Mental health of adolescents:variations by disability and borderline intellectual functioning and disability

Adolescence is a period of elevated stress for many young people, and it is possible that the challenges of adolescence are different for vulnerable groups. We aimed to document the mental health, emotional and behavioral difficulties and suicidal/self-harming behaviors among adolescents with borderline intellectual functioning (BIF) or a disability, compared to those with neither disability nor BIF. Data was drawn from the Longitudinal Study of Australian Children, a nationally representative Australian study. Participants were 2950 adolescents with complete data for Waves 3-6 (years 2008-2014), aged 14-15 years in 2014. Mental health items and self-harming/suicidal thought/behaviors were self-reported. Emotional-behavioral difficulties items came from the Strengths and Difficulties Questionnaire, and were parent-, and adolescent-reported. Results of logistic regression analyses indicate that the emotional-behavioral difficulties of adolescents with either a disability or BIF, was worse than for those with neither disability nor BIF. Additionally, adolescents with a disability reported more symptoms of anxiety and depression, and were more likely to report self-harming/suicidal thoughts and behaviors. Adolescents with BIF or a disability are at higher risk of emotional-behavioral difficulties than those with neither disability nor BIF. There is some evidence that adolescents with a disability are at higher risk of anxiety, self-harming/suicidal thoughts and behaviors than adolescents without a disability

Change in weight and waist circumference and risk of colorectal cancer: Results from the Melbourne Collaborative Cohort Study

Background: Studies reporting the association between change in weight or body mass index during midlife and risk of colorectal cancer have found inconsistent results, and only one study to date has reported the association between change in waist circumference (a measure of central adiposity) and risk of colorectal cancer. Methods: We investigated the association between risk of colorectal cancer and changes in directly measured waist circumference and weight from baseline (1990-1994) to wave 2 (2003-2007). Cox regression, with age as the time metric and follow-up starting at wave 2, adjusted for covariates selected from a causal model, was used to estimate the Hazard Ratios (HRs) and 95 % Confidence Intervals (CIs) for the change in waist circumference and weight in relation to risk of colorectal cancer. Results: A total of 373 cases of colorectal cancer were diagnosed during an average 9 years of follow-up of 20,605 participants. Increases in waist circumference and weight were not associated with the risk of colorectal cancer (HR per 5 cm increase in waist circumference = 1.02; 95 % CI: 0.95, 1.10; HR per 5 kg increase in weight = 0.93; 0.85, 1.02). For individuals with a waist circumference at baseline that was less than the sex-specific mean value there was a slight increased risk of colorectal cancer associated with a 5 cm increase in waist circumference at wave 2 (HR = 1.08; 0.97, 1.21). Conclusion: Increases in waist circumference and weight during midlife do not appear to be associated with the risk of colorectal cancer

An investigation of the impact of using different methods for network meta-analysis: a protocol for an empirical evaluation.

BACKGROUND: Network meta-analysis, a method to synthesise evidence from multiple treatments, has increased in popularity in the past decade. Two broad approaches are available to synthesise data across networks, namely, arm- and contrast-synthesis models, with a range of models that can be fitted within each. There has been recent debate about the validity of the arm-synthesis models, but to date, there has been limited empirical evaluation comparing results using the methods applied to a large number of networks. We aim to address this gap through the re-analysis of a large cohort of published networks of interventions using a range of network meta-analysis methods. METHODS: We will include a subset of networks from a database of network meta-analyses of randomised trials that have been identified and curated from the published literature. The subset of networks will include those where the primary outcome is binary, the number of events and participants are reported for each direct comparison, and there is no evidence of inconsistency in the network. We will re-analyse the networks using three contrast-synthesis methods and two arm-synthesis methods. We will compare the estimated treatment effects, their standard errors, treatment hierarchy based on the surface under the cumulative ranking (SUCRA) curve, the SUCRA value, and the between-trial heterogeneity variance across the network meta-analysis methods. We will investigate whether differences in the results are affected by network characteristics and baseline risk. DISCUSSION: The results of this study will inform whether, in practice, the choice of network meta-analysis method matters, and if it does, in what situations differences in the results between methods might arise. The results from this research might also inform future simulation studies

Rota tecnológica para a gestão sustentável de resíduos sólidos domiciliares

Orientador : Prof. Dr. Vitor Afonso HoeflichMonografia (especialização) - Universidade Federal do Paraná, Setor de Ciências Agrárias, Curso de Especialização em Direito AmbientalInclui referência

The relationship between markers of antenatal iron stores and birth outcomes differs by malaria prevention regimen—a prospective cohort study

Abstract: Background: Iron deficiency (ID) has been associated with adverse pregnancy outcomes, maternal anaemia, and altered susceptibility to infection. In Papua New Guinea (PNG), monthly treatment with sulphadoxine-pyrimethamine plus azithromycin (SPAZ) prevented low birthweight (LBW; <2500 g) through a combination of anti-malarial and non-malarial effects when compared to a single treatment with SP plus chloroquine (SPCQ) at first antenatal visit. We assessed the relationship between ID and adverse birth outcomes in women receiving SPAZ or SPCQ, and the mediating effects of malaria infection and haemoglobin levels during pregnancy. Methods: Plasma ferritin levels measured at antenatal enrolment in a cohort of 1892 women were adjusted for concomitant inflammation using C-reactive protein and α-1-acid glycoprotein. Associations of ID (defined as ferritin <15 μg/L) or ferritin levels with birth outcomes (birthweight, LBW, preterm birth, small-for-gestational-age birthweight [SGA]) were determined using linear or logistic regression analysis, as appropriate. Mediation analysis assessed the degree of mediation of ID-birth outcome relationships by malaria infection or haemoglobin levels. Results: At first antenatal visit (median gestational age, 22 weeks), 1256 women (66.4%) had ID. Overall, ID or ferritin levels at first antenatal visit were not associated with birth outcomes. There was effect modification by treatment arm. Amongst SPCQ recipients, ID was associated with a 81-g higher mean birthweight (95% confidence interval [CI] 10, 152; P = 0.025), and a twofold increase in ferritin levels was associated with increased odds of SGA (adjusted odds ratio [aOR] 1.25; 95% CI 1.06, 1.46; P = 0.007). By contrast, amongst SPAZ recipients, a twofold increase in ferritin was associated with reduced odds of LBW (aOR 0.80; 95% CI 0.67, 0.94; P = 0.009). Mediation analyses suggested that malaria infection or haemoglobin levels during pregnancy do not substantially mediate the association of ID with birth outcomes amongst SPCQ recipients. Conclusions: Improved antenatal iron stores do not confer a benefit for the prevention of adverse birth outcomes in the context of malaria chemoprevention strategies that lack the non-malarial properties of monthly SPAZ. Research to determine the mechanisms by which ID protects from suboptimal foetal growth is needed to guide the design of new malaria prevention strategies and to inform iron supplementation policy in malaria-endemic settings. Trial registration: ClinicalTrials.gov NCT01136850

The impact of missing data in a longitudinal cohort study on the risks of colorectal cancer and mortality associated with change in body size

© 2013 Dr. Amalia KarahaliosBackground: Obesity is considered a global epidemic. Overweight and obesity, measured by attained weight and Waist Circumference (WC), is associated with an increased risk of Colorectal Cancer (CRC) and mortality. Measuring change in weight or WC accounts for changes in body composition (i.e. increased abdominal obesity and decreased lean muscle mass) associated with ageing, and may be a better predictor of the risks of CRC and/or mortality. Body weight, WC and hips circumference were measured in all participants of the Melbourne Collaborative Cohort Study (MCCS) at baseline, but missing data at follow-up (wave 2) complicates the analysis of changing body composition. This thesis will determine the best statistical approach for dealing with the missing WC data in the MCCS and estimates the risks of CRC and mortality associated with change in body composition. Methods: The literature was reviewed to determine how other large cohort studies have reported and dealt with missing data in the analysis of repeated exposures. The two most common statistical methods for handling missing data identified in the literature review were compared in a comprehensive simulation study. Next, I estimated the associations between change in body composition and the risks of CRC and mortality using the MCCS data and adopting the method for handling missing data that was the least biased in the simulation study. Results: Complete-case analysis was the most common method used to handle missing data in analyses with repeated exposures. Of the more complex approaches, multiple imputation was the most frequently used method. Comparing multiple imputation with complete-case analysis in an extensive simulation study showed that the estimates obtained from both complete-case analysis and multiple imputation were similar to the “true” values (i.e. very little bias was observed). As well, multiple imputation only showed gains in the precision of the estimates when an auxiliary variable was included in the imputation model that was not already included in the analysis model of interest. I used complete-case analysis to handle the missing anthropometric data at wave 2 for the MCCS participants. I found that a 5 cm increase in WC was associated with a slightly increased risk of CRC (Hazard Ratio (HR) = 1.05; 95% Confidence Interval (CI): 0.96, 1.14). For mortality, there was a non-linear association with change in body composition; weight loss (quintile 1: <-2.3 kg) and decreased WC (quintile 1: <1 cm) were associated with an increased risk of all-cause mortality (for weight, HR = 1.80; 1.54, 2.11; for WC, HR = 1.26; 1.09, 1.47) and Cardiovascular Disease mortality (for weight, HR = 2.40; 1.57, 3.65; for WC, HR = 1.39; 0.99, 1.97). This increased risk of all-cause mortality associated with weight loss was of greater magnitude for those older than 55 years at baseline (for age <55 years, HR = 1.30; 0.88, 1.92; for age 55 years, HR = 1.92; 1.61, 2.30). No association was observed for weight loss and death due to obesity-related cancer (for weight, HR = 1.20; 0.71, 2.02; for WC, HR = 1.27; 0.73, 2.23). As well, there was no association between weight gain or increased WC and all-cause or cause-specific mortality. Conclusion: Researchers need to consider the data that is both missing and available for their analyses and decide whether to use complete-case analysis or multiple imputation to handle the missing data. Increased WC increased the risk of CRC, however, weight loss and a decreased WC increased the risk of mortality, especially in older adults. From the results of this observational cohort study of middle-aged adults, weight stability seems to be the recommended option. Of note, the increased risk of mortality associated with weight loss and decreasing WC may be affected by the problem of “reverse-causation”; where an illness on the causal pathway to death is inducing the association between weight loss and mortality

A comparison of arm-based and contrast-based models for network meta-analysis.

Differences between arm-based (AB) and contrast-based (CB) models for network meta-analysis (NMA) are controversial. We compare the CB model of Lu and Ades (2006), the AB model of Hong et al(2016), and two intermediate models, using hypothetical data and a selected real data set. Differences between models arise primarily from study intercepts being fixed effects in the Lu-Ades model but random effects in the Hong model, and we identify four key difference. (1) If study intercepts are fixed effects then only within-study information is used, but if they are random effects then between-study information is also used and can cause important bias. (2) Models with random study intercepts are suitable for deriving a wider range of estimands, eg, the marginal risk difference, when underlying risk is derived from the NMA data; but underlying risk is usually best derived from external data, and then models with fixed intercepts are equally good. (3) The Hong model allows treatment effects to be related to study intercepts, but the Lu-Ades model does not. (4) The Hong model is valid under a more relaxed missing data assumption, that arms (rather than contrasts) are missing at random, but this does not appear to reduce bias. We also describe an AB model with fixed study intercepts and a CB model with random study intercepts. We conclude that both AB and CB models are suitable for the analysis of NMA data, but using random study intercepts requires a strong rationale such as relating treatment effects to study intercepts

A review of the reporting and handling of missing data in cohort studies with repeated assessment of exposure measures

Abstract Background Retaining participants in cohort studies with multiple follow-up waves is difficult. Commonly, researchers are faced with the problem of missing data, which may introduce biased results as well as a loss of statistical power and precision. The STROBE guidelines von Elm et al. (Lancet, 370:1453-1457, 2007); Vandenbroucke et al. (PLoS Med, 4:e297, 2007) and the guidelines proposed by Sterne et al. (BMJ, 338:b2393, 2009) recommend that cohort studies report on the amount of missing data, the reasons for non-participation and non-response, and the method used to handle missing data in the analyses. We have conducted a review of publications from cohort studies in order to document the reporting of missing data for exposure measures and to describe the statistical methods used to account for the missing data. Methods A systematic search of English language papers published from January 2000 to December 2009 was carried out in PubMed. Prospective cohort studies with a sample size greater than 1,000 that analysed data using repeated measures of exposure were included. Results Among the 82 papers meeting the inclusion criteria, only 35 (43%) reported the amount of missing data according to the suggested guidelines. Sixty-eight papers (83%) described how they dealt with missing data in the analysis. Most of the papers excluded participants with missing data and performed a complete-case analysis (n = 54, 66%). Other papers used more sophisticated methods including multiple imputation (n = 5) or fully Bayesian modeling (n = 1). Methods known to produce biased results were also used, for example, Last Observation Carried Forward (n = 7), the missing indicator method (n = 1), and mean value substitution (n = 3). For the remaining 14 papers, the method used to handle missing data in the analysis was not stated. Conclusions This review highlights the inconsistent reporting of missing data in cohort studies and the continuing use of inappropriate methods to handle missing data in the analysis. Epidemiological journals should invoke the STROBE guidelines as a framework for authors so that the amount of missing data and how this was accounted for in the analysis is transparent in the reporting of cohort studies.</p