124 research outputs found

    Joint modelling of bivariate longitudinal data : Application to the recovery of sexual function and urinary continence

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    (E0871) The following methodological issues occur in the context of the longitudinal study of sexual dysfunction and urinary incontinence after radical prostatectomy: (i) high dropout rate due to the extremely sensitive nature of the investigated outcomes; (ii) correlation between the two outcomes; (iii) non-linearity of the recovery trajectories. To address all these issues, we propose the use of a joint modelling approach, including a bivariate linear mixed model with splines for the two outcomes and a proportional hazards model for the time to dropout. We applied the model to data from consecutive patients underwent robotic-assisted radical prostatectomy at European institute of oncology from May 2015 to July 2016. Preand post-surgical sexual and urinary functional conditions were evaluated using the expanded prostate cancer index composite questionnaire. Six hundred forty three patients were included in the analysis. At one year after surgery, only 55% of patients returned the questionnaire. Parameters estimation was based on the maximisation of the likelihood function achieved through the implementation of an EM algorithm. A Gauss Hermite approximation was also used for some of the integrals involved. To assess the effect of nonrandom dropout mechanisms on the parameter estimates, we calculated the index of local sensitivity to non-ignorability

    The influence of socioeconomic environment on the effectiveness of alcohol prevention among European students: a cluster randomized controlled trial

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    <p>Abstract</p> <p>Background</p> <p>Although social environments may influence alcohol-related behaviours in youth, the relationship between neighbourhood socioeconomic context and effectiveness of school-based prevention against underage drinking has been insufficiently investigated. We study whether the social environment affects the impact of a new school-based prevention programme on alcohol use among European students.</p> <p>Methods</p> <p>During the school year 2004-2005, 7079 students 12-14 years of age from 143 schools in nine European centres participated in this cluster randomised controlled trial. Schools were randomly assigned to either control or a 12-session standardised curriculum based on the comprehensive social influence model. Randomisation was blocked within socioeconomic levels of the school environment. Alcohol use and alcohol-related problem behaviours were investigated through a self-completed anonymous questionnaire at baseline and 18 months thereafter. Data were analysed using multilevel models, separately by socioeconomic level.</p> <p>Results</p> <p>At baseline, adolescents in schools of low socioeconomic level were more likely to report problem drinking than other students. Participation in the programme was associated in this group with a decreased odds of reporting episodes of drunkenness (OR = 0.60, 95% CI = 0.44-0.83), intention to get drunk (OR = 0.60, 95% CI = 0.45-0.79), and marginally alcohol-related problem behaviours (OR = 0.70, 95% CI = 0.46-1.06). No significant programme's effects emerged for students in schools of medium or high socioeconomic level. Effects on frequency of alcohol consumption were also stronger among students in disadvantaged schools, although the estimates did not attain statistical significance in any subgroup.</p> <p>Conclusions</p> <p>It is plausible that comprehensive social influence programmes have a more favourable effect on problematic drinking among students in underprivileged social environments.</p> <p>Trial registration</p> <p>ISRCTN: <a href="http://www.controlled-trials.com/ISRCTN18092805">ISRCTN18092805</a></p
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