Silvia de Magalhães Simões

Early infection with Trichuris trichiura and allergen skin test reactivity in later childhood

Background Allergic diseases cause a large and increasing burden in developed countries and in urban centres in middle‐income countries. The causes of this increase are unknown and, currently, there are no interventions to prevent the development of allergic diseases. The ‘hygiene hypothesis’ has tried to explain the increase through a reduction in the frequency of childhood infections causing a failure to program the immune system for adequate immune regulation. Intestinal helminth parasites are prevalent in childhood in developing countries and are associated with a lower prevalence of allergen skin test reactivity and asthma.

Asthma cases in childhood attributed to atopy in tropical area in Brazil.

OBJECTIVE This study aimed to explore the association between asthma and atopy in a cohort of children living in a large urban center in Brazil. Atopy was defined by the presence of allergen-specific IgE in serum or by a positive skin prick test. METHODS In a sample of 1 445 Brazilian children, the association between the prevalence of asthma, skin prick test positivity, and allergen-specific IgE in serum was investigated. RESULTS The prevalence of asthma was 22.6%. The presence of serum allergen-specific IgE was frequent in asthmatics and nonasthmatics, and the prevalence of asthma increased only with levels of allergen-specific IgE > 3.5 kilounits/L. The proportion of asthma attributable to atopy was estimated to be 24.5% when atopy was defined by the presence of allergen-specific IgE. With a given level of specific IgE, no association between skin test reactivity and asthma was observed. Skin prick tests were less sensitive than specific IgE for detection of atopy. CONCLUSIONS Most asthma cases in an urban underprivileged setting in Brazil were not attributable to atopy. This observation has important implications for understanding the risk factors for the asthma epidemic in Latin America.

Distribuição da gravidade da asma na infância

OBJETIVO: Estimar a distribuicao dos padroes de gravidade da asma em uma amostra populacional de criancas em Salvador (BA). METODOS: Questionario epidemiologico (International Study of Asthma and Allergies in Childhood - ISAAC) foi aplicado juntamente com questionario elaborado com base em criterios de gravidade adotados na pratica clinica (Global Initiative for Asthma - GINA) em 417 criancas de 5 a 12 anos com sintomas de asma nos ultimos 12 meses. Com base nas questoes do ISAAC, as criancas foram classificadas em asma grave e nao grave. De acordo com os criterios clinicos da GINA, quatro categorias de gravidade foram criadas: intermitente, persistente leve, persistente moderada e grave. RESULTADOS: Noventa criancas (22,3%) apresentaram indicadores de gravidade segundo o ISAAC. Com base nos criterios da GINA, havia 143 criancas com asma intermitente, 160 com asma leve persistente, 51 com asma moderada e 43 com asma grave. A concordância entre os dois questionarios foi de 81,3%, com indice kappa de 0,5. CONCLUSOES: A maioria das criancas asmaticas em Salvador possui asma persistente. Ha bom nivel de concordância na identificacao da asma grave, entre a classificacao epidemiologica e a clinica.

Overweight, asthma symptoms, atopy and pulmonary function in children of 4-12 years of age: findings from the SCAALA cohort in Salvador, Bahia, Brazil.

OBJECTIVE To evaluate the association between overweight and the occurrence of asthma and atopy in a cohort of children of 4-12 years of age living in the city of Salvador in 2005. DESIGN Cross-sectional study nested in a cohort. SETTING The metropolitan region of Salvador, Bahia, Brazil. SUBJECTS The study included 1129 children of 4-12 years age who presented complete information on the variables used here. Skin tests for allergy, spirometry, faecal parasitology, serum IgE and anthropometric surveys were conducted. Poissons multivariate regression was adopted. RESULTS Wheezing was found in 29·1% and asthma in 22·8% of children, both conditions being more common in those under 6 years of age and 34% more common in overweight children (prevalence ratio (PR) = 1·34; 95% CI 1·07, 1·67) following adjustment. The ratio between forced expiratory volume in 1s and forced vital capacity was associated with overweight (PR = 1·35; 95% CI 1·11, 1·61). No statistically significant association was found between overweight and allergen-specific IgE or with wheezing. CONCLUSIONS These results are in agreement with the hypothesis that overweight is associated with asthma and pulmonary function, even following adjustment for intervening variables known to be associated with the pathogeny of asthma.

Distribution of severity of asthma in childhood

OBJECTIVE To estimate the distribution of asthma severity in a population-based sample of children from Salvador, Brazil. METHODS An epidemiologically oriented questionnaire (International Study of Asthma and Allergies in Childhood, ISAAC) and a questionnaire based on criteria used in clinical practice (The Global Initiative for Asthma, GINA) were administered simultaneously to 417 children aged 5 to 12 years who reported symptoms of asthma in the past 12 months. According to the ISAAC instrument, children were classified into severe and non-severe asthma, whereas GINA clinical criteria produced four categories of severity: intermittent, mild persistent, moderate persistent and severe asthma. RESULTS Ninety children reported symptoms indicative of severity according to the ISAAC questionnaire. According to GINA criteria, 143 children had intermittent asthma, 160 mild persistent, 51 moderate and 43 severe asthma. Agreement between the two instruments was 81.3% (kappa = 0.5). CONCLUSIONS Most asthmatic children in the Salvador urban area have persistent asthma. Agreement between epidemiological and clinical classifications of asthma severity was satisfactory.

A community study of factors related to poorly controlled asthma among Brazilian urban children.

Background Asthma constitutes a serious public health problem in many regions of the world, including the city of Salvador, State of Bahia – Brazil. The purpose of this study was to analyse the factors associated with poor asthma control. Methodology/Principal Findings Two definitions were used for asthma: 1) wheezing in the last 12 months; 2) wheezing in the last 12 months plus other asthma symptoms or asthma diagnosis ever. The definition of poorly controlled asthma was: at least one reported hospitalisation due to asthma and/or high frequency of symptoms, in the last year. Children with poorly controlled asthma (N = 187/374) were compared with wheezing children with controlled asthma regarding age, gender, atopy, parental asthma, rhinitis, eczema, exposure to second hand tobacco smoke, presence of moulds, pets and pests in the house, helminth infections and body mass index. Crude and logistic regression adjusted odds ratios were used as measures of association. There was a higher proportion of poorly controlled asthma among children with eczema (OR = 1.55; 95% CI 1.02; 2.37). The strength of the association was greater among children with eczema and rhinitis (42.6%, 53.4% and 57.7%, respectively, in children who had no rhinitis nor eczema, had only one of those, and had both (p = 0.02 for trend test). The presence of mould in the houses was inversely associated with poorly controlled asthma (OR = 0.54; 95% CI 0.34; 0.87). Conclusions/Significance Our results indicate an association between eczema and poor asthma control in this environment, but emphasize the role of various other individual and environmental factors as determinants of poor control.

Pulmonary function and symptoms in asthmatics adolescents

Background Asthma is a chronic inflammatory disease that may impose limitations to daily activities when not appropriately treated. It can be under-diagnosed in adolescents due to possible denial of symptoms in this age group or low perception of airflow obstruction. The aim of this study was to measure the degree of airway dysfunction in adolescents with asthma and determine the degree of disease control.

Respiratory muscle strength and pulmonary function in children with rhinitis and asthma after a six-minute walk test

ABSTRACT Objective: Rhinitis and asthma decrease quality of life. Few studies have assessed the performance of children with asthma or rhinitis under submaximal exercise. We evaluated maximal respiratory pressures, spirometric parameters, and ability to sustain submaximal exercise in these children before and after the 6-minute walk test (6MWT), compared to healthy children. Methods: This cross-sectional, analytical study included 89 children aged 6–12 years in outpatient follow-up: 27 healthy (H), 31 with rhinitis (R), and 31 with mild asthma under control (A). Pulmonary function parameters and maximal respiratory pressures were measured before and 5, 10, and 30 minutes after the 6MWT. Wilcoxon test was used to compare numerical numerical variables between two groups and analysis of variance or Kruskal–Wallis test for comparison among three groups. Results: Total distance traveled in the 6MWT was similar among the three groups. Compared to pre-test values, VEF1 (Forced Expiratory Volume in 1 second), VEF0.75 (Forced Expiratory Volume in 0.75 second), and FEF25–75 (Forced Expiratory Flow 25–75% of the Forced Vital Capacity – CVF – curve) decreased significantly after the 6MWT in group A, and VEF0.75, FEF25–75, and VEF1/CVF decreased significantly in group R. Groups A and R had lower Maximum Inspiratory Pressure values than group H before and after the 6MWT at all time points assessed. Conclusions: The findings suggest that children with rhinitis and mild asthma present with alterations in respiratory muscle strength and pulmonary function not associated with clinical complaints, reinforcing the concept of the united airways.

Dissociation between skin test reactivity and anti-aeroallergen IgE: Determinants among urban Brazilian children

Background The dissociation between specific IgE and skin prick test reactivity to aeroallergens, a common finding in populations living in low and middle-income countries, has important implications for the diagnosis and treatment of allergic diseases. Few studies have investigated the determinants of this dissociation. In the present study, we explored potential factors explaining this dissociation in children living in an urban area of Northeast Brazil, focusing in particular on factors associated with poor hygiene. Methods Of 1445 children from low income communities, investigated for risk factors of allergies, we studied 481 with specific IgE antibodies to any of Blomia tropicalis, Dermatophagoides pteronyssinus, Periplaneta americana and Blatella germanica allergens. Data on demographic, environmental and social exposures were collected by questionnaire; serum IgG and stool examinations were done to detect current or past infections with viral, bacterial, protozoan and intestinal helminth pathogens. We measured atopy by skin prick testing (SPT) and specific IgE (sIgE) to aerollergens in serum (by ImmunoCAP). SIgE reactivity to B. tropicalis extract depleted of carbohydrates was measured by an in-house ELISA. Total IgE was measured by in house capture ELISA. SNPs were typed using Illumina Omni 2.5. Results Negative skin prick tests in the presence of specific IgE antibodies were frequent. Factors independently associated with a reduced frequency of positive skin prick tests were large number of siblings, the presence of IgG to herpes simplex virus, Ascaris lumbricoides and Trichuris trichiura infections, living in neighborhoods with infrequent garbage collection, presence of rodents and cats in the household and sIgE reactivity to glycosylated B. tropicalis allergens. Also, SNP on IGHE (rs61737468) was negatively associated with SPT reactivity. Conclusions A variety of factors were found to be associated with decreased frequency of SPT such as unhygienic living conditions, infections, total IgE, IgE response to glycosylated allergens and genetic polymorphisms, indicating that multiple mechanisms may be involved. Our data, showing that exposures to an unhygienic environment and childhood infections modulate immediate allergen skin test reactivity, provide support for the “hygiene hypothesis”.

Weight gain in the first two years of life, asthma and atopy: the SCAALA cohort study

OBJECTIVE To evaluate the association between weight gain in the first two years of life and the occurrence of wheezing, asthma, serum IgE, skin reactivity and pulmonary function. DESIGN Cohort study. SETTING The metropolitan region of Salvador, Bahia, Brazil. SUBJECTS The association was studied between 1997 and 2005 in 669 children up to 11 years of age. Data were collected on asthma and risk factors, both current factors and those present in the first years of life. Weight gain was considered fast when the Z-score was >0·67. Poisson regression was used in the multivariate statistical analysis. RESULTS Wheezing was reported in 25·6 % of the children. Weight gain was considered fast (Z-score >0·67) in 29·6 % of the children and slow (Z-score <-0·67) in 13·9 %. Children in the slow weight gain group had 36 % fewer symptoms of asthma (prevalence ratio = 0·65; 95 % CI 0·42, 0·99). CONCLUSIONS Slower weight gain in the early years of life may constitute a protective factor against symptoms of asthma. The relevance of this finding for public health is not yet certain, since it is known that children with slow and fast weight gain may be more likely to develop adverse health consequences related to both these situations.