scholarly journals Multilevel Linear Models, Gibbs Samplers and Multigrid Decompositions

2020 ◽  
Author(s):  
Giacomo Zanella ◽  
Gareth Roberts
Keyword(s):  
Linear Models ◽  
Gibbs Samplers ◽  
Multilevel Linear Models

scholarly journals Clinical Factors Influencing the Efficacy of Systemic Moxifloxacin in the Therapy of Patients With Generalized Aggressive Periodontitis: A Multilevel Analysis From a Clinical Trial

2015 ◽  
Vol 8 (3) ◽  
pp. 80 ◽  
Author(s):  
Carlos M. Ardila ◽  
Isabel C. Guzmán
Keyword(s):  
Clinical Trial ◽  
Multilevel Analysis ◽  
Linear Models ◽  
Clinical Results ◽  
Aggressive Periodontitis ◽  
Continuous Variables ◽  
Clinical Factors ◽  
Probing Depth ◽  
Clinical Benefits ◽  
Multilevel Linear Models

<p><strong>BACKGROUND:</strong> It has been reported that clinical results of mechanical periodontal treatment could differ between subjects and among different sites of the tooth in the patient. The objective of this multilevel analysis is to investigate clinical factors at subject and sites of the tooth that influence variations in clinical attachment (CAL) increase and probing depth (PD) diminution of adjunctive moxifloxacin (MOX) at six months post-treatment in generalized aggressive periodontitis.</p> <p><strong>METHODS:</strong> This clinical trial included 40 patients randomly distributed to two therapy protocols: scaling and root planing alone or combined with MOX. Multilevel linear models for continuous variables were formulated to evaluate the clinical impact of the hierarchical configuration of periodontal data.</p> <p><strong>RESULTS:</strong> Six months following therapy, the divergences between both protocols were statistically significant in PD diminution and CAL increase, favouring the MOX therapy (p&lt;0.001). Besides, the multilevel analysis revealed that adjunctive MOX at the subject level, non-molar and the interaction non-molar x MOX at the tooth level, interproximal sites and the interaction interproximal sites x MOX at the site level, were statistically significant factors in determining CAL increase and PD diminution.</p> <p><strong>CONCLUSIONS:</strong> The main cause of variability in CAL gain and PD reduction following adjunctive MOX was attributable to the tooth level. Adjunctive MOX and their interactions with non-molar and interproximal sites showed higher clinical benefits at the tooth and site levels which could be essential for PD reduction and CAL gain in generalized aggressive periodontitis subjects.</p>

scholarly journals Association between environmental stimulation and apathy in nursing home residents with dementia

2019 ◽  
Vol 31 (08) ◽  
pp. 1109-1120 ◽  
Author(s):  
Ying-Ling Jao ◽  
Wen Liu ◽  
Kristine Williams ◽  
Habib Chaudhury ◽  
Jyotsana Parajuli
Keyword(s):  
Nursing Home ◽  
Linear Models ◽  
Rating Scale ◽  
Nursing Home Residents ◽  
Repeated Measure ◽  
Future Research ◽  
Video Observations ◽  
Environmental Stimulation ◽  
Multilevel Linear Models ◽  
Environmental Feedback

ABSTRACTObjectives:Prior research and theories established the link between care environments and apathy. Yet, empirical evidence on how environmental stimulation impacts apathy is lacking. This study examined the association between environmental stimulation and apathy in nursing home residents with dementia.Design:This repeated-measure study analyzed 104 video observations of staff caregiver–resident interactions.Setting:12 nursing homes.Participants:63 unique staff caregiver–resident dyads that involved 42 caregivers and 44 residents with moderate to severe dementia.Measurements:Second-by-second behavioral coding using Noldus Observer software was conducted to assess apathy and environmental stimulation, using the Person-Environment Apathy Rating scale. The environment subscale includes six items: stimulation clarity, stimulation strength, stimulation specificity, interaction involvement, physical accessibility, and environmental feedback. The apathy subscale includes six items: facial expression, eye contact, physical engagement, purposeful activity, verbal tone, and verbal expression. Multilevel linear models were used for analysis.Results:Results showed that apathy was not associated with the overall quality of environmental stimulation but was significantly associated with stimulation specificity (coefficient = −2.23,p= 0.049). However, the association was not significant after controlling for resident characteristics (p= 0.082). In addition, higher levels of environmental feedback were associated with lower apathy levels (coefficient = −2.14,p= 0.001). The association remained significant after controlling for resident characteristics (coefficient = −1.65,p= 0.014).Conclusion:Findings reveal that when environmental stimulation is individually tailored and prompts engagement, residents are less apathetic. This study highlights the effect of environmental stimulation on apathy. Future research should explore interventions that modify environmental stimulation to reduce apathy and improve dementia care.

scholarly journals Knowledge of Dental Academics about the COVID-19 Pandemic: A Multi-Country Online Survey

2020 ◽  
Author(s):  
Nour Ammar ◽  
Nourhan M. Aly ◽  
Morenike O. Folayan ◽  
Simin Z. Mohebbi ◽  
Sameh Attia ◽  
...  
Keyword(s):  
Living Arrangements ◽  
Online Survey ◽  
Linear Models ◽  
Dental Treatment ◽  
Diagnostic Methods ◽  
Cross Sectional ◽  
Country Level ◽  
Global Pandemic ◽  
The Mean ◽  
Multilevel Linear Models

Abstract Background: COVID-19 is a global pandemic affecting all aspects of life in all countries. We assessed COVID-19 knowledge and associated factors among dental academics in various countries. Method: We invited dental academics to participate in a cross-sectional, multi-country, online survey from March to April 2020. The survey assessed knowledge of COVID-19 regarding the mode of transmission, symptoms, diagnosis, treatment, protection, and dental treatment precautions as well as participants’ background variables. The analysis was based on multilevel linear models to assess the association between knowledge and factors at individual levels (personal and professional) and country-level (number of COVID-19 cases/ million population), accounting for random variation among countries. Results: Two thousand forty-five academics from 26 countries participated in the survey (response rate= 14.3%, with 54.7% female and 67% younger than 46 years of age). The mean (SD) knowledge percent score was 73.2% (11.2), and the knowledge of symptoms score was significantly lower than the diagnostic methods score (53.1% and 85.4%). Knowledge was significantly higher among those living with partner/spouse than those living alone (regression coefficient (B)= 0.48); those with PhD than those with BDS (B= 0.48), those seeing 21 to 30 patients daily than those seeing no patients (B= 0.65) and those from countries with a higher number of COVID-19 cases/million population (B= 0.0007). Conclusions: Dental academics had poorer knowledge of COVID-19 symptoms than diagnostic methods. Living arrangements, academic degrees, patient load, and magnitude of epidemic in the country were associated with COVD-19 knowledge among dental academics. COVID-19 training can be designed using these factors to target academics with the greatest need.

Estimating Multilevel Linear Models as Structural Equation Models

2003 ◽  
Vol 28 (2) ◽  
pp. 135-167 ◽  
Author(s):  
Daniel J. Bauer
Keyword(s):  
Structural Equation ◽  
Linear Models ◽  
Structural Equation Models ◽  
Broad Class ◽  
Causal Chain ◽  
Latent Factors ◽  
Measurement Models ◽  
Multiple Indicator ◽  
Current Article ◽  
Multilevel Linear Models

Multilevel linear models (MLMs) provide a powerful framework for analyzing data collected at nested or non-nested levels, such as students within classrooms. The current article draws on recent analytical and software advances to demonstrate that a broad class of MLMs may be estimated as structural equation models (SEMs). Moreover, within the SEM approach it is possible to include measurement models for predictors or outcomes, and to estimate the mediational pathways among predictors explicitly, tasks which are currently difficult with the conventional approach to multilevel modeling. The equivalency of the SEM approach with conventional methods for estimating MLMs is illustrated using empirical examples, including an example involving both multiple indicator latent factors for the outcomes and a causal chain for the predictors. The limitations of this approach for estimating MLMs are discussed and alternative approaches are considered.

scholarly journals Urinary Sodium Excretion and Blood Pressure Relationship across Methods of Evaluating the Completeness of 24-h Urine Collections

Nutrients ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2772
Author(s):  
Abu Mohd Naser ◽  
Feng J. He ◽  
Mahbubur Rahman ◽  
K. M. Venkat Narayan ◽  
Norm R. C. Campbell
Keyword(s):  
Blood Pressure ◽  
Positive Relationship ◽  
Linear Models ◽  
Sodium Intake ◽  
Urinary Sodium Excretion ◽  
Urinary Sodium ◽  
Urine Sodium ◽  
Urine Creatinine ◽  
The Difference ◽  
Multilevel Linear Models

We compared the sodium intake and systolic blood pressure (SBP) relationship from complete 24-h urine samples determined by several methods: self-reported no-missed urine, creatinine index ≥0.7, measured 24-h urine creatinine (mCER) within 25% and 15% of Kawasaki predicted urine creatinine, and sex-specific mCER ranges (mCER 15–25 mg/kg/24-h for men; 10–20 mg/kg/24-h for women). We pooled 10,031 BP and 24-h urine sodium data from 2143 participants. We implemented multilevel linear models to illustrate the shape of the sodium–BP relationship using the restricted cubic spline (RCS) plots, and to assess the difference in mean SBP for a 100 mmol increase in 24-h urine sodium. The RCS plot illustrated an initial steep positive sodium–SBP relationship for all methods, followed by a less steep positive relationship for self-reported no-missed urine, creatinine index ≥0.7, and sex-specific mCER ranges; and a plateaued relationship for the two Kawasaki methods. Each 100 mmol/24-h increase in urinary sodium was associated with 0.64 (95% CI: 0.34, 0.94) mmHg higher SBP for self-reported no-missed urine, 0.68 (95% CI: 0.27, 1.08) mmHg higher SBP for creatinine index ≥0.7, 0.87 (95% CI: 0.07, 1.67) mmHg higher SBP for mCER within 25% Kawasaki predicted urine creatinine, 0.98 (95% CI: −0.07, 2.02) mmHg change in SBP for mCER within 15% Kawasaki predicted urine creatinine, and 1.96 (95% CI: 0.93, 2.99) mmHg higher SBP for sex-specific mCER ranges. Studies examining 24-h urine sodium in relation to health outcomes will have different results based on how urine collections are deemed as complete.

scholarly journals Associations between Sociodemographic, Dietary, and Substance Use Factors with Self-Reported 24-Hour Movement Behaviors in a Sample of Brazilian Adolescents

2021 ◽  
Vol 18 (5) ◽  
pp. 2527
Author(s):  
Bruno Gonçalves Galdino da Costa ◽  
Jean-Philippe Chaput ◽  
Marcus Vinicius Veber Lopes ◽  
Luis Eduardo Argenta Malheiros ◽  
Kelly Samara da Silva
Keyword(s):  
Physical Activity ◽  
Substance Use ◽  
Sleep Duration ◽  
Leisure Time ◽  
Linear Models ◽  
Dietary Behaviors ◽  
Processed Food ◽  
Factors Associated ◽  
Use Factors ◽  
Multilevel Linear Models

We aimed to identify sociodemographic, dietary, and substance use factors associated with self-reported sleep duration, physical activity (PA), and sedentary behavior (SB) indicators in a sample of Brazilian adolescents. Adolescents (n = 731, 51% female, mean age: 16.4 years) answered a questionnaire. The volume of total PA, sports, non-sports, total SB, leisure-time SB, involuntary SB, sleep duration, dietary behaviors, sociodemographic, and substance use indicators were self-reported. Multilevel linear models were fitted. Females engaged in less total PA, sports, total SB, and leisure-time SB, but in more involuntary SB than males. Age was positively associated with non-sports and involuntary SB. Socioeconomic status was positively associated with total PA. Adolescents who lived with the mother only practiced more sports compared to those living with two parents. Unprocessed food was positively associated with total PA and sports. Processed food was inversely associated with total PA and non-sports, and positively associated with total SB and leisure-time SB. Alcohol use was positively associated with total PA, and tobacco smoking was negatively associated with total PA. No associations were observed for sleep duration. In conclusion, sociodemographic, dietary, and substance use factors are associated with the 24 h movement behaviors among Brazilian adolescents, and some associations are type specific.

scholarly journals Differences of Type I error rates for ANOVA and Multilevel-Linear-Models using SAS and SPSS for repeated measures designs

2019 ◽  
Vol 3 ◽  
Author(s):  
Nicolas Haverkamp ◽  
André Beauducel
Keyword(s):  
Repeated Measures ◽  
Linear Models ◽  
Type I Error ◽  
Error Rates ◽  
Small Sample ◽  
Small Samples ◽  
Type I ◽  
Sample Sizes ◽  
Type I Error Rates ◽  
Multilevel Linear Models

  To derive recommendations on how to analyze longitudinal data, we examined Type I error rates of Multilevel Linear Models (MLM) and repeated measures Analysis of Variance (rANOVA) using SAS and SPSS. We performed a simulation with the following specifications: To explore the effects of high numbers of measurement occasions and small sample sizes on Type I error, measurement occasions of m = 9 and 12 were investigated as well as sample sizes of n = 15, 20, 25 and 30. Effects of non-sphericity in the population on Type I error were also inspected: 5,000 random samples were drawn from two populations containing neither a within-subject nor a between-group effect. They were analyzed including the most common options to correct rANOVA and MLM-results: The Huynh-Feldt-correction for rANOVA (rANOVA-HF) and the Kenward-Roger-correction for MLM (MLM-KR), which could help to correct progressive bias of MLM with an unstructured covariance matrix (MLM-UN). Moreover, uncorrected rANOVA and MLM assuming a compound symmetry covariance structure (MLM-CS) were also taken into account. The results showed a progressive bias for MLM-UN for small samples which was stronger in SPSS than in SAS. Moreover, an appropriate bias correction for Type I error via rANOVA-HF and an insufficient correction by MLM-UN-KR for n < 30 were found. These findings suggest MLM-CS or rANOVA if sphericity holds and a correction of a violation via rANOVA-HF. If an analysis requires MLM, SPSS yields more accurate Type I error rates for MLM-CS and SAS yields more accurate Type I error rates for MLM-UN.

scholarly journals HIERARCHICAL STRUCTURE OF DENTAL DATA IN THE RANDOM EFFECTS INCLUSION APPROACH

2018 ◽  
Vol 36 (3) ◽  
pp. 700
Author(s):  
Tiago Peres da Silva SUGUIURA ◽  
Omar Cléo Neves PEREIRA ◽  
Waenya Fernandez de CARVALHO ◽  
Isolde Terezinha Santos PREVIDELLI
Keyword(s):  
Hierarchical Structure ◽  
Linear Models ◽  
Intraclass Correlation ◽  
Hierarchical Structures ◽  
Aluminium Chloride ◽  
Data Sets ◽  
Complex Structures ◽  
The Hierarchical Structure ◽  
Level Model ◽  
Multilevel Linear Models

Data sets with complex structures is increasingly common in dental research. As consequences, statistical  methods to analyze and interpret these data must be efficient and robust. Hierarchical structures is one of  the most common kind of complex structures, and a proper approach is required. The multilevel modeling used to study hierarchical structures is a powerful tool which allows the collected data to be  analyzes in several levels. This study has as objective to make a literature review on multilevel linear models and to illustrate a three level model through a matrix procedure, without the use of specific software to estimate the parameters. With this model, we analyzed the vertical gingival retraction when using the substances: Naphazoline Chloridrate, Aluminium Chloride and without any substance. The intraclass correlation coefficient on dental level within patients showed that the hierarchical structure was important to accommodate the dependence within clusters.

Sign in / Sign up

Export Citation Format

Share Document