Vassilis G. S. Vasdekis

Fruit and vegetable availability among ten European countries : how does it compare with the five-a-day' recommendation?

Recasting the role of fruit and vegetables (FV furthermore, interventions that would specifically focus on vegetables are probably needed.

The Effect of Diode Laser (980 nm) Treatment on Aggressive Periodontitis: Evaluation of Microbial and Clinical Parameters

OBJECTIVE The aim was to compare the effect of scaling and root planing (SRP) alone, diode laser treatment (LAS) alone, and SRP combined with LAS (SRP + LAS) on clinical and microbial parameters in patients with aggressive periodontitis. MATERIALS AND METHODS Thirty patients with aggressive periodontitis were assessed for plaque, bleeding on probing (BOP), probing pocket depth (PPD), and clinical attachment level (CAL). Four plaque samples were randomly obtained, one from each quadrant that was randomly assigned to SRP alone, SRP + LAS, LAS alone, and control (CRL). A 980-nm diode laser was used in continuous mode at 2 W power. Plaque samples were collected 2 wk, 12 wk, and 6 mo post-treatment. The levels of Porphyromonas gingivalis, Tannerella forsythia, Aggregatibacter actinomycetemcomitans, Treponema denticola, and total bacterial load (TBL) were evaluated using ssrRNA probes. RESULTS Bacterial counts were decreased with all three treatment modalities and they did not reach baseline levels at 6 mo post-treatment. The SRP + LAS group showed statistically significantly lower TBL and bacterial levels of P. gingivalis and T. denticola at 6 mo post-treatment compared to SRP or LAS treatments alone. At the end of the observation period significant differences were observed for PPD and CAL between the SRP + LAS group and both the SRP alone and LAS alone groups. No differences were detected for percentage of plaque and percentage of BOP between any of the treatment groups at 6 mo post-treatment. CONCLUSIONS Within the limits of this study, diode laser-assisted treatment with SRP showed a superior effect over SRP or LAS alone for certain microbial and clinical parameters in patients with aggressive periodontitis over the 6-mo monitoring period.

Latent variable models for multivariate longitudinal ordinal responses

The paper proposes a full information maximum likelihood estimation method for modelling multivariate longitudinal ordinal variables. Two latent variable models are proposed that account for dependencies among items within time and between time. One model fits item-specific random effects which account for the between time points correlations and the second model uses a common factor. The relationships between the time-dependent latent variables are modelled with a non-stationary autoregressive model. The proposed models are fitted to a real data set.

A Composite Likelihood Inference in Latent Variable Models for Ordinal Longitudinal Responses.

The paper proposes a composite likelihood estimation approach that uses bivariate instead of multivariate marginal probabilities for ordinal longitudinal responses using a latent variable model. The model considers time-dependent latent variables and item-specific random effects to be accountable for the interdependencies of the multivariate ordinal items. Time-dependent latent variables are linked with an autoregressive model. Simulation results have shown composite likelihood estimators to have a small amount of bias and mean square error and as such they are feasible alternatives to full maximum likelihood. Model selection criteria developed for composite likelihood estimation are used in the applications. Furthermore, lower-order residuals are used as measures-of-fit for the selected models.

Cytokines in gingival crevicular fluid of adolescents and young adults.

BACKGROUND/AIM The purpose of this study was to compare the levels of the cytokines interleukin-1beta (IL-1beta), IL-4, and IL-8 in the gingival crevicular fluid (GCF) of adolescents and young adults. METHODS Twenty-five adolescents aged between 14 and 16 years (Group A) and 20 periodontally healthy young adults aged between 25 and 35 years (Group B) were selected from two private dental clinics limited to pedodontics and periodontics respectively in Piraeus Greece. All subjects were systemically healthy. Clinical examination included probing pocket depth (PPD), presence or absence of plaque, and bleeding on probing (BOP). GCF was collected from four sites per subject. IL-1beta, IL-4, and IL-8, measured as total amounts (pg/30 s), were evaluated in 180 samples using a commercially available sandwich enzyme-linked immunosorbent assay. RESULTS IL-1beta mean levels of Groups A and B were adjusted for BOP and PPD. Differences of IL-1beta mean levels between the two age groups were statistically significant (F = 50.245, P < 0.001) in favour of Group A. Adolescents showed statistically significantly lower mean levels of IL-4 than young adults in the presence of BOP (F = 10.690, P = 0.001). There was no statistically significant difference between adolescents and adults for the means of IL-8 adjusted for BOP and plaque presence (F = 2.032, P = 0.161). CONCLUSIONS Within the limits of this study the differences reported in mean levels of IL-1beta and IL-4 may be attributed to the different age status.

The impact of comorbidity and other clinical and sociodemographic factors on health-related quality of life in Greek patients with Parkinson's disease

Objectives: This study was designed to evaluate the impact of other common self-reported comorbid disorders (hypertension, dyslipidemia, ischemic heart disease, diabetes mellitus, minor stroke, arthritis, low back pain or osteoporosis and depression) on health-related Quality of Life (HRQoL) of Parkinsons disease (PD) patients and to explore the association of their HRQoL with various sociodemographic and clinical factors. Methods: Data about age, gender, education, occupation, income, marital and residential status, social relations, disease duration, functional status, treatment and concomitant diseases were collected of 139 Greek patients (68 men and 71 women) with PD. Patients were consecutively recruited from the outpatient clinic of the first Neurology Department of Athens National University at Aeginition Hospital. Disease severity was assessed using the unified Parkinsons disease rating scale including Hoehn and Yahr and Schwab and England (S&E) scales. HRQoL was measured by the specific Parkinsons disease questionnaire (PDQ-39). A multivariate multiple regression model with normal errors was used for the statistical analysis. Results: The main determinants of HRQoL were low degree of independence measured by the S&E scale (F = 35.942, p < 0.001), social isolation (F = 20.508, p < 0.001), disease duration (F = 14.983, p < 0.001), sleep (F = 6.507, p = 0.013) and gastrointestinal disturbances (F = 4.643, p = 0.035) and the presence of depression (F = 6.022, p = 0.017). Conclusion: Among the other chronic comorbidities only depression was associated with a poor HRQoL in PD patients. Functional dependence and social isolation contributed most to worse HRQoL. Our findings suggest that adequate social support and management of depression, sleep and gastrointestinal disturbances could reduce the distress and improve HRQoL in patients with PD.

Detection of gingival crevicular fluid cytokines in children and adolescents with and without fixed orthodontic appliances

Objective. To study the expression of IL-1β, IL-4, and IL-8 in the gingival crevicular fluid (GCF) of children, adolescents, and young adults with and without fixed orthodontic appliances. Material and methods. Eighty systemically healthy children and adolescents participated in the study: 56 aged between 8 and 16 years without any orthodontic appliance (Group A) and 24 aged between 10 and 20 years having worn fixed orthodontic appliances for at least 12 months (Group B). Clinical examination included presence or absence of plaque, probing depth, bleeding on probing, and gingival overgrowth. GCF was collected by means of Durapore strips from four randomly selected sites per subject. The contents of interleukin-1 beta (IL-1β), interleukin-4 (IL-4), and interleukin-8 (IL-8) were detected by ELISA, measured as total amounts (pg/30s) and expressed in log scale. Results. Statistically significant differences were noted for the mean log IL-1β, IL-4, and IL-8 between the two groups: Group B showed significantly higher mean levels in log IL-1β and log IL-8 compared to Group A. Mean levels of log IL-4 were lower in Group B, although they did not reach statistical significance. Furthermore, mean levels of log IL-1β and log IL-8 were associated with bleeding sites (p<0.001) and gingival overgrowth, while mean level of log IL-4 was associated with non-bleeding sites and no gingival overgrowth (p<0.001). Conclusion. Our findings suggest that fixed orthodontic appliances result in an increase in the expression of IL-1β and IL-8. This may reflect biologic activity in the periodontium during orthodontic tooth movement.

Weighted pairwise likelihood estimation for a general class of random effects models

Models with random effects/latent variables are widely used for capturing unobserved heterogeneity in multilevel/hierarchical data and account for associations in multivariate data. The estimation of those models becomes cumbersome as the number of latent variables increases due to high-dimensional integrations involved. Composite likelihood is a pseudo-likelihood that combines lower-order marginal or conditional densities such as univariate and/or bivariate; it has been proposed in the literature as an alternative to full maximum likelihood estimation. We propose a weighted pairwise likelihood estimator based on estimates obtained from separate maximizations of marginal pairwise likelihoods. The derived weights minimize the total variance of the estimated parameters. The proposed weighted estimator is found to be more efficient than the one that assumes all weights to be equal. The methodology is applied to a multivariate growth model for binary outcomes in the analysis of four indicators of schistosomiasis before and after drug administration.

On a class of change-point models in covariance structures for growth curves and repeated measurements

Models for growth curves or repeated measurements usually consist of a polynomial trend for the mean response plus error terms. We consider a general covariance structure for the errors which includes a class of autoregressive models with ‘change- points’. Such models depend on a small number of parameters, but are of sufficient generality to be useful in practical applications, especially when enviromental or physiological changes on different times lead to nonstationary error processes. Failure to take this into account leads to inefficient estimatiors of the mean trend. The estimation procedure includes both ML and REML methods. The effect of using these methods on the efficiency of the estimation is also studied by theoretical and Monte Carlo methods.

A cross-cultural study on early vocal imitative phenomena in different relationships

The present study constitutes an effort to extend our understanding of the universality of vocal imitative exchanges. It aimed to investigate early vocal imitative phenomena in different countries and relationships. In particular, several basic aspects of vocal imitation, such as frequency across the age range of the study, structure, the linguistic nature, the direction and the temporal patterns of it, were micro-analysed, and compared in spontaneous dyadic interactions of fathers and mothers with their infant boys and girls in Scotland and Greece. Fifteen infants (eight boys and seven girls) born in Crete, Greece, and 15 infants (eight boys and seven girls) born in Edinburgh, Scotland, were observed in dyadic interactions with their mothers and fathers at home from the second to the sixth month of their life at 15-day intervals. It was found that: • most aspects of vocal imitation differ between Greece and Scotland; • the frequency of vocal imitation across the age range of the study, the structure (turn-takings, co-actions, multiple series), the linguistic nature (vowels, consonants, vowel-consonant combinations), and the durations of imitative interactions, but not the imitative direction (who imitates whom) were found to differ between girls and boys; • maternal and paternal vocal imitative exchanges were found to be different, rather than similar. It is suggested that vocal imitation constitutes a flexible mode of intersubjective communication that reflects differences in the styles and patterns of interaction of certain relationships and cultures.