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At least 199 records · Page 11Linked to original sources
PubMed2006

The potential prognostic value of some periodontal factors for tooth loss: a retrospective multilevel analysis on periodontal patients treated and maintained over 10 years.

BACKGROUND: The great challenge in clinical periodontology is assigning a prognosis to a periodontally affected patient. Many different factors can affect the long-term maintenance of periodontally compromised teeth. The main questions usually considered by the periodontist are: 1) Will a tooth lose more bone in the future? 2) Will the tooth itself be lost in the future? The purpose of this retrospective study was to evaluate the value of some clinical, genetic, and radiographic variables in predicting tooth loss in periodontal patients (aged 40 to 60 years) treated and maintained for 10 years. METHODS: Sixty consecutive non-smoking patients (aged 46.77 +/- 4.96 years) with moderate to severe chronic periodontitis (CP) were treated with scaling and root planing (SRP). Some patients also underwent additional surgical treatments. All patients were maintained in the same private practice for 10 years. The frequency of recall appointments was 3.4 +/- 1.0 months. At baseline (T(0)) and 10 years later (T(2)) the following clinical variables were evaluated: the number of teeth, probing depths (PD), tooth mobility (TM), and presence of prosthetic restorations (PR). In addition, radiographic measurements were taken of the mesial and distal distances from the cemento-enamel junction (CEJ) to the bottom of the defect (BD), to the bone crest (BC), and to the root apex (RA). At T(2), a genetic test to determine the IL-1 genotype and genetic susceptibility for severe periodontal disease was performed for all 60 patients, and they were classified as IL-1 genotype positive (G+) or negative (G-) according to the test results. Tooth loss was used as the outcome variable. Different predictor variables were then tested using a two-level statistical model (patient and tooth levels). At the patient level, these were: age, gender, mean bone loss (mean CEJ-BD)(T0), the interleukin-1 (IL-1) genotype, the interaction between mean bone loss, and IL-1 genotype (mean CEJ-BD(T0) x IL-1 genotype). At the tooth level, the variables were: TM(T0), prosthetic restorations (PR)(T0), molar teeth (MT)(T0), the infrabony component of the defect (BC-BD)(T0), PD(T0), bone level (CEJ-BD)(T0), and residual supporting bone (BD-RA)(T0). RESULTS: Among the considered predictor variables, the following were significantly associated with the outcome variable: 1) MT(T0) (P <0.0001); 2) BC-BD(T0) (P = 0.0377); and 3) BD-RA(T0) (P <0.0001). MT(T0) were found to be more prone to loss and the amount of BD-RA(T0) prognostic for tooth loss: the lower the residual amount of supporting bone, the higher the probability of tooth loss. Conversely, the BC-BD(T0)was associated with a reduced probability of future tooth loss: the greater the infrabony component, the lower the probability of tooth loss. None of the other considered predictors proved predictive for tooth loss. CONCLUSIONS: Within the scope of this study, many traditional prognostic factors were ineffective in predicting future tooth loss and, therefore, were of no prognostic value. Conversely, a few specific factors at the tooth level emerged as viable prognostic factors. The use of these factors may be of great value to practitioners as predictors of tooth loss when assigning a prognosis.

Adult↗
PubMed2002

A multilevel analysis of the relationship between institutional and individual racial discrimination and health status.

OBJECTIVES: This study examined whether individual (self-perceived) and institutional (segregation and redlining) racial discrimination was associated with poor health status among members of an ethnic group. METHODS: Adult respondents (n = 1503) in the cross-sectional Chinese American Psychiatric Epidemiologic Study were geocoded to the 1990 census and the 1995 Home Mortgage Disclosure Act database. Hierarchical linear modeling assessed the relationship between discrimination and scores on the Medical Outcomes Study Short-Form 36 and revised Symptom Checklist 90 health status measures. RESULTS: Individual and institutional measures of racial discrimination were associated with health status after control for acculturation, sex, age, social support, income, health insurance, employment status, education, neighborhood poverty, and housing value. CONCLUSIONS: The data support the hypothesis that discrimination at multiple levels influences the health of minority group members.

Acculturation↗
PubMedDate not supplied

Cell damage, aging and transformation: a multilevel analysis of carcinogenesis.

There is a vast scientific literature on cancer which no individual can hope to assimilate. To put it mildly, cancer is an enormously complex biological problem that needs to be considered at multiple levels to achieve reasonable understanding. I describe details of work at the cellular level of "spontaneous" neoplastic transformation in culture to point out parallels with the development of cancer in the organism. One of the most surprising relations is that inhibition of cell growth in a transformation-competent population by long term confluence or acutely lowered serum concentration is a strong enhancer of neoplastic change. The transformation is preceded and accompanied by heritable damage to the entire cell population as expressed among progeny cells in a heterogeneous reduction in growth rate at low density as well as delayed reproductive death in some of the cells. The picture bears resemblance to the relation in vivo between local atrophy in the stomach and prostate and cancer in those organs, as well as the relation between tissue damage and cancer in relatively quiescent organs such as pancreas, urinary bladder, etc. Such damage accumulates with age, as does an increasingly permissive local environment for tumor growth. The most common genetic changes found in tumors are large chromosomal deletions. These are precisely the changes that have been found by somatic cell geneticists to cause heritable reduction in growth rate and delayed reproductive death in mutagen-treated and carcinogen-treated somatic cells. Thus, there is a convergence of findings related to cancer in culture and in the organism. The results in cell culture help to focus attention on proximal mechanisms of malignant cell behavior in the organism. However, they are incomplete without considering fundamental aspects of biological behavior such as Elsasser's first principle of ordered heterogeneity in which there can be regularity in the large where there is heterogeneity in the small. The order that controls heterogeneity is weakened with age and contributes to the origin and progression of disordered growth.

Animals↗
PubMed2001

The influence of school environment and self-regulation on transitions between stages of cigarette smoking: a multilevel analysis.

In this research, hierarchical linear modeling (HLM) was used to address how school context influences the likelihood of transitioning between stages of cigarette smoking as well as modifies the individual-level risk factor of self-regulation. Survey data were collected from 25,186 middle and high school students attending 38 public schools in Kentucky. Results show that students are less likely to increase use in schools with higher levels of teacher discipline and faculty involvement. The analyses of the multi-level interactions between self-regulation and school context reveal that students possessing low emotional regulation are more likely to initiate experimental smoking in schools with poor levels of discipline and involvement than similar types of students in schools with higher levels of these characteristics. This study illustrates how psychological risk factors for substance use may vary across social environments.

Adolescent↗
PubMed1999

Gender differences in determinants of temporary labor migration in China: a multilevel analysis.

Data from a 1998 migration survey in Hubei province are used to examine gender differences in the determinants of temporary labor migration from a multi-level perspective. The authors find that community level factors play a key role in temporary labor migration; models omitting community level variables are poor in predicting temporary labor migration. Significant gender differences exist in determinants of temporary labor migration. For men, temporary labor migration is mainly a response to community level factors; individual or household characteristics have little predictive power. For women, by contrast, temporary labor migration is predominantly determined by individual characteristics; community level factors are not as important.

Asia↗
PubMed1995

The determinants of the duration of postpartum sexual abstinence in West Africa: a multilevel analysis.

The question of how postpartum sexual abstinence responds to social change in West Africa is important because declines in the practice could increase fertility levels and worsen child and maternal health. This study uses data from the late 1970s in Cote d'Ivoire, Ghana, and Cameroon to examine effects of modernization and women's status on the length of abstinence. The results show that modernization and female status should be associated with declines in abstinence, which could lead to an increase in fertility and deterioration in maternal and child health.

Adolescent↗
PubMed1994

A random-effects ordinal regression model for multilevel analysis.

A random-effects ordinal regression model is proposed for analysis of clustered or longitudinal ordinal response data. This model is developed for both the probit and logistic response functions. The threshold concept is used, in which it is assumed that the observed ordered category is determined by the value of a latent unobservable continuous response that follows a linear regression model incorporating random effects. A maximum marginal likelihood (MML) solution is described using Gauss-Hermite quadrature to numerically integrate over the distribution of random effects. An analysis of a dataset where students are clustered or nested within classrooms is used to illustrate features of random-effects analysis of clustered ordinal data, while an analysis of a longitudinal dataset where psychiatric patients are repeatedly rated as to their severity is used to illustrate features of the random-effects approach for longitudinal ordinal data.

Adolescent↗
PubMedDate not supplied

The effects of individual and nursing-unit characteristics on willingness to adopt an innovation. A multilevel analysis.

In this study, the authors investigate the effects of efficacy and cooperativeness on willingness to adopt an innovation at the individual and nursing-unit levels. The results of a field report showed that efficacy was significantly associated with willingness to adopt an innovation at both the individual and nursing-unit levels, whereas cooperativeness was significant only at the individual level. These results suggest that examining innovation adoption at multiple levels provides more valid information than does examining it at a single level.

Adult↗
PubMedDate not supplied

The impact of centering first-level predictors on individual and contextual effects in multilevel data analysis.

BACKGROUND: Multilevel data analysis is a powerful analytical tool. Properly applying the models and correctly interpreting the findings are two interrelated general issues in using multilevel modeling (MLM). There are two specific issues when using MLM: (a) separating the individual-level effects of a predictor variable from its contextual effects and (b) centering first-level predictor variables. This can have major implications for interpreting the results at higher levels, and its impact on second-level interpretation is not always apparent. OBJECTIVES: The major purposes of this article are to show how to separate organizational-level effects from individual-level effects and to show how first-level centering decisions affect the interpretation of second-level coefficients. METHODS: The hierarchical linear models (HLM) are used to analyze a hypothetical data set with 385 patients nested within 10 hospitals, using uncentered, group-mean-centered, and grand-mean-centered versions of the predictor variable. RESULTS: Uncentered and grand-mean-centered models are equivalent, but group-mean-centered models are not equivalent to the other two. For the grand-mean-centered and uncentered models, second-level coefficients provide correct estimates of the individual effect and the contextual effect when the contextual predictor variable is included in the second-level model. The group-mean-centered model leads to a second-level coefficient where individual-level effects are confounded with contextual-level effects. DISCUSSION: There is no single best answer to the question of whether to use group-mean centering or grand-mean centering. The theory and specific questions to be answered should be the researcher's guide to selecting which centering approach to use. Understanding the implications of first-level centering is essential to interpreting second-level coefficients correctly.

Data Interpretation, Statistical↗
PubMed2005

Racial residential segregation and geographic heterogeneity in black/white disparity in poor self-rated health in the US: a multilevel statistical analysis.

Existing evidence demonstrating a relationship between racial residential segregation and health has been based on aggregate analysis. Using a multilevel analytical framework, we assess the extent of geographic variation in black/white disparities in self-rated health across US metropolitan areas, and whether racial residential segregation accounts for such variation. We estimated multilevel regression models of poor self-rated health among 51,316 non-Hispanic white and non-Hispanic black adults nested within 207 metropolitan areas to assess the multilevel relationship between segregation and racial disparities in health. We found statistically significant variation in the black/white disparity in poor self-rated health across metropolitan areas, after controlling for individual level factors (age, sex, marital status, education and income) and residential segregation. High black isolation was associated with increased odds of reporting poor health among blacks (p<0.05). While a similar pattern was observed for white/black dissimilarity and white isolation, they were not statistically significant. Our multilevel analysis only partially supports the previously reported aggregate findings linking segregation to health. Additional multilevel statistical investigations across different health outcomes are required to draw firmer conclusions regarding the adverse effects of segregation on health.

Black or African American↗
PubMed2006

Multilevel component analysis.

A general framework for the exploratory component analysis of multilevel data (MLCA) is proposed. In this framework, a separate component model is specified for each group of objects at a certain level. The similarities between the groups of objects at a given level can be expressed by imposing constraints on component models of the groups using the approach adopted in simultaneous component analysis. The constraints used are based on the loading matrices and on the covariances of the component scores of each group. MLCA is related to three-way component analysis and to currently available multilevel structural equation models. It is shown that the latter are less flexible than MLCA. The use of MLCA is illustrated by means of an empirical example.

Comorbidity↗
PubMed1994

Multilevel models for hierarchically nested data: potential applications in substance abuse prevention research.

This chapter reports on an application of a multilevel analysis. A multilevel analysis is a data analysis that uses variables that are measured at different levels of the hierarchy. A hierarchy can have many levels, such as student level, class level, school level, and State or country level, where students are nested within classes, classes are nested within schools or school districts, and school districts can be nested within towns, States, or countries. As soon as one pays attention, hierarchies are present in all data. In large-scale prevention research, researchers usually have information about two or more levels involved, for instance, variables describing individuals (such as achievement, drug use, gender, and measures of socioeconomic status or home environment); variables describing schools (such as school environment, urban versus rural, and type of treatment administered); and perhaps variables describing districts, States, or countries. It is well known that the analysis of variables (i.e., measures at different levels of the hierarchy) on any of these levels separately can be misleading, as will be shown in this chapter. It is more satisfactory to construct a model and technique that simultaneously take information on all levels into account. This chapter introduces such a multilevel model for hierarchically nested data by evaluating the effect of a drug prevention program, Normative Education (NORM), wherein data are collected on students nested within schools. The model is a linear regression model. The difference between this model and the traditional linear regression model is that it takes the intraclass correlation into account and treats variables measured at different levels of the hierarchy in a more appropriate way.

Analysis of Variance↗
PubMed2006

Effect of aging and degeneration on disc volume and shape: A quantitative study in asymptomatic volunteers.

Debate continues on the effect of disc degeneration and aging on disc volume and shape. So far, no quantitative in vivo MRI data is available on the factors influencing disc volume and shape. The objective of this MRI study was to quantitatively investigate changes in disc height, volume, and shape as a result of aging and/or degeneration omitting pathologic (i.e., painful) disc alterations. Seventy asymptomatic volunteers (20-78 years) were investigated with sagittal T1- and T2-weighted MR-images encompassing the whole lumbar spine. Disc height was determined by the Dabbs method and the Farfan index. Disc volume was calculated by the Cavalieri method. For the disc shape the "disc convexity index" was calculated by the ratio of central disc height and mean anterior/posterior disc height. Disc height, disc volume, and the disc convexity index measurements were corrected for disc level and the individuals age, weight, height, and sex in a multilevel regression analysis. Multilevel regression analysis showed that disc volume was negatively influenced by disc degeneration (p < 0.001) and positively correlated with body height (p < 0.001) and age (p < 0.01). Mean disc height and the disc convexity index were negatively influenced by disc degeneration but not by gender, weight, and height. Disc height was positively correlated with age (p < 0.01). From the results of this study, it can be concluded that disc degeneration generally results in a decrease of disc height and volume as well as a less convex disc shape. In the absence of disc degeneration, however, age tends to result in an inverse relationship on disc height, volume, and shape.

Adult↗
PubMed2002

Multilevel survival analysis of amalgam restorations amongst RAF personnel.

OBJECTIVE: To introduce the concepts of multilevel survival analysis through an investigation into the longevity of amalgam restorations. BASIC RESEARCH DESIGN: The multilevel Cox proportional hazard model is illustrated using amalgam restoration data comprising three levels: repeated restorations at level-1, teeth at level-2, and subjects at level-3. The outcome was duration of amalgam restoration survival. Single-level and multilevel Cox methods are contrasted. PARTICIPANTS: The data were from a survey of amalgam restorations (reported elsewhere), involving 200 RAF personnel aged between 16 and 37 years at enlistment between 1947 and 1979, having served continuously for a minimum of 16 years prior to 1994. RESULTS: Differences existed between single-level and multilevel methods; the latter being the method of choice. Initial caries experience was a good predictor of longevity. Molar teeth fared worse than pre-molars and MOD & B, MOD & L, and MOD & BL restorations experienced considerably greater risk of failure than did MOD, MO, DO and MO/DO ext types, which in turn fared worse than occlusal restorations. Root-treated and pinned teeth also experienced an elevated risk of premature failure. There was a moderate but significant increase in restoration failure amongst subjects who were seen by more dentists throughout their service. CONCLUSIONS: The application of multilevel modelling to survival analysis provides an appropriate and powerful solution to the problem of lack of independence amongst dental restorations. It is beneficial that studies undertake a multilevel analysis in preference to ignoring hierarchy or omitting swathes of information in order to perform a single-level analysis.

Adolescent↗
PubMed2004

Effect of antenatal glucocorticoid therapy on arterial and venous blood flow velocity waveforms in severely growth-restricted fetuses.

OBJECTIVE: To study the effects of antenatal glucocorticoid (betamethasone) therapy on blood flow velocity waveform patterns in the umbilical artery (UA), middle cerebral artery (MCA) and ductus venosus (DV) in severely intrauterine growth-restricted (IUGR) fetuses. METHODS: Fifty-five severely IUGR fetuses at 24-34 weeks of gestation were included in the study. The effect of antenatal glucocorticoid administration on Doppler findings in the UA, MCA and DV was studied using two statistical approaches, namely paired sample analysis and multilevel analysis. RESULTS: There were no effects of betamethasone on the pulsatility index (PI) of the vessels studied. The only changes noticed during the 14 days of observation were a gradual decrease of PI in the MCA, an increase in the UA-PI/MCA-PI ratio and an increase in the DV-PI. These changes with time may be explained by a progressive and gradual deterioration of the fetal condition. CONCLUSION: Antenatal glucocorticoids (betamethasone) do not affect fetal Doppler waveform patterns of the UA, MCA and DV in severely IUGR fetuses.

Betamethasone↗
PubMed2005

Patterns of enhancing lesion evolution in multiple sclerosis are uniform within patients.

BACKGROUND: Histopathologic studies suggest that lesion development differs between patients with multiple sclerosis (MS), but that all lesions appear similar within patients. It is unclear whether the same applies to the evolution of lesions on T1-weighted MRI. OBJECTIVE: To evaluate lesion evolution on MRI, comparing variance within and between patients, as well as the relationship between MRI lesion development and clinical characteristics. METHODS: In 48 patients, signal intensity at baseline and at follow-up on T1-weighted MRI of 789 newly enhancing lesions was studied in relationship with clinical data. Patients were included on the basis of showing at least five enhancing lesions that could be followed on monthly scans for 6 months. Variance component analysis and multilevel analysis were used to compare within-patient and between-patient variability. RESULTS: Although various types of lesion evolution could be observed within a single patient, between-patient variance was considerably larger than within-patient variance for MRI parameters used to describe lesion evolution, indicating that lesion evolution is a patient-specific phenomenon. Evolution of lesions in patients with secondary progressive disease more frequently followed a hypointense-hypointense pattern than in patients with relapsing-remitting disease (odds ratio 4.2). Patients with a benign disease course had more persistent isointense lesions at follow-up, whereas patients with aggressive disease had more hypointense lesions. CONCLUSION: Lesion evolution on MRI appears to be a patient-specific phenomenon, although the outcome seems to vary according to the phase and severity of the disease.

Central Nervous System↗
PubMed2004

Computer-controlled, multilevel, morphometric analysis of blastomere size as biomarker of fragmentation and multinuclearity in human embryos.

BACKGROUND: Little is known about blastomere size at different cleavage stages and its correlation with embryo quality in human embryos. Using a computer system for multilevel embryo morphology analysis we have analysed blastomeres of human embryos and correlated mean blastomere size with embryonic fragmentation and multinuclearity. METHODS: A consecutive cohort of 232 human 2-, 3- and 4-cell embryos from patients referred for ICSI treatment were included. Sequences of digital images were taken by focusing at 5- micro m intervals through the embryo. Blastomere sizes and number of nuclear structures were evaluated based on these sequences. The degree of embryonic fragmentation was evaluated by normal morphological assessment prior to transfer and correlated to the blastomere sizes. RESULTS: As a result of normal cell cleavage, mean blastomere size decreased significantly from a volume of 0.28 x 10(6) microm(3) at the 2-cell stage to 0.15 x 10(6) microm(3) at the 4-cell stage (P < 0.001). Mean blastomere size decreased significantly (P < 0.001) with increasing degree of embryonic fragmentation, where highly fragmented embryos showed a 43-67% reduction in blastomere volume compared with embryos with no fragmentation. Multinucleated blastomeres were significantly larger than non-multinucleated blastomeres (P < 0.001). On average, multinucleated blastomeres were 51.5, 67.8 and 73.1% larger than their non-multinucleated sibling blastomeres at the 2-, 3- and 4-cell stage, respectively. Furthermore, the average volume of non-multinucleated blastomeres originating from multinucleated embryos was significantly smaller than the average volume of the blastomeres from mononucleated embryos (P < 0.001). CONCLUSIONS: The results of this study show that the average blastomere size is significantly affected by degree of fragmentation and multinuclearity, and that computer-assisted, multilevel analysis of blastomere size may function as a biomarker for embryo quality.

Adult↗