Influence of internal migration on body mass index: Results of the ELSA-Brasil study.

OBJECTIVES: To investigate the association between internal migration and body mass index (BMI) in the adult population with data from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) and to determine whether the association differs by the urban hierarchical levels (or influence regions) of Brazilian municipalities. METHODS: Baseline data from 13 084 participants aged 35 to 74 (2008-2010) in the ELSA-Brasil were analyzed. A migrant was defined as an individual whose municipality of residence at the beginning of schooling (origin) was different from the municipality of residence at the study baseline (destination). The origin and destination municipalities were classified by urban hierarchical levels, or influence regions, and migration was categorized as nonmigrant, stable migrant, downward migrant, or upward migrant. RESULTS: Of the ELSA-Brasil participants, 51% were migrants. Using gamma regression models, it was observed that for women and men, upward migration was associated with lower mean BMI after adjusting for age, mother's education level, participant's education level, and income. Downward migration, on the other hand, was associated with the highest mean BMI, but this result was statistically significant only for women. CONCLUSION: These findings highlight the role of environmental factors on nutritional status, noting that the effects on BMI may be positive or negative, depending on the trajectory of displacements between origin and destination.

Four-year adiposity change and remission of hypertension: an observational evaluation from the Longitudinal Study of Adult Health (ELSA-Brasil).

The degree to which weight reduction leads to the remission of hypertension in population studies is not clear. We investigated whether the changes in adiposity measures predicted the remission of hypertension in a racially admixed population over a mean 4-year follow-up. All 4847 hypertensive individuals at baseline (2008-2010) from the multicenter Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) were included. Changes in weight, waist circumference (WC), or body mass index (BMI) (reduction or increase ≥5% from baseline values, vs stability) and remission of hypertension (SBP < 140 and DBP < 90 mmHg and no use of antihypertensive medication at follow-up visit, in 2012-2014) were investigated using mixed effects logistic regression models. Proportional attributable benefit was additionally calculated. Analyses were stratified by sex and antihypertensive medication use at baseline. Remission of hypertension was 11.3% (n = 546). Among men, after adjustments, the reduction of weight (OR = 1.52 95% CI 1.10-2.10), WC (OR = 1.56 95% CI 1.04-2.35) or BMI (OR = 1.60 95% CI 1.13-2.27) was associated with the remission of hypertension. Among those not taking antihypertensive medication at baseline, after adjustments, the reduction of weight (OR = 1.64 95% CI 1.18-2.27), WC (OR = 1.76 95% CI 1.18-2.61) or BMI (OR = 1.57 95% CI 1.10-2.25) was associated with the remission of hypertension. Proportional attributable benefit among those with adiposity reduction was about 30%, indicating its potential for prevention. In conclusion, our study reinforces the role of adiposity-reducing strategies (e.g., healthy diet and regular physical activity) for the treatment and prevention of hypertension, which might have potential applications for clinical practice.

Depression is Associated With Sarcopenia Due to Low Muscle Strength: Results From the ELSA-Brasil Study.

OBJECTIVES: To investigate the association of sarcopenia and its defining components with depression in Brazilian middle-aged and older adults. DESIGN: Cross-sectional study. SETTING AND PARTICIPANTS: This analysis included 5927 participants from the ELSA-Brasil Study second data collection, aged 55 years and older, with complete data for exposure, outcome, and covariates. MEASURES: Muscle mass was evaluated by bioelectrical impedance analysis and muscle strength by hand-grip strength. Sarcopenia was defined according to the Foundation for the National Institutes of Health (FNIH) criteria. Depression was assessed using the Clinical Interview Scheduled Revised (CIS-R). Information on sociodemographic characteristics, lifestyle, and clinical comorbidities were also obtained. RESULTS: The frequencies of sarcopenia, presarcopenia, low muscle mass, low muscle strength, and low muscle strength without loss of muscle mass was 1.9%, 18.8%, 20.7%, 4.8%, and 2.9%, respectively. After adjustment for sociodemographic characteristics, clinical conditions, and lifestyle factors, depression was associated with sarcopenia (odds ratio [OR] = 2.23, 95% confidence interval [CI] = 1.11-4.48, P = .024) and low muscle strength (OR = 1.94, 95% CI = 1.20-3.15, P = .007), but it was not associated with presarcopenia, low muscle mass, and low muscle strength without loss of muscle mass. CONCLUSIONS: Depression is associated with sarcopenia defined by the FNIH criteria mainly because of its association with weakness. Future studies are needed to clarify the temporal relationship between both conditions.

Multiobjective grammar-based genetic programming applied to the study of asthma and allergy epidemiology.

BACKGROUND: Asthma and allergies prevalence increased in recent decades, being a serious global health problem. They are complex diseases with strong contextual influence, so that the use of advanced machine learning tools such as genetic programming could be important for the understanding the causal mechanisms explaining those conditions. Here, we applied a multiobjective grammar-based genetic programming (MGGP) to a dataset composed by 1047 subjects. The dataset contains information on the environmental, psychosocial, socioeconomics, nutritional and infectious factors collected from participating children. The objective of this work is to generate models that explain the occurrence of asthma, and two markers of allergy: presence of IgE antibody against common allergens, and skin prick test positivity for common allergens (SPT). RESULTS: The average of the accuracies of the models for asthma higher in MGGP than C4.5. IgE were higher in MGGP than in both, logistic regression and C4.5. MGGP had levels of accuracy similar to RF, but unlike RF, MGGP was able to generate models that were easy to interpret. CONCLUSIONS: MGGP has shown that infections, psychosocial, nutritional, hygiene, and socioeconomic factors may be related in such an intricate way, that could be hardly detected using traditional regression based epidemiological techniques. The algorithm MGGP was implemented in c ++ and is available on repository: http://bitbucket.org/ciml-ufjf/ciml-lib .

Leisure-Time Physical Activity, but not Commuting Physical Activity, is Associated with Cardiovascular Risk among ELSA-Brasil Participants.

BACKGROUND: Despite reports in the literature that both leisure-time physical activity (LTPA) and commuting physical activity (CPA) can promote health benefits, the literature lacks studies comparing the associations of these domains of physical activity with cardiovascular risk scores. OBJECTIVE: To investigate the association between LTPA and CPA with different cardiovascular risk scores in the cohort of the Longitudinal Study of Adult Health ELSA-Brasil. METHODS: Cross-sectional study with data from 13,721 participants of both genders, aged 35-74 years, free of cardiovascular disease, from ELSA Brazil. Physical activity was measured using the International Physical Activity Questionnaire (IPAQ). Five cardiovascular risk scores were used: Framingham score - coronary heart disease (cholesterol); Framingham score - coronary heart disease (LDL-C); Framingham score - cardiovascular disease (cholesterol); Framingham score - cardiovascular disease (body mass index, BMI); and pooled cohort equations for atherosclerotic cardiovascular disease (ASCVD). Associations adjusted for confounding variables between physical activity and different cardiovascular risk scores were analyzed by logistic regression. Confidence interval of 95% (95%CI) was considered. RESULTS: LTPA is inversely associated with almost all cardiovascular risk scores analyzed, while CPA shows no statistically significant association with any of them. Dose-response effect in association between LTPA and cardiovascular risk scores was also found, especially in men. CONCLUSIONS: LTPA was shown to be associated with the cardiovascular risk scores analyzed, but CPA not. The amount of physical activity (duration and intensity) was more significantly associated, especially in men, with cardiovascular risk scores in ELSA-Brasil.

Leisure-Time Physical Activity, but not Commuting Physical Activity, is Associated with Cardiovascular Risk among ELSA-Brasil Participants / Atividade Física no Tempo Livre, porém não Atividade Física no Deslocamento, está Associada com Risco Cardiovascular em Participantes do ELSA-Brasil

Abstract Background: Despite reports in the literature that both leisure-time physical activity (LTPA) and commuting physical activity (CPA) can promote health benefits, the literature lacks studies comparing the associations of these domains of physical activity with cardiovascular risk scores. Objective: To investigate the association between LTPA and CPA with different cardiovascular risk scores in the cohort of the Longitudinal Study of Adult Health ELSA-Brasil. Methods: Cross-sectional study with data from 13,721 participants of both genders, aged 35-74 years, free of cardiovascular disease, from ELSA Brazil. Physical activity was measured using the International Physical Activity Questionnaire (IPAQ). Five cardiovascular risk scores were used: Framingham score - coronary heart disease (cholesterol); Framingham score - coronary heart disease (LDL-C); Framingham score - cardiovascular disease (cholesterol); Framingham score - cardiovascular disease (body mass index, BMI); and pooled cohort equations for atherosclerotic cardiovascular disease (ASCVD). Associations adjusted for confounding variables between physical activity and different cardiovascular risk scores were analyzed by logistic regression. Confidence interval of 95% (95%CI) was considered. Results: LTPA is inversely associated with almost all cardiovascular risk scores analyzed, while CPA shows no statistically significant association with any of them. Dose-response effect in association between LTPA and cardiovascular risk scores was also found, especially in men. Conclusions: LTPA was shown to be associated with the cardiovascular risk scores analyzed, but CPA not. The amount of physical activity (duration and intensity) was more significantly associated, especially in men, with cardiovascular risk scores in ELSA-Brasil.

Resumo Fundamento: Apesar dos relatos na literatura de que tanto a atividade física no tempo livre (AFTL) quanto a atividade física no deslocamento (AFDESL) promovem benefícios à saúde, estudos comparando a associação desses domínios da atividade física com escores de risco cardiovascular são escassos. Objetivo: Verificar a associação entre AFTL e AFDESL com escores de risco cardiovascular na coorte Estudo Longitudinal de Saúde do Adulto (ELSA-Brasil). Métodos: Estudo transversal com dados da linha de base de 13.721 participantes de ambos os sexos, com idades entre 35 e 74 anos, livres de doenças cardiovasculares, do ELSA-Brasil. A atividade física foi mensurada por meio do International Physical Activity Questionnary (IPAQ). Foram utilizados cinco escores de risco cardiovascular: escore de Framingham - doença coronariana (colesterol); escore de Framingham - doença coronariana (lipoproteína de baixa densidade - LDL-C); escore de Framingham - doença cardiovascular (colesterol); escore de Framingham - doença cardiovascular (índice de massa corpórea - IMC); e equações de coorte agrupadas para doença cardiovascular aterosclerótica. As associações ajustadas por variáveis de confundimento foram analisadas por meio de regressão logística. Utilizou-se intervalo de confiança de 95% (IC95%). Resultados: Com quase todos os escores de risco cardiovascular analisados, a AFTL apresenta-se inversamente associada, enquanto a AFDESL não demonstra associação estatisticamente significante com nenhum deles. Observou-se, ainda, a existência de efeito dose-resposta na associação entre AFTL e escores de risco cardiovascular principalmente em homens. Conclusões: A AFTL, porém não a AFDESL, apresenta associação com os escores de risco cardiovascular analisados. A maior quantidade de atividade física (duração e intensidade) está associada de forma mais significativa, principalmente em homens, aos escores de risco cardiovascular em participantes da coorte ELSA-Brasil. (Arq Bras Cardiol. 2017; [online].ahead print, PP.0-0)

Cohort Profile: Longitudinal Study of Adult Health (ELSA-Brasil).

Chronic diseases are a global problem, yet information on their determinants is generally scant in low- and middle-income countries. The Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) aims to contribute relevant information regarding the development and progression of clinical and subclinical chronic diseases, particularly cardiovascular diseases and diabetes, in one such setting. At Visit 1, we enrolled 15 105 civil servants from predefined universities or research institutes. Baseline assessment (2008-10) included detailed interviews and measurements to assess social and biological determinants of health, as well as various clinical and subclinical conditions related to diabetes, cardiovascular diseases and mental health. A second visit of interviews and examinations is under way (2012-14) to enrich the assessment of cohort exposures and to detect initial incident events. Annual surveillance has been conducted since 2009 for the ascertainment of incident events. Biological samples (sera, plasma, urine and DNA) obtained at both visits have been placed in long-term storage. Baseline data are available for analyses, and collaboration via specific research proposals directed to study investigators is welcome.

[Dietary pattern, asthma, and atopic and non-atopic wheezing in children and adolescents: SCAALA study, Salvador, Bahia State, Brazil]. / Padrão alimentar, asma e sibilo atópico e não atópico em crianças e adolescentes: estudo SCAALA, Salvador, Bahia, Brasil.

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.

Padrão alimentar, asma e sibilo atópico e não atópico em crianças e adolescentes: estudo SCAALA, Salvador, Bahia, Brasil / Dietary pattern, asthma, and atopic and non-atopic wheezing in children and adolescents: SCAALA study, Salvador, Bahia State, Brazil / Patrón dietético, asma y sibilancias atópicas y no atópicas en niños y adolescentes: estudio SCAALA, Salvador, Bahía, Brasil

Avaliou-se, em estudo transversal, a influência do padrão alimentar sobre a ocorrência de sibilo e asma atópica e não atópica em 1.168 crianças e adolescentes em Salvador, Bahia, Brasil. Sibilo e sintomas de asma nos últimos 12 meses foram obtidos por meio do questionário ISAAC. Atopia foi definida pela presença de IgE específica a aerolérgenos. Questionário de frequência alimentar foi usado para definir padrões alimentares. Empregou-se regressões logística e logística politômica multivariadas. O consumo de pescados reduziu a ocorrência de sibilo em 27% (IC95%: 0,56-0,94) e asma em 37% (IC95%: 0,47-0,83); asma não atópica em 51% (IC95%: 0,31-0,79) e sibilo não atópico em 38% (IC95%: 0,46-0,83). O maior tercil do padrão alimentar reduziu o sibilo em 27% (IC95%: 0,57-0,95), sibilo atópico em 46% (IC95%: 0,30-0,98), asma em 36% (IC95%: 0,49-0,83) e asma atópica em 50% (IC95%: 0,28-0,89). O consumo de pescados pode conferir efeito protetor para sibilo e asma não atópica e o padrão alimentar para sibilo e asma atópica.

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.

Este estudio transversal se llevó a cabo para estudiar la influencia de los hábitos alimentarios en la aparición del asma y sibilancias atópicas y no atópicas en una muestra de 1.168 niños y adolescentes en Salvador, Bahía, Brasil. Las sibilancias y síntomas de asma en los últimos 12 meses se han obtenido a partir del cuestionario ISAAC. Se identificó la presencia de IgE específica de alérgeno aéreo. Se utilizó un cuestionario de frecuencia de alimentos para definir hábitos alimentarios. Se aplicó la regresión logística y el modelo logístico multinomial. El consumo de pescado redujo las sibilancias en un 27% (IC95%: 0,56-0,94) y el asma en un 37% (IC95%: 0,47-0,83), las sibilancias atópicas en un 51% (IC95%: 0,31-0,79) y no atópicas en un 38% (IC95%: 0,46-0,83). El tercil más alto de los hábitos alimentarios reduce sibilancias en un 27% (IC95%: 0,57-0,95), sibilancias atópicas en un 46% (IC95%: 0,30-0,98), el asma en un 36% (IC95%: 0,49-0,83) y un 50% en el asma atópico (IC95%: 0,28-0,89). El consumo de pescado puede promover un efecto protector, dentro el patrón de dieta, contra sibilancias atópicas y no atópicas y asma.

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.

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.

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. Poisson's 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.

Condições socioeconômicas e padrões alimentares de crianças de 4 a 11 anos: estudo SCAALA - Salvador/ Bahia / The socio-economic conditions and patterns of food intake in children aged between 4 and 11 years: the SCAALA study - Salvador/ Bahia

OBJETIVOS: identificar os padrões alimentares de crianças e sua associação com o nível socioeconômico das famílias. MÉTODOS: estudo transversal com 1260 crianças de 4 a 11 anos, residentes em Salvador-Bahia que incluiu aplicação de um Questionário de Frequência Alimentar semi-quantitativo. Os padrões alimentares foram identificados, empregando-se análise fatorial por componentes principais. O nível socioeconômico foi avaliado por meio de um indicador socioeconômico composto. Regressão logística multivariada foi empregada. RESULTADOS: identificaram-se quatro padrões que explicaram 45,9 por cento da variabilidade dos dados de frequência alimentar. Crianças que pertencem ao nível socioeconômico mais alto têm 1,60 vezes mais chance (p<0,001) de apresentarem maior frequência de consumo de alimentos do padrão 1 (frutas, verduras, leguminosas, cereais e pescados) e 3,09 vezes mais chance (p<0,001) de apresentarem maior frequência de consumo dos alimentos do padrão 2 (leite/ derivados, catchup/ maionese/ mostarda e frango), quando se compara com aquele de crianças de nível socioeconômico mais baixo. Resultado inverso foi observado no padrão 4 (embutidos, ovos e carnes vermelhas); isto é, quanto maior o nível socioeconômico menor a chance da adoção desse padrão. Tendência similar foi notada para o padrão 3 (frituras, doces, salgadinhos, refrigerante/ suco artificial). CONCLUSÕES: padrões alimentares de crianças são dependentes das condições socioeconômicas das famílias e a adoção de itens alimentares mais saudáveis associa-se aos grupos de mais altos níveis socioeconômicos.

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 percent 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.

Structural equation modeling in epidemiology / Modelagem de equações estruturais em epidemiologia

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 child's home environment, parenting style, and the child's 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.

A modelagem de equações estruturais (MEE) é uma ferramenta estatística importante para avaliar relações complexas em várias áreas do conhecimento. Em Epidemiologia sua divulgação e uso são limitados. Este artigo apresenta princípios e conceitos básicos da MEE, com exemplo de aplicação na análise de dados epidemiológicos. A análise de dados é realizada em estudo que investiga determinantes do desenvolvimento cognitivo infantil, sendo definidos construtos relacionados à organização do ambiente da criança, ao seu status de saúde, e às práticas e estilo de vida dos pais. O impacto positivo da qualidade de estimulação psicossocial do ambiente doméstico sobre o índice de desempenho cognitivo (IDC) esclarece que parte do efeito da estimulação sobre o IDC deve-se ao estilo parental de interação com a criança e às características físico-ambientais do contexto familiar. As potencialidades do uso da MEE em Epidemiologia são apresentadas, enfatizando-se a definição do modelo teórico e seu uso para aprofundamento de questões epidemiológicas sob nova perspectiva.

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 child's home environment, parenting style, and the child's 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.

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

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.