Mariya Shiyko

A time-varying effect model for intensive longitudinal data.

Understanding temporal change in human behavior and psychological processes is a central issue in the behavioral sciences. With technological advances, intensive longitudinal data (ILD) are increasingly generated by studies of human behavior that repeatedly administer assessments over time. ILD offer unique opportunities to describe temporal behavioral changes in detail and identify related environmental and psychosocial antecedents and consequences. Traditional analytical approaches impose strong parametric assumptions about the nature of change in the relationship between time-varying covariates and outcomes of interest. This article introduces time-varying effect models (TVEMs) that explicitly model changes in the association between ILD covariates and ILD outcomes over time in a flexible manner. In this article, we describe unique research questions that the TVEM addresses, outline the model-estimation procedure, share a SAS macro for implementing the model, demonstrate model utility with a simulated example, and illustrate model applications in ILD collected as part of a smoking-cessation study to explore the relationship between smoking urges and self-efficacy during the course of the pre- and postcessation period.

Associations between Menarcheal Timing and Behavioral Developmental Trajectories for Girls from Age 6 to Age 15.

Substantial evidence from cross-sectional and short time-span longitudinal studies exists about negative associations between early pubertal maturation on a number of psychological outcomes. The objective of the present study was to assess the association between early maturation and developmental trajectories of social skills and internalizing and externalizing problems in girls from grades 1 through 9, including pre- and post-pubertal periods. The sample came from the NICHD Study of Early Child Care and Youth Development and included 398 Caucasian and 60 African American girls. Multilevel modeling revealed early maturing Caucasian girls were at risk for higher internalizing and externalizing problems and experiencing higher levels of problems pre-pubertally. African American youth had lower social skills and internalizing problems with no group differences due to early pubertal development. Findings are discussed in light of literature on continuity of girls’ psychosocial development before and during the pubertal transition.

Effect of a Safe Patient Handling Program on Rehabilitation Outcomes

OBJECTIVE To evaluate the effect of a safe patient handling (SPH) program on rehabilitation mobility outcomes. DESIGN Retrospective cohort study. SETTING A rehabilitation unit in a hospital system. PARTICIPANTS Consecutive patients (N=1291) over a 1-year period without an SPH program in place (n=507) and consecutive patients over a 1-year period with an SPH program in place (n=784). INTERVENTIONS The SPH program consisted of administrative policies and patient handling technologies. The policies limited manual patient handling. Equipment included ceiling- and floor-based dependent lifts, sit-to-stand assists, ambulation aides, friction-reducing devices, motorized hospital beds and shower chairs, and multihandled gait belts. MAIN OUTCOME MEASURES The mobility subscale of the FIM. RESULTS Patients rehabilitated in the group with SPH achieved similar outcomes to patients rehabilitated in the group without SPH. A significant difference between groups was noted for patients with initial mobility FIM scores of 15.1 and higher after controlling for initial mobility FIM score, age, length of stay, and diagnosis. Those patients performed better with SPH. CONCLUSIONS SPH programs do not appear to inhibit recovery. Fears among therapists that the use of equipment may lead to dependence may be unfounded.

Families as Coordinated Symbiotic Systems: Making use of Nonlinear Dynamic Models

Family and dynamic systems theories have emerged from basic principles of general systems theory (von Bertalanffy General systems theory. George Braziller. New York, 1968). In this chapter, we illustrate how one of the modeling frameworks being used in ecology (nonlinear dynamic models) can be used to study family systems. First, we review some of the theoretical principles at the core of dynamic systems theory that can be applied to the study of families. Second, we briefly summarize how the taxonomies used in biological ecology to describe interspecies interactions (e.g., symbiosis) have been articulated using the general mathematical framework for nonlinear dynamic models. Third, we consider how this ecological framework is being applied in the study of family systems. Fourth, we introduce an example with data collected from a married couple around the birth of their first child using an ecological momentary assessment (EMA) multiple-burst design. Finally, we indicate what we anticipate will be fruitful pursuits for future thinking and research.

Modeling nonlinear time-dependent treatment effects: an application of the generalized time-varying effect model (TVEM).

OBJECTIVE The goal of this article is to introduce to social and behavioral scientists the generalized time-varying effect model (TVEM), a semiparametric approach for investigating time-varying effects of a treatment. The method is best suited for data collected intensively over time (e.g., experience sampling or ecological momentary assessments) and addresses questions pertaining to effects of treatment changing dynamically with time. Thus, of interest is the description of timing, magnitude, and (nonlinear) patterns of the effect. METHOD Our presentation focuses on practical aspects of the model. A step-by-step demonstration is presented in the context of an empirical study designed to evaluate effects of surgical treatment on quality of life among early stage lung cancer patients during posthospitalization recovery (N = 59; 61% female, M age = 66.1 years). Frequency and level of distress associated with physical symptoms were assessed twice daily over a 2-week period, providing a total of 1,544 momentary assessments. RESULTS Traditional analyses (analysis of covariance [ANCOVA], repeated-measures ANCOVA, and multilevel modeling) yielded findings of no group differences. In contrast, generalized TVEM identified a pattern of the effect that varied in time and magnitude. Group differences manifested after Day 4. CONCLUSIONS Generalized TVEM is a flexible statistical approach that offers insight into the complexity of treatment effects and allows modeling of nonnormal outcomes. The practical demonstration, shared syntax, and availability of a free set of macros aim to encourage researchers to apply TVEM to complex data and stimulate important scientific discoveries.

The time-varying association between perceived stress and hunger within and between days

OBJECTIVE Examine the association between perceived stress and hunger continuously over a week in free-living individuals. METHODS Forty five young adults (70% women, 30% overweight/obese) ages 18 to 24 years (Mean = 20.7, SD = 1.5), with BMI between 17.4 and 36.3 kg/m(2) (Mean = 23.6, SD = 4.0) provided between 513 and 577 concurrent ratings of perceived stress and hunger for 7 days via hourly, text messaging assessments and real-time eating records. Time-varying effect modeling was used to explore whether the within-day fluctuations in stress are related to perceived hunger assessed on a momentary basis. RESULTS A generally positive stress-hunger relationship was confirmed, but we found that the strength of the relationship was not linear. Rather, the magnitude of the association between perceived stress and hunger changed throughout the day such that only during specific time intervals were stress and hunger significantly related. Specifically, the strength of the positive association peaked during late afternoon hours on weekdays (β = 0.31, p < .05) and it peaked during evening hours on weekend days (β = 0.56, p < .05). CONCLUSION This is the first empirical study to demonstrate potentially maladaptive, nonlinear stress-hunger associations that peak in the afternoon or evening hours. While we are unable to infer causality from these analyses, our findings provide empirical evidence for a potentially high-risk time of day for stress-induced eating. Replication of these findings in larger, more diverse samples will aid with the design and implementation of real-time intervention studies aimed at reducing stress-eating.

Exploring healthy eating among ethnic minority students using mobile technology: Feasibility and adherence

Interventions aiming to help ethnically diverse emerging adults engage in healthy eating have had limited success. The aim of this study was to assess the feasibility of and adherence to an intervention capitalizing on mobile technology to improve healthy eating. Participants created an online photo food journal and received motivational text messages three times a day. Satisfaction with the intervention was assessed, as were control variables including depression and body dissatisfaction. In addition, weight and height were measured. Levels of adherence to the photo food journal were high with approximately two photos posted a day at baseline. However, adherence rates decreased over the course of the study. Body dissatisfaction positively predicted adherence, while body mass index negatively predicted study satisfaction. Mobile technology provides innovative avenues for healthy eating interventions. Such interventions appear acceptable and feasible for a short period; however, more work is required to evaluate their viability regarding long-term engagement.

Poisson Growth Mixture Modeling of Intensive Longitudinal Data: An Application to Smoking Cessation Behavior.

Intensive longitudinal data (ILD) have become increasingly common in the social and behavioral sciences; count variables, such as the number of daily smoked cigarettes, are frequently used outcomes in many ILD studies. We demonstrate a generalized extension of growth mixture modeling (GMM) to Poisson-distributed ILD for identifying qualitatively distinct trajectories in the context of developmental heterogeneity in count data. Accounting for the Poisson outcome distribution is essential for correct model identification and estimation. In addition, setting up the model in a way that is conducive to ILD measures helps with data complexities—large data volume, missing observations, and differences in sampling frequency across individuals. We present technical details of model fitting, summarize an empirical example of patterns of smoking behavior change, and describe research questions the generalized GMM helps to address.

Sensitivity and Specificity: A Review of Related Statistics and Controversies in the Context of Physical Therapist Education

Background and Purpose. Sensitivity and specificity are important factors to consider when evaluating the validity of a diagnostic test. The 2 measures can help to determine whether test results are indicative of the actual disease status during client assessment and evaluation. Their properties, however, can be misinterpreted in clinical settings. The purpose of this paper is three‐fold: (1) to review the appropriate interpretation of sensitivity and specificity, positive and negative predictive values, likelihood ratios, posttest probabilities, and receiver operating characteristic (ROC) curves; (2) to discuss limitations of sensitivity and specificity as sole indicators of test validity; and (3) to offer recommendations for educators to improve related curricular content. Position and Rationale. The position adopted in this paper is that physical therapist education programs should cover the concepts of sensitivity and specificity in depth and in combination with other elements of test characteristics prior to discussing specific clinical tests and their applications to clinical decision making. Related content should include a review of the appropriate interpretation of sensitivity and specificity as well as an introduction to positive and negative predictive values, likelihood ratios, posttest probabilities, and ROC curves. The limitations of sensitivity and specificity as sole indicators of test validity should also be discussed. The rationale for this approach is based on the potential over‐reliance of students and educators on sensitivity and specificity alone to establish the validity of clinical measures. Conclusion and Recommendations. Sensitivity and specificity will continue to be very important concepts in physical therapist education. Educators, however, should thoroughly discuss sensitivity and specificity prior to using them across the curriculum and emphasize limitations of these test properties in clinical diagnostic practice. Specific recommendations include a review of the 2 x 2 table, evaluation of specific studies on diagnostic tests, using related measures to evaluate validity, class exercises using interval estimates, and a review of the Standards for Reporting of Diagnostic Accuracy Studies (STARD) and Quality Assessment of Diagnostic Accuracy Studies (QUADAS) initiatives for research on diagnostic test validity.

Capitalizing on mobile technology to support healthy eating in ethnic minority college students

ABSTRACT Objective: To evaluate the capacity of a mobile technology–based intervention to support healthy eating among ethnic minority female students. Participants: Forty-three African American and Hispanic female students participated in a 3-week intervention between January and May 2013. Methods: Participants photographed their meals using their smart phone camera and received motivational text messages 3 times a day. At baseline, postintervention, and 10 weeks after the intervention, participants reported on fruit, vegetable, and sugar-sweetened beverage consumption. Participants were also weighed at baseline. Results: Among participants with body mass index (BMI) ≥25, fruit and vegetable consumption increased with time (p < .01). Among participants with BMI <21, consumption of fruit decreased (p < .05), whereas the consumption of vegetables remained stable. No effects were found for sugar-sweetened beverage consumption. Conclusion: Mobile technology–based interventions could facilitate healthy eating among female ethnic minority college students, particularly those with higher BMI.