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PubMed2005

Estimating between- and within-individual variation in cortisol levels using multilevel models.

Cortisol measures often are used to examine variation in hypothalamic-pituitary-adrenal axis (HPA) activity as well as broader patterns of differential health. However, substantial within-individual variation renders single cortisol measurements unreliable as estimates for probing differences between individuals and groups. A standard practice to clarify between-individual differences involves collecting multiple samples from each participant and then deriving person-specific averages. By ignoring information about variation at between- and within-individual levels, this technique impedes cross-study comparison of results, ignores data useful for future study design, and hinders the analysis of cross-level interactions. This report describes how multilevel approaches can simultaneously model between- and within-individual variation in diurnal cortisol levels without using crude averages. We apply these models to data from children in Nepal (n=29, 11-15 samples per child), Mongolia (n=47, 8-12 samples per child) and the US (n=1269, 1-6 samples per child). Using the Nepal data, we show how an analysis of crude time-adjusted aggregates does not detect an association between aggressive behavior and cortisol levels, while a multilevel analysis does. More importantly, we argue that the 'roadmap' to variation generated by these multilevel models provides meaningful information about the predictive accuracy--not just statistical significance--of relationships between cortisol levels and individual-level variables, such as psychopathology, age, and gender. The 'roadmap' also facilitates comparison between the results from different studies and estimation of the necessary number of cortisol measurements for future investigations.

Adolescent↗
PubMed2006

Familial violence socialization in childhood and later life approval of corporal punishment: a cross-cultural perspective.

The use of corporal punishment has been associated with several negative outcomes for children. As a result, scholars have begun to study factors that are associated with the approval of corporal punishment. Using data from the International Dating Violence Study, the author implemented analysis of covariance and multilevel modeling analyses to determine that there were significant associations among culture, personal and group experiences of familial violence socialization, and attitudes about corporal punishment.

Adult↗
PubMed2006

Variation in spirometry utilization between trained general practitioners in practices equipped with a spirometer.

OBJECTIVE: To explore spirometry utilization among general practitioners and identify practitioner and practice-related factors associated with spirometry utilization. DESIGN: Multivariate multilevel cross-sectional analysis of a questionnaire survey. SETTING: Some 61 general practices involved in a spirometry evaluation programme in the Netherlands. All practices owned a spirometer and were trained to perform spirometry. SUBJECTS: A total of 144 general practitioners and 179 practice assistants. MAIN OUTCOME MEASURES: Extent of spirometry utilization for five indications from national COPD/asthma guidelines, practitioner and practice-related factors associated with spirometry utilization. RESULTS: The response rate was 97%. General practitioners used spirometry mostly to evaluate treatment with inhaled steroids (58%). Significant practitioner-related factors associated with spirometry utilization were: general practitioners' job satisfaction, general practitioners' general interest in research, and prior participation in spirometry training. Practice-related factors associated with spirometry utilization were: presence of a practice nurse, delegation of medical tasks to practice assistants, use of spirometry in different rooms, and use of protocols in practice. CONCLUSION: Practitioner- as well as practice-related factors were associated with the extent of spirometry utilization. In particular, it is essential to improve practice-related factors (e.g. presence of a practice nurse, more delegation of medical tasks to the practice assistant).

Adult↗
PubMed2004

Coping and family functioning predict longitudinal psychological adaptation of siblings of childhood cancer patients.

OBJECTIVE: To assess associations of coping and family functioning with psychosocial adjustment in siblings of pediatric cancer patients at 1, 6, 12, and 24 months after diagnosis. METHODS: Eighty-three siblings (ages 7-19 years) participated. Effects on anxiety, quality of life, behavioral-emotional problems, and emotional reactions to the illness were investigated. Data-analysis was performed with multilevel mixed modeling. RESULTS: Psychosocial functioning was impaired at 1 month but ameliorated over time. Adjustment problems were associated with high family adaptation and cohesion, older age, and female gender. Lower anxiety, insecurity, loneliness, and illness involvement were related to siblings' ability to remain optimistic. Insecurity and illness involvement were positively related to reliance on the medical specialist and a tendency to seek information about the illness. CONCLUSIONS: Siblings of pediatric cancer patients are most affected by the illness in the first months. Children at risk may be identified according to sibling age and gender and according to long-term family adaptation processes and sibling coping abilities.

Adaptation, Psychological↗
PubMed2006

The mortality divide in India: the differential contributions of gender, caste, and standard of living across the life course.

OBJECTIVES: We investigated the contributions of gender, caste, and standard of living to inequalities in mortality across the life course in India. METHODS: We conducted a multilevel cross-sectional analysis of individual mortality, using the 1998-1999 Indian National Family Health Survey data for 529321 individuals from 26 states. RESULTS: Substantial mortality differentials were observed between the lowest and highest standard-of-living quintiles across all age groups, ranging from an odds ratio (OR) of 4.61 (95% confidence interval [CI]=2.98, 7.13) in the age group 2 to 5 years to an OR of 1.97 (95% CI=1.68, 2.32) in the age group 45 to 64 years. Excess mortality for girls was evident only for the age group 2 to 5 years (OR=1.33, 95% CI=1.13, 1.58). Substantial caste differentials were observed at the beginning and end stages of life. Area variation in mortality is partially a result of the compositional effects of household standard of living and caste. CONCLUSIONS: The mortality burden, across the life course in India, falls disproportionately on economically disadvantaged and lower-caste groups. Residual state-level variation in mortality suggests an underlying ecology to the mortality divide in India.

Adolescent↗
PubMed2004

Experiences of racism among African American parents and the mental health of their preschool-aged children.

OBJECTIVES: We examined the relationship between parents' experiences of racism and children's well-being and the influence of the residential neighborhood characteristics on this relationship. METHODS: African American families were recruited from Baltimore neighborhoods. Parental measures included racism experiences and coping. Neighborhood measures included demographic characteristics, social cohesion, and social climate. Children's mental health was assessed with the Child Behavior Checklist. Analysis was performed with multilevel modeling. RESULTS: Parents who denied experiences of racism also reported higher rates of behavior problems among their preschool-aged children. For families living in neighborhoods characterized by fear of victimization, parents who actively coped with racism experiences by confronting the person involved or taking some sort of action in response to racism reported lower rates of anxiety and depression for their preschool-aged children. CONCLUSIONS: Experiences of and responses to racism among African American parents have important effects on the well-being of their young children.

Adaptation, Psychological↗
PubMed1990

Behavioral competence as a predictor of perceived control in nursing home elders.

The purpose of this study was to describe the relationship between behavioral competence and perceived control in nursing home elders. The literature strongly supports perceived control as a primary determinant of psychological well-being in nursing home residents. Identifying predictors of this salient variable will enhance the development of interventions to increase and maintain control in nursing home elders. A nonrandom sample of 134 cognitively intact nursing home elders with poor to excellent self-rated physical health was selected from 13 nursing homes in four counties of a southeastern state. Instruments used included the Desired Control Measure and the Philadelphia Geriatric Center Multilevel Assessment Instrument. Regression analysis demonstrated that components of behavioral competence, time use and self-rated health, explained 34% of the variance of perceived control. Additional research questions were identified.

Activities of Daily Living↗
PubMed2004

Bifurcation geometry and the presence of cerebral artery aneurysms.

OBJECT: The angles of arterial bifurcations are governed by principles of work minimization (optimality principle). This determines the relationship between the angle of a bifurcation and the radii of the vessels. Nevertheless, the model is predicated on an absence of significant communication between these branches. The circle of Willis changes this relationship because the vessels proximal to the ring of vessels have additional factors that determine work minimization compared with more distal branches. This must have an impact on understanding of the relationship between shear stress and aneurysm formation. The authors hypothesized that normal bifurcations of cerebral arteries beyond the circle of Willis would follow optimality principles of minimum work and that the presence of aneurysms would be associated with deviations from optimum bifurcation geometry. Nevertheless, the vessels participating in (or immediately proximal to) the circle of Willis may not follow the geometric model as it is generally applied and this must also be investigated. METHODS: One hundred seven bifurcations of the middle cerebral artery (MCA), distal internal carotid artery (ICA), and basilar artery (BA) were studied in 55 patients. The authors analyzed three-dimensional reconstructions of digital subtraction angiography images with respect to vessel radii and bifurcation angles. The junction exponent (that is, a calculated measure of the division of flow at the bifurcation) and the difference between the predicted optimal and observed branch angles were used as measures of deviation from the geometry thought best to minimize work. The mean junction exponent for MCA bifurcations was 2.9 +/- 1.2 (mean +/- standard deviation [SD]), which is close to the theoretical optimum of 3, but it was significantly smaller (p < 0.001; 1.7 +/- 0.8, mean +/- SD) for distal ICA bifurcations. In a multilevel multivariate logistic regression analysis, only the observed branch angles were significant independent predictors for the presence of an aneurysm. The odds ratio (OR) (95% confidence interval) for the presence of an aneurysm was 3.46 (1.02-11.74) between the lowest and highest tertile of the observed angle between the parent vessel and the largest branch. The corresponding OR for the smallest branch was 48.06 (9.7-238.2). CONCLUSIONS: The bifurcation beyond the circle of Willis (that is, the MCA) closely approximated optimality principles, whereas the bifurcations within the circle of Willis (that is, the distal ICA and BA) did not. This indicates that the confluence of hemodynamic forces plays an important role in the distribution of work at bifurcations within the circle of Willis. In addition, the observed branch angles were predictors for the presence of aneurysms.

Angiography, Digital Subtraction↗
PubMed2007

Plant architecture: a dynamic, multilevel and comprehensive approach to plant form, structure and ontogeny.

BACKGROUND AND AIMS: The architecture of a plant depends on the nature and relative arrangement of each of its parts; it is, at any given time, the expression of an equilibrium between endogenous growth processes and exogenous constraints exerted by the environment. The aim of architectural analysis is, by means of observation and sometimes experimentation, to identify and understand these endogenous processes and to separate them from the plasticity of their expression resulting from external influences. SCOPE: Using the identification of several morphological criteria and considering the plant as a whole, from germination to death, architectural analysis is essentially a detailed, multilevel, comprehensive and dynamic approach to plant development. Despite their recent origin, architectural concepts and analysis methods provide a powerful tool for studying plant form and ontogeny. Completed by precise morphological observations and appropriated quantitative methods of analysis, recent researches in this field have greatly increased our understanding of plant structure and development and have led to the establishment of a real conceptual and methodological framework for plant form and structure analysis and representation. This paper is a summarized update of current knowledge on plant architecture and morphology; its implication and possible role in various aspects of modern plant biology is also discussed.

Body Patterning↗
PubMed2006

Whole-brain T1 mapping in multiple sclerosis: global changes of normal-appearing gray and white matter.

PURPOSE: To prospectively investigate whether T1 changes in normal-appearing white matter (WM) and normal-appearing gray matter (GM) in multiple sclerosis (MS) are global or regional and their relationship to disease type. MATERIALS AND METHODS: The institutional ethics review board approved study; written informed consent was obtained. Whole-brain T1 maps were obtained in 67 patients with MS and 24 healthy control subjects with three-dimensional fast low-angle shot flip angle-array method, with correction for B(1) imperfections. Analysis of variance was performed on T1 histogram parameters of global normal-appearing WM and GM. Regional mean T1 values were analyzed with a multilevel approach. Multiple linear regression analysis was performed to investigate associations with clinical disability and overall atrophy. For patients, T2 lesion load was determined. RESULTS: T1 histograms of normal-appearing WM had significantly higher peak positions for patients with MS (792 msec +/- 36 in secondary progressive [SP] MS) than for control subjects (746 msec +/- 23) and were significantly broader and lower (all P < .001). Histograms for cortical normal-appearing GM were significantly shifted (peak positions, 1263 msec +/- 44 in control subjects and 1355 msec +/- 62 in patients with SP MS) (P < .001). Histogram peak positions were significantly higher in SP MS than in relapsing-remitting (RR) and primary progressive MS (P < .05). In SP disease, at least 31% of normal-appearing WM and 20% of cortical normal-appearing GM were affected. In MS, T1 was significantly elevated in all normal-appearing WM and cortical normal-appearing GM regions (all P < .01) but was elevated only in the thalamus in deep GM (P < .05). Cortical T1 histogram peak position was associated with clinical disability; T2 lesion load was not. CONCLUSION: Results suggest that a global disease process affects large parts of both normal-appearing WM and GM in MS and effects are worse for SP MS than for RR MS.

Adult↗
PubMed1998

Registration of real and CT-derived virtual bronchoscopic images to assist transbronchial biopsy.

This paper describes research work motivated by an innovative medical application: computer-assisted transbronchial biopsy. This project involves the registration, with no external localization device, of a preoperative three-dimensional (3-D) computed tomography (CT) scan of the thoracic cavity (showing a tumor that requires a needle biopsy), and an intraoperative endoscopic two-dimensional (2-D) image sequence, in order to provide assistance in transbronchial puncture of the tumor. Because of the specific difficulties resulting from the data being processed, a multilevel strategy was introduced. For each analysis level, the relevant information to process and the corresponding algorithms were defined. This multilevel strategy, thus, provides the best possible accuracy. Original image processing methods were elaborated, dealing with segmentation, registration and 3-D reconstruction of the bronchoscopic images. In particular, these methods involve adapted mathematical morphology tools, a "daemon-based" registration algorithm, and a model-based shape-from-shading algorithm. This pilot study presents the application of these algorithms to recorded bronchoscopic video sequences for five patients. The preliminary results presented here demonstrate that it is possible to precisely localize the endoscopic camera within the CT data coordinate system. The computer can thus synthesize in near real-time the CT-derived virtual view that corresponds to the actual endoscopic view.

Biopsy, Needle↗
PubMed2004

Force field analysis: a model for promoting adolescents' involvement in their own health care.

This article advances a three-step model for engaging adolescents in shaping their own health care supports and services through systems and social change that rely on principles of force field analysis. Consistent with health promotion values and trends for evidence-based practice, force field analysis provides a systematic and multilevel approach to problem assessment, resolution, and social change that is particularly appropriate for adolescents. The article reviews relevant literature, proposes the model, and concludes with a comparative illustration and critical analysis of the use of force field analysis to promote adolescent health.

Adolescent↗
PubMed1997

Rigid internal fixation with lateral mass plates in multilevel anterior and posterior reconstruction of the cervical spine.

STUDY DESIGN: A retrospective clinical and radiographic analysis was performed on 17 patients with multilevel cervical disease who were treated with anterior and posterior reconstruction with a new rigid, segmental, internal fixation system applied to the lateral masses. OBJECTIVES: To determine the applicability, safety, and clinical efficacy of an instrumentation system used as a cervical lateral mass plate in the management of complex spinal disorders. SUMMARY OF BACKGROUND DATA: Cervical disorders involving three or more levels present a difficult reconstruction problem, especially if the posterior elements are deficient. Segmental fixation with lateral mass plating provides an alternative method to situations that would otherwise require a halo. METHODS: Seventeen patients treated by a single surgeon underwent cervical reconstruction surgery involving three or more levels. All patients had anterior decompression and reconstruction and a posterior fusion with rigid internal fixation with a device applied to the lateral masses of the cervical vertebrae. Patients were reviewed clinically and radiographically to determine the efficacy and safety of this method of fixation. RESULTS: Of the 15 patients with adequate follow-up data that were studied, the condition of 13 patients, (87%) was improved, that of one patient (6.7%) was the same, and that of another (6.7%) was worse after surgical intervention. Sagittal alignment was restored to within 5 degrees of the preoperative lordosis in active extension by the modified Cobb method and the Gore method. No patient had radiographic nonunion. One patient had a sensory radiculopathy associated with an overpenetrated lateral mass screw that partially resolved after hardware removal. One patient had asymptomatic loosening of a C7 lateral mass screw. CONCLUSIONS: Segmental posterior fixation with lateral mass plating provides more rigid immobilization than traditional techniques, allows restoration and maintenance of spinal alignment, obviates the need for halo immobilization, and is associated with a low incidence of neurovascular injury.

Adult↗
PubMedDate not supplied

Multilevel surgery in spastic diplegia: evaluation by physical examination and gait analysis in 25 children.

Gait improvement surgery was performed on 25 ambulatory children with the diplegic type of cerebral palsy. Multiple soft tissue and bony procedures were performed (mean 8.2 procedures) according to criteria defined on the basis of physical examination and gait analysis. Relevant physical examination findings and kinematic and kinetic data in the sagittal plane were evaluated before surgery and at least 3 years after surgery. Physical examination showed a reduction in the ankle plantar-flexor power and in the range of hip flexion and ankle plantarflexion after surgery. Analysis of gait data showed significant improvements in the sagittal plane kinematics and the power generation at the hip and the ankle. At the knee joint there was maintenance of power of the flexor and extensor group of muscles on physical examination, with significant improvements in the kinematics after surgery. The authors conclude that well-selected surgery improves function of the spastic muscle. The importance of assessing clinical, kinematic, and kinetic data together for proper evaluation of gait is stressed.

Adolescent↗
PubMed2005

Multilevel methods for modeling observed sequences of family interaction.

Observation of interaction plays a central role in family research. This article discusses how to analyze sequential data generated by discrete microcoding methods to test hypotheses about family interaction. Current methods for studying sequential data are presented, and their limits are discussed. Building on recent applications of contingency table analysis to such data, a multilevel log-linear model is presented that can specify and estimate indicators of individual behavioral tendencies and antecedent-consequent relationships among behaviors, both within and across samples of families. An example of this method is presented using data from a study of couples facing job loss. Potential extensions of this framework for future research are discussed.

Algorithms↗
PubMed2005

Impact of definition on the study of avoidable mortality: geographical trends in British deaths 1981-1998 using Charlton and Holland's definitions.

Avoidable mortality is defined as deaths that should not occur given current medical knowledge and technology. Numerous different lists of causes of death and the ages at which they should be considered avoidable have been used to measure avoidable mortality. In this analysis of the importance of definition we compare the two most commonly used approaches using a data set including all 11.8 million deaths that occurred in Britain in 1981-1998. These mortality data, disaggregated by age and sex, are analysed within a multilevel statistical framework, which allows analysis at a number of geographical scales simultaneously. A substantial difference in both the average trends and spatial patterns of the two definitions of avoidable mortality is found, indicating that the causes of death chosen have a considerable impact on the results found. Indeed, one particular cause of death was found to be largely responsible for the differences between the definitions. In addition, the spatial pattern of the two types of avoidable mortality is very different at the larger geographical scale while the pattern at the smaller scale is very similar. The findings illustrate the importance of considering the goals of any study before deciding on the definition of avoidable mortality to use.

Adolescent↗
PubMed1996

Recovery of speed of information processing in closed-head-injury patients.

After severe traumatic brain injury, patients almost invariably demonstrate a slowing of reaction time, reflecting a slowing of central information processing. Methodological problems associated with the traditional method for the analysis of longitudinal data (MANOVA) severely complicate studies on cognitive recovery. It is argued that multilevel models are often better suited for the analysis of improvement over time in clinical settings. Multilevel models take into account individual differences in both overall performance level and recovery. These models enable individual predictions for the recovery of speed of information processing. Recovery is modelled in a group of closed-head-injury patients (N = 24). Recovery was predicted by age and severity of injury, as indicated by coma duration. Over a period up to 44 months post trauma, reaction times were found to decrease faster for patients with longer coma duration.

Adolescent↗
PubMed2004

Healthy passages. A multilevel, multimethod longitudinal study of adolescent health.

PURPOSE: To provide an overview of a multisite, long-term study that focuses on risk and protective factors, health behaviors (e.g., dietary practices, physical inactivity, tobacco use, and violent activity), and health outcomes (e.g., diabetes, obesity, and sexually transmitted diseases) for a fifth-grade cohort to be followed biennially from ages 10 to 20 years. METHODS: A two-stage probability sampling procedure was used to select 5250 fifth-grade students from schools in Birmingham AL, Houston TX, and Los Angeles CA to ensure a sufficient sample size of African Americans, Hispanics, and non-Hispanic whites, to support precise statistical inferences. Computer-assisted technology was used to collect data from children and their primary caregivers. Teachers and other school personnel responded to questionnaires, and observational procedures were used to obtain information about schools and neighborhoods. RESULTS: To exploit the multilevel, multimethod structure of the data, statistical models include latent-growth mixture modeling, multilevel modeling, time-series analysis, survival analysis, latent transition analysis, and structural equation modeling. Analyses focus both on the co-occurrence and predictors of growth trajectories for different health behaviors across time. CONCLUSIONS: By using a prospective research design and studying the predictors and time course of multiple health behaviors with a multilevel, multimethod assessment protocol, this research project could provide an empirical basis for effective social and educational policies and intervention programs that foster positive health and well-being during both adolescence and adulthood.

Adolescent↗