Nested Markov Compliance Class Model in the Presence of Time-Varying Noncompliance

We consider a Markov structure for partially unobserved time-varying compliance classes in the Imbens-Rubin (1997) compliance model framework. The context is a longitudinal randomized intervention study where subjects are randomized once at baseline, outcomes and patient adherence are measured at multiple follow-ups, and patient adherence to their randomized treatment could vary over time. We propose a nested latent compliance class model where we use time-invariant subject-specific compliance principal strata to summarize longtudinal trends of subject-specific time-varying compliance patterns. The principal strata are formed using Markov models that related current compliance behavior to compliance history. Treatment effects are estimated as intent-to -treat effects within the compliance principal strata

Casual Mediation Analyses with Structural Mean Models

We represent a linear structural mean model (SMM)approach for analyzing mediation of a randomized baseline intervention\u27s effect on a univariate follow-up outcome. Unlike standard mediation analyses, our approach does not assume that the mediating factor is randomly assigned to individuals (i.e., sequential ignorability). Hence, a comparison of the results of the proposed and standard approaches in with respect to mediation offers a sensitivity analyses of the sequential ignorability assumption. The G-estimation procedure for the proposed SMM represents an extension of the work on direct effects of randomized treatment effects for survival outcomes by Robins and Greenland (1994) (Section 5.0 and Appendix B) and on treatment non-adherence for continuous outcomes by TenHave et al. (2004). Simulations show good estimation and confidence interval performance under unmeasured confounding relative mediation approach. Sensitivity analyses of the sequential ignorability assumption comparing the results of the two approaches are presented in the context of two suicide/depression treatment studies

Why would caregivers not want to treat their relative\u27s Alzheimer\u27s disease?

Objectives: To determine family caregivers\u27 willingness to use Alzheimer\u27s disease (AD)-slowing medicines and to examine the relationships between this willingness, dementia severity, and caregiver characteristics. Design: Cross-sectional survey. Setting: In-home interviews of patients from the Memory Disorders Clinic of the University of Pennsylvania\u27s Alzheimer\u27s Disease Center. Participants: One hundred two caregivers of patients with mild to severe AD who were registered at an Alzheimer\u27s disease center. Measurements: Subjects participated in an in-home interview to assess their willingness to use a risk-free AD-slowing medicine and a medicine with 3% annual risk of gastrointestinal bleeding. Results: Half of the patients had severe dementia (n=52). Seventeen (17%) of the caregivers did not want their relative to take a risk-free medicine that could slow AD. Half (n=52) did not want their relative to take an AD-slowing medicine that had a 3% annual risk of gastrointestinal bleeding. Caregivers who were more likely to forgo risk-free treatment of AD were older (odds ratio (OR)=1.7, P=.04), were depressed (OR=3.66, P=.03), had relatives living in a nursing home (OR=3.6, P=.02), had relatives with more-severe dementia according to the Mini-Mental State Examination (MMSE) (OR=2.29, P=.03) or Dementia Severity Rating Scale (DSRS) (OR=2.55, P=.002), and rated their relatives\u27 quality of life (QOL) poorly on a single-item global rating (OR=0.25, P=.001) and the 13-item quality-of-life (QOL)-AD scale (OR=0.38, P=.002). Caregivers who were more likely to forgo a risky treatment were nonwhite (OR=6.53, P=.005), had financial burden (OR=2.93, P=.02), and rated their relative\u27s QOL poorly on a single-item global rating (OR=0.61, P=.01) and the QOL-AD (OR=0.56, P=.01). Conclusion: These results suggest that caregivers are generally willing to slow the progression of their relative\u27s dementia even into the severe stage of the disease, especially if it can be done without risk to the patient. Clinical trials and practice guidelines should recognize that a caregiver\u27s assessment of patient QOL and the factors that influence it affect a caregiver\u27s willingness to use AD-slowing treatments

Imprecision and bias in orthodontic treatment results

Imprecision in treatment response has been defined as inconsistent unpredictable results from the same treatment. Bias has been defined as systematic failure to achieve defined treatment goals. Concepts of imprecision and bias are applied to the results of a study of soft-tissue response to Class II treatment with edgewise and Herbst appliances.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27413/1/0000448.pd

A multivariate approach to analyzing the relation between occlusion and craniofacial morphology

This study examined the association between occlusion and craniofacial morphology using univariate and multivariate statistical methods. Data were obtained from study casts and lateral cephalometric radiographs of 164 children in the early permanent dentition. The following multiple features of occlusion were assessed: molar relation, overjet, overbite, and anterior crowding. Angular skeletal measures assessed cranial base flexure, maxillary horizontal and vertical positions, mandibular horizontal and vertical positions, horizontal and vertical maxillary-mandibular relations, and positions of the incisors. The relation between the Occlusal Index, which is a malocclusion severity index, and skeletal morphology was also investigated. Associations were examined by use of linear correlation, stepwise multiple regression, and canonical correlation analyses. Individually and in combination, occlusal features were poorly associated with individual skeletal measures (r2 [les] 0.35). The strongest association occurred between a linear combination of occlusal features and a linear combination of skeletal measures (R2 = 0.66, p = 0.0001). A malocclusion severity index did not aid in the identification of craniofacial morphology. The results suggested that combinations of certain occlusal characteristics may be associated with specific skeletal types; however, a generalized statement of this concept could not be supported.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27993/1/0000426.pd

Methods for Linking Community Views to Measureable Outcomes in a Youth Violence Prevention Program

Background: All parties in community–academic partnerships have a vested interest prevention program success. Markers of success that reflect community’s experiences of programmatic prevention success are not always measurable, but critically speak to community-defined needs. Objective: The purpose of this manuscript was to (1) describe our systematic process for linking locally relevant community views (community-defined indicators) to measurable outcomes in the context of a youth violence prevention program and (2) discuss lessons learned, next steps, and recommendations for others trying to replicate a similar process. Methods: A research team composed of both academic and community researchers conducted a systematic process of matching community-defined indicators of youth violence prevention programmatic success to standardized youth survey items being administered in the course of a program evaluation. The research team of three community partners and five academic partners considered 43 community-defined indicators and 208 items from the youth surveys being utilized within the context of a community-based aggression prevention program. At the end of the matching process, 92 youth survey items were identified and agreed upon as potential matches to 11 of the community-defined indicators. Conclusions: We applied rigorous action steps to match community-defined indicators to survey data collected in the youth violence prevention intervention. We learned important lessons that inform recommendations for others interested in such endeavors. The process used to derive and assess community-defined indicators of success emphasized the principles of community-based participatory research (CBPR) and use of existing and available data to reduce participant burden

Longitudinal Nested Compliance Class Model in the Presence of Time-Varying Noncompliance

This article discusses a nested latent class model for analyzing longitudinal randomized trials when subjects do not always adhere to the treatment to which they are randomized. In the Prevention of Suicide in Primary Care Elderly: Collaborative Trial (PROSPECT) study, subjects were randomized to either the control treatment, where they received standard care, or to the intervention, where they received standard care in addition to meeting with depression health specialists. The health specialists educate patients, their families, and physicians about depression and monitor their treatment. Those randomized to the control treatment have no access to the health specialists; however, those randomized to the intervention could choose not to meet with the health specialists, hence, receiving only the standard care. Subjects participated in the study for two years where depression severity and adherence to meeting with health specialists were measured at each follow-up. The outcome of interest is the effect of meeting with the health specialists on depression severity. Traditional intention-to-treat and as-treated analyses may produce biased causal effect estimates in the presence of subject noncompliance. Utilizing a nested latent class model that uses subject-specific and time-invariant superclasses allows us to summarize longitudinal trends of compliance patterns, and estimate the effect of the intervention using intent-to-treat contrasts within principal strata corresponding to longitudinal compliance behavior patterns. Analyses show that subjects with more severe depression are more likely to adhere to treatment randomization, and those that are compliant and meet with health specialists benefit from the meetings and show improvement in depression. Simulation results show that our estimation procedure produces reasonable parameter estimates under correct model assumptions

Towards Patient-Centered Care for Depression: Conjoint Methods to Tailor Treatment Based on Preferences

Background: Although antidepressants and counseling have been shown to be effective in treating patients with depression, non-treatment or under-treatment for depression is common, especially among the elderly and minorities. Previous work on patient preferences has focused on medication versus counseling, but less is known about the value that patients place on attributes of medication and counseling. Objective: To examine, using conjoint analysis, the relative importance of various attributes of depression treatment at the group level as well as to determine the range of individual-level relative preference weights for specific depression treatment attributes. In addition, to predict what modifications in treatment characteristics are associated with a change in the stated preferred alternative. Methods: A total of 86 adults who participated in an internet-based panel responded to an online discrete-choice task about depression treatment. Participants chose between medication and counseling based on choice sets presented first for a 'mild depression' scenario and then for a 'severe depression' scenario. Participants were given 18 choice sets that varied for medication based on type of side effect (nausea, dizziness, and sexual dysfunction) and severity of side effect (mild, moderate, and severe); and for counseling based on frequency of counseling sessions (once per week or every other week) and location of the sessions (mental health professional's office, primary-care doctor's office, or office of a spiritual counselor). Results: Treatment type (counseling vs medication) appeared to be more important in driving treatment choice than any specific attribute that was studied; specifically, counseling was preferred by most of the respondents. After treatment type, location and frequency of treatment were important considerations. Preferred attributes were similar in both the mild and severe depression scenarios. Side effect severity appeared to be most important in driving treatment choice compared with the other attributes studied. Individual-level relative preferences for treatment type revealed a distribution that was roughly bimodal; 27 participants had a strong preference for counseling and 14 had a strong preference for medication. Conclusions: Estimating individual-level preferences for treatment type allowed us to see the variability in preferences and determine which participants had a strong affinity for medication or counseling. We found that participants preferred counseling over medication, avoided options with severe side effects, and wanted to be seen in the primary-care doctor's office as opposed to other venues.adverse-drug-reactions, antidepressants, therapeutic use, conjoint-analysis, counselling, depression, treatment.