Imputation of Repeatedly-observed Multinomial Variables in Longitudinal Surveys

It is now a standard practice to replace missing data in longitudinal surveys with imputed values, but there is still much uncertainty about the best approach to adopt. Using data from a real survey, we compared different strategies combining multiple imputation and the chained equations method, the two main objectives being 1) to explore the impact of the explanatory variables in the chained regression equations, 2) to study the effect of imputation on causality between successive waves of the survey. Results were very stable from one simulation to another, and no systematic bias did appear. The critical points of the method lied in the proper choice of covariates and in the respect of the temporal relation between variables

Markovian-based clustering of internet addiction trajectories

A hidden Markov clustering procedure is applied to a sample of n=185 longitudinal Internet Addiction Test trajectories collected in Switzerland. The best solution has 4 groups. This solution is related to the level of emotional wellbeing of the subjects, but no relation is observed with age, gender and BMI

Tobacco and cannabis use trajectories from adolescence to young adulthood

The main objective of this longitudinal research is to answer the following question: What is the relationship between tobacco and cannabis use trajectories from adolescence to young adulthood? And more specifically we are interested in: A. If the use of one of the substances (tobacco or cannabis) decreases overtime, does the use of the other one increase to compensate? Are other substances (such as alcohol, for example) also used to compensate in these cases? B. Does the probability to become a tobacco smoker increase when cannabis use is heavier or has lasted longer? C. What are the risk and protective factors that can predict that the use of tobacco and/or cannabis will increase or decrease overtime

Improvement in 6-Minute Walking Distance after Supervised Exercise Training Is Related to Changes in Quality of Life in Patients with Lower Extremity Peripheral Artery Disease.

This study aimed to investigate the relationship between supervised exercise training (SET)-induced changes in treadmill performance and 6 min walking distance, and changes in general (physical and mental) self-perceived health-related quality of life (HRQoL) in symptomatic patients with lower extremity peripheral artery disease (PAD). This is an observational study investigating Fontaine stage II PAD patients participating in 3-month SET. Before and following SET, treadmill performance (pain-free (PFWD) and maximal (MWD)), and 6 min walking distance (6MWD) were assessed. Self-perceived HRQoL was assessed with the Medical Outcomes Study Short-Form 36 (SF-36). Ankle- and toe-brachial indexes were also measured. One-hundred forty-seven patients with PAD were included (64.9 ± 9.6 y, 70% men). After SET, PFWD (+102%, p ≤ 0.001), MWD (+87%, p ≤ 0.001), and 6MWD (+14%, p ≤ 0.001) significantly increased. All eight SF-36 subscale scores significantly improved following SET (p ≤ 0.04). SET significantly improved physical and mental component summaries of the SF-36 (p ≤ 0.001). Larger increases in 6MWD were associated with greater improvements in physical (β = 0.19; p = 0.02) and mental (β = 0.24; p = 0.005) component summaries of the SF-36. No significant relationship was observed between changes in treadmill performance and changes in physical and mental component summaries of the SF-36. These results show that improvements in 6MWD following SET are related to improvements in general self-perceived HRQoL in patients with symptomatic lower extremity PAD. On the contrary, changes in treadmill performance were not related to improvements in HRQoL. These results suggest that the 6 min walking test is an essential outcome measure to assess overall patient functional status following interventions in patients with PAD

Rapport final de l'étude longitudinale [email protected]

En Suisse, à l'instar de ce que l'on constate dans d'autres pays d'Europe, le pourcentage des 14 à 19 ans utilisant régulièrement Internet a augmenté de manière spectaculaire entre 1997 (4%) et 2013 (97%) selon les chiffres de l'Office fédéral de la statistique. De par sa commodité d'accès en tout lieu et en tout temps, les jeunes ont su s'approprier les usages et les activités variées d'Internet et ils y passent une partie importante de leur temps pour se divertir, s'informer ou étudier. A ce jour, rares sont encore les études longitudinales qui permettent d'examiner l'évolution de leurs usages d'internet ou les implications à moyen et long terme de ce média sur la santé des adolescents. Pratiques en constante mutation, il est impératif de suivre l'évolution d'Internet des adolescents, car ces derniers constituent un groupe particulièrement vulnérable aux multiples attractions du web. Objectifs : Les objectifs principaux de cette étude étaient de: 1. Quantifier l'évolution sur les deux ans de l'utilisation d'Internet chez les adolescents vaudois en faisant la distinction entre le temps dédié à l'école/au travail et le temps dédié aux loisirs ; 2. Décrire les activités en ligne qui occupent les adolescents et investiguer si ces activités changent au fil du temps

Living With a Chronic Condition and Risk Behaviors

Purpose: To assess whether living with a chronic condition (CC) is associated with risk behaviors among youths. Methods: Data were drawn from the baseline wave (2014-15; N¼5179) of the GenerationFRee survey, a longitudinal study among post-mandatory youths aged 15-24 years in Fribourg, Switzerland. Students were divided into three groups depending on whether they reported having a CC or not: healthy controls (no CC: N¼4529; 46.2% females), CC without limitation (CCWL: N¼536; 52.6% females) and CC limiting daily activities (CCLDA: N¼114; 58.9% females). At the bivariate level groups were compared on sociodemographic data and six risk behaviors (current smoking; current (at least once in the past 30 days) alcohol misuse, cannabis use and use of other illegal drugs; violent behavior and antisocial behavior at least once in the past 12 months). In a second step, a multinomial logistic regression was conducted including all variables significant at the .05 level. Results are given as Relative Risk Ratios (RRR) with 95% confidence intervals

Quantum Gravitational Bremsstrahlung, Massless versus Massive Gravity

The massive spin-2 quantum gauge theory previously developed is applied to calculate gravitational bremsstrahlung. It is shown that this theory is unique and free from defects. In particular, there is no strong coupling if the graviton mass becomes small. The cross sections go over smoothly into the ones of the massless theory in the limit of vanishing graviton mass. The massless cross sections are calculated for the full tensor theory.Comment: 13 pages, 1 figur

Siblings of youths with chronic conditions: a school-based survey.

The purpose of this study was to explore the differences between youths with a sibling affected by a chronic condition or a disability (SCCD) and their peers with healthy siblings. Using data from the second wave of GenerationFRee study, we compared adolescents from each gender with healthy siblings to adolescents with SCDD on demographical, familial, internalizing and externalizing behavior variables. Subsequently we repeated the analysis excluding from each group adolescents who suffered from a chronic condition or disability themselves. At the bivariate and multivariate level, among those with SCDD, healthy females reported more somatic symptoms, healthy males more violent behaviors, and both genders lived more often in non-intact families. When considering both healthy and unhealthy adolescents, at bivariate analysis female adolescents with SCDD were more likely to have a poorer relationship to their mother, to be unhealthy, to smoke, to be at risk for disordered eating and to report somatic symptoms. At multivariate level, only the association with SCDD and smoking remained. Male adolescents with SCDD, at both bivariate and multivariate analyses, were more likely to be unhealthy and to live in larger and non-intact families. Healthy adolescents with an SCDD are more at risk of somatic symptoms and violent behaviors than their peers with healthy siblings. Health professionals in contact with adolescents should always consider them with a systemic approach. Parents should be informed about the potential effect on the siblings of a CDD child, but also reassured, as adolescents with SCDD are not different from their peers with healthy siblings

V(D)J recombination frequency is affected by the sequence interposed between a pair of recombination signals: sequence comparison reveals a putative recombinational enhancer element

The immunoglobulin heavy chain intron enhancer (Eμ) not only stimulates transcription but also V(D)J recombination of chromosomally integrated recombination substrates. We aimed at reproducing this effect in recombination competent cells by transient transfection of extrachromosomal substrates. These we prepared by interposing between the recombination signal sequences (RSS) of the plasmid pBlueRec various fragments, including Eμ, possibly affecting V(D)J recombination. Our work shows that sequences inserted between RSS 23 and RSS 12, with distances from their proximal ends of 26 and 284 bp respectively, can markedly affect the frequency of V(D)J recombination. We report that the entire Eμ, the Eμ core as well as its flanking 5′ and 3′ matrix associated regions (5′ and 3′ MARs) upregulate V(D)J recombination while the downstream section of the 3′ MAR of Eμ does not. Also, prokaryotic sequences markedly suppress V(D)J recombination. This confirms previous results obtained with chromosomally integrated substrates, except for the finding that the full length 3′ MAR of Eμ stimulates V(D)J recombination in an episomal but not in a chromosomal context. The fact that other MARs do not share this activity suggests that the effect is not mediated through attachment of the recombination substrate to a nuclear matrix-associated recombination complex but through cis-activation. The presence of a 26 bp A-T-rich sequence motif in the 5′ and 3′ MARs of Eµ and in all of the other upregulating fragments investigated, leads us to propose that the motif represents a novel recombinational enhancer element distinct from those constituting the Eµ cor

Disordered Eating: The Young Male Side.

Disordered eating (DE) is known to predominate among girls, and historically studies have focused primarily on them. This cross-sectional study aimed to investigate the characteristics of adolescent and young adult males at risk of DE. Participants (N = 2269; 15-24 years) in a study assessing their lifestyle were divided into two groups based on the SCOFF five-question screening tool: a SCOFF[+] group for participants at risk of disordered eating, and a SCOFF[-] group for everyone else. SCOFF[+] participants were more likely to be overweight and obese; have a lower socio-economic status and non-Swiss parents; experience weight issues; and report a chronic condition, poorer emotional well-being and a less positive attitude towards life. With 10% of males at risk of DE, clinicians should be aware of their specific characteristics, which should be considered red flags. DE is no longer a female-specific issue