International Study On Asthma And Allergies In Childhood Research Articles

Respiratory Status in Children and Exposure to Animal Allergens-The Problem of Reverse Causality in Cross-Sectional Studies.

Some epidemiological studies suggest that early exposure to animal allergens during infancy reduces the risk of bronchial asthma in school-age children. However, the observed associations in some cases may be an effect of the study used (epidemiological observational studies, especially a cross-sectional study) and indicate reverse causality. This study aimed to determine the association between exposure to animal allergens and the prevalence of respiratory diseases, including bronchial asthma, considering the potential impact of reverse causality on the observed relationships. An analysis of data from a cross-sectional epidemiological study conducted in 2020 involving 3237 primary school students aged 7-15 years in the Silesian Province (Southern Poland) was carried out. The parents of students completed a questionnaire based on The International Study on Asthma and Allergies in Childhood (ISAAC). The relationship between the occurrence of chronic cough, wheezing, and dyspnea in the last 12 months, night waking due to dyspnea, and asthma in the presence of pets was assessed. Exposure to animal allergens was determined by answering the question, "Are there any furry or feathered animals in the home?" with three response options: "yes; they have been in the past; no" (Scenario 1). For the analyses and to reveal a potential reverse causality effect, the last two response categories regarding pet ownership were combined to form a "no" category in Scenario 2, and the first two answers were combined into a "yes" category in Scenario 3. A chi-square test was used to assess the relationship between variables, and a statistical significance level of p < 0.05 was adopted. Chronic cough affected 9.5% of children, wheezing in the last 12 months-9.2%, night waking due to dyspnea-5.8%, dyspnea in the last 12 months-4.8%, bronchial asthma-9.2%. Analysis considering the category of having or not having pets (yes vs. no) showed that bronchial asthma was statistically significantly more common in children who did not have pets at home (10.9% vs. 7.9%, p = 0.002). A similar situation was observed for wheezing in the past 12 months (10.7% vs. 8.1%; p = 0.01) and nocturnal awakening due to dyspnea (6.8% vs. 5.1%, p = 0.03). No statistically significant differences were observed for the other symptoms. Analysis by time of pet ownership (a. present; b. present but in the past; c. not present) highlighted similar relationships. Asthma (a. 7.7% vs. b. 13.4% vs. c. 7.7%; p = 0.004), wheezing in the past 12 months (a. 8.1% vs. b. 8.9% vs. c. 10.9%, p = 0.03) and night waking (a. 5.0% vs. b. 4.5% vs. c. 7.1%; p = 0.04) were more common in children without pets and those who had owned pets in the past. The highest proportion of children with asthma was in homes where pets were present in the past. Analyses indicating a relationship between a higher prevalence of asthma and some respiratory symptoms, and the absence of pets cannot be considered as a casual association. The analysis conducted did not reveal a reverse causality effect. The results of observational epidemiological studies, especially a cross-sectional study, should always be interpreted with caution, considering possible distortions and conclusions drawn.

Socioeconomic and Health Determinants of the Prevalence of COVID-19 in a Population of Children with Respiratory Diseases and Symptoms.

Most epidemiological studies indicate that bronchial asthma is not a risk factor for COVID-19, but previous analyses have not additionally focused on the socioeconomic determinants of SARS-CoV-2 infection in children with asthma, bronchitis, and respiratory symptoms. This research aimed to investigate the correlation between the socioeconomic status of families and the prevalence of respiratory conditions such as asthma, bronchitis, and respiratory symptoms in children, in addition to exploring their association with the prevalence of COVID-19. The study involved a cross-sectional epidemiological investigation conducted in 2022, encompassing 2454 students from elementary schools in Poland. The parents of the students completed a questionnaire modeled after the International Study on Asthma and Allergies in Childhood (ISAAC). Socioeconomic status (SES) indicators were determined based on parental education, self-reported economic status, and housing conditions. To assess the impact of social factors and health on the occurrence of COVID-19, odds ratios (ORs) were calculated. The findings revealed several COVID-19 risk factors, including higher maternal (OR 2.2; 95%CI: 1.3-3.0) and paternal education (OR 1.9; 95%CI: 1.3-2.4), urban residence (OR 1.7; 95%CI: 1.3-2.1), the presence of mold in residences (OR 1.7; 95%CI: 1.0-2.3), bronchitis (OR 1.5; 95%CI: 1.2-2.0), and chronic cough (OR 1.8; 95%CI: 1.3-2.4). Further analysis, stratifying children based on their baseline health status (i.e., presence or absence of asthma, bronchitis, and chronic cough), indicated that higher parental education increased the risk of COVID-19 solely for children without pre-existing conditions. The occurrence of SARS-CoV-2 infections was found to be notably associated with mold exposure in children who did not have bronchial asthma. Rigorous multivariate analyses substantiated the collective impact of factors such as residential environment, the existence of mold and moisture, and a history of bronchitis. This study's conclusions highlight a higher frequency of SARS-CoV-2 infections in cases where bronchitis had been diagnosed previously and chronic cough was prevalent. Interestingly, the initially hypothesized higher prevalence of COVID-19 among children with bronchial asthma did not receive confirmation in our findings. This study highlights the importance of urban residence, exposure to mold or dampness, and higher parental education in the incidence of COVID-19. Higher parental education was a significant factor in increasing the risk of COVID-19 among children without bronchitis, chronic cough, and asthma.

Social Inequalities: Do They Matter in Asthma, Bronchitis, and Respiratory Symptoms in Children?

Background: Social inequalities (e.g., poverty and low level of education) generate inequalities in health. Aim: The aim of the study was to determine the relationships between indicators of social inequalities and the frequency of respiratory symptoms, asthma, and bronchitis in children. Material and Methods: In 2019, an epidemiological cross-sectional study on 3237 students from elementary schools in Silesia Voivodships (South Poland) was conducted. The students' parents completed a questionnaire based on the International Study on Asthma and Allergies in Childhood (ISAAC). Social inequalities in the children's families were determined according to parents' education and professional status (working vs. unemployed), self-assessment of economic status, and housing conditions. To determine the influence of social factors on the occurrence of asthma, bronchitis, and respiratory symptoms, the odds ratio (OR) was calculated. Results: Children living in apartments with traces of mold had a higher risk of developing asthma (OR = 1.5, 95%CI: 1.17-1.96; p = 0.002) or bronchitis (OR = 1.4, 95%CI: 1.13-1.72; p = 0.002), wheezing attacks at nights (OR = 1.4; 95%CI: 1.01-1.93), wheezy in the last 12 months (OR = 1.6; 95%CI:1.24-2.08; p &lt; 0.001), and chronic cough (OR = 1.9; 95%CI: 1.49-2.46; p &lt; 0.001). Exposure to environmental tobacco smoke (ETS) was associated with higher risk of cough (OR = 1.5 95%CI: 1.22-1.96; p &lt; 0.001) and dyspnea in the last 12 months (OR = 1.4; 95%CI: 1.04-2.00; p = 0.02). Low socioeconomic status (SES) was associated with increased risk of chronic cough (OR = 1.5; 95%CI: 1.09-2.03; p = 0.009) and increased risk of wheezy in the last 12 months (OR = 1.4; 95%CI: 1.06-1.97; p = 0.008). Asthma and bronchitis were not dependent on parents' education or professional status. Conclusions: Social inequalities have significant impacts on the occurrence of respiratory symptoms, bronchitis, and asthma in children. Interventions aimed at preventing bronchitis and childhood asthma should also focus on social health determinants.

Prevalence and association of asthma and allergic sensitization with dietary factors in schoolchildren: data from the french six cities study

BackgroundThe prevalence of asthma and allergy has recently risen among children. This increase in prevalence might be related to various factors, particularly diet. The aim of this study is to assess the prevalence and association of asthma and allergic sensitization with dietary factors in the French Six Cities Study.MethodsCross-sectional studies were performed among 7432 schoolchildren aged 9–11 years in Bordeaux, Clermont-Ferrand, Créteil, Marseille, Reims, and Strasbourg. Parental questionnaires, based on the International Study on Asthma and Allergies in Childhood (ISAAC), were used to collect information on allergic diseases and potential exposure factors including a food frequency questionnaire to evaluate dietary habits. Skin prick testing to common allergens for allergic sensitization and bronchial hyper-responsiveness (BHR) testing to exercise were performed. Confounders control was performed with multiple logistic regressions.ResultsAsthma symptoms, asthma and allergic sensitization were more prevalent in boys than in girls and were more prevalent in the South than in the North of France. After adjustment for confounders, fruit juice intake was associated with a low prevalence of lifetime asthma (ORa [95 % CI]; 0.73 [0.56–0.97]), butter intake was positively associated with atopic wheeze (1.48 [1.07–2.05]) and having lunch at the canteen 1–2 times/week compared to never or occasionally was associated with a lower prevalence of past year wheeze (0.71 [0.52–0.96]), lifetime asthma (0.76 [0.60–0.96]) and allergic sensitization (0.80 [0.67–0.95]). Meat intake was inversely related to past year wheeze among atopic children (0.68 [0.50–0.98]) while fast food consumption and butter intake were associated with an increase prevalence of asthma (2.39 [1.47–3.93] and 1.51 [1.17–2.00] respectively). Fish intake was associated with a lower prevalence of asthma among non-atopic children (0.61 [0.43–0.87]. None of the dietary factors was associated with BHR.ConclusionsDiet is associated with wheeze, asthma and allergic sensitization but not with BHR in children. These results provide further evidence that adherence to a healthy diet including fruits, meat and fish seems to have a protective effect on asthma and allergy in childhood. However, prospective and experimental studies are needed to provide causal evidence concerning the effect of diet on asthma and atopy.

High body mass index and allergies in schoolchildren: the French six cities study

BackgroundThe prevalence of allergic diseases such as asthma, allergic rhinitis and atopic dermatitis is increasing rapidly worldwide, especially among children and in western countries. This coincides with an increase in...

High prevalence of asthma symptoms in Warao Amerindian children in Venezuela is significantly associated with open-fire cooking: a cross-sectional observational study

BackgroundThe International Study on Asthma and Allergies in Childhood (ISAAC) reported a prevalence of asthma symptoms in 17 centers in nine Latin American countries that was similar to prevalence rates reported in non-tropical countries. It has been proposed that the continuous exposure to infectious diseases in rural populations residing in tropical areas leads to a relatively low prevalence of asthma symptoms. As almost a quarter of Latin American people live in rural tropical areas, the encountered high prevalence of asthma symptoms is remarkable. Wood smoke exposure and environmental tobacco smoke have been identified as possible risk factors for having asthma symptoms.MethodsWe performed a cross-sectional observational study from June 1, 2012 to September 30, 2012 in which we interviewed parents and guardians of Warao Amerindian children from Venezuela. Asthma symptoms were defined according to the ISAAC definition as self-reported wheezing in the last 12 months. The associations between wood smoke exposure and environmental tobacco smoke and the prevalence of asthma symptoms were calculated by means of univariate and multivariable logistic regression analyses.ResultsWe included 630 children between two and ten years of age. Asthma symptoms were recorded in 164 of these children (26%). The prevalence of asthma symptoms was associated with the cooking method. Children exposed to the smoke produced by cooking on open wood fires were at higher risk of having asthma symptoms compared to children exposed to cooking with gas (AOR 2.12, 95% CI 1.18 - 3.84). Four percent of the children lived in a household where more than ten cigarettes were smoked per day and they had a higher risk of having asthma symptoms compared to children who were not exposed to cigarette smoke (AOR 2.69, 95% CI 1.11 - 6.48).ConclusionOur findings suggest that children living in rural settings in a household where wood is used for cooking or where more than ten cigarettes are smoked daily have a higher risk of having asthma symptoms.

Housing characteristics and indoor environment in relation to children’s asthma, allergic diseases and pneumonia in Urumqi, China

In order to evaluate the prevalence of childhood asthma, allergic diseases and pneumonia in Urumqi City, China, as well as its associations with housing and home characteristics, a cross-sectional study was performed in 4618 children (81.7% response rate, average age 4.7±0.9 year, boys accounting for 53.7%). Questions on children’s asthma and allergic diseases were from the International Study on Asthma and Allergies in Childhood (ISAAC) and were integrated with questions on the home environment from the Dampness in Buildings and Health (DBH) study, slightly modified to account for Chinese building characteristics and life habits. The prevalences of physician diagnosed asthma, allergic rhinitis (AR) and pneumonia were 3.6%, 8.7% and 40.9%, respectively. One fourth of children reported wheezing and more than 40% AR symptoms in the last 12 months. Controlling for confounding factors, positive associations were found for home mold/dampness and wheezing (adjusted odds ratio, aOR 1.33, 95% CI 1.07–1.66), AR symptoms (1.34, 1.09–1.64) last 12 months and physician diagnosed pneumonia (1.33, 1.09–1.62). Floor material by wood, PVC or carpeting; and walls by wallpaper, painting or wood material, were positively associated with AR symptoms. Home environmental tobacco smoke (ETS) was positively associated with wheezing (1.23, 1.04–1.46) and pneumonia (1.25, 1.07–1.45). In conclusion, there was a relatively high prevalence of asthmatic and AR symptoms and diagnosed pneumonia in preschool children in Urumqi. Home signs of mold growth or dampness, windowpane condensation, as well as ETS and interior surface materials emitting chemicals were risk factors for allergic symptoms and pneumonia.

Prenatal and early life home environment exposure in relation to preschool children’s asthma, allergic rhinitis and eczema in Taiyuan, China

Prenatal and early life home environment might be related to children’s asthma or allergic diseases later in life. A cross-sectional epidemiological study was designed and a questionnaire survey was performed in 3700 preschool children in urban areas in Taiyuan, Shanxi Province, China. Questions on children’s asthma and allergic diseases from the International Study on Asthma and Allergies in Childhood (ISAAC) were integrated with questions on home environment from the Swedish Dampness in Buildings and Health (DBH) study, appropriately modified for Chinese life habits. By multivariate regression analyses controlling for age, gender, heredity, location in urban/suburban or rural areas, environmental tobacco smoke (ETS) and breastfeeding, we found that home new furniture (HNF) before birth (referring to 1 year before pregnancy and during pregnancy) was positively associated with wheezing ever (odds ratio(OR) 1.23 with 95% CI of 1.03–1.48) and wheezing last 12 months (1.24,1.00–1.54), allergic rhinitis (AR) (1.26,1.06–1.51), and eczema (1.42,1.01–1.99). HNF between 0–1 years old was also positively associated with wheezing last 12 months. Home new decoration (HND) during 0–1 years old was positively associated with AR symptoms and eczema symptoms, more in the last 12 months. Stronger positive associations were found for signs of home mold and dampness with almost all children’s asthmatic and allergic symptoms (OR ranging from 1.23–1.85, P<0.05). By mutual adjustment between HNF before children’s birth and home mold or dampness, all the significance remained unchanged. Prenatal HNF and home mold or dampness was independently associated with children’s asthmatic and allergic diseases later in life.

Risk Factors for Wheezing, Eczema and Rhinoconjunctivitis in the Previous 12 Months among Six-Year-Old Children in Himeji City, Japan: Food Allergy, Older Siblings, Day-Care Attendance and Parental Allergy History

The aim of this study was to clarify whether some environmental and genetic factors (food allergy, older siblings, early day-care attendance and parents' allergy history) are related to the development of allergic symptoms (wheezing in the previous 12 months [WP], eczema symptoms in the previous 12 months [EP], and rhinoconjunctivitis symptoms in the previous 12 months [RP]) in Japanese children. Using the modified version of the International Study on Asthma and Allergies in Childhood (ISSAC) questionnaire, we studied the prevalence of WP, EP and RP among six-year-old children attending 72 primary schools throughout Himeji City, Japan, during the two years from 2005 to 2006. Food allergy and parents' history of allergy showed a significant relationship with the prevalence of WP, EP and RP. Day-care attendance in the first two years of life and presence of older siblings showed a significant inverse relationship with the prevalence of RP. However, neither day-care attendance nor presence of older siblings was related to the development of W and ER. Among Japanese children, food allergy and parents' history of allergy are risk factors for WP, ES or RS. However, early day-care attendance and presence of older siblings might be protective factors against RS. Infections in early life may affect the prevalence of rhinoconjunctivitis in six-year-old children.

Home Exposures to Environmental Tobacco Smoke and Allergic Symptoms Among Young Children in Singapore

Zuraimi MS, Tham KW, Chew FT, Ooi PL, David K. Int Arch Allergy Immunol. 2008;146(1):57–65 PURPOSE OF THE STUDY. To investigate the association of environmental tobacco smoke (ETS) exposure among preschool-aged children with allergic symptoms in homes in Singapore. STUDY POPULATION. The authors studied children between the ages of 1.5 and 6 years who were attending 687 child care centers in Singapore. METHODS. This study used a cross-sectional design, adopting an expanded and modified International Study on Asthma and Allergies in Childhood (ISAAC) questionnaire for the evaluation of asthma and allergies in 6794 children attending 120 randomly selected child care centers. Specific information on demographics and ETS exposures was obtained. Adjusted prevalence ratios (PRs) and 95% confidence intervals (CIs) were determined by using Poisson multivariate regression with a log-link function and robust variance estimates as recommended for cross-sectional studies. RESULTS. The response rate was 70.0%, and 4759 children from 97 centers participated. After adjusting for covariates, it was found that home ETS exposure was associated with increased risks of current symptoms of rhinitis (PR: 1.23 [95% CI: 1.01–1.50]) and rhinoconjunctivitis (PR: 1.79 [95% CI: 1.26–2.54]). These associations followed dose-response trends with respect to the number of cigarettes smoked or smokers in the home. Home ETS exposures were also associated with higher PRs of wheeze, nocturnal cough, and doctor-diagnosed asthma. Compared with paternal smoking, higher risks of the above-listed outcomes were found for maternal smoking. CONCLUSIONS. Home ETS exposure is a risk factor associated with rhinitis and asthma among preschool-aged children. REVIEWER COMMENTS. This article provides additional evidence that exposure to ETS is associated with asthma and rhinitis. These findings support the continued need to discuss the risks of ETS exposure when reviewing anticipatory guidance items with families.

Home Exposures to Environmental Tobacco Smoke and Allergic Symptoms among Young Children in Singapore

Background: Research relating environmental tobacco smoke (ETS) exposures have focused on childhood asthma. There have been fewer studies with conflicting results performed on associations of ETS exposures with allergic symptoms. We are interested to see if ETS exposures in the homes are associated with allergic symptoms among preschool children in Singapore where public smoking is banned. Methods: A cross-sectional study adopting an expanded and modified ISAAC (International Study on Asthma and Allergies in Childhood) questionnaire for the evaluation of asthma and allergies was conducted on 6,794 children attending 120 randomly selected child care centers. Specific information on demographics and ETS exposures was obtained. Adjusted prevalence ratios (PRs) and 95% confidence intervals (CIs) were determined using Poisson multivariate regression with a log-link function and robust variance estimates as recommended for cross-sectional studies. Results: The response proportion was 70.0%, and 4,759 children from 97 centers participated. After adjusting for covariates, it was found that home ETS exposure was associated with increased risks of current symptoms of rhinitis (PR 1.23; 95% CI 1.01–1.50) and rhinoconjunctivitis (PR 1.79; 95% CI 1.26–2.54). These associations followed dose-response trends with respect to number of cigarettes smoked or smokers in the homes. Home ETS exposures were also associated with higher PRs of wheeze, nocturnal cough and doctor-diagnosed asthma. Compared with paternal smoking, higher risks of the above outcomes were found for maternal smoking. Conclusion: Home ETS exposure is a risk factor associated with rhinitis and asthma among preschool children.

Association Between PM2.5 Exposure in Child Care Centers and Wheeze Among Young Children in Singapore

ISEE-440 Objective: Numerous epidemiologic studies have reported adverse effects of air PM2.5 on children's health. The objective of this study was to determine the associations between current wheeze symptom among children attending child care centers (CCCs) in Singapore and exposures to PM2.5. Material and Methods: From a large survey using the International Study on Asthma and Allergies in Childhood (ISAAC) questionnaire on 4759 children attending 104 CCCs, 15 high- and 15 low-current wheeze prevalence CCCs were selected. A total of 1551 children participated in this study. PM2.5 exposure measurements were performed indoors as well as outdoors of the CCCs. The concentrations were computed into quartiles. Prevalence ratios (PR) and 95% confidence interval (95% CI) were evaluated using Cox proportional hazard regression assuming a constant risk period controlled for the influence of confounders such as age, gender, race, familial atopy, socioeconomic status, preterm births, breast-feeding, respiratory infections, ETS, home dampness, and CCC status. Results: We found higher indoor concentrations of PM2.5 in high-prevalence CCCs than in low-prevalence CCCs (mean: 79.3 vs. 77.3 mg/m3). We found that current wheeze was associated with outdoor PM2.5 levels, as well as indoor PM2.5 levels. Comparing the categories of fourth, third, and second quartiles of indoor PM2.5, respectively, with first quartile, the adjusted PRs (95% CIs) for wheeze were 1.52 (1.00–2.31), 1.28 (0.79–2.06), and 1.13 (0.70–1.84). The corresponding adjusted PRs (95% CIs) for outdoor PM2.5 were 1.57 (1.03–2.39), 1.21 (0.80–1.84), and 1.15 (0.75–1.77). Conclusions: The slightly stronger association found for outdoor PM2.5 with wheeze symptoms suggests outdoor source of causal agent and reduction of toxicity as it is transported indoors. Given that fine particulate matter exposures of children have been considered a health risk from ambient data, the results from this study of Singapore children revealed that indoor exposures within CCC needs to be equally addressed. Therefore, CCCs should consider mitigation strategies to reduce indoor PM2.5 exposures of outdoor origin via ventilation and/or filtration.

Wheeze and urban variation in South Asia.

Typically, urban South Asia is characterised by narrow streets, heavy traffic, visible haze, unplanned city architecture and the use of kerosene or wood-burning stoves at home. However, some urban areas in South Asia are clean and modern, with concrete housing, vehicle emission regulations and use of smoke-free household fuel. The purpose of this study was to compare wheeze prevalence in 13-14-year-olds between two South Asian cities (Galle, Chandigarh), representing each of the above two archetypes. The validated one-page International Study on Asthma and Allergies in Childhood (ISAAC) questionnaire for 13-14-year-olds was used for the study. Of 1814 distributed questionnaires, 1737 (95.8%) were completed correctly and returned (Galle: n=1162; Chandigarh: n=575). Crude prevalence rates, and prevalence odds ratios (with 95% two-sided confidence intervals (CI) for comparison of prevalence rates), were calculated. The prevalence rate for wheezing in Galle (28.7%) was higher than in Chandigarh (12.5%). The prevalence odds ratios (Galle versus Chandigarh) for lifetime wheezing (2.3; 1.8-2.9), wheezing in the previous year (2.1; 1.6-2.7), exercise-related wheeze (4.8; 3.5-6.7) and physician-diagnosed wheeze (1.7; 1.2-2.3) demonstrated significant differences in wheeze prevalence between the two cities ( P<0.05). The numbers of 13-14-year-olds experiencing less than 12 wheezing episodes per year or sleep disturbance due to wheeze of less than 1 night per week were also significantly higher for Galle than Chandigarh. There is a higher prevalence of wheeze in 13-14-year-old children living in an old-fashioned, congested city than in a clean and modern city in South Asia.

Individual and area-based indicators of socioeconomic status and childhood asthma.

The current study evaluated the association between individual and area-based indicators of socioeconomic status and the prevalence, severity, and lifetime hospitalisation for asthma in children. The representative sample of 4,027 children from Rome, aged 6-7 yrs, used for the 1994 ISAAC (International Study on Asthma and Allergies in Childhood) initiative, was selected. Individual and small area indicators of socioeconomic status were used. Individual data on parents' education and on childhood asthma were gathered from self-administered parental questionnaires. Two small-area indicators (socioeconomic status index (SES) and average income in 1994) were derived using information available at the census tract of residence. Logistic regression models were used to estimate the association of parental education and small area indicators with asthma prevalence, severity, and hospitalisation. Parental smoking was considered in the analysis as a potential confounder. Prevalence of physician diagnosis of asthma (11.3%) increased as father's education decreased. Prevalence of severe asthma (1.6%) increased as maternal and paternal educational levels decreased. Lifetime hospitalisation for asthma (2.8%) was strongly associated with both parental education and small-area indicators of social disadvantage, even when considered simultaneously in the same logistic model. Socioeconomic conditions are associated with asthma occurrence, its severity, and hospitalisation. The association was stronger for asthma severity and hospitalisation. Individual indicators correlated better with the outcomes than area-based indicators. However, living in an underprivileged area is a strong independent predictor of hospital admission for asthma.

Early, current and past pet ownership: associations with sensitization, bronchial responsiveness and allergic symptoms in school children

Studies have suggested that early contact with pets may prevent the development of allergy and asthma. To study the association between early, current and past pet ownership and sensitization, bronchial responsiveness and allergic symptoms in school children. A population of almost 3000 primary school children was investigated using protocols of the International Study on Asthma and Allergies in Childhood (ISAAC). Allergic symptoms were measured using the parent-completed ISAAC questionnaire. Sensitization to common allergens was measured using skin prick tests (SPT)s and/or serum immunoglobulin (Ig)E determinations. Bronchial responsiveness was tested using a hypertonic saline challenge. Pet ownership was investigated by questionnaire. Current, past and early exposure to pets was documented separately for cats, dogs, rodents and birds. The data on current, past and early pet exposure were then related to allergic symptoms, sensitization and bronchial responsiveness. Among children currently exposed to pets, there was significantly less sensitization to cat (odds ratio (OR) = 0.69) and dog (OR = 0.63) allergens, indoor allergens in general (OR = 0.64), and outdoor allergens (OR = 0.60) compared to children who never had pets in the home. There was also less hayfever (OR = 0.66) and rhinitis (OR = 0.76). In contrast, wheeze, asthma and bronchial responsiveness were not associated with current pet ownership. Odds ratios associated with past pet ownership were generally above unity, and significant for asthma in the adjusted analysis (OR = 1.85), suggesting selective avoidance in families with sensitized and/or symptomatic children. Pet ownership in the first two years of life only showed an inverse association with sensitization to pollen: OR = 0.71 for having had furry or feathery pets in general in the first two years of life, and OR = 0.73 for having had cats and/or dogs in the first two years of life, compared to not having had pets in the first two years of life. These results suggest that the inverse association between current pet ownership and sensitization and hayfever symptoms was partly due to the removal of pets in families with sensitized and/or symptomatic children. Pet ownership in the first two years of life only seemed to offer some protection against sensitization to pollen.

Breastfeeding and Asthma Among Brazilian Children

We examined the association of breastfeeding and the presence of chronic respiratory symptoms among 5182 Brazilian schoolchildren 7–14 years of age who were participants in the International Study on Asthma and Allergies in Childhood (ISAAC). The prevalence of medically diagnosed asthma and current wheeze were respectively 4.6% (95% confidence interval [CI] 4.0%–5.2%) and 11.9% (95% CI 11.0%–12.8%). Ninety percent of the mothers in our study population had breastfed their child. After adjusting for potential confounding factors, we found that children who had not been breastfed were more likely to have a medical diagnosis of asthma (odds ration [OR] = 1.51, 95% CI 1.00–2.51), experience current wheeze (OR = 1.29, 95% CI 0.96–1.74), and wheeze after exercise (OR = 1.51, 95% CI 1.01–2.27) than children who had been breastfed for more than 6 months. This effect was only present among children with no family history of asthma (OR = 1.54, 95% CI 0.90–2.42 for medical diagnosis of asthma; OR = 1.27, 95% CI 0.93–1.75 for current wheezing; and OR = 1.74, 95% CI 1.12–2.6 for wheeze after exercise). We conclude that the low prevalence of asthma and wheeze observed in our population may be partly related to the high level of breastfeeding.

Prevalence of Asthma and Other Childhood Allergies in Brazilian Schoolchildren

We determined the prevalence of asthma, rhinitis, and eczema among Brazilian children using the standardized protocol of the International Study on Asthma and Allergies in Childhood (ISAAC) to facilitate the comparison of our results with other studies using the ISAAC methodology. We conducted a cross-sectional study from June to October 1994 to determine the prevalence of asthma, rhinitis, and eczema in 5182 school children aged 7-8 years and 13-14 years residing in the Brazilian towns of Santa Maria and Itabira (iron-mining cities located in Minas Gerais). Parents completed questionnaires at their child's school in the presence of trained interviewers. The cumulative prevalence of doctor-diagnosed asthma was 4.6% for all ages with no significant difference between the age groups. In general, there was a higher prevalence of symptoms in the younger age group than the older. The prevalence of wheezing in the previous 12 months was 14.3% (7-8 years old) and 9.3% (13-14 years old) (p ≤ 0.01), of chronic cough in the previous 12 months was 25.6% (7-8 years old) and 22.1% (13-14 years old) (p ≤ 0.01), and of nighttime cough in the previous 12 months was 22.3% (7-8 years old) and 19.4% (13-14 years old) (p ≤ 0.05). Overall the prevalences of asthma and wheezing symptoms in the previous 12 months were higher for boys than girls (5.2% vs. 3.9% for asthma, p ≤ 0.01, and 13.2% vs. 10.6% for wheezing, p ≤ 0.01, respectively). These results suggest that asthma-related respiratory illnesses affect a substantial part of the childhood population in Itabira and Santa Maria, Minas Gerais. Some factors such as male gender and younger age may be associated with an increase risk for chronic respiratory symptoms. Prevalences of asthma and allergic diseases in these Brazilian cities on the basis of self-reporting of symptoms and of one's medical history may more accurately portray the true prevalence of asthma than the use of medical records.