72 research outputs found
A Normal-Mixture Model with Random-Effects for RR-Interval Data
In many applications of random-effects models to longitudinal data, such as heart rate variability (HRV) data, a normal-mixture distribution seems to be more appropriate than the normal distribution assumption. While the random-effects methodology is well developed for several distributions in the exponential family, the case of the normal-mixture has not been dealt with adequately in the literature. The models and the estimation methods that have been proposed in the past assume the conditional model (fixing the random-effects) to be normal and allow a mixture distribution for the random effects (Xu and Hedeker, 2001, Xu, 1995). The methods proposed in this dissertation assume the conditional model to be a normal-mixture while the random-effects are assumed to be normal. This is primarily to fit the HRV data, which seems to follow a normal-mixture within subjects. Another advantage of this model is that the estimation becomes much simpler through the use of an EM-algorithm. Existing methods and software such as the PROC MIXED in SAS are exploited to facilitate the estimation procedure.A simulation study is performed to examine the properties of the random-effects model with normal-mixture distribution and the estimation of the parameters using the EM-algorithm. The study shows that the estimates have similar properties to the usual normal random-effects models. The between subject variance parameter seems to require larger numbers of subjects to achieve reasonable accuracy, which is typical in all random-effects models.The HRV data is used to illustrate the random-effects normal-mixture method. These data consist of 9 subjects who completed a series of five speech tasks (Cacioppo et al., 2002). For each of the tasks, a series of RR-intervals was collected during baseline, preparation, and delivery periods. Information about their age and gender were also available. The random-effects mixture model presented in this dissertation treats the subjects as random and models age, gender, task, type, and task Ă— type as fixed-effects. The analysis leads to the conclusion that all the fixed effects are statistically significant. The model further indicates a two-component normal-mixture with the same mixture proportion across individuals fit the data adequately
A Standard Method for Determining the Minimal Clinically Important Difference for Rehabilitation Measures
The minimal clinically important difference (MCID) is receiving increasing interest and importance in medical practice and research. The MCID is the smallest improvement in scores in the domain of interest that patients perceive as beneficial. In clinical trials, comparing the proportion of individuals between treatment and control groups who obtain a MCID may be more informative than comparisons of mean change between groups because a statistically significant mean difference does not necessarily represent a difference that is perceived as meaningful by treatment recipients. The MCID may also be useful in advancing personalized medicine by characterizing those who are most likely to benefit from a treatment. In clinical practice, the MCID can be used to identify if a participant is experiencing a meaningful change in status.
A variety of methods have been used to determine the MCID with no clear agreement on the most appropriate approach. Two major sets of methods are either (1) distribution-based, that is, referencing the MCID to a measure of variability or effect size in the measure of interest or (2) anchor-based, that is, referencing the MCID to an external assessment of change in the condition, ability, or activity represented by the measure of interest. In prior literature, using multiple methods to “triangulate” on the value of the MCID has been proposed. In this commentary, we describe a systematic approach to triangulate on the MCID using both distribution-based and anchor-based methods. Adaptation of a systematic approach for obtaining the MCID in rehabilitation would facilitate communication and comparison of results among rehabilitation researchers and providers
Social Competence Treatment after Traumatic Brain Injury: A Multicenter, Randomized, Controlled Trial of Interactive Group Treatment versus Non-Interactive Treatment
Objective
To evaluate the effectiveness of a replicable group treatment program for improving social competence after traumatic brain injury (TBI).
Design
Multicenter randomized controlled trial comparing two methods of conducting a social competency skills program, an interactive group format versus a classroom lecture.
Setting
Community and Veteran rehabilitation centers.
Participants
179 civilian, military, and veteran adults with TBI and social competence difficulties, at least 6 months post-injury.
Experimental Intervention
Thirteen weekly group interactive sessions (1.5 hours) with structured and facilitated group interactions to improve social competence.
Alternative (Control) Intervention
Thirteen traditional classroom sessions using the same curriculum with brief supplemental individual sessions but without structured group interaction.
Primary Outcome Measure
Profile of Pragmatic Impairment in Communication (PPIC), an objective behavioral rating of social communication impairments following TBI.
Secondary Outcomes
LaTrobe Communication Questionnaire (LCQ), Goal Attainment Scale (GAS), Satisfaction with Life Scale (SWLS), Post-Traumatic Stress Disorder Checklist – (PCL-C), Brief Symptom Inventory 18 (BSI-18), Scale of Perceived Social Self Efficacy (PSSE).
Results
Social competence goals (GAS) were achieved and maintained for most participants regardless of treatment method. Significant improvements in the primary outcome (PPIC) and two of the secondary outcomes (LCQ and BSI) were seen immediately post-treatment and at 3 months post-treatment in the AT arm only, however these improvements were not significantly different between the GIST and AT arms. Similar trends were observed for PSSE and PCL-C.
Conclusions
Social competence skills improved for persons with TBI in both treatment conditions. The group interactive format was not found to be a superior method of treatment delivery in this study
Race/Ethnicity and Retention in Traumatic Brain Injury Outcomes Research: A Traumatic Brain Injury Model Systems National Database Study
Objective: To investigate the contribution of race/ethnicity to retention in traumatic brain injury (TBI) research at 1 to 2 years post-injury. Setting: Community. Participants: 5548 Whites, 1347 Blacks, and 790 Hispanics enrolled in the Traumatic Brain Injury Model Systems National Database with dates of injury between October 1, 2002 and March 31, 2013. Design:
Retrospective database analysis. Main Measure: Retention, defined as completion of at least one question on the follow-up interview by the person with TBI or a proxy. Results: Retention rates 1-2 years post-TBI were significantly lower for Hispanic (85.2%) than for White (91.8%) or Black participants (90.5%) and depended significantly on history of problem drug or alcohol use. Other variables associated with low retention included older age, lower education, violent cause of injury, and discharge to an institution versus private residence. Conclusions: The findings emphasize the importance of investigating retention rates separately for Blacks and Hispanics rather than combining them or grouping either with other races or ethnicities. The results also suggest the need for implementing procedures to increase retention of Hispanics in longitudinal TBI researc
Prevalence of suicidal behaviour following traumatic brain injury: Longitudinal follow-up data from the NIDRR Traumatic Brain Injury Model Systems
Objective: This study utilized the Traumatic Brain Injury Model Systems (TBIMS) National Database to examine the prevalence of depression and suicidal behaviour in a large cohort of patients who sustained moderate-to-severe TBI.
Method: Participants presented to a TBIMS acute care hospital within 72 hours of injury and received acute care and comprehensive rehabilitation in a TBIMS designated brain injury inpatient rehabilitation programme. Depression and suicidal ideation were measured with the Patient Health Questionnaire (PHQ-9). Self-reported suicide attempts during the past year were recorded at each follow-up examination, at 1, 2, 3, 10, 15 and 20 years post-injury.
Results: Throughout the 20 years of follow-up, rates of depression ranged from 24.8–28.1%, suicidal ideation ranged from 7.0–10.1% and suicide attempts (past year) ranged from 0.8–1.7%. Participants who endorsed depression and/or suicidal behaviour at year 1 demonstrated consistently elevated rates of depression and suicidal behaviour 5 years after TBI.
Conclusion: Compared to the general population, individuals with TBI are at greater risk for depression and suicidal behaviour many years after TBI. The significant psychiatric symptoms evidenced by individuals with TBI highlight the need for routine screening and mental health treatment in this population
The Longitudinal Effects of Comorbid Health Burden on Functional Outcomes for Adults With Moderate to Severe Traumatic Brain Injury
Objective: To evaluate the impact of physical, mental, and total health condition burden on functional outcome and life satisfaction up to 10 years after moderate to severe traumatic brain injury (TBI).
Setting: Six TBI Model Systems centers.
Participants: Three hundred ninety-three participants in the TBI Model Systems National Database.
Design: Retrospective cohort study.
Main measures: Self-reported physical and mental health conditions at 10 years postinjury. Functional Independence Measure Motor and Cognitive subscales and the Satisfaction With Life Scale measured at 1, 2, 5, and 10 years.
Results: In 10-year longitudinal individual growth curve models adjusted for covariates and inverse probability weighted to account for selection bias, greater physical and mental health comorbidity burden was negatively associated with functional cognition and life satisfaction trajectories. Physical, but not mental, comorbidity burden was negatively associated with functional motor trajectories. Higher total health burden was associated with poorer functional motor and cognitive trajectories and lower life satisfaction.
Conclusions: This study offers evidence that comorbidity burden negatively impacts longitudinal functional and life satisfaction outcomes after TBI. The findings suggest that better identification and treatment of comorbidities may benefit life satisfaction, functional outcome, reduce healthcare costs, and decrease reinjury. Specific guidelines are needed for the management of comorbidities in TBI populations
Relationship Between Hispanic Nativity, Residential Environment, and Productive Activity Among Individuals With Traumatic Brain Injury: A TBI Model Systems Study
Objective: To examine the influence of nativity and residential characteristics on productive activity among Hispanics at 1 year after traumatic brain injury (TBI).
Setting: Acute rehabilitation facilities and community follow-up.
Participants: A total of 706 Hispanic individuals in the TBI Model Systems National Database.
Design: Secondary data analysis from a multicenter longitudinal cohort study.
Main Measures: Nativity (foreign born or US native), productive activity derived from interview questions regarding employment status, and other demographic information. Census data were extracted by zip code to represent residential characteristics of aggregate household income and proportion of foreign language speakers (FLS).
Results: Among foreign-born individuals with TBI, those living in an area with a higher proportion of FLS were 2.8 times more likely to be productive than those living in areas with a lower proportion of FLS. Among individuals living in an area with a lower proportion of FLS, US-born Hispanics were 2.7 times more likely to be productive compared with Hispanic immigrants.
Conclusion: The relationship between nativity and productive activity at 1 year post-TBI was moderated by the residential proportion of FLS. Findings underscore the importance of considering environmental factors when designing vocational rehabilitation interventions for Hispanics after TBI
Functional Outcome Trajectories following Inpatient Rehabilitation for TBI in the United States: A NIDILRR TBIMS and CDC Interagency Collaboration
Objective: To describe trajectories of functioning up to 5 years after traumatic brain injury (TBI) that required inpatient rehabilitation in the United States using individual growth curve models conditioned on factors associated with variability in functioning and independence over time.
Design: Secondary analysis of population-weighted data from a multicenter longitudinal cohort study.
Setting: Acute inpatient rehabilitation facilities.
Participants: A total of 4624 individuals 16 years and older with a primary diagnosis of TBI.
Main outcome measures: Ratings of global disability and supervision needs as reported by participants or proxy during follow-up telephone interviews at 1, 2, and 5 years postinjury.
Results: Many TBI survivors experience functional improvement through 1 and 2 years postinjury, followed by a decline in functioning and decreased independence by 5 years. However, there was considerable heterogeneity in outcomes across individuals. Factors such as older age, non-White race, lower preinjury productivity, public payer source, longer length of inpatient rehabilitation stay, and lower discharge functional status were found to negatively impact trajectories of change over time.
Conclusions: These findings can inform the content, timing, and target recipients of interventions designed to maximize functional independence after TBI
Longitudinal Effects of Medical Comorbidities on Functional Outcome and Life Satisfaction After Traumatic Brain Injury: An Individual Growth Curve Analysis of NIDILRR Traumatic Brain Injury Model System Data
Objective:
To explore associations of specific physical and neuropsychiatric medical conditions to motor and cognitive functioning and life satisfaction over the first 10 years following traumatic brain injury (TBI).
Setting:
Telephone follow-up through six TBI Model System centers.
Participants:
404 individuals or proxies with TBI enrolled in the TBI Model System longitudinal study participating in 10 year follow-up.
Design:
Individual growth curve analysis.
Main Measures:
FIM™ Motor and Cognitive subscales, Life Satisfaction Scales, Medical and Mental Health Co-Morbidities Interview.
Results:
Hypertension, diabetes, cancers, rheumatoid arthritis, and anxiety negatively affected the trajectory of motor functioning over time. Diabetes, cancers, chronic bronchitis, anxiety, and depression negatively impacted cognitive functioning. Numerous neuropsychiatric conditions (sleep disorder, alcoholism, drug addiction, anxiety, panic attacks, PTSD, depression, bipolar disorder), as well as hypertension, liver disease, and cancers diminished life satisfaction. Other medical conditions had a negative effect on functioning and satisfaction at specific follow-up periods.
Conclusion:
Natural recovery after TBI may include delayed onset of functional decline or early recovery followed by progressive deterioration and is negatively affected by medical comorbidities. Results contribute to the growing evidence that TBI is most appropriately treated as a chronic medical condition complicated by a variety of comorbid conditions
Prevalence of Medical and Psychiatric Comorbidities Following Traumatic Brain Injury
Objective:
To examine the prevalence of selected medical and psychiatric comorbidities that existed prior to, or up to 10 years following, traumatic brain injury (TBI) requiring acute rehabilitation.
Design:
Retrospective cohort.
Setting:
Six TBI Model Systems centers.
Participants:
404 participants in the TBI Model System National Database who experienced TBI 10 years prior.
Interventions:
Not applicable.
Main Outcome Measure:
Self-reported medical and psychiatric comorbidities and the onset time of each endorsed comorbidity.
Results:
At 10 years post-injury, the most common comorbidities developing post-injury, in order, were: back pain, depression, hypertension, anxiety, fractures, high blood cholesterol, sleep disorders, panic attacks, osteoarthritis, and diabetes. Comparing those 50 years and older to those less than 50 years, diabetes (OR = 3.54; p = 0.0016), high blood cholesterol (OR = 2.04; p = 0.0092), osteoarthritis (OR = 2.02; p = 0.0454), and hypertension (OR = 1.84; p = 0.0175) were significantly more prevalent in the older cohort while panic attacks (OR = 0.33; p = 0.0022) were significantly more prevalent in the younger cohort. No significant differences in prevalence rates between the older and younger cohorts were found for back pain, depression, anxiety, fractures, or sleep disorders.
Conclusions:
People with moderate-severe TBI experience other medical and mental health comorbidities during the long-term course of recovery and life after injury. The findings can inform further investigation into comorbidities associated with TBI and the role of medical care, surveillance, prevention, lifestyle, and healthy behaviors in potentially modifying their presence and/or prevalence over the life span
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