Matildes da Silva Prado

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.

Determinants of cognitive function in childhood: A cohort study in a middle income context

BackgroundThere is evidence that poverty, health and nutrition affect childrens cognitive development. This study aimed to examine the relative contributions of both proximal and distal risk factors on child cognitive development, by breaking down the possible causal pathways through which poverty affects cognition.MethodsThis cohort study collected data on family socioeconomic status, household and neighbourhood environmental conditions, child health and nutritional status, psychosocial stimulation and nursery school attendance. The effect of these on Wechsler Pre-School and Primary Scale of Intelligence scores at five years of age was investigated using a multivariable hierarchical analysis, guided by the proposed conceptual framework.ResultsUnfavourable socioeconomic conditions, poorly educated mother, absent father, poor sanitary conditions at home and in the neighbourhood and low birth weight were negatively associated with cognitive performance at five years of age, while strong positive associations were found with high levels of domestic stimulation and nursery school attendance.ConclusionChildrens cognitive development in urban contexts in developing countries could be substantially increased by interventions promoting early psychosocial stimulation and preschool experience, together with efforts to prevent low birth weight and promote adequate nutritional status.

Asymptomatic giardiasis and growth in young children; a longitudinal study in Salvador, Brazil

This study sought to assess the effect of giardiasis on growth of young children. In Salvador, northeast Brazil, 597 children initially aged 6 to 45 months were followed for a year in 1998/9, measured anthropometrically thrice, every 6 months, and monitored for diarrhoea prevalence twice weekly. Stool samples were collected and examined during the second round of anthropometry, and infected children were treated 39 days later, on average (S.D. 20 days). For each 6-month interval, the gains in z-scores of infected and uninfected children were compared, after adjustment for potential confounding factors, including longitudinal prevalence of diarrhoea. No significant difference was found for the first interval but in the second, the gain in adjusted height-for-age z-score was 0.09 less in infected than uninfected children, equivalent to a difference in height gain of 0.5 cm. The shortfall in growth was greater in children who remained free of diarrhoea, and was significantly correlated with the proportion of the second interval during which the child had remained untreated. We conclude that Giardia can impede child growth even when asymptomatic, presumably through malabsorption. This finding challenges the view that young children found to have asymptomatic giardiasis in developing countries should not be treated.

Risk Factors for Childhood Diarrhea Incidence: Dynamic Analysis of a Longitudinal Study

Background: Several longitudinal studies have investigated factors associated with childhood diarrhea in developing countries. However, most studies have neglected important dynamic features of the longitudinal design and hierarchical interrelationships among the potential risk factors. Methods: We conducted a longitudinal study of 902 children, age 0 to 36 months at baseline, in a large urban center in northeastern Brazil. Diarrhea data were collected by following children from October 2000 until January 2002 with biweekly home visits. We used a dynamic time-to-event analysis to account for several longitudinal features. We applied an effect-decomposition strategy to quantify direct and indirect effects of risk factors grouped in different blocks. Results: Childs age and an autoregressive effect of past diarrhea episodes explained some of the decline of diarrhea incidence observed throughout the study (from more than 14 episodes to 2 episodes per child-year), a phenomenon already observed but not explained in other longitudinal diarrhea studies. We identified the following major diarrhea determinants: low socioeconomic status, poor sanitation conditions, presence of intestinal parasites, and absence of prenatal examination. The effect of socioeconomic status was mediated mostly by living and sanitation conditions. Conclusion: Our study shows important advantages of applying a dynamic analysis approach to longitudinal observational studies of diarrhea or other acute diseases and highlights the complex interrelationships of diarrhea determinants. Our results confirm the importance of sanitation as a major determinant of child health in urban settings of developing countries.

Risk factors for infection with Giardia duodenalis in pre-school children in the city of Salvador, Brazil

A cross-sectional study of 694 children aged 2 to 45 months selected from 30 clusters throughout the city of Salvador, Bahia (pop. 2.3 million) was carried out as part of a longitudinal study of diarrhoea in order to identify risk factors for infection with Giardia duodenalis. Variables studied included three social and demographic factors (such as mothers education and marital status), five relating to the peri-domestic environment (rubbish disposal, open sewers, paving of the street), seven relating to the home itself (house construction, susceptibility to flooding, water supply and sanitation) as well as a score for hygiene behaviour based on structured observation. After multivariate analysis using a hierarchical model, only four significant risk factors were found: (a) number of children in the household under five years (b) rubbish not collected from the house (c) presence of visible sewage nearby, and (d) absence of a toilet. All four were significant at the 1% level.

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.

Sentinel areas: a monitoring strategy in public health

Resumo As tecnicas disponiveis para monitoramento da situacao de saude tem-se mostrado insuficientes, razao pela qual se discute a necessidade de aperfeicoa-las com base no desenvolvimento de novas estrategias de coleta de informacoes, de modo a permitir seu uso pelos sistemas locais de saude. Este artigo apresenta as bases metodologicas de uma estrategia de monitoramento de problemas de saude que emprega espacos intra-urbanos delimitados – areas sentinelas – para coleta de informacoes sociais, economicas, comportamentais e biologicas fundamentais para a Saude Publica, por permitirem uma maior aproximacao com a realidade de espacos sociais complexos. Os autores apresentam uma experiencia que esta sendo desenvolvida em Salvador/Bahia, Brasil, para avaliacao de impacto epidemiologico resultante da implantacao de um programa de saneamento ambiental. Discutem-se os criterios de selecao das areas e as potencialidades de uso dessa estrategia para possibilitar o emprego agil dos recursos epidemiologicos pelos servicos de saude de forma agil e a aplicacao oportuna de seus resultados na reorientacao e aprimoramento das praticas de intervencao em saude. Palavras-chave: areas sentinelas; monitoramento; saude publica; vigilância sentinela. Summary Because available techniques for monitoring the health situation have shown to be insufficient, this article discusses methods to improve these techniques based on the development of new strategies of data collection that permit their use by local health systems. The methodological basis of a strategy of health monitoring using well-defined inner-urban spaces, called sentinel areas, is presented. The proposed strategy permits the collection of social, economic, behavioral, and biological information essential for public health practice, including a better approach to the reality of complex social spaces. The authors present an experience developed in the city of Salvador, the capital of Bahia state, Brazil, which has been used to evaluate the epidemiological impact of an environment sanitation program. Criteria for area selection are discussed, as well as the potential use of this strategy by health services, as it allows the use of epidemiological resources and their results for improving health intervention programs in a timely manner.

Impact of a city-wide sanitation intervention in a large urban centre on social, environmental and behavioural determinants of childhood diarrhoea: analysis of two cohort studies

BACKGROUND Poor socioeconomic status (SES) increases diarrhoea risk, mostly mediated by lack of sanitation, poor infrastructure and living conditions. The effectiveness of a city-wide sanitation intervention on diarrhoea in a large urban centre in Northeast Brazil has recently been demonstrated. This article aims to explore how this intervention altered the magnitude of relative and attributable risks of diarrhoea determinants and the pathways by which those factors affect diarrhoea risk. METHODS We investigated determinants of prevalence of diarrhoea in two cohort studies conducted before and after the intervention. Each study enrolled pre-school children followed up for 8 months. For both cohorts, we calculated relative, attributable and mediated risks of diarrhoea determinants by a hierarchical effect decomposition strategy. RESULTS The intervention reduced diarrhoea and also changed attributable and relative risks of diarrhoea determinants by altering the pathways of mediation. Before the intervention SES was a major distal diarrhoea determinant (attributable risk: 24%) with 90% of risk mediated by other factors, mostly by lack of sanitation and poor infrastructure (53%). After the intervention, only 13% of risk was attributed to SES, with only 42% mediated by other factors (18% by lack of sanitation and poor infrastructure). CONCLUSION The intervention reduced diarrhoea risk by reducing direct exposure to unfavourable sanitation conditions. At the same time it altered the effect and mediation pathways of most distal diarrhoea determinants, especially SES. This finding corroborates the importance of public sanitation measures in reducing the impact of poverty on diarrhoea. It also underlines the value of studying the impact of public health interventions to improve our understanding of health determinants.

Alimentação complementar nos primeiros dois anos de vida

Este e um estudo transversal, com amostra constituida de 724 criancas residentes na cidade de Salvador, BA,Brasil, elegiveis por meio de amostragem por conglomerados em tres estagios. As informacoes referentes aoconsumo alimentar foram coletadas por meio do inquerito recordatorio de 24 horas e processadas peloprograma

Childhood anemia prevalence and associated factors in Salvador, Bahia, Brazil

A cross-sectional study was conducted in 1996 to estimate the prevalence of anemia in a stratified sample of 603 preschool children and identify factors associated with the disease. Hemoglobin assays were conducted in finger-prick blood samples using a Hemocue hemoglobinometer. Anemia was defined as hemoglobin below 11.0 g/dl. Logistic regression analysis was used to evaluate the potential associations. Observed anemia prevalence was 46.3%. Associated factors were: the 6-12-month and 12-24-month age brackets, the lowest tertiles for iron density and protein content dietary intake, and any degree of deficit in the height-for-age anthropometric parameter. Inadequate physical, sanitary, and environmental conditions in the home were associated with a significantly increased risk of anemia. Anemia constitutes an important health problem in this studys child population. Improvements in living conditions and dietary quality could contribute to a reduction in anemia prevalence.