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PubMed1977

[Isocount scanning in the diagnosis of the brain abscess (author's transl)].

The purpose of this study is to investigate salient diagnostic features of the brain abscess in RI brain scanning. In 27 patients with brain abscess, 37 scannings were performed in the various stages of their clinical courses. The results were positive in all cases. Among 27 cases, ten cases were investigated by means of the ISOCOUNT SCANNING SYSTEM, the technical detail of which was reported previously. It was proved that the isocount scanning method combined with the multilevel analysis was more sensitive diagnostic aid than the conventional RI scintigraphy. Using the newly developed method, it was not difficult to diagnose the brain abscess in its early stage, even in the stage of presuppurative cerebritis. Doughnut sign was seemed to be more frequently visualized by this method. Surgical indication of the brain abscess was discussed from nucleomedical view point, and it was emphasized that so-called doughnut sign in brain scanning would indicate the appropriate stage of the brain abscess to be operated on.

Adolescent↗
PubMed1996

Individual differences, daily fluctuations, and developmental changes in amounts of infant waking, fussing, crying, feeding, and sleeping.

Measures of the amounts of time infants spent asleep, awake-content, feeding, fussing, and crying at 2, 6, 12, and 40 weeks of age were examined using multilevel analysis. This method enables the proportion of the variance in each behavior due to individual differences to be compared to the proportion due to age changes (development) and to day-to-day fluctuations at each age in the same infants. Day-to-day fluctuations were found to account for the largest proportion of the variance in amounts of sleeping, fussing, and crying (between 44% and 53%), testifying to the importance of instability in these behaviors as a characteristic of infancy. Against this background, both development and individual differences explained substantial proportions of the variance, with a somewhat different picture in each area of behavior. Amounts of waking and feeding were mainly accounted for by development, and no evidence of enduring individual differences was found. For sleeping, development and individual difference each contributed approximately a quarter of the variance, and the amounts infants slept remained moderately stable from 6 weeks to 9 months of age. Crying decreased linearly with age, with development accounting for 38% and individual difference 15% of the variance. Fussing proved a more stable characteristic than crying, and "high fussers" at 6 weeks of age were particularly likely to retain this characteristic at 9 months, whereas amount of crying in the first 3 months did not predict 9-month behavior. The study's clinical, conceptual, and methodological implications are discussed.

Circadian Rhythm↗
PubMed2005

The measurement of nursing home quality: multilevel confirmatory factor analysis of panel data.

This study examined the validity of a measurement model of nursing home quality by using multilevel confirmatory factor analysis. Based on Mullan and Harrington's (2001) facility-level quality measurement model, a two-level analysis (facility and state) of the measurement model were performed. Two research questions were asked: (1) Can the measurement model developed at the facility-level be applied to state-level nursing home quality measurement? (2) Is the measurement model of nursing home quality stable over time? Panel data of 1997 and 2001, from the national OSCAR database, were used to test the assumptions. The results show that the state-level measurement model fits the data better than the facility-level model does. When the indicator "assessment" was removed from the state-level measurement model, a better-fitted measurement model was found. The two-level measurement model is relatively stable over time, demonstrating the construct validity of this measurement model.

Cohort Studies↗
PubMed2002

Comparing the Fourier modal method with the C method: analysis of conducting multilevel gratings in TM polarization.

The coordinate transformation method (C method) with adaptive spatial resolution and the Fourier modal method (FMM) are compared in the case of conducting discontinuous multilevel gratings in TM polarization. A procedure permitting analysis of such gratings more efficiently with the C method than with the FMM is presented. The C method is observed to converge more rapidly than the FMM, whose instabilities are shown to harm the convergence in the aforementioned case.

Journal Article↗
PubMed2004

Job decision latitude, organizational justice and health: multilevel covariance structure analysis.

A total of 2969 hospital employees from 162 wards participated in a 2-year follow-up study that examined the relationship between job decision latitude, organizational justice and employee health in Finland. We used medically certified sickness absence records as indicators of health problems. Multilevel covariance structure analysis was applied to take into account the hierarchical nature of the data. Responses from individuals within work units seem not always to be independent, and any models that ignore this lack of independence may incorrectly estimate the between individual relationships. Our results suggest that both job decision latitude and organizational justice varied considerably between work units in addition to individual level variation. Furthermore job decision latitude was associated with organizational justice both at individual and work unit level. Justice evaluations predicted sickness absence only at the individual level.

Career Mobility↗
PubMed2005

Assessing generalisability by location in trial-based cost-effectiveness analysis: the use of multilevel models.

Cost-effectiveness analysis (CEA) in health care is increasingly conducted alongside multicentre and multinational randomised controlled clinical trials (RCTs). The increased use of stochastic CEA is designed to account for between-patient sampling variability in cost-effectiveness data assuming that observations are independently distributed. However, between-location variability in cost-effectiveness may result if there is a hierarchical structure in the data; that is, if there is correlation in costs and outcomes between patients recruited in particular locations. This may be expected in multi-location trials given that centres and countries often differ in factors such as clinical practice, patient case-mix and the unit costs of delivering health care. A failure to acknowledge this feature may lead to misleading conclusions in a trial-based economic study. Multilevel modelling (MLM) is an analytical framework that can be used to handle hierarchical cost-effectiveness data. Using data from a recently conducted economic analysis, this paper shows how multilevel modelling can be used to obtain (a) more appropriate estimates of the population average incremental cost-effectiveness and associated standard errors compared to standard stochastic CEA; and (b) location-specific estimates of incremental cost-effectiveness which can be used to explore appropriately the variability between centres/countries of the cost-effectiveness results.

Cost-Benefit Analysis↗
PubMed2004

Exploratory data analysis of the multilevel anthropogenic copper cycle.

A comprehensive multilevel contemporary cycle for stocks and flows of copper is analyzed by the tools of exploratory data analysis (EDA). The analysis is performed at three discrete spatial levels--country (56 countries or country groups that comprise essentially all anthropogenic stocks and flows of copper), eight world regions, and the planet as a whole. Among the most interesting results are the following: (1) EDA is employable and valuable for use in the analysis of material flows, especially those across multiple spatial levels; (2) All distributions of country-level stock and flow data are highly skewed, a few countries having large magnitudes, many having small magnitudes; (3) Rates of fabrication of copper-containing products for the countries are poorly correlated with rates of extraction, reflecting the fact that many countries that extract copper do not fabricate products from copper to any significant degree and vice versa; (4) Virtually all countries are adding copper to stock (in pipe, wire, etc.); These rates of addition are highly correlated with rates of copper entering use in all regions and are higher in regions under vigorous development; (5) With weak confidence, the rate of copper landfilling by regions is about one-half the rate of copper discarded; (6) The statistical distributions of both country-level and regional-level copper cycle parameters have successively lower standard deviations at later life stages; and (7) Copper flow distributions at different life stages tend to reflect those of lower spatial level extreme values, but Asia's and Europe's regional patterns are much more reflective of country-level distributions as a whole.

Asia↗
PubMed2026

Adherence and effectiveness of multicomponent exercise fall prevention programmes across delivery formats in community-dwelling older adults: a systematic review and multilevel meta-analysis.

BACKGROUND: Multicomponent exercise is widely implemented for fall prevention in older adults, but the role of exercise adherence and delivery format in determining intervention effectiveness remains inadequately understood, particularly in analyses that account for within-study outcome dependence. METHODS: We searched five databases to 23 November 2025 for RCTs of multicomponent exercise in adults aged ≥60 years. Fall outcomes were synthesised using three-level random-effects meta-analysis and meta-regression, with adherence evaluated as continuous/categorical factors and as moderator alongside delivery format, accounting for within-study effect-size dependence. RESULTS: Forty-one publications were included, comprising 36 distinct cohorts and involving 20,202 participants. Multicomponent exercise programmes significantly reduced fall incidence (IRR = 0.776, 95% CI 0.641-0.939), risk of experiencing at least one fall (RR = 0.914, 95% CI 0.858-0.974), and fall-related injury incidence (IRR = 0.754, 95% CI 0.663-0.858). Programmes achieving adherence ≥75% were independently associated with greater reductions in fall incidence (IRR = 0.501, 95% CI 0.336-0.747) and fall risk (RR = 0.821, 95% CI 0.697-0.967). Mean adherence was highest in combined individual and group delivery, lower in single-format programmes, though including a group component may enhance adherence. CONCLUSIONS: Multicomponent exercise fall prevention programmes are effective for fall prevention in community-dwelling older adults, whereas evidence for their protective effects on fall-related injury outcomes remains limited. Adherence is an important factor influencing programme implementation and intervention effectiveness.

Aged↗
PubMed2005

[The preparation of the multilevel holes and analysis of the pure titanium surface].

PURPOSE: Using sandblast, double acid-etching and H(2)O(2)/HCl solution treatment to establish a new implant surface, and to analyze the surface's morphology. METHODS: After being polished, sandblasted, cleaned, the titanium specimens were divided into six groups, i.e.A to F group. The specimens of group A were treated with low concentration of HF/HNO(3) solution, Group B was treated with low concentration of HF/HNO(3) solution and then H(2)SO(4)/HCl solution, Group C was treated after Group B and further with H(2)O(2)/HCl solution at 80degrees centigrade for 30 minutes, and subsequently heated at 400degrees centigrade for 1 hour. Group D was treated with high concentration of HF/HNO(3) solution, Group E was treated after Group D and then H(2)SO(4)/HCl solution, Group F was treated after E group and further with H(2)O(2)/HCl solution at 80degrees centigrade for 30 minutes, and subsequenty heated at 400degrees centigrade for 1 hour. RESULTS: The titanium surface sandblasted and ultrasonically cleaned exhibited a great deal of particles. The titanium plates treated with low concentration of HF/HNO(3) solution still had some particles, but there were much nano-holes on the titanium surface. The titanium plates treated with high concentration of HF/HNO(3) solution had no particles on the surface, but showed much micron-holes on the titanium surface. The titanium plates treated with H(2)SO(4)/HCl solution after HF/HNO(3) solution etching had all particles removed and got multilevel holes on the surface.The last H(2)O(2)/HCl method produced an anatase titania gel layer on the specimen surface. CONCLUSION: By altering the concentration of HF/HNO(3) solution, we could make different sizes of apertures on the titanium surface. Double acid-etching can remove all sandblasting particles embedded in titanium surfaces and form multilevel holes. The H(2)O(2)/HCl method can turn the rough non- crystallographic TiO(2) layer into the anatase titania gel layer.

Acid Etching, Dental↗
PubMed2004

Biomechanical analysis of cervical multilevel oblique corpectomy: an in vitro study in sheep.

BACKGROUND: Anterolateral oblique corpectomy is an alternative approach to treatment of multilevel cervical spinal disease. It is stated that the approach does not cause instability in the patients with hard discs, so fusion or instrumentation is not required. The authors undertook a study on stability of the cervical spine by an animal model to establish if this approach causes instability. MATERIAL AND METHODS: Thirty-seven C3 to C6 spinal segments obtained from 3 to 4-year-old male sheep were used. In vitro maximal loading values were obtained from seven sheep cervical specimens for flexion, extension, lateral flexion in both directions, axial rotation in both directions and axial loading, and load deformation curves were drawn by an electrohydrolic testing machine. Other specimens were divided into three groups: Control (n=10), C4 (n=10) and C4-5 (n=10) groups. In two study groups, one or two level oblique corpectomies were performed. In the control and study groups, biomechanical tests were obtained according to the maximal loading values. Load-deformation curves were drawn and displacement amounts were determined for all seven movements. RESULTS: No statistically significant differences were observed in load deformation curves and displacement amounts between all three groups for seven movements. CONCLUSION: These results support the opinion that anterolateral oblique corpectomy does not cause cervical instability.

Animals↗
PubMed2006

Multi-layered network structure of amino acid (AA) metabolism characterized by each essential AA-deficient condition.

The concentrations of free amino acids in plasma change coordinately and their profiles show distinctive features in various physiological conditions; however, their behavior can not always be explained by the conventional flow-based metabolic pathway network. In this study, we have revealed the interrelatedness of the plasma amino acids and inferred their network structure with threshold-test analysis and multilevel-digraph analysis methods using the plasma samples of rats which are fed diet deficient in single essential amino acid. In the inferred network, we could draw some interesting interrelations between plasma amino acids as follows: 1) Lysine is located at the top control level and has effects on almost all of the other plasma amino acids. 2) Threonine plays a role in a hub in the network, which has direct links to the most number of other amino acids. 3) Threonine and methionine are interrelated to each other and form a loop structure.

Amino Acids, Essential↗
PubMed2001

The mind over the Web: the quest for the definition of a method for Internet research.

Psychology is increasingly interested in understanding the characteristics of the Internet and its effects on people, groups and organizations. However, studying the Internet is not a simple task. First, the Internet is a medium that can be experienced in many different ways. Though a computer and keyboard are usually the mediator of our Internet experience, there are different ways in which users can explore the Internet, present themselves, and communicate using it. Second, the Internet is a social and cognitive space. The handling of information is linked to the activation of psychosocial relationships in which cognitions are elaborated. This happens inside a rather special kind of container--Cyberspace--which tends to rarefy the structural and process features of communication. Third, the Internet experience is always situated in a specific context, even when we are chatting alone in a room. In this sense it can only be fully understood through detailed analysis of the social context in which it happens. Starting from a general three-level model of interpersonal interaction in the Web, this paper tries to define a model of data analysis (Complementary Explorative Multilevel Data Analysis--CEMDA) suited to the constraints of Internet research. The main characteristics of the model are: the focus on different frames and objects for each considered unit of research; the mixed use of quantitative and qualitative tools; and the final integration of results in a general framework.

Cognition↗
PubMed2006

The role of rural health clinics in hospitalization due to ambulatory care sensitive conditions: a study in Nebraska.

CONTEXT: Hospitalization due to ambulatory care sensitive conditions (ACSCs) is often used as an indicator for measuring access to primary care. Rural health clinics (RHCs) provide basic primary care services for rural residents in health professional shortage areas (HPSAs). The relationship between RHCs and ACSCs is unclear. PURPOSE: The purpose of this study was to examine the relationship between the presence of RHCs in rural HPSAs and the likelihood of having an acute or chronic ACSC as the reason for hospitalization. METHODS: Nebraska hospital discharge data (1999-2001) and the 2003 Area Resource File were used in this analysis. A multilevel logistic regression analysis was used to examine the relationship between the presence of RHCs in rural HPSAs and the likelihood of having an ACSC as the reason for hospitalization, after controlling for individual characteristics and county-level contextual factors stratified by 3 age groups. The eligibility for logistic regression was limited to patients from 28 rural Nebraska counties designated as HPSAs in 2001. Patients with commercial payers were excluded from the study. FINDINGS: Elderly patients residing in rural Nebraska HPSAs with at least one RHC were significantly less likely to have a hospitalization due to chronic ACSCs. CONCLUSIONS: The presence of RHC is a significant factor associated with fewer hospitalizations for chronic ACSCs among the rural elderly residing in HPSAs.

Adult↗
PubMed2003

A comparison between traditional methods and multilevel regression for the analysis of multicenter intervention studies.

This article reviews three traditional methods for the analysis of multicenter trials with persons nested within clusters, i.e., centers, namely naïve regression (persons as units of analysis), fixed effects regression, and the use of summary measures (clusters as units of analysis), and compares these methods with multilevel regression. The comparison is made for continuous (quantitative) outcomes, and is based on the estimator of the treatment effect and its standard error, because these usually are of main interest in intervention studies. When the results of the experiment have to be valid for some larger population of centers, the centers in the intervention study have to present a random sample from this population and multilevel regression may be used. It is shown that the treatment effect and especially its standard error, are generally incorrectly estimated by the traditional methods, which should, therefore, not in general be used as an alternative to multilevel regression.

Adolescent↗
PubMed2002

The mixed or multilevel model for behavior genetic analysis.

We propose the mixed model or multilevel model as a general alternative approach to existing behavior genetic analysis-an alternative to correlation analysis, the DeFries-Fulker analysis, and structural equation modeling. The mixed or multilevel model handles readily families of behavioral genetic data, which include paired sibling data (e.g., pairs of MZ and DZ twins) and clustered sibling data (e.g., a family of more than two biological siblings) as special cases. Not only can a family of behavioral genetic data have more than two siblings, it can also contain multiple types of siblings (e.g., a pair of MZ twins, a pair of DZ twins, a full sibling, and a half sibling). In contrast to the traditional approaches, the mixed or multilevel model is insensitive to the order of the siblings in a sibling cluster. We apply our approach to a large, nationally representative behavior genetic sample collected recently by the Add Health Study. We demonstrate the approach through several applications using both clustered and family complex behavioral genetic data: conventional variance decomposition analysis, analysis of interactions between genetic and environmental influences, and analysis of the possible genetic basis for friendship selection. We compare results from the mixed or multilevel model, Pearson's correlation analysis, and the structural equation model.

Adolescent↗
PubMed2001

Multilevel models for survival analysis with random effects.

A method for modeling survival data with multilevel clustering is described. The Cox partial likelihood is incorporated into the generalized linear mixed model (GLMM) methodology. Parameter estimation is achieved by maximizing a log likelihood analogous to the likelihood associated with the best linear unbiased prediction (BLUP) at the initial step of estimation and is extended to obtain residual maximum likelihood (REML) estimators of the variance component. Estimating equations for a three-level hierarchical survival model are developed in detail, and such a model is applied to analyze a set of chronic granulomatous disease (CGD) data on recurrent infections as an illustration with both hospital and patient effects being considered as random. Only the latter gives a significant contribution. A simulation study is carried out to evaluate the performance of the REML estimators. Further extension of the estimation procedure to models with an arbitrary number of levels is also discussed.

Biometry↗
PubMed2001

Multilevel models for meta-analysis, and their application to absolute risk differences.

Meta-analysis can be considered a multilevel statistical problem, since information within studies is combined in the presence of potential heterogeneity between studies. Here a general multilevel model framework is developed for meta-analysis to combine either summary data or individual patient outcome data from each study, and to include either study or individual level covariates that might explain heterogeneity. Classical and Bayesian approaches to estimation are contrasted. These methods are applied to a meta-analysis of trials of thrombolytic therapy after myocardial infarction. Subgroups within the trials were available, categorized by the time delay until treatment, so that a three-level random effects model that includes time delay as a covariate is proposed. In addition it was desired to represent the treatment effect as an absolute risk reduction, rather than the conventional odds ratio. We show how this can be achieved within a Bayesian analysis, while still recognizing the binary nature of the original outcome data.

Bayes Theorem↗
PubMed2002

[The contribution of multilevel models in contextual analysis in the field of social epidemiology: a review of literature].

Using contextual factors beyond individual factors, contextual analysis allows a more accurate identification of at-risk populations, which could be useful when planning health programs. Multilevel models, widely used in British and North-American social epidemiology research but less frequently in France, are particularly suitable to analyse contextual data, because they take into account their hierarchical structure. This paper addresses methodological issues in the utilization of multilevel models, and reports some results which illustrate their potentials compared to those of more conventional statistical methods. As well as other methods, multilevel models are able to take into account the hierarchical structure of the data when estimating parameters. Furthermore, and more specifically, these models can also be viewed as useful tools to investigate contextual effects. Their particular interest is to disentangle individual-level variability and between-group variability. Comparing the group-level variance before and after introduction of individual-level characteristics allows to assess the extent to which between-group variability is linked to compositional effects. Multilevel models can also help examine whether the between-group variations affect all the members of the groups, or only specific sub-groups. Finally, they can estimate how much of this complex between-group variability is explained by the contextual factors included in the model. The overall conclusion is that multilevel statistical methods should be used in social epidemiology studies dealing with individual and contextual data, to produce results that are both richer and more consistent.

Bias↗