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PubMed2006

[A multilevel study on the relationship between the residential distribution of high class (power elites) and smoking in Seoul].

OBJECTIVES: We examined whether the neighborhood socioeconomic position predicts the smoking rates after adjusting for individual socioeconomic position indicators. METHODS: Data were obtained from the 2001 Seoul Health Indicators Survey. The neighborhood socioeconomic position was the residential distribution of the high class (power elites), as measured by the location quotients (LQ) for each administrative dong (district). A high LO denotes a high neighborhood socioeconomic status. The individual socioeconomic position included education, occupation and income. Age-adjusted smoking rates according to the LQ level were computed with the direct method. The total number of subjects in this study (26,022 men and 28,007 women) was the reference. A multilevel logistic regression analysis was conducted with the individuals at the first level and the neighborhoods at the second level to estimate the odds ratios of smoking with 95% confidence intervals. RESULTS: For men, the age-adjusted smoking rates increased with a decrease in the LQ. For women, the relationship between the age-adjusted smoking rate and the LQ was not clear. The odds of smoking for both genders were greater among those subjects with lower incomes and lower education. The manual occupational class had greater odds of smoking than the non-manual class for the males, while the odds ratio of smoking among females with a manual occupation tended to be lower than those females with a non-manual occupation. For the males, the LQ levels independently predicted smoking after adjustment for individual income. However, this relation between the LQ and smoking in males was explained by full adjustment for the individual socioeconomic position indicators (education, occupation and income). CONCLUSIONS: A low level of neighborhood socioeconomic position was associated with higher smoking rates among the men residing in Seoul. This association between the neighborhood socioeconomic position and smoking in men was explained by the individual socioeconomic position. Anti-smoking efforts to reduce geographical inequality in smoking should be directed at reducing the smoking rates between the individuals with different socioeconomic backgrounds in the metropolitan city of Seoul, South Korea.

Adult↗
PubMed2002

Diary methods: capturing life as it is lived.

In diary studies, people provide frequent reports on the events and experiences of their daily lives. These reports capture the particulars of experience in a way that is not possible using traditional designs. We review the types of research questions that diary methods are best equipped to answer, the main designs that can be used, current technology for obtaining diary reports, and appropriate data analysis strategies. Major recent developments include the use of electronic forms of data collection and multilevel models in data analysis. We identify several areas of research opportunities: 1. in technology, combining electronic diary reports with collateral measures such as ambulatory heart rate; 2. in measurement, switching from measures based on between-person differences to those based on within-person changes; and 3. in research questions, using diaries to (a) explain why people differ in variability rather than mean level, (b) study change processes during major events and transitions, and (c) study interpersonal processes using dyadic and group diary methods.

Data Collection↗
PubMed1997

A multilevel model of sudden infant death syndrome in England and Wales.

The relationship between migration and sudden infant death syndrome (SIDS) in England and Wales is analyzed using official data for the period 1979-1983. "In this paper, multilevel modelling is used to examine the variability in SIDS deaths at different geographical scales, namely district, county, and regional levels. Given the population-mixing hypothesis, it is possible that high levels of population mixing in one district will have an effect on the spread of infections in an adjacent district, and the rates for individual districts will not be spatially independent of each other. Factors such as climate varying at regional scale may also be important. A log-linear multilevel model is developed to examine these issues, and the discussion focuses on the methodological issues raised by the analysis such as appropriate multilevel structure, methods of estimation, dispersion of residuals, and significance of parameter estimates."

Climate↗
PubMed2005

Analysis of differences in amino acid substitution patterns, using multilevel G-tests.

In this paper, a new algorithm is presented, which makes possible multilevel comparison of BLOSUM protein substitution matrices based on data from different groups of organisms. As an example, a comparison between substitution matrices based on data from two groups of bacterial genomes with different GC content is presented. Our approach includes evaluating the number of amino acid pairs in BLOCKS databases created separately for the two groups of bacteria using protein sequences deposited in the COG database. Differences of distributions of amino acid pair counts are tested using the chi-squared based G-test. Different analysis levels make it possible to distinguish different patterns of amino acid substitution. Application of the algorithm reveals statistically significant differences in amino acid substitution patterns between AT-rich and GC-rich groups of bacterial organisms. The differences are particularly visible in the overall substitution pattern, amino acid conservation pattern and in comparison of substitution patterns for single amino acids. The algorithm presented in this paper can be considered a novel method for multi-level comparison of amino acid substitution patterns. The presented approach is not limited to bacterial organisms and BLOSUM substitution matrices. Statistically significant differences between substitution patterns in the two groups of bacterial organisms with respect to amino acid conservation pattern can be the evidence of different rate of evolutionary change between AT-rich and GC-rich bacterial organisms.

Algorithms↗
PubMed2003

Alcohol culture, family structure and adolescent alcohol use: multilevel modeling of frequency of heavy drinking among 15-16 year old students in 11 European countries.

OBJECTIVE: Frequency of heavy alcohol use among adolescents is examined by family structure and propensity toward heavy alcohol use on the individual level, and by alcohol availability and drinking patterns among adolescents on the societal level. The analysis includes direct effects and moderating effects of societal-level indicators on individual-level associations between family structure and frequency of heavy alcohol use. METHOD: The study drew upon self-reports from 34,001 students in Cyprus, France, Hungary, Iceland, Ireland, Lithuania, Malta, the Slovak Republic, Slovenia, Sweden and the United Kingdom participating in the 1999 European School Survey Project on Alcohol and Other Drugs study. Distinctions were drawn between adolescents living with both parents, a single mother, a single father, a mother and stepfather, a father and stepmother, and neither biological parent. The multilevel analysis estimated the effects of societal-level factors on the intercepts and slopes of individual-level regression models. RESULTS: Adolescents living with both biological parents engaged less frequently in heavy alcohol use than those living in any other arrangements. Living with a single mother was associated with less heavy drinking than living with a single father or with neither biological parent. National beer sales figures and societal patterns of heavy adolescent alcohol use predicted more frequent heavy drinking and greater effects of living in nonintact families. CONCLUSIONS: Adolescent heavy drinking is more common in all types of nonintact families. The adverse effect of living in nonintact families is greater in societies where alcohol availability is greater and where adolescents drink more heavily.

Adolescent↗
PubMed2005

People are variables too: multilevel structural equations modeling.

The article uses confirmatory factor analysis (CFA) as a template to explain didactically multilevel structural equation models (ML-SEM) and to demonstrate the equivalence of general mixed-effects models and ML-SEM. An intuitively appealing graphical representation of complex ML-SEMs is introduced that succinctly describes the underlying model and its assumptions. The use of definition variables (i.e., observed variables used to fix model parameters to individual specific data values) is extended to the case of ML-SEMs for clustered data with random slopes. Empirical examples of multilevel CFA and ML-SEM with random slopes are provided along with scripts for fitting such models in SAS Proc Mixed, Mplus, and Mx. Methodological issues regarding estimation of complex ML-SEMs and the evaluation of model fit are discussed. Further potential applications of ML-SEMs are explored.

Analysis of Variance↗
PubMed2001

Dispositions and work reactions: a multilevel approach.

Multiple levels of analysis were used to examine the link between stable dispositions and more state-oriented work reactions such as job satisfaction. Participants in the study were employees from a large state education system and an urban hospital. The proportion of between-group variance in positive work affect, negative work affect, and job satisfaction increased after dispositional measures of neuroticism and extraversion were included, although the confidence intervals overlapped. Aggregate perceptions of excessive job demands explained more between-group variance in work reactions after dispositions were included. Previous research conducted at a single level of analysis suggests that the inclusion of stable dispositions can attenuate the link between work characteristics and work reactions. The present study suggests the opposite pattern when group-level variance is considered.

Adult↗
PubMed2003

Complications of multilevel cervical corpectomies and reconstruction with titanium cages and anterior plating.

The ideal surgical treatment of multilevel cervical spondylosis remains unclear. This study analyzed the complications in using titanium cages and plating to reconstruct multilevel cervical corpectomies. This was a retrospective analysis of 21 consecutive patients who had multilevel cervical corpectomies and reconstruction with titanium cages and anterior plating. Sixteen had 2-level, one had 2.5-level, three had 3-level, and one had 3.5-level corpectomies. All had reconstruction with titanium cages and anterior plating. Thirty-three percent of the patients developed complications. Radiographs revealed bony consolidation in 95% of patients. Reconstructing multilevel cervical corpectomies with titanium cages and plating is associated with complications. Advantages include rigid immobilization and the avoidance of iliac crest bone graft harvesting. Major complications are largely the result of failures of the cage and plate construct, especially in patients with osteopenic bone. Supplemental posterior stabilization may be considered for cases with spasticity or greater than 2-level corpectomies with profound osteoporosis.

Adult↗
PubMed1999

Simultaneous analysis of individual and aggregate responses in psychometric data using multilevel modeling.

Psychometric data on risk perceptions are often collected using the method developed by Slovic, Fischhoff, and Lichtenstein, where an array of risk issues are evaluated with respect to a number of risk characteristics, such as how dreadful, catastrophic or involuntary exposure to each risk is. The analysis of these data has often been carried out at an aggregate level, where mean scores for all respondents are compared between risk issues. However, this approach may conceal important variation between individuals, and individual analyses have also been performed for single risk issues. This paper presents a new methodological approach using a technique called multilevel modelling for analysing individual and aggregated responses simultaneously, to produce unconditional and unbiased results at both individual and aggregate levels of the data. Two examples are given using previously published data sets on risk perceptions collected by the authors, and results between the traditional and new approaches compared. The discussion focuses on the implications of and possibilities provided by the new methodology.

Humans↗
PubMedDate not supplied

Multilevel and continuous pleural fluid pH likelihood ratios for draining parapneumonic effusions.

BACKGROUND: Although clinical practice guidelines endorse the use of pleural fluid pH to select patients with parapneumonic effusions for pleural drainage, no studies have reported likelihood ratios for pleural fluid pH. OBJECTIVES: We derived and tested the value of continuous likelihood ratios for selecting pneumonia patients for pleural drainage. METHODS: Patient level pleural fluid pH results were obtained from a registry of primary studies that assessed the discriminative properties of pH. Multilevel likelihood ratios were calculated for four pH intervals. Continuous likelihood ratios were derived from logistic regression using discrete pH values. Binary, multilevel and continuous likelihood ratios were compared to evaluate the statistical (chi2) and clinical advantages of continuous likelihood ratios. RESULTS: Hundred and ninety-seven pleural fluid pH results were retrieved from published reports and categorized into four pH ordinal intervals. Multilevel likelihood ratios ranged from a low of 0.13 (95% CI, 0.04-0.41) for pH values >7.40 to a high of 15.80 (95% CI, 7.04-35.45) for pH values < or =7.00. Logistic regression derived the following equation for continuous likelihood ratios: exp[-7.168(measured pH - 7.207)]. Continuous likelihood ratios offered more diagnostic information both statistically (p < 0.005) and clinically compared with binary and multilevel likelihood ratios. CONCLUSIONS: Analysis of a patient registry allows the derivation of an exponential equation that calculates continuous likelihood ratios for discrete pleural fluid pH values. Continuous likelihood ratios provide more clinically and statistically significant information compared with binary and multilevel likelihood ratios for calculating posttest probabilities of the need to drain parapneumonic effusions.

Decision Support Techniques↗
PubMed2001

Multilevel modelling of hierarchical data in developmental studies.

This report attempts to give nontechnical readers some insight into how a multilevel modelling framework can be used in longitudinal studies to assess contextual influences on child development when study samples arise from naturally formed groupings. We hope to achieve this objective by: (1) discussing the types of variables and research designs used for collecting developmental data; (2) presenting the methods and data requirements associated with two statistical approaches to developmental data--growth curve modelling and discrete-time survival analysis; (3) describing the multilevel extensions of these approaches, which can be used when the study of development includes intact clusters or naturally formed groupings; (4) demonstrating the flexibility of these two approaches for addressing a variety of research questions; and (5) placing the multilevel framework developed in this report in the context of some important issues, alternative approaches, and recent developments. We hope that readers new to these methods are able to visualize the possibility of using them to advance their work.

Adolescent↗
PubMed2000

The application of multilevel modelling to periodontal research data.

OBJECTIVE: To explain the theory of multilevel modelling and demonstrate its application in the analysis of dental research data. BASIC RESEARCH DESIGN: Multilevel modelling was introduced using dental data comprising four levels: repeated measurements at level-1, sites at level-2, teeth at level-3, and subjects at level-4. Variance components models (which have no explanatory variables) were evaluated for all outcome measures. Explanatory variables were added to the models with outcomes for both lifetime cumulative attachment loss and pocket probing depth. Salient features of the multilevel models were discussed. PARTICIPANTS: Research data were obtained from a longitudinal survey of periodontal disease conducted on 100 white male trainee engineers aged between 16 and 20 years entering the apprentice training school at Royal Air Force Halton, England. RESULTS: The statistical methods revealed that periodontal measures demonstrate considerable variation at all levels of the multilevel structure. Models for lifetime cumulative attachment loss and pocket probing depth illustrated that risk factors operated at more than one level. Supragingival calculus was a risk factor at the subject-level (subjects experiencing more sites with the condition had greater attachment loss and greater pocketing) whilst there was apparently a protective effect occurring at the site (sites with the condition had less attachment loss and less pocketing). CONCLUSIONS: This study demonstrates that multilevel modelling is a more powerful research tool than single-level techniques for the analysis of hierarchical dental data. Researchers using these techniques are well equipped to analyse complex hierarchical data structures, such as those often found within dentistry.

Adolescent↗
PubMed2006

An infrastructure for high-throughput microscopy: instrumentation, informatics, and integration.

High-throughput, image-based cell assays are rapidly emerging as valuable tools for the pharmaceutical industry and academic laboratories for use in both drug discovery and basic cell biology research. Access to commercially available assay reagents and automated microscope systems has made it relatively straightforward for a laboratory to begin running assays and collecting image-based cell assay data, but doing so on a large scale can be more challenging. Challenges include process bottlenecks with sample preparation, image acquisition, and data analysis as well as day-to-day assay consistency, managing unprecedented quantities of image data, and fully extracting useful information from the primary assay data. This chapter considers many of the decisions needed to build a robust infrastructure that addresses these challenges. Infrastructure components described include integrated laboratory automation systems for sample preparation and imaging, as well as an informatics infrastructure for multilevel image and data analysis. Throughout the chapter we describe a variety of strategies that emphasize building processes that are scaleable, highly efficient, and rigorously quality controlled.

Animals↗
PubMed1980

Overlapping functional systems: a theory for vertebrate central nervous system function in terms of informal systems analysis.

An holistic theory of the functional organization of the central nervous system, a system at the level of the organ, in vertebrate organisms is presented as an alternative to localization of function by using two sets of complementary rules for systems designation derived from systems theory. These rules reveal three types of systems according to levels of operation and the origins of goals. These are: (1) the teleogenic or primary systems (reproductive, food-water intake-use, thermoregulative, immune, oxygen intake-use); (2) the teleozetic or subsystems (internal sensory and motor, external motor, external sensory); (3) the teleonomic systems or echelons (field, local circuit, basic functional unit, basic excitation unit). The systems, subsystems, and echelons are discussed with regard to their hierarchical relationships, the nature of their goals, and the supporting experimental evidence. The theory is discussed as an explicit statement of multileveled relationships for the analysis of the vertebrate CNS and, therefore, as presenting a paradigm for, or a way of thinking about, local and global brain theories, brain dysfunction, and brain evolution.

Animals↗
PubMed2004

Multilevel investigation of variation in HoNOS ratings by mental health professionals: a naturalistic study of consecutive referrals.

Episodes of mental healthcare in specialist psychiatric services often begin with the assessment of clinical and psychosocial needs of patients by healthcare professionals. Particularly for patients with complex needs or severe problems, ratings of clinical and social functioning at the start of each episode of care may serve as a baseline against which subsequent measures can be compared. Currently, little is known about service variations in such assessments on referrals from primary care. We set out to quantify variability in initial assessments performed by healthcare professionals in three CMHTs in Bristol (UK) using the Health of the Nation Outcome Scales (HoNOS). We tested the hypothesis that variations in HoNOS total and sub-scale scores are related to referral source (general practices), healthcare assessor (in CMHTs) and the assessor's professional group. Statistical analysis was performed using multilevel variance components models with cross-classified random effects. We found that variation due to assessor substantially exceeded that due to referral source (general practices). Furthermore, patient variance differed by assessor profession for the HoNOS--Impairment scores. Assessor variance differed by assessor profession for the HoNOS--Social scores. As HoNOS total and subscale scores show much larger variation by assessor than by referral source, investigations of HoNOS scores must take assessors into account. Services should implement and evaluate interdisciplinary training to improve consistency in use of rating thresholds; such initiatives could be evaluated using these extensions of multilevel models. Future research should aim to integrate routine diagnostic data with continuous outcomes to address selection effects (of patients to assessors) better.

Adolescent↗
PubMed2005

Estimating variability in outcomes attributable to therapists: a naturalistic study of outcomes in managed care.

To estimate the variability in outcomes attributable to therapists in clinical practice, the authors analyzed the outcomes of 6,146 patients seen by approximately 581 therapists in the context of managed care. For this analysis, the authors used multilevel statistical procedures, in which therapists were treated as a random factor. When the initial level of severity was taken into account, about 5% of the variation in outcomes was due to therapists. Patient age, gender, and diagnosis as well as therapist age, gender, experience, and professional degree accounted for little of the variability in outcomes among therapists. Whether or not patients were receiving psychotropic medication concurrently with psychotherapy did affect therapist variability. However, the patients of the more effective therapists received more benefit from medication than did the patients of less effective therapists.

Adult↗
PubMed2005

Use of bone morphogenetic protein-2 for adult spinal deformity.

STUDY DESIGN: Prospective, single-center, nonblinded clinical and radiographic analysis of consecutive adult deformity patients treated with recombinant human bone morphogenetic protein-2 (rhBMP-2) without iliac or rib bone graft supplementation. OBJECTIVES: To determine the ability of rhBMP-2 to achieve both anterior and posterior spinal fusion in patients undergoing multilevel fusions for adult spinal deformity. SUMMARY OF BACKGROUND DATA: The literature concerning one-level anterior fusions, and potentially one-level posterior fusions, using rhBMP-2 has demonstrated clinical efficacy. No published data exist on the use of rhBMP-2 in multilevel spine fusions. METHODS: Prospective analysis of patients treated with rhBMP-2 in multilevel anterior and posterior fusions with a minimum 1-year follow-up. There were a total of 95 patient samples (70 total patients; 25 patients had rhBMP-2 used circumferentially): 46 anterior fusions (Group 1), 41 posterior fusions (Group 2), and 8 patients were "compassionate use" fusions (Group 3). In the anterior fusion group (n = 46), mean rhBMP-2/level was 10.8 mg in titanium mesh cages without any bone graft or other substance. The posterior fusion group had only local bone graft, no harvested rib or iliac bone graft (n = 41). The mean rhBMP-2/level was 13.7 mg. The "compassionate use" group (n = 8 patients) consisted of patients who had prior surgeries, prior iliac harvesting, and substantial comorbidities and therefore a higher concentration and different carrier was used. No local bone graft, no harvested bone was used. The mean rhBMP-2/level was 28.6 mg. The median dose was 40 mg for Group 3. RESULTS: For the anterior fusion group (n = 46), operative levels were deemed fused in 89 of the 93 (96%) levels. For the posterior fusion group (n = 41), a solid fusion was assessed in 110 of the 118 (93%) operative levels. For the "compassionate-use" patients, the overall fusion rate was 100% (52 of 52 operative levels). CONCLUSIONS: With the use of rhBMP-2, a high rate of apparent fusion was observed for anterior (96%) and posterior (93%) fusions in adult spinal deformity patients. Use of rhBMP-2 results in a promising early fusion rate without the graft harvest site morbidity.

Adult↗
PubMed2006

Reliability and validity of arm volume measurements for assessment of lymphedema.

BACKGROUND AND PURPOSE: Arm lymphedema following breast cancer surgery is a continuing problem. In this study, we assessed the reliability and validity of circumferential measurements and water displacement for measuring upper-limb volume. SUBJECTS: Participants included subjects who had had breast cancer surgery, including axillary dissection--19 with and 22 without a diagnosis of arm lymphedema--and 25 control subjects. METHODS: Two raters measured each subject by using circumferential tape measurements at specified distances from the fingertips and in relation to anatomic landmarks and by using water displacement. Interrater reliability was calculated by analysis of variance and multilevel modeling. Volumes from circumferential measurements were compared with those from water displacement by use of means and correlation coefficients, respectively. The standard error of measurement, minimum detectable change (MDC), and limits of agreement (LOA) for volumes also were calculated. RESULTS: Arm volumes obtained with these methods had high reliability. Compared with volumes from water displacement, volumes from circumferential measurements had high validity, although these volumes were slightly larger. Expected differences between subjects with and without clinical lymphedema following breast cancer were found. The MDC of volumes or the error associated with a single measure for data based on anatomic landmarks was lower than that based on distance from fingertips. The mean LOA with water displacement were lower for data based on anatomic landmarks than for data based on distance from fingertips. DISCUSSION AND CONCLUSION: Volumes calculated from anatomic landmarks are reliable, valid, and more accurate than those obtained from circumferential measurements based on distance from fingertips.

Adult↗