Sheila M. A. Matos

Effect of city-wide sanitation programme on reduction in rate of childhood diarrhoea in northeast Brazil: assessment by two cohort studies

Summary Background A city-wide sanitation intervention was started in Salvador, Brazil, in 1997 to improve sewerage coverage from 26% of households to 80%. Our aim was to investigate the epidemiological effect of this city-wide sanitation programme on diarrhoea morbidity in children less than 3 years of age. Methods The investigation was composed of two longitudinal studies done in 1997–98 before the intervention (the sanitation programme) and in 2003–04 after the intervention had been completed. Each study consisted of a cohort of children (841 in the preintervention study and 1007 in the postintervention study; age 0–36 months at baseline) who were followed up for a maximum of 8 months. Children were sampled from 24 sentinel areas that were randomly chosen to represent the range of environmental conditions in the study site. At the start of each study an individual or household questionnaire was applied by trained fieldworkers; an environmental survey was done in each area before and after introduction of the sanitation programme to assess basic neighbourhood and household sanitation conditions. Daily diarrhoea data were obtained during home visits twice per week. The effect of the intervention was estimated by a hierarchical modelling approach fitting a sequence of multivariate regression models. Findings Diarrhoea prevalence fell by 21% (95% CI 18–25%)—from 9·2 (9·0–9·5) days per child-year before the intervention to 7·3 (7·0–7·5) days per child-year afterwards. After adjustment for baseline sewerage coverage and potential confounding variables, we estimated an overall prevalence reduction of 22% (19–26%). Interpretation Our results show that urban sanitation is a highly effective health measure that can no longer be ignored, and they provide a timely support for the launch of 2008 as the International Year of Sanitation.

Impact of a citywide sanitation program in Northeast Brazil on intestinal parasites infection in young children.

Background Sanitation affects health, especially that of young children. Residents of Salvador, in Northeast Brazil, have had a high prevalence of intestinal parasites. A citywide sanitation intervention started in 1996 aimed to raise the level of sewer coverage from 26% to 80% of households. Objectives We evaluated the impact of this intervention on the prevalence of Ascaris lumbricoides, Trichuris trichuria, and Giardia duodenalis infections in preschool children. Methods The evaluation was composed of two cross-sectional studies (1998 and 2003–2004), each of a sample of 681 and 976 children 1–4 years of age, respectively. Children were sampled from 24 sentinel areas chosen to represent the range of environmental conditions in the study site. Data were collected using an individual/household questionnaire, and an environmental survey was conducted in each area before and after the intervention to assess basic household and neighborhood sanitation conditions. Stool samples were examined for the presence of intestinal parasites. The effect of the intervention was estimated by hierarchical modeling, fitting a sequence of multivariate regression models. Findings The prevalence of A. lumbricoides infection was reduced from 24.4% to 12.0%, T. trichuria from 18.0% to 5.0%, and G. duodenalis from 14.1% to 5.3%. Most of this reduction appeared to be explained by the increased coverage in each neighborhood by the sewage system constructed during the intervention. The key explanatory variable was thus an ecological measure of exposure and not household-based, suggesting that the parasite transmission prevented by the program was mainly in the public (vs. the domestic) domain. Conclusion This study, using advanced statistical modeling to control for individual and ecological potential confounders, demonstrates the impact on intestinal parasites of sanitation improvements implemented at the scale of a large population.

Environmental conditions, immunologic phenotypes, atopy, and asthma: New evidence of how the hygiene hypothesis operates in Latin America

BACKGROUND It has been proposed that improved hygiene and reduced experience of infections in childhood influences the development of allergic diseases. The mechanisms by which the hygiene operates are not well established but are underpinned by two apparently incompatible immunologic paradigms, the balance of TH1 versus TH2 cytokines and IL-10-mediated regulation of TH2 cytokines. OBJECTIVE This study defined immunologic phenotypes with the use of latent class analysis and investigated their associations with environmental factors, markers of allergy and asthma, in a Latin American population. METHODS We studied 1127 children living in urban Brazil. Data on wheeze and environmental exposures were collected with standardized questionnaires. Atopy was measured by specific IgE in serum and skin prick test reactivity to aeroallergens. Cytokines were measured in culture after the stimulation of peripheral blood leukocytes with mitogen. Infections with pathogens were assessed by serology and stool examinations. Children were classified as having high or low burden of infection. Latent class analysis was used to identify immune phenotypes on the basis of cytokine production. Logistic regression was used to evaluate the adjusted effects of environment and burden of infection on the immunologic phenotypes and the effect of the phenotypes on atopy and asthma. RESULTS Three phenotypes were identified, labeled underresponsive, intermediate, and responsive. Children of more educated mothers, living in improved environmental conditions, and with a low burden of infection were significantly more likely to have the responsive phenotype. The responsive phenotype was significantly associated with an increased prevalence of atopy but not asthma. CONCLUSION Our findings contribute to a better understanding of the immune mechanisms by which the hygiene hypothesis operates in urban Latin America.

Effectiveness of rotavirus vaccine against hospitalized rotavirus diarrhea: A case-control study

Rotavirus is one of the leading cause of hospitalization and outpatients visits among children under five years. This study evaluated overall and genotype-specific vaccine effectiveness of oral monovalent rotavirus vaccine (G1P[8] strain) in preventing hospital admission of Brazilian children with rotavirus acute diarrhea. A hospital based case-control study was conducted in five Regions of Brazil using the National Rotavirus Acute Diarrhea Surveillance System from July 2008 to August 2011. A total of 215 cases (aged 4-24 months) admitted with confirmed rotavirus diarrhea were recruited and 1961 controls hospitalized without diarrhea were frequency matched by sex and age group to cases. Two-dose adjusted vaccine effectiveness (adjusted by year of birth and the frequency matching variables) was 76% (95%CI: 58-86) lasting for two years. Effectiveness controlled by the available potential confounders was 72% (95%CI: 44-85), suggesting no appreciable confounding by those factors for which adjustment was made. In a half of the cases the rotavirus genotype was G2P[4] and in 15% G1P[8]. Genotype-specific VE (two doses) was 89% (95%CI: 78-95), for G1P[8] and 76% (95%CI: 64-84) for G2P[4]. For all G1, it was 74% (95%CI: 35-90), for all G2, 76% (95%CI: 63-84), and for all non G1/G2 genotypes, 63% (95%CI: -27-99). Effectiveness for one dose was 62% (95%CI: 39-97). Effectiveness of two-dose monovalent rotavirus vaccine in preventing hospital admission with rotavirus diarrhea was high, lasted for two years and it was similar against both G1P[8] and G2P[4]. Based on the findings of the study we recommend the continued use of rotavirus in the Brazilian National Immunization Program and the monitoring of the early emergence of unusual and novel rotavirus genotypes.

Structural equation modeling in epidemiology

Structural equation modeling (SEM) is an important statistical tool for evaluating complex relations in several research areas. In epidemiology, the use and discussion of SEM have been limited thus far. This article presents basic principles and concepts in SEM, including an application using epidemiological data analysis from a study on the determinants of cognitive development in young children, considering constructs related to organization of the childs home environment, parenting style, and the childs health status. The relations between the constructs and cognitive development were measured. The results showed a positive association between psychosocial stimulus at home and cognitive development in young children. The article presents the contributions by SEM to epidemiology, highlighting the need for an a priori theoretical model for improving the study of epidemiological questions from a new perspective.

Condições socioeconômicas e padrões alimentares de crianças de 4 a 11 anos: estudo SCAALA - Salvador/ Bahia

OBJECTIVE: to identify the patterns of food intake in children and the association between these and the socio-economic conditions of their families. METHODS: a cross-sectional study was carried out with 1260 children aged between 4 and 11 years, resident in the city of Salvador, in the Brazilian State of Bahia, including application of a semi-quantitative Food Intake Frequency questionnaire. The pattern of food intake of the children was assessed using factorial analysis by principal components. socio-economic level was assessed using a compound socio-economic indicator. Multivariate logistic regression was employed. RESULTS: four food groups were identified that explained 45.9% of the variability in food intake frequency data. Children from a more privileged socio-economic background were found to be 1.6 times more likely (p<0.001) to have a higher frequency of intake of food from group 1 (fruit, vegetables, pulses, cereals and sea food) and 3.09 times more likely (p<0.001) to have a higher frequency of consumption of food from group 2 (milk and dairy products, ketchup/mustard/mayonnaise and chicken), compared with children from a less privileged background. The opposite was found for group 4 (processed meat products, eggs, and red meat); with the children from more privileged backgrounds less likely to consume food from this group. A similar tendency was found for food from group 3 (fried food, sweets, snacks, soda/artificial fruit juice). CONCLUSION: patterns of food intake in children depend on the socio-economic conditions of their families and the choice of healthier food is associated with a more privileged socio-economic background.

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.

Padrão alimentar, asma e sibilo atópico e não atópico em crianças e adolescentes: estudo SCAALA, Salvador, Bahia, Brasil

Avaliou-se, em estudo transversal, a influencia do padrao alimentar sobre a ocorrencia de sibilo e asma atopica e nao atopica em 1.168 criancas e adolescentes em Salvador, Bahia, Brasil. Sibilo e sintomas de asma nos ultimos 12 meses foram obtidos por meio do questionario ISAAC. Atopia foi definida pela presenca de IgE especifica a aerolergenos. Questionario de frequencia alimentar foi usado para definir padroes alimentares. Empregou-se regressoes logistica e logistica politomica multivariadas. O consumo de pescados reduziu a ocorrencia de sibilo em 27% (IC95%: 0,56-0,94) e asma em 37% (IC95%: 0,47-0,83); asma nao atopica em 51% (IC95%: 0,31-0,79) e sibilo nao atopico em 38% (IC95%: 0,46-0,83). O maior tercil do padrao alimentar reduziu o sibilo em 27% (IC95%: 0,57-0,95), sibilo atopico em 46% (IC95%: 0,30-0,98), asma em 36% (IC95%: 0,49-0,83) e asma atopica em 50% (IC95%: 0,28-0,89). O consumo de pescados pode conferir efeito protetor para sibilo e asma nao atopica e o padrao alimentar para sibilo e asma atopica.A cross-sectional study was conducted on dietary patterns and their influence on the occurrence of wheezing and atopic and non-atopic asthma in a sample of 1,168 children and adolescents in Salvador, Bahia State, Brazil. Wheezing and asthma symptoms in the previous 12 months were obtained using the ISAAC questionnaire. The presence of aeroallergen-specific IgE was identified. A food frequency questionnaire was used to define dietary patterns. The study applied logistic regression and multinomial polytomous logistic regression. Fish consumption was associated with a 27% reduction in wheezing (95%CI: 0.56-0.94), 37% in asthma (95%CI: 0.47-0.83), 51% in non-atopic asthma (95%CI: 0.31-0.79), and 38% in non-atopic wheezing (95%CI: 0.46-0.83). The highest tertile of dietary patterns reduced wheezing by 27% (95%CI: 0.57-0.95), atopic wheezing by 46% (95%CI: 0.30-0.98), asthma by 36% (95%CI: 0.49-0.83), and atopic asthma by 50% (95%CI: 0.28-0.89). Fish consumption may thus have a protective effect against wheezing and non-atopic asthma and dietary pattern against atopic asthma and wheezing.

Associations of Dairy Intake with Arterial Stiffness in Brazilian Adults: The Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

Recent studies have suggested the possible effect of dairy product intake on cardiovascular risk markers, including arterial stiffness. Our aim was to investigate whether dairy food intake is associated with arterial stiffness, which we assessed by carotid-femoral pulse wave velocity (cfPWV) and pulse pressure (PP) in a cross-sectional analysis of baseline data (2008–2010; n = 12,892) of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil). Dairy consumption was evaluated with a validated food-frequency questionnaire (FFQ) by computing servings per day for total and subgroups of dairy products. Dairy consumption was described in four categories (≤1 serving/day to >4 servings/day). Covariance analysis (ANCOVA) was used to compare cfPWV across increasing intake of dairy food, adjusting for confounding factors, including non-dairy food groups. The intake of total dairy was inversely associated with cfPWV and PP (−0.13 m/s and −1.3 mmHg, from the lowest and to the highest category of dairy intake). Low-fat dairy, fermented dairy and cheese showed an inverse relationship with cfPWV and PP. These findings suggest a beneficial effect of dairy consumption to reduce arterial stiffness. However, further evidence from longitudinal studies or long-term intervention is needed to support reduction of cfPWV and PP mediating the beneficial effects of dairy products on cardiovascular health.

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”.