scholarly journals Distinctive Mediating Effects of Subcortical Structure Changes on the Relationships Between Amyloid or Vascular Changes and Cognitive Decline

2021 ◽  
Vol 12 ◽  
Author(s):  
Na-Yeon Jung ◽  
Jeong-Hyeon Shin ◽  
Hee Jin Kim ◽  
Hyemin Jang ◽  
Seung Hwan Moon ◽  
...  
Keyword(s):  
Cognitive Function ◽  
Indirect Effect ◽  
Rating Scale ◽  
Memory Function ◽  
Mediation Effect ◽  
Subcortical Structure ◽  
Vascular Changes ◽  
Subcortical Structures ◽  
Volume Changes ◽  
Mediation Effects

Objective: We investigated the mediation effects of subcortical volume change in the relationship of amyloid beta (Aβ) and lacune with cognitive function in patients with mild cognitive impairment (MCI).Methods: We prospectively recruited 101 patients with MCI who were followed up with neuropsychological tests, MRI, or Pittsburgh compound B (PiB) PET for 3 years. The mediation effect of subcortical structure on the association of PiB or lacunes with cognitive function was analyzed using mixed effects models.Results: Volume changes in the amygdala and hippocampus partially mediated the effect of PiB changes on memory function (direct effect = −0.168/−0.175, indirect effect = −0.081/−0.077 for amygdala/hippocampus) and completely mediated the effect of PiB changes on clinical dementia rating scale sum of the box (CDR-SOB) (indirect effect = 0.082/0.116 for amygdala/hippocampus). Volume changes in the thalamus completely mediated the effect of lacune on memory, frontal executive functions, and CDR-SOB (indirect effect = −0.037, −0.056, and 0.047, respectively).Conclusions: Our findings provide a better understanding of the distinct role of subcortical structures in the mediation of the relationships of amyloid or vascular changes with a decline in specific cognitive domains.

scholarly journals Causal mediation analysis with multiple causally non-ordered mediators

2015 ◽  
Vol 27 (1) ◽  
pp. 3-19 ◽  
Author(s):  
Masataka Taguri ◽  
John Featherstone ◽  
Jing Cheng
Keyword(s):  
Indirect Effect ◽  
Interactive Effect ◽  
Mediation Effect ◽  
Mediation Effects ◽  
Mediation Analyses ◽  
Intermediate Variable ◽  
Causal Mediation ◽  
Health Studies ◽  
Using Data ◽  
The Individual

In many health studies, researchers are interested in estimating the treatment effects on the outcome around and through an intermediate variable. Such causal mediation analyses aim to understand the mechanisms that explain the treatment effect. Although multiple mediators are often involved in real studies, most of the literature considered mediation analyses with one mediator at a time. In this article, we consider mediation analyses when there are causally non-ordered multiple mediators. Even if the mediators do not affect each other, the sum of two indirect effects through the two mediators considered separately may diverge from the joint natural indirect effect when there are additive interactions between the effects of the two mediators on the outcome. Therefore, we derive an equation for the joint natural indirect effect based on the individual mediation effects and their interactive effect, which helps us understand how the mediation effect works through the two mediators and relative contributions of the mediators and their interaction. We also discuss an extension for three mediators. The proposed method is illustrated using data from a randomized trial on the prevention of dental caries.

scholarly journals Depression Mediates the Causal Effect of Food Insecurity Transition on Cognitive Function

2021 ◽  
Vol 5 (Supplement_1) ◽  
pp. 973-973
Author(s):  
Peiyi Lu ◽  
Katrina Kezios ◽  
Adina Zeki Al Hazzouri
Keyword(s):  
Cognitive Function ◽  
Food Insecurity ◽  
Indirect Effect ◽  
Verbal Memory ◽  
Cognitive Aging ◽  
Causal Effect ◽  
Mediation Effects ◽  
Language Functions ◽  
Effect Of Food ◽  
Underlying Mechanisms

Abstract Despite substantial evidence on the relationship between food insecurity and worse cognition, few studies have examined the underlying mechanisms. This study examined whether and to what extent depression mediated the casual effect of food insecurity on cognition in midlife. Longitudinal data from the Coronary Artery Risk Development in Young Adults Study were used. The 2000 survey was used as our study’s baseline, when respondents aged 33-45. We lagged the explanatory and mediator variables to set up temporality. Food insecurity transition from 2000-2005 surveys was recoded (persistent food secure, persistent food insecure, became food insecure, and became food secure). Depression was measured in 2010, while cognitive functions were measured in 2015. Causal mediation analysis examined and decomposed the direct and indirect effect. Compared to persistent food security, both persistent and became food insecure were linked to worse cognition, after adjusting demographic and cardiovascular risk factors. Further, for both exposure groups, depression had significant and strong mediation effects (natural indirect effect ranged from -0.037 to -0.018). Specifically, as respondents experienced persistent food insecurity or became food insecure, their depression increased, which, in turn, reduced their cognition. The proportion of the total effect of food insecurity transition on cognition mediated by depression ranged from 7-24% for processing speed, verbal memory, cognitive, and language functions. Persistent and became food insecure reduced cognitive function directly or indirectly through increasing depression among middle-aged adults. Interventions targeting either food insecurity or treatment of depression among food insecure individuals may have the potential to slow premature cognitive aging.

scholarly journals Estimation and Inference for the Mediation Effect in a Time-Varying Mediation Model

2021 ◽  
Author(s):  
Xizhen Cai ◽  
Donna Coffman ◽  
Megan Piper ◽  
Runze Li
Keyword(s):  
Indirect Effect ◽  
Mediation Analysis ◽  
Mediation Effect ◽  
Outcome Variable ◽  
Time Varying ◽  
Mediation Model ◽  
Real World Data ◽  
Mediation Effects ◽  
Simulation Based ◽  
Time Invariant

Abstract Background: Traditional mediation analysis typically examines the relations among an intervention, a time-invariant mediator, and a time-invariant outcome variable. Although there may be a total effect of the intervention on the outcome, there is a need to understand the process by which the intervention affects the outcome (i.e. the indirect effect through the mediator). This indirect effect is frequently assumed to be time-invariant. With improvements in data collection technology, it is possible to obtain repeated assessments over time resulting in intensive longitudinal data. This calls for an extension of traditional mediation analysis to incorporate time-varying variables as well as time-varying effects. Methods: We focus on estimation and inference for the time-varying mediation model, which allows mediation effects to vary as a function of time. We propose a two-step approach to estimate the time-varying mediation effect. Moreover, we use a simulation-based approach to derive the corresponding point-wise conffidence band for making inference of the time-varying mediation effect. Results: Simulation studies show that the proposed procedures perform well when comparing the conffidence band and the true underlying model. We further apply the proposed model and the statistical inference procedure to real-world data collected from a smoking cessation study. Conclusions: We present a practical model for estimating the time-varying mediation effects to allow time-varying outcome as well as time-varying mediator. Simulation-based inference tool is also proposed and implemented an R package on CRAN.

Understanding How Cumulative Victimization Predicts Future Victimization Risk: Relevance of Cognitive Versus Social Mediation

2021 ◽  
pp. 073401682110157
Author(s):  
Thomas Wojciechowski
Keyword(s):  
Indirect Effect ◽  
Sensation Seeking ◽  
Service Providers ◽  
Social Factor ◽  
Equation Modeling ◽  
Mediation Effects ◽  
Systems Model ◽  
Victimization Risk ◽  
Increased Risk ◽  
Peer Association

Cumulative victimization represents the summation of victimization experiences across multiple contexts, with greater accumulation generally predicting greater dysfunction than less accumulation of exposures. Past research has indicated that cumulative victimization predicts increased risk for future revictimization also. The dual systems model may help to understand this relationship. This framework comprises constructs of sensation-seeking and impulse control in developmental context. Deviant peer association may provide a social factor that helps to understand this relationship. Victimization has been found to influence all of these constructs identified here. It is predicted that increased accumulation of victimization experiences may drive variation in these constructs that results in elevated risk for revictimization. This study sought to test the theory that each of these three constructs independently mediated the cumulative victimization–revictimization relationship. The Pathways to Desistance data were used in analyses. This sample was comprised of 1,354 juvenile offenders followed for 7 years after a recent adjudication prior to baseline measurements. The first three waves of data were used in analyses. Generalized structural equation modeling was used to test for the relationships of interest. A bootstrapping process of computing standard errors was carried out to determine significance of mediation effects. Results indicated that increased cumulative victimization scores at baseline predicted increased probability of experiencing victimization at Wave 3. This relationship was attenuated by about 15% when all mediators were added to the model and the relationship remained significant. Further analyses indicated that the specific indirect effect running through deviant peer association was significant, as was the total indirect effect. Findings indicate that increases in cumulative victimization may result in increased affiliation with deviant peers that further increases their future victimization risk. Service providers for survivors of violence should focus on screening of social relationships of those they provide care for in order to assess safety concerns.

scholarly journals How Can Agricultural Corporate Build Sustainable Competitive Advantage through Green Intellectual Capital? A New Environmental Management Approach to Green Agriculture

2021 ◽  
Vol 18 (15) ◽  
pp. 7900
Author(s):  
Chulin Pan ◽  
Yufeng Jiang ◽  
Mingliang Wang ◽  
Shuang Xu ◽  
Ming Xu ◽  
...  
Keyword(s):  
Environmental Management ◽  
Competitive Advantage ◽  
Intellectual Capital ◽  
Moderated Mediation ◽  
Mediation Effect ◽  
Relational Model ◽  
Management Approach ◽  
Sustainable Competitive Advantage ◽  
Green Innovation ◽  
Mediation Effects

Based on natural resource-based theory, this study constructed a relational model between green intellectual capital, green innovation, and an agricultural corporate sustainable competitive advantage. The samples included a total of 341 agricultural companies in China, and multiple regression methods are used for the analysis. The results showed that green product innovation and green process innovation had a mediation effect between green human capital, green structural capital, green relational capital, and the sustainable competitive advantage of agricultural corporate. Beyond the simple moderation effect, a new integrated moderated-mediation effect model was established. It was shown that environmental leadership, green organizational identification, and green dynamic capability had different moderated-mediation effects under different conditions. The study is expected to close the previous research gaps and insufficiency in agricultural corporate environmental management and green agricultural. The empirical results and conclusions bring enlightenment and meaningful theoretical guidance to managers, researchers, practitioners, and policy makers in the green and sustainable development of agricultural corporates. The new environmental management path can help agricultural corporates conduct green innovation effectively, adapt to the green agricultural products market, and achieve sustainable competitive advantage. Ultimately, this will help to accelerate the development of green agriculture.

scholarly journals Efficacy of Different Types of Exercise on Cognitive Function in People With MCI or Dementia: A Network Meta-Analysis

2020 ◽  
Vol 4 (Supplement_1) ◽  
pp. 293-293
Author(s):  
Qiaoqin Wan ◽  
Xiuxiu Huang ◽  
Xiaoyan Zhao ◽  
Bei Li ◽  
Ying Cai ◽  
...  
Keyword(s):  
Executive Function ◽  
Cognitive Function ◽  
Cognitive Dysfunction ◽  
Meta Analysis ◽  
Memory Function ◽  
Controlled Trials ◽  
Exercise Interventions ◽  
Exercise Treatment ◽  
Different Types ◽  
Global Cognition

Abstract With the accelerating progress of population aging, cognitive dysfunction is becoming increasingly prevalent. Exercise, as a promising non-pharmaceutical therapy, showed favorable effects on cognitive function. But which type is the most effective exercise treatment is still unclear. This study compared the efficacy of different types of exercise interventions based on network meta-analysis and aimed to explore the optimal exercise treatment for cognitive decline. The electronic databases of PubMed, Web of Science, Embase, Cochrane Central Register of Controlled Trials, SPORTDiscus, PsycInfoy, and OpenGrey were searched from inception to September 2019. We only included randomized controlled trials that examined the effectiveness of exercise interventions in people with MCI or dementia. Primary outcomes were global cognition, executive function and memory function. Standard mean difference (SMD) and its 95% confidence interval (CI) were calculated to estimate the effect sizes. Finally, 73 articles with 5748 participants were included. The results showed all kinds of exercise interventions were effective on global cognition and resistance exercise was probably the most effective exercise treatment to prevent the decrease of global cognition (SMD=1.05, 95%CI 0.56-1.54), executive function (SMD=0.85, 95%CI 0.21-1.49) and memory function (SMD=0.32, 95%CI 0.01-0.63) for people with cognitive dysfunction. Subgroup analysis revealed multi-component exercise showed more favorable effects on global cognition (SMD=0.99, 95%CI 0.44-1.54) and executive function (SMD=0.72, 95%CI 0.06-1.38) in people with MCI. In conclusion, resistance exercise tended to be the optimal exercise type for people with cognitive dysfunction, especially for people with dementia. And multi-component exercise also should be recommended for people with MCI.

scholarly journals Variable selection for causal mediation analysis using LASSO-based methods

2021 ◽  
pp. 096228022199750
Author(s):  
Zhaoxin Ye ◽  
Yeying Zhu ◽  
Donna L Coffman
Keyword(s):  
Propensity Score ◽  
Indirect Effect ◽  
Adaptive Lasso ◽  
Mediation Effect ◽  
Regularization Methods ◽  
Causal Mediation ◽  
Outcome Information ◽  
Causal Mediation Analysis ◽  
Selection For ◽  
Mimic Iii

Causal mediation effect estimates can be obtained from marginal structural models using inverse probability weighting with appropriate weights. In order to compute weights, treatment and mediator propensity score models need to be fitted first. If the covariates are high-dimensional, parsimonious propensity score models can be developed by regularization methods including LASSO and its variants. Furthermore, in a mediation setup, more efficient direct or indirect effect estimators can be obtained by using outcome-adaptive LASSO to select variables for propensity score models by incorporating the outcome information. A simulation study is conducted to assess how different regularization methods can affect the performance of estimated natural direct and indirect effect odds ratios. Our simulation results show that regularizing propensity score models by outcome-adaptive LASSO can improve the efficiency of the natural effect estimators and by optimizing balance in the covariates, bias can be reduced in most cases. The regularization methods are then applied to MIMIC-III database, an ICU database developed by MIT.

Effects of perceived social isolation, fear of social isolation and gratitude during COVID-19 pandemic on anxiety in Malaysia (Preprint)

2021 ◽  
Author(s):  
Cher Yi Tan ◽  
Jia Yi Ng ◽  
Mei-Hua Lin ◽  
Min Hooi Yong
Keyword(s):  
Older Adults ◽  
Young Adults ◽  
Social Isolation ◽  
Indirect Effect ◽  
Moderating Effect ◽  
Mediating Effect ◽  
Mediation Effect ◽  
Mediation Model ◽  
Middle Aged ◽  
Perceived Social Isolation

BACKGROUND The COVID-19 pandemic compelled many countries including Malaysia to impose movement restrictions to curb spreading the virus. Evidence shows that prolonged isolation has negative effects on both physical and mental health. OBJECTIVE Our aims were to examine (1) the mediating effect of perceived social isolation (SI) and fear of social isolation (FSI) on the relationship between gratitude and anxiety, and (2) to explore the moderating effect of age, education and socioeconomic status on the mediation model. METHODS We collected data from 427 participants currently living in Malaysia during the movement restriction order (Mage = 37.90, SD = 16.51, 313 females) from an online survey containing questions pertaining to isolation and gratitude. RESULTS Our mediation analysis showed that gratitude has a positive effect on overcoming anxiety as it also lowers feelings of SI and FSI (B = -.229, β = .128, bootstrap SE = .049, 95% bootstrap CI = [-.332, -.138]). The moderated mediation analyses revealed the indirect effect of gratitude on anxiety through SI was significant for young adults (B = -.148, β = .083, 95% bootstrap CI [-.274, -.042]) and middle-aged (B = -.099, β = -.055, 95% bootstrap CI [-.177, -.033]) but not for older adults (B = -.026, β = -.015, 95% bootstrap CI [-.129, .047]). Results were similar for FSI in that it was significant for middle aged and not significant for older adults (all CIs does not include zero). However the mediation effect was not significant for young adults (B = -.020, β = -.011, 95% bootstrap CI [-.066, .016]). When we examined the moderating effect of education and SES in the parallel mediation model, results showed that the mediation effect of SI and FSI for those with lower levels of education was significant for all SES levels (all CIs did not contain zero). As for those with medium levels of education, the conditional indirect effect of SI and FSI was significant only for low and medium levels of SES but not for high SES. CONCLUSIONS Our findings highlight the importance of having some coping mechanism and social connection during the pandemic to have higher wellbeing and quality of life, especially for middle-aged sample and people from low education and SES background. CLINICALTRIAL None

scholarly journals Low self-control and aggression exert serial mediation between inattention/hyperactivity problems and severity of internet gaming disorder features longitudinally among adolescents

2020 ◽  
Vol 9 (2) ◽  
pp. 401-409
Author(s):  
Hyunsuk Jeong ◽  
Hyeon Woo Yim ◽  
Seung-Yup Lee ◽  
Hae Kook Lee ◽  
Marc N. Potenza ◽  
...  
Keyword(s):  
Indirect Effects ◽  
Rating Scale ◽  
Internet Gaming Disorder ◽  
Self Control ◽  
Self Report ◽  
Mediation Effect ◽  
Gaming Disorder ◽  
Internet Gaming ◽  
Serial Mediation ◽  
Low Self Control

AbstractObjectivesWe examined serial mediating roles of low self-control and aggression in explaining relationships between levels of inattention and hyperactivity problems (IHPs) and severity of Internet gaming disorder (IGD) features when exposed to online games among adolescents without Attention deficit hyperactivity disorder (ADHD) stratified by gender using three-wave longitudinal study.MethodThe sample comprised a total of 1,732 family dyads from a study that was conducted among seventh graders without diagnoses of ADHD at baseline. Levels of IHPs were assessed by the parent reported Korean version of the ADHD rating scale at baseline (wave1). Severity of IGD features was assessed by the Internet Game Use-Elicited Symptom Screen (IGUESS) at wave3. Both levels of self-control (wave1) and aggression (wave2) were assessed by self-report. The mediating role of low self-control and aggression in the relationships between level of IHPs and severity of IGD were evaluated using serial mediation analysis separately for each gender.ResultsLevels of IHPs were related directly to severity of IGD features in both genders. The indirect effects via low self-control were also significant in both genders, however, the indirect effects via aggression was significant only in women. The serial mediation effect via low self-control and aggression between levels of IHPs and IGD features was significant in both genders (men, coefficient:0.009, 95%CI 0.005–0.019; women, coefficient:0.010, 95%CI:0.005–0.026).ConclusionWe revealed a possible mechanism underlying a serial mediation chain from low self-control to aggression explaining the effects of IHPs on severity of IGD features. However, this conclusion should be taken with a caution, because the effect sizes were very low.

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