101 resultados para Multilevel SEM


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There has been an increasing interest in the use of inter-organisational groups to address regional implications in sustainable development. These groups bring together local knowledge and expertise and span boundaries between government and industry organisations. Our focus is in understanding how knowledge is shared in such inter-organisational groups. Utilising interviews, observations and social network analysis, we examine the knowledge sharing implications derived from the mixed membership, multilevel interaction, and the need to span boundaries with external organisations in these collaborations.

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Background
There is increasing community and government recognition of the magnitude and impact of adolescent depression. Family based interventions have significant potential to address known risk factors for adolescent depression and could be an effective way of engaging adolescents in treatment. The evidence for family based treatments of adolescent depression is not well developed. The objective of this clinical trial is to determine whether a family based intervention can reduce rates of unipolar depressive disorders in adolescents, improve family functioning and engage adolescents who are reluctant to access mental health services.

Methods/Design
The Family Options study will determine whether a manualized family based intervention designed to target both individual and family based factors in adolescent depression (BEST MOOD) will be more effective in reducing unipolar depressive disorders than an active (standard practice) control condition consisting of a parenting group using supportive techniques (PAST). The study is a multicenter effectiveness randomized controlled trial. Both interventions are delivered in group format over eight weekly sessions, of two hours per session. We will recruit 160 adolescents (12 to 18 years old) and their families, randomized equally to each treatment condition. Participants will be assessed at baseline, eight weeks and 20 weeks. Assessment of eligibility and primary outcome will be conducted using the KID-SCID structured clinical interview via adolescent and parent self-report. Assessments of family mental health, functioning and therapeutic processes will also be conducted. Data will be analyzed using Multilevel Mixed Modeling accounting for time x treatment effects and random effects for group and family characteristics. This trial is currently recruiting. Challenges in design and implementation to-date are discussed. These include diagnosis and differential diagnosis of mental disorders in the context of adolescent development, non-compliance of adolescents with requirements of assessment, questionnaire completion and treatment attendance, breaking randomization, and measuring the complexity of change in the context of a family-based intervention.

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Objectives To investigate the ‘adaptation’ versus ‘sensitisation’ hypotheses in relation to mental health and labour market transitions out of employment to determine whether mental health stabilised (adaptation) or worsened (sensitisation) as people experienced one or more periods without work. Methods The Household Income and Labour Dynamics of Australia (HILDA) longitudinal survey was used to investigate the relationship between the number of times a person had been unemployed or had periods out of the labour force (ie, spells without work) and the Mental Component Summary (MCS) of the Short Form 36 (SF-36). Demographic, health and employment related confounders were included in a series of multilevel regression models. Results During 2001–2010, 3362 people shifted into unemployment and 1105 shifted from employment to not in the labour force. Compared with participants who did not shift, there was a 1.64-point decline (95% CI −2.05 to −1.23, p<0.001) in scores of the MCS SF-36 among those who had one spell of unemployment (excluding not in the labour force), and a 2.56-point decline (95% CI −3.93 to −1.19, p<0.001) among those who had two or more spells of unemployment after adjusting for other variables. Findings for shifts from employment to ‘not in the labour force’ were in the same direction; however, effect sizes were smaller. Conclusions These results indicate that multiple spells of unemployment are associated with continued, though small, declines in mental health. Those who leave employment for reasons other than unemployment experience a smaller reduction in mental health.

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Background People living in neighbourhoods of lower socioeconomic status have been shown to have higher rates of obesity and a lower likelihood of meeting physical activity recommendations than their more affluent counterparts. This study examines the sociospatial distribution of access to facilities for moderate or vigorous intensity physical activity in Scotland and whether such access differs by the mode of transport available and by Urban Rural Classification. Methods A database of all fixed physical activity facilities was obtained from the national agency for sport in Scotland. Facilities were categorised into light, moderate and vigorous intensity activity groupings before being mapped. Transport networks were created to assess the number of each type of facility accessible from the population weighted centroid of each small area in Scotland on foot, by bicycle, by car and by bus. Multilevel modelling was used to investigate the distribution of the number of accessible facilities by small area deprivation within urban, small town and rural areas separately, adjusting for population size and local authority. Results Prior to adjustment for Urban Rural Classification and local authority, the median number of accessible facilities for moderate or vigorous intensity activity increased with increasing deprivation from the most affluent or second most affluent quintile to the most deprived for all modes of transport. However, after adjustment, the modelling results suggest that those in more affluent areas have significantly higher access to moderate and vigorous intensity facilities by car than those living in more deprived areas. Conclusions The sociospatial distributions of access to facilities for both moderate intensity and vigorous intensity physical activity were similar. However, the results suggest that those living in the most affluent neighbourhoods have poorer access to facilities of either type that can be reached on foot, by bicycle or by bus than those living in less affluent areas. This poorer access from the most affluent areas appears to be reversed for those with access to a car.

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Results from a direct recharge experiment conducted in the field to investigate DOC and UVA(254) attenuation rates during the direct injection of UF treated wastewater into a artificial coastal sandfill are presented in this paper. Approximately 500 m(3) of ultra-filtered wastewater was injected into the saturated zone, over a period of 9 days. The movement of the plume was tracked over 80 days, during which time samples were obtained from multilevel samplers installed in transects across the drift axis of the plume. An analysis of fluorescein in the samples obtained during the drift of the UF plume showed that DOC and UVA were attenuated beyond rates predicted by conservative mixing, by up to a maximum of 45%. A degradation coefficient of 0.0175 day(-1) was found to be applicable for DOC degradation. After a drift period of 80 days, DOC and UVA reduced to approximately 4.5 mg/l and 0.100 cm(-1), respectively, from initial values of 8.06 mg/l and 0.199 cm(-1).

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This study investigated whether the number of alcohol outlets per 10,000 population in a given area (density) influenced parental supply of alcohol to adolescents; differences in Australian born and acculturating parents were also examined. A state-representative student survey in Victoria identified that the majority of adolescents (55%) reported that they had used alcohol in the past 12 months; 34 % of those who had consumed alcohol reported that it had been supplied by their parents. Multilevel modelling identified that there were no overall effects of density, however there were different effects based on parent country of birth and type of license. Specifically, each unit increase in the density of takeaway liquor stores increased the likelihood by 2.03 that children with both Australian-born parents would be supplied alcohol. Adolescents with both migrant parents on the other hand, had a 1.36 increased risk of being supplied alcohol as the density of outlets requiring at-venue consumption increased. The findings of this study suggest that in Australia, alcohol outlet density is associated with parental supply of alcohol to children, with this effect moderated by the cultural background of the parent and type of outlet density. Future research should investigate the association between the density of alcohol outlets and public approval of parents supplying alcohol to adolescents.

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Using data from waves 3, 7 and 9 of the Household, Income and Labour Dynamics in Australia (HILDA) survey, a group-mean-centred multilevel mixed model and self-reported chronic conditions, this study contributes to the limited longitudinal evidence on the nativity health gap in Australia. We investigated whether differences exist in the reporting of any chronic condition (including cancer, cardiovascular disease (CVD), arthritis, diabetes and respiratory disease), and in the total number of chronic conditions, between foreign-born (FB) from English speaking (ES) and non-English speaking (NES) countries and native-born (NB) Australians. We also investigated differences between these groups in the reporting of any chronic condition, and the total number of chronic conditions, by duration of residence. After adjusting for time varying and time invariant covariates, we found a significant difference by nativity status in the reporting of chronic condition, with immigrants from both ES and NES countries less likely to report a chronic condition and having fewer chronic conditions compared with the NB. Immigrants from both ES and NES countries living in Australia for less than 20 years were significantly less likely to report a chronic condition compared with the NB. However, the health of both these groups converged to that of the NB population in terms of reporting a chronic condition after 20 years of stay in Australia.

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Purpose Although previous studies have suggested that greater community densities of alcohol sales outlets are associated with greater alcohol use and problems, the mechanisms are unclear. The present study examined whether density was associated with increased purchasing of alcohol by adolescents younger than the legal purchase age of 18 in Australia. Methods The number of alcohol outlets per 10,000 population was identified within geographic regions in Victoria, Australia. A state-representative student survey (N = 10,143) identified adolescent reports of purchasing alcohol, and multilevel modeling was then used to predict the effects for different densities of outlet types (packaged, club, on-premise, general, and overall). Results Each extra sales outlet per 10,000 population was associated with a significant increase in the risk of underage adolescent purchasing. The strongest effect was for club density (odds ratio = 1.22) and packaged (takeaway) outlet density (odds ratio = 1.12). Males, older children, smokers, and those with substance-using friends were more likely to purchase alcohol. Conclusions One mechanism by which alcohol sales outlet density may influence population rates of alcohol use and related problems is through increasing the illegal underage purchasing of alcohol. © 2015 Society for Adolescent Health and Medicine.

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Emerging research suggests that prolonged sedentary behaviour (SB) is detrimental to health. Changes in SB patterns are likely to occur during particular life stages, for example at retirement age (55-65-year-old). Evidence on socio-ecological SB correlates is scarce and inconsistent in this age group. Moreover, the influence of socio-ecological correlates may vary depending on health and retirement status. This study examined social and environment correlates of overall weekend day sitting among adults at or approaching retirement age, and moderating effects of perceived physical health and retirement status. Baseline data from the Wellbeing, Eating and Exercise for a Long Life study in 2839 Australian adults (55-65-year-old) were analysed. Participants self-reported proximal social factors, neighbourhood social and physical environment, physical health and retirement status. MLwiN multilevel regression analyses were conducted. In the multivariable model, only social support from friends/colleagues to discourage sitting (B = -0.891; p = 0.036) was associated with overall weekend day sitting. No moderation of retirement status, nor physical health were found in the multivariable results. Results from this study suggest the importance of social factors in relation to weekend day sitting among 55-65-year-old adults. Health promotion initiatives in this age group should pay special attention to enhancing social interaction opportunities. Moreover, findings suggest that SB-specific correlates may need to be examined in future research.

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This article is devoted to a new iterative construction of hierarchical classifiers in SimpleCLI for the detection of phishing websites. Our new construction of hierarchical systems creates ensembles of ensembles in SimpleCLI by iteratively linking a top-level ensemble to another middle-level ensemble instead of a base classifier so that the top-level ensemble can generate a large multilevel system. This new construction makes it easy to set up and run such large systems in SimpleCLI. The present article concentrates on the investigation of performance of the iterative construction of such classifiers for the example of detection of phishing websites. We carried out systematic experiments evaluating several essential ensemble techniques as well as more recent approaches and studying their performance as parts of the iterative construction of hierarchical classifiers. The results presented here demonstrate that the iterative construction of hierarchical classifiers performed better than the base classifiers and standard ensembles. This example of application to the classification of phishing websites shows that the new iterative construction combining diverse ensemble techniques into the iterative construction of hierarchical classifiers can be applied to increase the performance in situations where data can be processed on a large computer. © 2014 ACADEMY PUBLISHER.

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 Background: The Dutch Obesity Intervention in Teenagers (DOiT) programme is an evidence-based obesity prevention programme tailored to adolescents attending the first two years of prevocational education in the Netherlands. The initial programme showed promising results during an effectiveness trial. The programme was adapted and prepared for nationwide dissemination. To gain more insight into the process of translating evidence-based approaches into ‘real world’ (i.e., ‘natural’) conditions, our research aims were to evaluate the impact of the DOiT-implementation programme on adolescents’ adiposity and energy balance-related behaviours during natural dissemination and to explore the mediating and moderating factors underlying the DOiT intervention effects.
Methods: We conducted a cluster-controlled implementation trial with 20 voluntary intervention schools (n=1002 adolescents) and 9 comparable control schools (n = 484 adolescents). We measured adolescents’ body height and weight, skinfold thicknesses, and waist circumference. We assessed adolescents’ dietary and physical activity behaviours by means of self-report. Data were collected at baseline and at 20-months follow-up. We used multivariable multilevel linear or logistic regression analyses to evaluate the intervention effects and to test the hypothesised behavioural mediating factors. We checked for potential effect modification by gender, ethnicity and education level.
Results: We found no significant intervention effects on any of the adiposity measures or behavioural outcomes. Furthermore, we found no mediating effects by any of the hypothesised behavioural mediators. Stratified analyses for gender showed that the intervention was effective in reducing sugar-containing beverage consumption in girls (B = -188.2 ml/day; 95% CI = -344.0; -32.3). In boys, we found a significant positive intervention effect on breakfast frequency (B = 0.29 days/week; 95% CI = 0.01; 0.58). Stratified analyses for education level showed an adverse intervention effect (B = 0.09; 95% CI = 0.02; 0.16) on BMI z-scores for adolescents attending the vocational education track.
Conclusions: Although not successful in changing adolescents’ adiposity, the DOiT-implementation programme had some beneficial effects on specific obesity-related behaviours in subgroups. This study underlines the difficulty of translating intervention effectiveness in controlled settings to real world contexts. Adaptations to the implementation strategy are needed in order to promote implementation as intended by the teachers.

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Identifying specific aspects of peer social norms that influence adolescent substance use may assist international prevention efforts. This study examines two aggregated measures of social norms in the school setting and their predictive association with substance (alcohol, tobacco and marijuana) use 2 years later in a large cross-national population-based cohort of adolescents. The primary hypothesis is that in Grade 7 both "injunctive" school norms (where students associate substance use with "coolness") and "descriptive" norms (where student substance use is common) will predict Grade 9 substance use. Data come from the International Youth Development Study, including 2,248 students (51.2% female) in the US and Australia attending 121 schools in Grade 7. Independent variables included injunctive norms (aggregating measures of school-wide coolness ratings of each substance use) and descriptive norms (aggregating the prevalence of school substance use) in Grade 7. Dependent variables included binge drinking and current use of alcohol, tobacco and marijuana in Grade 9. Associations between each type of school-wide social norm and substance use behaviors in Grade 9 were tested using multilevel logistic regression, adjusting for covariates. In unadjusted models, both injunctive and descriptive norms each significantly predicted subsequent substance use. In fully adjusted models, injunctive norms were no longer significantly associated with Grade 9 use, but descriptive norms remained significantly associated with tobacco and marijuana use in the expected direction. The findings identify descriptive social norms in the school context as a particularly important area to address in adolescent substance use prevention efforts.

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Few studies use comprehensive ecological approaches considering multilevel factors to understand correlates of healthy (and unhealthy) dietary intake. The aim of this study was to examine the association between individual, social, and environmental factors on composite measures of healthy and unhealthy dietary intake in adults.

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Objective: To investigate: (i) how lunch frequency of adolescents varies between schools and between classes within schools; (ii) the associations between frequency of lunch and individual sociodemographic factors and school characteristics; and (iii) if any observed associations between lunch frequency and school characteristics vary by gender and age groups. Design: Cross-sectional study in which students and school headmasters completed self-administered questionnaires. Associations were estimated by multilevel multivariate logistic regression. Setting: The Danish arm of the Health Behaviour in School-Aged Children study 2010. Subjects: Students (n 4922) aged 11, 13 and 15 years attending a random sample of seventy-three schools. Results: The school-level and class-level variations in low lunch frequency were small (intraclass correlation coefficient <2·1 %). At the individual level, low lunch frequency was most common among students who were boys, 13- and 15-year-olds, from medium and low family social class, descendants of immigrants, living in a single-parent family and in a reconstructed family. School-level analyses suggested that having access to a canteen at school was associated with low lunch frequency (OR=1·47; 95% CI 1·14, 1·89). Likewise not having an adult present during lunch breaks was associated with low lunch frequency (OR=1·44; 95% CI 1·18, 1·75). Cross-level interactions suggested that these associations differed by age group. Conclusions: Lunch frequency among Danish students appears to be largely influenced by sociodemographic factors. Additionally, the presence of an adult during lunch breaks promotes frequent lunch consumption while availability of a canteen may discourage frequent lunch consumption. These findings vary between older and younger students.