mHealth-Based Just-in-Time Adaptive Intervention to Improve the Physical Activity Levels of Individuals With Spinal Cord Injury: Protocol for a Randomized Controlled Trial.

BACKGROUND: The lack of regular physical activity (PA) in individuals with spinal cord injury (SCI) in the United States is an ongoing health crisis. Regular PA and exercise-based interventions have been linked with improved outcomes and healthier lifestyles among those with SCI. Providing people with an accurate estimate of their everyday PA level can promote PA. Furthermore, PA tracking can be combined with mobile health technology such as smartphones and smartwatches to provide a just-in-time adaptive intervention (JITAI) for individuals with SCI as they go about everyday life. A JITAI can prompt an individual to set a PA goal or provide feedback about their PA levels. OBJECTIVE: The primary aim of this study is to investigate whether minutes of moderate-intensity PA among individuals with SCI can be increased by integrating a JITAI with a web-based PA intervention (WI) program. The WI program is a 14-week web-based PA program widely recommended for individuals with disabilities. A secondary aim is to investigate the benefit of a JITAI on proximal PA, defined as minutes of moderate-intensity PA within 120 minutes of a PA feedback prompt. METHODS: Individuals with SCI (N=196) will be randomized to a WI arm or a WI+JITAI arm. Within the WI+JITAI arm, a microrandomized trial will be used to randomize participants several times a day to different tailored feedback and PA recommendations. Participants will take part in the 24-week study from their home environment in the community. The study has three phases: (1) baseline, (2) WI program with or without JITAI, and (3) PA sustainability. Participants will provide survey-based information at the initial meeting and at the end of weeks 2, 8, 16, and 24. Participants will be asked to wear a smartwatch every day for ≥12 hours for the duration of the study. RESULTS: Recruitment and enrollment began in May 2023. Data analysis is expected to be completed within 6 months of finishing participant data collection. CONCLUSIONS: The JITAI has the potential to achieve long-term PA performance by delivering tailored, just-in-time feedback based on the person's actual PA behavior rather than a generic PA recommendation. New insights from this study may guide intervention designers to develop engaging PA interventions for individuals with disability. TRIAL REGISTRATION: ClinicalTrials.gov NCT05317832; https://clinicaltrials.gov/study/NCT05317832. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID): DERR1-10.2196/57699.

Sampling weighting strategies in causal mediation analysis.

BACKGROUND: Causal mediation analysis plays a crucial role in examining causal effects and causal mechanisms. Yet, limited work has taken into consideration the use of sampling weights in causal mediation analysis. In this study, we compared different strategies of incorporating sampling weights into causal mediation analysis. METHODS: We conducted a simulation study to assess 4 different sampling weighting strategies-1) not using sampling weights, 2) incorporating sampling weights into mediation "cross-world" weights, 3) using sampling weights when estimating the outcome model, and 4) using sampling weights in both stages. We generated 8 simulated population scenarios comprising an exposure (A), an outcome (Y), a mediator (M), and six covariates (C), all of which were binary. The data were generated so that the true model of A given C and the true model of A given M and C were both logit models. We crossed these 8 population scenarios with 4 different sampling methods to obtain 32 total simulation conditions. For each simulation condition, we assessed the performance of 4 sampling weighting strategies when calculating sample-based estimates of the total, direct, and indirect effects. We also applied the four sampling weighting strategies to a case study using data from the National Survey on Drug Use and Health (NSDUH). RESULTS: Using sampling weights in both stages (mediation weight estimation and outcome models) had the lowest bias under most simulation conditions examined. Using sampling weights in only one stage led to greater bias for multiple simulation conditions. DISCUSSION: Using sampling weights in both stages is an effective approach to reduce bias in causal mediation analyses under a variety of conditions regarding the structure of the population data and sampling methods.

Differential relationships between physical activity and pain phenotypes in individuals with spinal cord injury.

BACKGROUND: Chronic pain affects 70% of individuals with spinal cord injury (SCI) and leads to declines in health and quality of life. Neuropathic and nociceptive pain are phenotypes derived from different mechanisms that contribute to pain perception. The objective of this research was to investigate differential pain responses to moderate-to-vigorous physical activity (MVPA) in two chronic pain phenotypes: neuropathic and nociceptive pain. METHODS: Community-based physical activity levels were collected for one week in 17 individuals with SCI using a wrist-worn accelerometer, and daily pain ratings were assessed and categorized by phenotype. Physical activity levels were summarized to calculate minutes of MVPA. Correlational analyses were conducted to compare relationships between pain intensity and MVPA across individual participants and between pain phenotype groups. RESULTS: The neuropathic pain group revealed significant negative correlation between MVPA and pain intensity. In the nociceptive pain group, there was no significant correlation between MVPA and pain intensity. Further analysis revealed two subgroups of positive (N = 4) and negative (N = 3) correlations between MVPA and pain intensity. Pain location differed between the subgroups of nociceptive pain. Individuals with negative correlation experienced neck and upper back pain, whereas individuals with positive correlation experienced unilateral upper extremity pain. CONCLUSION: Differential relationships exist between pain phenotypes and MVPA in individuals with SCI. Pain location differed between the subgroups of nociceptive pain, which we presume may indicate the presence of nociplastic pain in some individuals. These results may contribute to the advancement of personalized pain management by targeting non-pharmacological interventions for specific pain phenotypes.Trial registration: ClinicalTrials.gov identifier: NCT05236933..

Estimating generalized propensity scores with survey and attrition weighted data.

Prior work in causal inference has shown that using survey sampling weights in the propensity score estimation stage and the outcome model stage for binary treatments can result in a more robust estimator of the effect of the binary treatment being analyzed. However, to date, extending this work to continuous treatments and exposures has not been explored nor has consideration been given for how to handle attrition weights in the propensity score model. Nonetheless, generalized propensity score (GPS) analyses are being used for estimating continuous treatment effects on outcomes when researchers have observational data, and those data sets often have survey or attrition weights that need to be accounted for in the analysis. Here, we extend prior work and show with analytic results that using survey sampling or attrition weights in the GPS estimation stage and the outcome model stage for continuous treatments can result in a more robust estimator than one that does not. Simulation study results show that, although using weights in both estimation stages is sufficient for robust estimation, it is not necessary and unbiased estimation is possible in some cases under various approaches to using weights in estimation. Analysts do not know if the conditions of our simulation studies hold, so use of weights in both estimation stages might provide insurance for reducing potential bias. We discuss the implications of our results in the context of an empirical example.

Why Are Adolescent Cannabis Use Disorder Treatment Admissions Declining in the US? The Mediated Pathway of State Treatment Admissions Rates before and after Recreational Cannabis Legalization.

Purpose: State-level prevalence data are used to investigate whether recreational cannabis legalization moderates the mediated pathway from the perception of low risk of harm, to cannabis use, to cannabis use disorder (CUD) treatment admissions, among adolescents (age 12-17) in the US. Methods: Annual state prevalence measures of perception of low risk, cannabis use, and CUD treatment admissions between 2008 and 2019 (N = 542 state-year observations) were collected from the National Survey on Drug Use and Health (NSDUH) and the Treatment Episode Dataset - Admissions (TEDS-A). A two-way fixed effects (state and year) moderated mediation model was used to test whether recreational legalization moderated the indirect effect of perception of low risk on treatment admissions via cannabis use. Results: A positive indirect effect of perceiving cannabis as low risk on CUD treatment admissions via cannabis use was observed prior to legalization but not afterwards. After legalization, the positive association of perceiving cannabis as low risk with cannabis use was strengthened, and the positive association of cannabis use with treatment admissions was suppressed, as compared to before legalization. Discussion: Recreational legalization may alter the social acceptability and medical self-administration of cannabis, potentially leading to CUD treatment utilization decline among adolescents even as risk factors for CUD increase. Linking recreational cannabis legalization to advancing awareness of the health risks associated with adolescent cannabis use and promoting adolescent CUD treatment engagement through mHealth approaches and primary care providers are key to addressing potential adolescent health challenges brought about by expanding cannabis legalization.

A Tutorial for Propensity Score Weighting for Moderation Analysis With Categorical Variables: An Application Examining Smoking Disparities Among Sexual Minority Adults.

OBJECTIVE: To provide step-by-step guidance and STATA and R code for using propensity score (PS) weighting to estimate moderation effects with categorical variables. RESEARCH DESIGN: Tutorial illustrating the key steps for estimating and testing moderation using observational data. Steps include: (1) examining covariate overlap across treatment groups within levels of the moderator; (2) estimating the PS weights; (3) evaluating whether PS weights improved covariate balance; (4) estimating moderated treatment effects; and (5) assessing the sensitivity of findings to unobserved confounding. Our illustrative case study uses data from 41,832 adults from the 2019 National Survey on Drug Use and Health to examine if gender moderates the association between sexual minority status (eg, lesbian, gay, or bisexual [LGB] identity) and adult smoking prevalence. RESULTS: For our case study, there were no noted concerns about covariate overlap, and we were able to successfully estimate the PS weights within each level of the moderator. Moreover, balance criteria indicated that PS weights successfully achieved covariate balance for both moderator groups. PS-weighted results indicated there was significant evidence of moderation for the case study, and sensitivity analyses demonstrated that results were highly robust for one level of the moderator but not the other. CONCLUSIONS: When conducting moderation analyses, covariate imbalances across levels of the moderator can cause biased estimates. As demonstrated in this tutorial, PS weighting within each level of the moderator can improve the estimated moderation effects by minimizing bias from imbalance within the moderator subgroups.

Tutorial on causal mediation analysis with binary variables: An application to health psychology research.

Mediation analysis has been widely applied to explain why and assess the extent to which an exposure or treatment has an impact on the outcome in health psychology studies. Identifying a mediator or assessing the impact of a mediator has been the focus of many scientific investigations. This tutorial aims to introduce causal mediation analysis with binary exposure, mediator, and outcome variables, with a focus on the resampling and weighting methods, under the potential outcomes framework for estimating natural direct and indirect effects. We emphasize the importance of the temporal order of the study variables and the elimination of confounding. We define the causal effects in a hypothesized causal mediation chain in the context of one exposure, one mediator, and one outcome variable, all of which are binary variables. Two commonly used and actively maintained R packages, mediation and medflex, were used to analyze a motivating example. R code examples for implementing these methods are provided. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Age-related differences in eating location, food source location, and timing of snack intake among U.S. children 1-19 years.

BACKGROUND: Snacking is nearly universal and contributes significant energy to U.S. children's diets. Little is known, however, about where and when snacking intake occurs and if such patterns change with age. This research evaluated age-related differences in eating location, food source location, and timing of snacking among U.S. children aged 1-19 years (y). METHODS: A cross-sectional analysis of snacking among 14,666 children in the 2007-2018 U.S. National Health and Nutrition Examination Survey was conducted using a single 24-hour dietary recall. Snacking was participant-defined and included all eating occasions outside of meals. Linear regression and analysis of covariance were used to examine the effects of age (toddler 1-2 y, preschooler 3-5 y, school-age 6-11 y, adolescent 12-19 y) on the percentage of daily snack energy consumed by eating location (at home vs. away from home), food source location (grocery store, convenience store, school/childcare, restaurant, from someone else (i.e. "socially"), and other), and time of day (morning, 6am-12pm; early afternoon, 12pm-3pm; late afternoon/afterschool 3pm-6pm; evening 6pm-9pm, late-night 9pm-12am, and overnight 12am-6am). RESULTS: On average, U.S. children consumed most of their daily snacking energy at home (71%), from foods and beverages obtained from grocery stores (75%), and in the late afternoon/afterschool (31%). Toddlers and preschoolers consumed a greater percentage of their daily snack energy during the morning hours compared to school-age children and adolescents (both p < 0.001); school-age children consumed the most in the evening (27%, p < 0.001), and adolescents consumed the most in the late-night period (22%, p < 0.001). Age-related increases were seen in the percentage of daily snacking energy eaten outside the home (p < 0.001), and obtained socially (p < 0.001), from restaurants (p < 0.001), and convenience stores (p < 0.001). CONCLUSION: Findings reveal age-related differences in eating location, food source location, and timing of snack intake among U.S. children aged 1-19 y. Younger children consume a greater percentage of snacking calories in the morning and at home relative to older children. School-age children and adolescents show greater snacking in the evening and at night and from foods obtained and eaten outside the home. Efforts to promote healthy snacking behaviors among children should consider developmental differences in snacking patterns.

Assessing functional recovery for individuals with spinal cord injury post-discharge from inpatient rehabilitation.

OBJECTIVE: To determine the associations between trauma variables, acute phase-related variables, and patient-level characteristics with functional recovery during the first-year post-discharge from inpatient rehabilitation facilities (IRF) for individuals with spinal cord injury (SCI). DESIGN: Retrospective cohort analysis. SETTING: Two SCI Model Centers in Pennsylvania, United States. METHODS: We were able to link 378 individuals with traumatic SCI between the Pennsylvania Trauma Systems Outcomes Study and the National SCI Model Systems databases. Nineteen individuals with SCI were excluded due to missing data. We estimated functional recovery based on changes in functional independence measure (FIM) total motor score during the first-year post-discharge from IRF in 359 individuals with SCI, who did not have any missing data, using ordinary least squares regression (OLS). RESULTS: After discharge from IRF the majority of individuals with SCI improved over the first-year post-injury. Individuals with cervical A-C (injury severity group) who were older had a slight decrease in motor FIM at 1-year post-injury. Regression analysis indicated that lower functional recovery was associated with being of Black and Hispanic race and ethnicity, higher injury severity group, occurrence of non-pulmonary infection during acute care, and longer length of stay at IRF (R2 = 0.36). CONCLUSIONS: Patient-level characteristics, trauma variables, and acute phase-related variables were associated with functional recovery post-discharge from IRF. Further research is necessary to collect and assess post-rehabilitation and socio-economic factors that play a critical role in continued functional recovery in the community.

The Role of Pre-Treatment Traumatic Stress Symptoms in Adolescent Substance Use Treatment Outcomes.

Background: Prominent theories suggest that individuals with co-occurring traumatic stress symptoms (TSS) and substance use (SU) may be less responsive to SU treatment compared to those with SU only. However, empirical findings in adult samples are mixed, and there has been limited work among adolescents. This study assesses the association between TSS and SU treatment outcomes among trauma-exposed adolescents, using statistical methods to reduce potential confounding from important factors such as baseline SU severity. Method: 2,963 adolescents with lifetime history of victimization received evidence-based SU treatment in outpatient community settings. At baseline, 3- and 6-months, youth were assessed using the Global Appraisal of Individual Needs Traumatic Stress Scale and the Substance Frequency Scale. Propensity score weighting was used to mitigate potential confounding due to baseline differences in sociodemographic characteristics and SU across youth with varying levels of TSS. Results: Propensity score weighting successfully balanced baseline differences in sociodemographic factors and baseline SU across youth. Among all youth, mean SU was lower at both 3- and 6- month follow-up relative to baseline, indicating declining use. After adjusting for potential confounders, we observed no statistically significant relationship between TSS and SU at either 3- or 6-month follow-up. Conclusions: Based on this investigation, conducted among a large sample of trauma-exposed youth receiving evidence-based outpatient SU treatment, baseline TSS do not appear to be negatively associated with SU treatment outcomes. However, future research should examine whether youth with TSS achieve better outcomes through integrative treatment for both SU and TSS.

The results of this study provide keenly needed evidence that, among youth with prior victimization, presence and level of traumatic stress symptoms at substance use treatment initiation does not lead to significantly worse treatment outcomes for youth in outpatient treatment. This suggests that evidence-based outpatient substance use treatment modalities may be effective at improving substance use outcomes even when co-existing traumatic stress symptoms are present.

A Causal Approach to Functional Mediation Analysis with Application to a Smoking Cessation Intervention.

The increase in the use of mobile and wearable devices now allows dense assessment of mediating processes over time. For example, a pharmacological intervention may have an effect on smoking cessation via reductions in momentary withdrawal symptoms. We define and identify the causal direct and indirect effects in terms of potential outcomes on the mean difference and odds ratio scales, and present a method for estimating and testing the indirect effect of a randomized treatment on a distal binary variable as mediated by the nonparametric trajectory of an intensively measured longitudinal variable (e.g., from ecological momentary assessment). Coverage of a bootstrap test for the indirect effect is demonstrated via simulation. An empirical example is presented based on estimating later smoking abstinence from patterns of craving during smoking cessation treatment. We provide an R package, funmediation, available on CRAN at https://cran.r-project.org/web/packages/funmediation/index.html, to conveniently apply this technique. We conclude by discussing possible extensions to multiple mediators and directions for future research.

Association of Snacking Frequency, Size, and Energy Density with Weight Status among Preschool-Aged Children in the United States.

BACKGROUND: Snacking (ie, eating between meals) is common among US preschool-aged children, but associations with weight status are unclear. OBJECTIVE: This research evaluated associations of snack frequency, size, and energy density as well as the percent of daily energy from snacking with weight status and sociodemographic characteristics among US children aged 2 to 5 years. DESIGN: Cross-sectional analysis of 2007-2018 National Health and Nutrition Examination Survey data using two, caregiver proxy, 24-hour dietary recalls. PARTICIPANTS/SETTING: US children aged 2 to 5 years (n = 3,313) with at least one snack occasion over 2 days of intake. MAIN OUTCOME MEASURES: Snacking parameters included frequency (number of occasions per day), size (kilocalories per occasion), and energy density (kilocalories per gram per occasion) as well as percent of daily energy from snacking. STATISTICAL ANALYSES: Generalized linear regression models evaluated associations of snacking with child weight status (ie, normal weight and overweight/obesity), adjusting for survey weights, energy misreporting, mean meal size, and sociodemographic covariates. RESULTS: Children with overweight/obesity consumed more frequent snacks (2.8 [0.06] vs 2.5 [0.03] snacks/day, respectively; P < 0.001), larger snacks (188 [4] vs 162 [23] kcal/occasion, respectively; P < 0.001), and a greater percent of daily energy from snacking (29.80% [1.00%] vs 26.09% [0.40%], respectively; P < 0.001) than children with normal weight. Mean snack frequency and size as well as percentage of daily energy from snacking varied with child age, gender, and head of household education. Associations of snacking with child race and ethnicity were less consistent. CONCLUSIONS: These nationally representative findings provide evidence that the consumption of larger, more frequent snacks is associated with overweight/obesity among US children aged 2 to 5 years and snacking varies by sociodemographic characteristics.

Electrodermal and postural responses in dizzy adults: Diagnostic indicators of vestibular migraine.

INTRODUCTION: No reliable biometric measurement of vestibular involvement with migraine is currently available. OBJECTIVE: Measures of autonomic nervous system and postural responses could serve as quantifiable indicators of vestibular involvement with migraine. METHODS: A convenience sample of 22 young healthy adults (34±9 years old) and 23 young adults (34±8 years old) diagnosed with vestibular migraine (VM) participated. A rod and frame test and clinical outcome measures of dizziness and mobility were administered. Participants stood on foam while viewing two dynamic virtual environments. Trunk acceleration in three planes and electrodermal activity (EDA) were assessed with wearable sensors. Linear mixed models were used to examine magnitude and smoothness of trunk acceleration and tonic and phasic EDA. A Welch's t-test and associations between measures were assessed with a Pearson Correlation Coefficient. Effect sizes of group mean differences were calculated using Cohen's d. RESULTS: Visual dependence was present in 83% of the VM population. Individuals with VM exhibited lower baseline EDA (t(4.17) = -7.2, p = 0.001) and greater normalized trunk accelerations in the vertical (t(42.5) = 2.861, p = 0.006) and medial (t(46.6) = 2.65, p = 0.01) planes than healthy participants. Tonic EDA activity increased significantly across the period of the trial (F (1,417) = 23.31, p = 0.001) in the VM group. Significant associations appeared between vertical trunk acceleration and EDA, Dizziness Handicap Inventory, and Activities of Balance Confidence tools. CONCLUSIONS: Higher tonic EDA activity in healthy adults results in more accurate postural reactions. Results support the supposition that EDA activity and postural acceleration are significantly different between VM and healthy individuals when accommodating for postural instability and visual-vestibular conflict.

The Impact of Smoking Status and Smoking-Related Comorbidities on Coronavirus Disease 2019 Patient Outcomes: A Causal Mediation Analysis.

INTRODUCTION: Smoking history is a known risk factor for significant chronic diseases as well as pulmonary infections; however, the impact of smoking status on coronavirus disease 2019 (COVID-19) outcomes has not been conclusively characterized. This study aims to evaluate the association of smoking status on COVID-19 outcomes, and to explore the mechanism by which smoking and smoking-related comorbidities relate to COVID-19 outcomes. AIMS AND METHODS: Patients admitted with SARS-CoV-2 infection from November 2020 through January 2021 were included in this study. Causal mediation models investigating the associations between smoking status and the outcomes of mortality, intensive care unit (ICU) admission, advanced respiratory support, mechanical ventilation, ICU length of stay, and hospital length of stay, through mediation via smoking-related comorbidities, were examined. RESULTS: Active smokers did not experience worse COVID-19 outcomes once hospitalized. Former smokers had a higher odds of mortality (total effect OR 1.59, 95% CI 1.07 to 2.38, p = .01; indirect effect OR 1.45, 95% CI 1.09 to 1.93, p < .001), and advanced respiratory support (total effect OR 1.31, 95% CI 1.04 to 1.67, p = .02; indirect effect OR 1.26, 95% CI 1.03 to 1.54, p = .02), which were mediated by smoking-related comorbidities. While there was a nonsignificant increase in the total effect for mechanical ventilation, smoking-related comorbidities were significant mediators for their increased need (total effect OR 1.40, 95% CI 0.92 to 2.14, p = .13; indirect effect OR 1.47, 95% CI 1.10 to 1.87, p < .001). CONCLUSIONS: Although active smokers did not experience worse COVID-19 outcomes compared to never smokers, these results should be interpreted with caution. Compared to never smokers, former smokers had greater odds of mortality, advanced respiratory support, and mechanical ventilation which was significantly mediated through smoking-related comorbidities. IMPLICATIONS: Previous studies have linked smoking status with worse COVID-19 outcomes, and have inferred that smoking-related comorbidities may play a role in these findings. This causal mediation analysis provides statistical evidence supporting this hypothesis, clarifying the risk that smoking-related comorbidities impart on COVID-19 outcomes in those with a smoking history.

Varying Coefficient Mediation Model and Application to Analysis of Behavioral Economics Data.

This article is concerned with causal mediation analysis with varying indirect and direct effects. We propose a varying coefficient mediation model, which can also be viewed as an extension of moderation analysis on a causal diagram. We develop a new estimation procedure for the direct and indirect effects based on B-splines. Under mild conditions, rates of convergence and asymptotic distributions of the resulting estimates are established. We further propose a F-type test for the direct effect. We conduct simulation study to examine the finite sample performance of the proposed methodology, and apply the new procedures for empirical analysis of behavioral economics data.

The effects of visual context on visual-vestibular mismatch revealed by electrodermal and postural response measures.

BACKGROUND: No objective criteria exist for diagnosis and treatment of visual-vestibular mismatch (VVM). OBJECTIVE: To determine whether measures of electrodermal activity (EDA) and trunk acceleration will identify VVM when exposed to visual-vestibular conflict. METHODS: A modified VVM questionnaire identified the presence of VVM (+ VVM) in 13 of 23 young adults (34 ± 8 years) diagnosed with vestibular migraine. Rod and frame tests and outcome measures for dizziness and mobility were administered. Participants stood on foam while viewing two immersive virtual environments. Trunk acceleration in three planes and electrodermal activity (EDA) were assessed with wearable sensors. Linear mixed effect (LME) models were used to examine magnitude and smoothness of trunk acceleration and tonic and phasic EDA. Welch's t-test and associations between measures were assessed with a Pearson Correlation Coefficient. Effect sizes of group mean differences were calculated. RESULTS: Greater than 80% of all participants were visually dependent. Outcome measures were significantly poorer in the + VVM group: tonic EDA was lower (p < 0.001) and phasic EDA higher (p < 0.001). Postural accelerations varied across groups; LME models indicated a relationship between visual context, postural, and ANS responses in the + VVM group. CONCLUSIONS: Lower tonic EDA with + VVM suggests canal-otolith dysfunction. The positive association between vertical acceleration, tonic EDA, and visual dependence suggests that increased vertical segmental adjustments are used to compensate. Visual context of the spatial environment emerged as an important control variable when testing or treating VVM.

Association of weight status with the types of foods consumed at snacking occasions among US adolescents.

OBJECTIVE: This study aimed to evaluate snack food-group composition by weight status among United States adolescents. METHODS: Cross-sectional analysis of adolescent food-group-component intake from snacking occasions using two 24-hour dietary recalls from the 2007 through 2018 National Health and Nutrition Examination Survey (NHANES; n = 5264; 12-19 years) was conducted. ANCOVA models evaluated food intakes by BMI percentile (BMI%; normal weight [NW]: <85th BMI%; overweight [OW]: 85th-95th BMI%; and obesity [OB]: ≥95th BMI%), adjusting for energy misreporting and key covariates. RESULTS: Adolescents with OB consumed greater total daily energy from snacks (mean [SE]: NW = 424 [10] kcal; OW = 527 [16] kcal; OB = 603 [22] kcal; p < 0.001) than adolescents with OW and NW. Adolescents with OW or OB consumed higher amounts of refined grains, dairy, protein, oil, solid fat, and added sugar from snacks than adolescents with NW (p < 0.05-0.001). CONCLUSIONS: Adolescents with OW or OB consume more calories and higher levels of overconsumed dietary components, i.e., added sugar, solid fats, and refined grains, from snacks than adolescents with NW. Age-specific snacking recommendations to inform dietary guidance are needed to prevent excess intake of overconsumed nutrients and calories.

Evaluating associations between trauma-related characteristics and functional recovery in individuals with spinal cord injury.

OBJECTIVE: To determine the associations between trauma variables, acute phase-related variables, and patient-level characteristics with functional recovery during inpatient rehabilitation for individuals with spinal cord injury (SCI). The associations were evaluated by linking individuals' records between the Pennsylvania Trauma Systems Outcomes Study and the National SCI Model Systems databases. DESIGN: Retrospective cohort analysis. SETTING: Two SCI Model Centers in Pennsylvania, United States. METHODS: We used a record linkage toolkit in Python to link 735 individuals with traumatic SCI between the databases. The percentage for true-match and error were 92.0% and 0.1%, respectively. The functional recovery during inpatient rehabilitation was determined in 604 individuals with SCI by ordinary least squares regression (OLS) and gradient boosting regression (GBR) analyses. RESULTS: The OLS and GBR analyses indicated older age, greater impairment (SCI level combined with American Spinal Injury Association impairment scale), presence of diabetes mellitus, pulmonary complications during acute care, and longer length of stay at an inpatient rehabilitation facility were associated with lower functional recovery (OLS R2 = 0.56 and GBR R2 = 0.58). CONCLUSIONS: Trauma and acute care variables in addition to patient characteristics were associated with functional recovery during inpatient rehabilitation in individuals with SCI. Further investigation is needed to understand the role of diabetes mellitus and pulmonary complications, which have not been previously associated with functional recovery in individuals with SCI.

Estimation and inference for the mediation effect in a time-varying mediation model.

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 confidence band for the time-varying mediation effect. RESULTS: Simulation studies show that the proposed procedures perform well when comparing the confidence band and the true underlying model. We further apply the proposed model and the statistical inference procedure to data collected from a smoking cessation study. CONCLUSIONS: We present a model for estimating time-varying mediation effects that allows both time-varying outcomes and mediators. Simulation-based inference is also proposed and implemented in a user-friendly R package.