Breastfeeding and obesity in Brazilian children

The association between breastfeeding and obesity is inconsistent by the literature. This study aims to assess whether obesity is associated to occurrence of breastfeeding and to duration of total and exclusive breastfeeding in Brazilian children. A cross-sectional study was conducted with 764 children enrolled in public and private schools from Viçosa, Minas Gerais, Brazil. Obesity (outcome variable) was defined as body mass index above the +2 standard deviations score using sex and age specific standards of World Health Organization. Exposure was the occurrence and duration of breastfeeding. Potential confounders were controlled by multiple logistic regression analysis and were divided in two groups: children (gender, age, birth weight, gestational age, order of birth, number of siblings, number of persons in the residence, type of school, physical activity patterns and time watching television) and mothers (age, nutritional status, level of education, weight gain during pregnancy, smokes currently and during the pregnancy). Prevalence of obesity was 10.7%; 6.8% of the children were not breastfed and 59.0% did not receive exclusive breastfeeding. After adjustment for confounding variables by logistic regression analysis, no statistically significant association was observed between obesity and the occurrence and/or duration of total and exclusive breastfeeding. There was no dose-response effect of duration of breastfeeding on prevalence of obesity. Our results do not support the hypothesis that breastfeeding promotion would reduce obesity in this population. Controversial findings regarding this association by literature indicate a need for further investigations

Bayesian Inference for Power Law Processes with Applications in Repairable Systems

Abstract. Statistical models for recurrent events are of great interest in repairable systems reliability and maintenance. The adopted model under minimal repair maintenance is frequently a Nonhomogeneous Poisson Process with the Power Law Process (PLP) intensity function. Although inference for the PLP is generally based on maximum likelihood theory, some advantages of the Bayesian approach have been reported in the literature. In this paper it is proposed that the PLP intensity be reparametrized in terms of (β, η), where β is the elasticity of the mean number of events with respect to time and η is the mean number of events for the period in which the sistem was actually observed. It is shown that β and η are orthogonal and that the likelihood becomes proportional to a product of Gamma densities. Therefore, the family of natural conjugate priors is also a product of Gammas. The idea is extended to the case that several realizations of the same PLP are observed along overlapping periods of time. The results are applied to a real problem concerning the determination of the optimal periodicity of preventive maintenance for a set of power transformers. Some Monte Carlo simulations are provided to study the frequentist behavior of the Bayesian estimates and to compare them with the maximum likelihood estimates

Reducing occurrence of Giardia duodenalis in children living in semiarid regions: impact of a large scale rainwater harvesting initiative.

BACKGROUND: In Brazil, about two million people living in rural semiarid regions were benefited with the construction of rainwater cement cisterns, as an initiative from the program "One Million Cisterns" (P1MC). Nevertheless, few epidemiological studies have been conducted to assess health risks or protection effects associated with consumption of this water source. The aim of this study was to evaluate whether access to rainwater harvesting cisterns is associated with the decrease in the occurrence of Giardia duodenalis infections in children, compared to other children living in households supplied by other water sources. METHODOLOGY/PRINCIPAL FINDINGS: A quasi-experimental study with two concurrent cohorts was developed in two rural municipalities of the semiarid region of Brazil. A sample of 664 children, aged between 4 months and 5 years old, was followed up, of which 332 had access to rainwater cisterns (cistern group) and 332 did not, having water supplied from alternative sources (comparison group). In a period of approximately one year (2010) intestinal parasites were investigated in feces three times. The prevalence of G. duodenalis in children from the cistern group ranged from 4.8 to 10.5%, while the prevalence in the comparison group ranged from 7.6 to 16.7%. Multivariate analysis (GEE) showed a higher risk of G. duodenalis infection in children who did not have access to rainwater cisterns, when compared to children who did (OR 1.72; 95% CI 1.14-2.59). The other variables associated with G. duodenalis infection were: number of rooms per house (OR 0.89; 95% CI 0.80-0.99); family income (OR0.48; 95% CI 0.26-0.88); birth order (OR 1.72; 95% CI 1.17-2.51); preterm children (OR 1.70; 95% CI 1.19-2.43); and improper hand hygiene prior to food preparation (OR 4.78; 95% CI 1.95-11.76). CONCLUSIONS/SIGNIFICANCE: Ownership of a rainwater cistern is associated with a lower prevalence of G. duodenalis infection in children after adjustment for environmental and family-related factors. Nevertheless, the study suggests the necessity to complement physical interventions with actions related to personal and domestic hygiene to enable further reductions in parasite infections affecting mainly the underprivileged populations

Effect of combining multiple micronutrients with iron supplementation on Hb response in children: systematic review of randomized controlled trials

Objectives To study the effect of combining multiple (two or more) micronutrients with Fe supplementation on Hb response, when compared with placebo and with Fe supplementation, in children.Data sources Electronic databases, personal files, hand search of reviews, bibliographies of books, and abstracts and proceedings of international conferences.Review methods Randomized controlled trials evaluating change in Hb levels with interventions that included Fe and multiple-micronutrient supplementation in comparison to placebo alone or Fe alone were analysed in two systematic reviews.Results Twenty-five trials were included in the review comparing Fe and micronutrient supplementation with placebo. The pooled estimate (random effects model) for change in Hb with Fe and micronutrient supplementation (weighted mean difference) was 0·65 g/dl (95 % CI 0·50, 0·80, P &lt; 0·001). Lower baseline Hb, lower height-for-age Z score, non-intake of ‘other micronutrients’ and malarial non-hyperendemic region were significant predictors of greater Hb response and heterogeneity. Thirteen trials were included in the review comparing Fe and micronutrient supplementation with Fe alone. The pooled estimate for change in Hb with Fe and micronutrient supplementation (weighted mean difference) was 0·14 g/dl (95 % CI 0·00, 0·28, P = 0·04). None of the variables were found to be significant predictors of Hb response.Conclusions Synthesized evidence indicates that addition of multiple micronutrients to Fe supplementation may only marginally improve Hb response compared with Fe supplementation alone. However, addition of ‘other micronutrients’ may have a negative effect. Routine addition of unselected multiple micronutrients to Fe therefore appears unjustified for nutritional anaemia control programmes.<br/

Corrected score tests for exponential censored data

In this paper we discuss the issue of improving score statistics for exponential censored data. We give a general formula to compute corrected score statistics in exponential regression models. The formula derived is simple enough to be used analytically in order to obtain closed-form Bartlett-type corrections to improve score statistics in several special cases. The formula has also advantages for numerical purposes because it requires only simple operations on matrices. We show by Monte Carlo simulations that the corrected score test seems to improve over the usual score test.Bartlett-type correction Chi-squared distribution Exponential regression model Maximum likelihood estimate Score test Types I and II censoring

Computational Statistics & Data Analysis

Texto completo. Acesso restrito. p. 113–124Consider a repairable system operating under a maintenance strategy that calls for complete preventive repair actions at pre-scheduled times and minimal repair actions whenever a failure occurs. Under minimal repair, the failures are assumed to follow a nonhomogeneous Poisson process with an increasing intensity function. This paper departs from the usual power-law-process parametric approach by using the constrained nonparametric maximum likelihood estimate of the intensity function to estimate the optimum preventive maintenance policy. Several strategies to bootstrap the failure times and construct confidence intervals for the optimal maintenance periodicity are presented and discussed. The methodology is applied to a real data set concerning the failure histories of a set of power transformers.Salvado