year was 16% in eastern Finland (Kuopio County, n=2821), 23% in southern Finland (Helsinki area, n=2771), 15% in southwestern Finland (Turku and Pori County, n=2983), and 16% in northern Finland (Lapland, n=3032). The respective prevalences of flexural dermatitis were 15%, 19%, 16%, and 18%. The surveys were performed in winter, except in the Helsinki area where the survey was carried out mainly in the spring pollen season. Among the children studied in autumn in Helsinki, the prevalence of rhinoconjunctivitis was 19% and that of flexural dermatitis 17%. In multivariate analysis, flexural dermatitis was slightly more common in Lapland than in all other areas. In contrast, no significant differences were found in rhinoconjunctivitis. The prevalences of both disorders were twice as high in girls as in boys. In conclusion, regional differences in the prevalence of allergic rhinitis and atopic dermatitis were small in our country, and the prevalence figures were rather similar to those reported from other European countries. Almost half of the children had suffered from at least one atopic disorder, and over one-third had had symptoms in the past year. A clear season-of-response effect was observed; the prevalence of rhinoconjunctivitis was 25% when studied during the pollen seasons in the Helsinki area.

Outcome of children with respiratory symptoms without objective evidence of asthma: a two-year, prospective, follow-up study

This study evaluated the outcome of 33 children with asthma-like symptoms without objective evidence of asthma, and the role of certain factors in predicting the development of clinical asthma in these children. Data on symptom histories, lung functions (flow-volume spirometry, free running test and methacholine inhalation challenge test) and atopic sensitization (skin prick tests and markers of eosinophilic inflammation) were collected twice with an interval of 2 y, and the diagnoses were re-evaluated after the follow-up period. Based on the results, it was concluded that one-third of the children with prolonged or recurrent lower airway symptoms, such as cough or wheeze, either have mild asthma or will develop asthma in the near future. Children who had a significant response [> or = 10% fall in forced expiratory volume in 1 s (FEV1)] in the free running test formed a risk group for active asthma, whereas other baseline characteristics seemed not to predict the outcome.

Prevalence of asthma symptoms in video and written questionnaires among children in four regions of Finland

The aim of this study was to determine whether there are regional differences in the prevalence of childhood asthma in Finland. A secondary objective was to assess the concordance between a written and a video questionnaire on asthma symptoms. In 1994-1995, the self-reported prevalence of asthma symptoms in four regions of Finland was studied among 11,607 schoolchildren aged 13-14 yrs, as part of the International Study of Asthma and Allergies in Childhood (ISAAC). The ISAAC written and video (AVQ 3,0) questionnaires were administered in the school setting. The prevalences of any wheezing during the previous 12 months in the ISAAC video questionnaire were 10% in East Finland (Kuopio County, n=2,821), 12% in South Finland (Helsinki area, n=2,771), 12% in Southwest Finland (Turku and Pori County, n=2,983), and 11% in North Finland (Lapland, n=3,032). The prevalences in the ISAAC written questionnaire were 13, 20, 15, and 16%, respectively. The surveys were performed during winter, except in Helsinki where the survey was carried out mainly during the spring pollen season. During autumn, the prevalence in the written questionnaire in Helsinki was 16%. In multivariate analysis, boys had a lower prevalence than girls, and smokers a threefold higher prevalence than nonsmokers. In conclusion, the prevalence of childhood asthma is lower in Finland than in other European countries, and may be even lower in the eastern part of the country. In contrast to the results from some other European countries, prevalences were lower in the video than in the written questionnaire, which suggests that translating the word "wheezing" into other languages, including Finnish, may produce results that cannot be compared. The strong association of smoking with wheeze both in the video and written questionnaires should be considered in further analysis of the ISAAC study.

Asthma and atopy in schoolchildren in a defined population

We investigated the frequency of allergic disorders, the pattern of allergen sensitization and serum total IgE concentration in a population-based sample of schoolchildren screened on the basis of respiratory symptoms (N = 244). The children were classified on clinical grounds into three groups, asthma (N = 43), other symptoms from lower airways (OSLA; N = 34) and control children (N = 167). The frequency of allergic disorders (allergic rhinitis, conjunctivitis or dermatitis) differed significantly between children with asthma (81%), children with OSLA (62%) and in control children (48%) (p < 0.001). The presence of at least one positive skin prick test result was equally common in children with asthma or OSLA (77%), but lower in control children (40%) (p < 0.001). Serum total IgE concentrations did not differ between the three groups. Two conclusions can be drawn: (i) there is a strong association between clinical allergy, skin reactivity and asthma in school age children, and (ii) a similar association is present between allergy and asthma-like conditions.

Prevalence of asthma at school age: a clinical population-based study in eastern Finland

A questionnaire aimed at screening and identifying patients with asthmatic symptoms was sent to the parents of 2011 children aged 7 to 12 years; 1633 (81%) returned the questionnaire. A clinical examination was given to 165 symptomatic and 82 non-symptomatic children. The children were classified into three groups: 1, clinical asthma (n = 43); 2, other symptoms from lower airways (OSLA) (n = 34); 3, healthy children (n = 170). The prevalences of asthma and OSLA in the whole source population (n = 1633) were then estimated based on these figures. The lifetime prevalence of asthma was 4.0%. All children with asthma were either symptomatic or on continuous maintenance therapy during the preceding 12 months. The lifetime prevalence of OSLA was 5.0%, with 3.0% being symptomatic during the preceding 12 months. Asthma was more common in boys (5.0%) than in girls (2.8%). The respective figures for OSLA were 6.2 and 3.7%. The occurrence of asthma as well as respiratory symptoms suggestive of asthma was more common than previously observed in this area.