Tests of Mediation: Paradoxical Decline in Statistical Power as a Function of Mediator Collinearity

Vicarious experiences of long COVID: A protection motivation theory analysis for vaccination intentions

Context

Long COVID can appear as a severe late consequence (sequela) of a COVID-19 infection, leading to the inability to work or participate in social life for an unknown amount of time. To see friends or family struggling with long COVID might influence people's risk perceptions, vaccine efficacy expectations, and self-efficacy perceptions to prevent COVID-19 and its consequences.

Methods

In an online survey in August 2022, n = 989 German-speaking participants indicated whether they knew someone who suffered from long COVID illness. Four dimensions of protection motivation theory (PMT) were assessed afterwards, as well as vaccination intentions.

Results

Multiple mediation analysis with participants who knew vs. didn't know someone with long COVID (n = 767) showed that knowing someone with long COVID was associated with higher perceived affective and cognitive risk of long COVID-19 as well as higher perceived vaccine efficacy. Self-efficacy, i.e., the ease to protect oneself against long COVID, was lower in participants who knew long-COVID patients. Indirect positive effects for response efficacy and affective risk suggest that vicarious experience with long COVID is associated with increased intentions to get a COVID-19 vaccine.

Conclusion

The protection from long COVID through vaccination are relevant aspects for individual decisions and health communication.

Work immersion and perceived stress among clinical nurses: a latent profile analysis and moderated mediation analysis

BACKGROUND

Exploration of the relationship between individual work immersion and perceived stress is critical for clinical nurses' effective psychological interventions and human resource management, as well as to alleviate nursing staff shortages. In order to further dissect the influencing factors of perceived stress among nursing staff, our study introduces the concepts of perfectionism and social connectedness to analyze the specific pathways that influence perceived stress in terms of an individual's intrinsic and external personality traits. This study provides relevant recommendations for the development of stress management measures for nursing staff.

METHODS

This was a cross-sectional survey. 993 registered clinical nurses were included from four hospitals in Guangzhou through a convenience sampling method. Clinical nurses' work immersion, perceived stress, perfectionism, and social connectedness were investigated using questionnaires based on latent profile analysis. The relationships between variables were analyzed using t-tests, analysis of variance, Pearson's correlation analysis, latent profile analysis, and moderated mediation analysis.

RESULTS

The results showed that (1) general influences on nurses' perceived stress included only child, labor relationship, labor allowance, and family support; (2) nurses' work immersion contained four subgroups: lowest (12.6%), medium-low (39.8%), medium-high (39.9%), and highest (7.7%); (3) positive and negative perfectionism played a mediating role between the association of work immersion and perceived stress; (4) social connectedness played a moderating role in the mediation model of perceived stress.

CONCLUSIONS

Work immersion, perfectionism, and social connectedness have an important impact on clinical nurses' perceived stress. Nursing managers or leaders should pay attention to the differences of individual work immersion status, adopt reasonable stress management strategies, accurately identify positive perfectionist groups and strengthen the relationship between groups, so as to ensure the quality of nursing care, and reduce nursing turnover and alleviate the problem of staff shortage.

Heart rate reactivity mediates the relationship between trait gratitude and acute myocardial infarction

OBJECTIVE

This study examines the relationship between trait gratitude and acute myocardial infarction. A burgeoning body of literature suggests that gratitude can play a role in regulating individual's cardiovascular responses to stress which in turn, may reduce the incidence of cardiovascular disease such as acute myocardial infarction. However, to date no research has examined these effects.

METHOD

This study used the Mid-Life in the United States dataset (MIDUS; N = 1031) to assess these relationships. Participants completed a standardised cardiovascular stress-testing laboratory protocol and were assessed at a second time-point; on average 6.7 years later.

RESULTS

Results from logistic parallel mediation models suggest that trait gratitude was found to be significantly associated with reduced risk of acute myocardial infarction through the mechanism of increased heart rate reactivity, β = -0.098, 95%CI [- 0.331, - 0.010]. However, neither systolic nor diastolic blood pressure reactivity mediated this relationship.

CONCLUSIONS

These findings suggest that gratitude may be associated with certain aspects of physical health. Specifically, our study reveals a potential link between gratitude and cardiovascular reactivity, which could be a mechanism through which trait gratitude contributes to reductions in the risk of myocardial infarction. As such, this study highlights the potential utility of positive psychological factors, such as gratitude, in promoting cardiovascular health.

Refined revealing the chain path of multiple ecosystem services under diverse environmental factor gradients

A fragile karst ecosystem presents ecosystem services affected by the environment and interactions between ecosystem services. However, the ecosystem in the karst area is characterized by low environmental capacity and low resistance to force disturbance. Current research mainly focuses on the trade-off/synergy of ecosystem services in the karst area yet it lacks inductive analysis of the multiple chain path among ecosystem services. This paper quantitatively identified dominant factors influencing spatial differentiation of surface runoff, soil moisture, sediment yield, and net primary productivity (NPP) and determined the chain path. The chain paths of surface runoff-soil moisture-NPP and NPP-surface runoff-sediment yield were analyzed. The results showed that land use and soil type were the dominant factors, and chain effects of ecosystem services were diverse under the various dominant factor gradients. The mediation effects of paddy soil (97.21 %) and mountain meadow soil (55.56 %) were high, and surface runoff had a greater impact on NPP by affecting soil moisture. Among the diverse land use types, the mediation effect of surface runoff on NPP affecting sediment yield varied greatly (from 5 to 100 %). In addition, its variation trend was consistent with that of the soil moisture as the mediation variable. The mediation effect of surface runoff on construction land was the highest (99.43 %). This study provides the scientific basis for selecting more effective water and soil conservation measures by analyzing the chain relationships of multiple ecosystem services under different environmental factor gradients.

Lean Mass is Associated with, but Does Not Mediate Sex Differences in Pressure Pain Sensitivity in Healthy Adults

Background

Sex differences exist in pain sensitivity, however, the underlying mechanism(s) that explain these differences are not fully understood. Pain sensitivity has been shown to be influenced by body mass index, but limited data exist on the role of body composition on pain sensitivity. The purpose was to examine the influence of body composition on pain sensitivity in males and females.

Methods

This cross-sectional study design used pressure pain thresholds (PPT) of 87 participants (45 female) who were assessed in the vastus lateralis (leg PPT) and brachioradialis (arm PPT) using a pressure algometer. Fat and lean tissue were assessed via dual-energy X-ray absorptiometry (DXA). A two group by two limb, repeated measured ANOVA was used to assess differences between limbs and sex. Spearman correlations and hierarchical regression analyses were employed to determine the association between body composition and PPT.

Results

Males had higher PPTs then females (P<0.05) and had higher DXA assessed lean and lower levels fat mass (P<0.05). Total body and limb specific lean mass was associated with PPTs (r≥0.34; P<0.05). Hierarchical regression analysis revealed lean mass was a significant predictor of 8% of the variance in arm PPT (P<0.006) and 18% of the variance in leg PPT (P<0.001). However, lean mass was not found to statistically mediate the observed sex differences in PPT.

Conclusion

This finding suggests lean mass may play a previously unknown role in sex differences in pressure pain sensitivity. Future studies are needed to confirm this finding and a larger sample size is likely required to have sufficient power to perform the mediation analysis.

University of Alabama at Birmingham Nathan Shock Center: comparative energetics of aging

The UAB Nathan Shock Center focuses on comparative energetics and aging. Energetics, as defined for this purpose, encompasses the causes, mechanisms, and consequences of the acquisition, storage, and use of metabolizable energy. Comparative energetics is the study of metabolic processes at multiple scales and across multiple species as it relates to health and aging. The link between energetics and aging is increasingly understood in terms of dysregulated mitochondrial function, altered metabolic signaling, and aberrant nutrient responsiveness with increasing age. The center offers world-class expertise in comprehensive, integrated energetic assessment and analysis from the level of the organelle to the organism and across species from the size of worms to rats as well as state-of-the-art data analytics. The range of services offered by our three research cores, (1) The Organismal Energetics Core, (2) Mitometabolism Core, and (3) Data Analytics Core, is described herein.

Determining the potential links of self-compassion with eating pathology and body image among women and men: A cross-sectional mediational study

This study examined whether rumination, shame, self-criticism, and perfectionism mediate the previously established link between self-compassion and both eating and body image concerns. A cross-sectional online survey was completed by a community sample of non-clinical adult women (n = 369) and men (n = 201). Participants completed standardised measures of self-compassion (predictor), rumination, external shame, perfectionism and self-criticism (mediating variables), and eating pathology and body image (criterion variables). Path analyses confirmed that higher self-compassion was serially linked to lower eating pathology and body dissatisfaction through comparative self-criticism and external shame. Compared with women, the association between higher self-compassion and lower body dissatisfaction was weaker in men. However, there were no mediating effects of rumination, perfectionism, or internalized self-criticism. Overall results indicate notable similarities between women and men, and emphasise the potential value of targeting external shame during eating disorder prevention and treatment. Longitudinal study of these constructs is warranted in future research.

Power and Sample Size Determination for Multilevel Mediation in Three-Level Cluster-Randomized Trials

Mediation analyses supply a principal lens to probe the pathways through which a treatment acts upon an outcome because they can dismantle and test the core components of treatments and test how these components function as a coordinated system or theory of action. Experimental evaluation of mediation effects in addition to total effects has become increasingly common but literature has developed only limited guidance on how to plan mediation studies with multi-tiered hierarchical or clustered structures. In this study, we provide methods for computing the power to detect mediation effects in three-level cluster-randomized designs that examine individual- (level one), intermediate- (level two) or cluster-level (level three) mediators. We assess the methods using a simulation and provide examples of a three-level clinic-randomized study (individuals nested within therapists nested within clinics) probing an individual-, intermediate- or cluster-level mediator using the R package PowerUpR and its Shiny application.

Responding to uncertain threat: A potential mediator for the effect of mindfulness on anxiety

Mindfulness-based interventions have gained extensive support for their application in the treatment of anxiety. However, their mechanisms remain largely unexplored. Excessive reactivity to uncertainty plays a central role in anxiety, and may represent a mechanism for the effect of mindfulness on anxiety, as mindfulness training fosters an open and accepting stance towards all aspects of experience. The present study sought to investigate both (i) self-reported intolerance of uncertainty (IU) as well as (ii) physiological and subjective responding to uncertain threat in a threat-of-shock paradigm, the NPU-threat test, as mediators for the relationship between mindfulness and anxiety in a cross-sectional study of healthy participants (N = 53). The results indicated that IU mediated the effect of mindfulness on some anxiety symptoms. In contrast, scores of physiological as well as subjective responses to uncertain threat from the NPU-threat test were largely unrelated to mindfulness, anxiety, or the IU self-report measure. The results provide initial evidence that reactions to uncertainty may play a role in the mindfulness-anxiety relationship and suggest that studies are needed to address how methodological variations of the NPU-threat test affect perceived levels of uncertainty and uncertainty-related anxiety.

Statistical power in partially nested designs probing multilevel mediation

Objective: Analysis of the intermediate behaviors and mechanisms through which innovative therapies come to shape outcomes is a critical objective in many areas of psychotherapy research because it supports the iterative exploration, development and refinement of theories and therapies. Despite widespread interest in the intermediate behaviors and mechanisms that convey treatment effects, there is limited guidance on how to effectively and efficiently design studies to detect such mediated effects in the types of partially nested designs that commonly arise in psychotherapy research. In this study, we develop statistical power formulas to identify requisite sample sizes and guide the planning of studies probing mediation under two- and three-level partially nested designs. Method: We investigate multilevel mediation in partially nested structures and models for two- and three-level designs. Results: Well-powered studies probing mediation using partially nested designs will typically require moderate to large sample sizes or moderate to large effects. Discussion: We implement these formulas in the R package PowerUpR and a simple Shiny web application (https://poweruprshiny.shinyapps.io/PartiallyNestedMediationPower/) and demonstrate their use to plan studies using partially nested designs.

Association of Frailty and Postoperative Complications With Unplanned Readmissions After Elective Outpatient Surgery

IMPORTANCE

Ambulatory surgery in geriatric populations is increasingly prevalent. Prior studies have demonstrated the association between frailty and readmissions in the inpatient setting. However, few data exist regarding the association between frailty and readmissions after outpatient procedures.

OBJECTIVE

To examine the association between frailty and 30-day unplanned readmissions after elective outpatient surgical procedures as well as the potential mediation of surgical complications.

DESIGN, SETTING, AND PARTICIPANTS

In this retrospective cohort study of elective outpatient procedures from 2012 and 2013 in the National Surgical Quality Improvement Program (NSQIP) database, 417 840 patients who underwent elective outpatient procedures were stratified into cohorts of individuals with a length of stay (LOS) of 0 days (LOS = 0) and those with a LOS of 1 or more days (LOS ≥ 1). Statistical analysis was performed from June 1, 2018, to March 31, 2019.

EXPOSURE

Frailty, as measured by the Risk Analysis Index.

MAIN OUTCOMES AND MEASURES

The main outcome was 30-day unplanned readmission.

RESULTS

Of the 417 840 patients in this study, 59.2% were women and unplanned readmission occurred in 2.3% of the cohort overall (LOS = 0, 2.0%; LOS ≥ 1, 3.4%). Frail patients (mean [SD] age, 64.9 [15.5] years) were more likely than nonfrail patients (mean [SD] age, 35.0 [15.8] years) to have an unplanned readmission in both LOS cohorts (LOS = 0, 8.3% vs 1.9%; LOS ≥ 1, 8.5% vs 3.2%; P < .001). Frail patients were also more likely than nonfrail patients to experience complications in both cohorts (LOS = 0, 6.9% vs 2.5%; LOS ≥ 1, 9.8% vs 4.6%; P < .001). In multivariate analysis, frailty doubled the risk of unplanned readmission (LOS = 0: adjusted relative risk [RR], 2.1; 95% CI, 2.0-2.3; LOS ≥ 1: adjusted RR, 1.8; 95% CI, 1.6-2.1). Complications occurred in 3.1% of the entire cohort, and frailty was associated with increased risk of complications (unadjusted RR, 2.6; 95% CI, 2.4-2.8). Mediation analysis confirmed that complications are a significant mediator in the association between frailty and readmissions; however, it also indicated that the association of frailty with readmission was only partially mediated by complications (LOS = 0, 22.8%; LOS ≥ 1, 29.3%).

CONCLUSIONS AND RELEVANCE

These findings suggest that frailty is a significant risk factor for unplanned readmission after elective outpatient surgery both independently and when partially mediated through increased complications. Screening for frailty might inform the development of interventions to decrease unplanned readmissions, including those for outpatient procedures.

The Role of Hyperglycemia, Insulin Resistance, and Blood Pressure in Diabetes-Associated Differences in Cognitive Performance-The Maastricht Study

OBJECTIVE

To study to what extent differences in cognitive performance between individuals with different glucose metabolism status are potentially attributable to hyperglycemia, insulin resistance, and blood pressure-related variables.

RESEARCH DESIGN AND METHODS

We used cross-sectional data from 2,531 participants from the Maastricht Study (mean age ± SD, 60 ± 8 years; 52% men; n = 666 with type 2 diabetes), all of whom completed a neuropsychological test battery. Hyperglycemia was assessed by a composite index of fasting glucose, postload glucose, glycated hemoglobin (HbA_1c), and tissue advanced glycation end products; insulin resistance by the HOMA of insulin resistance index; and blood pressure-related variables included 24-h ambulatory pressures, their weighted SDs, and the use of antihypertensive medication. Linear regression analyses were used to estimate mediating effects.

RESULTS

After adjustment for age, sex, and education, individuals with type 2 diabetes, compared with those with normal glucose metabolism, performed worse in all cognitive domains (mean differences in composite z scores for memory -0.087, processing speed -0.196, executive function and attention -0.182; P values <0.032), whereas individuals with prediabetes did not. Diabetes-associated differences in processing speed and executive function and attention were largely explained by hyperglycemia (mediating effect 79.6% [bootstrapped 95% CI 36.6; 123.4] and 50.3% [0.6; 101.2], respectively) and, for processing speed, to a lesser extent by blood pressure-related variables (17.7% [5.6; 30.1]), but not by insulin resistance. None of the factors explained the differences in memory function.

CONCLUSIONS

Our cross-sectional data suggest that early glycemic and blood pressure control, perhaps even in the prediabetic stage, may be promising therapeutic targets for the prevention of diabetes-associated decrements in cognitive performance.

Experimental Power for Indirect Effects in Group-randomized Studies with Group-level Mediators

Mediation analyses have provided a critical platform to assess the validity of theories of action across a wide range of disciplines. Despite widespread interest and development in these analyses, literature guiding the design of mediation studies has been largely unavailable. Like studies focused on the detection of a total or main effect, an important design consideration is the statistical power to detect indirect effects if they exist. Understanding the sensitivity to detect indirect effects is exceptionally important because it directly influences the scale of data collection and ultimately governs the types of evidence group-randomized studies can bring to bear on theories of action. However, unlike studies concerned with the detection of total effects, literature has not established power formulas for detecting multilevel indirect effects in group-randomized designs. In this study, we develop closed-form expressions to estimate the variance of and the power to detect indirect effects in group-randomized studies with a group-level mediator using two-level linear models (i.e., 2-2-1 mediation). The results suggest that when carefully planned, group-randomized designs may frequently be well positioned to detect mediation effects with typical sample sizes. The resulting power formulas are implemented in the R package PowerUpR and the PowerUp!-Mediator software (causalevaluation.org).

The Role of Psychosocial Processes in the Development and Maintenance of Chronic Pain

The recently proposed Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks (ACTTION)-American Pain Society (APS) Pain Taxonomy (AAPT) provides an evidence-based, multidimensional, chronic pain classification system. Psychosocial factors play a crucial role within several dimensions of the taxonomy. In this article, we discuss the evaluation of psychosocial factors that influence the diagnosis and trajectory of chronic pain disorders. We review studies in individuals with a variety of persistent pain conditions, and describe evidence that psychosocial variables play key roles in conferring risk for the development of pain, in shaping long-term pain-related adjustment, and in modulating pain treatment outcomes. We consider "general" psychosocial variables such as negative affect, childhood trauma, and social support, as well as "pain-specific" psychosocial variables that include pain-related catastrophizing, self-efficacy for managing pain, and pain-related coping. Collectively, the complexity and profound variability in chronic pain highlights the need to better understand the multidimensional array of interacting forces that determine the trajectory of chronic pain conditions.

PERSPECTIVE

The AAPT is an evidence-based chronic pain classification system in which psychosocial concepts and processes are essential in understanding the development of chronic pain and its effects. In this article we review psychosocial processes that influence the onset, exacerbation, and maintenance of chronic pain disorders.

A cautionary note on the power of the test for the indirect effect in mediation analysis

Recent simulation studies have pointed to the higher power of the test for the mediated effect vs. the test for the total effect, even in the presence of a direct effect. This has motivated applied researchers to investigate mediation in settings where there is no evidence of a total effect. In this paper we provide analytical insight into the circumstances under which higher power of the test for the mediated effect vs. the test for the total effect can be expected in the absence of a direct effect. We argue that the acclaimed power gain is somewhat deceptive and comes with a big price. On the basis of the results, we recommend that when the primary interest lies in mediation only, a significant test for the total effect should not be used as a prerequisite for the test for the indirect effect. However, because the test for the indirect effect is vulnerable to bias when common causes of mediator and outcome are not measured or not accounted for, it should be evaluated in a sensitivity analysis.