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Permanent URI for this collectionhttps://hdl.handle.net/11443/932

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Author: search.filters.author.Diggle, Peter J.Has files: No

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    Linear mixed effects models for non-Gaussian continuous repeated measurement data
    (WILEY, 2020-01-01) Asar, Ozgur; Bolin, David; Diggle, Peter J.; Wallin, Jonas
    We consider the analysis of continuous repeated measurement outcomes that are collected longitudinally. A standard framework for analysing data of this kind is a linear Gaussian mixed effects model within which the outcome variable can be decomposed into fixed effects, time invariant and time-varying random effects, and measurement noise. We develop methodology that, for the first time, allows any combination of these stochastic components to be non-Gaussian, using multivariate normal variance-mean mixtures. To meet the computational challenges that are presented by large data sets, i.e. in the current context, data sets with many subjects and/or many repeated measurements per subject, we propose a novel implementation of maximum likelihood estimation using a computationally efficient subsampling-based stochastic gradient algorithm. We obtain standard error estimates by inverting the observed Fisher information matrix and obtain the predictive distributions for the random effects in both filtering (conditioning on past and current data) and smoothing (conditioning on all data) contexts. To implement these procedures, we introduce an R package: ngme. We reanalyse two data sets, from cystic fibrosis and nephrology research, that were previously analysed by using Gaussian linear mixed effects models.
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    Assessing Feasibility and Acceptability of Web-Based Enhanced Relapse Prevention for Bipolar Disorder (ERPonline): A Randomized Controlled Trial
    (JMIR PUBLICATIONS, INC, 2017-01-01) Lobban, Fiona; Dodd, Alyson L.; Sawczuk, Adam P.; Asar, Ozgur; Dagnan, Dave; Diggle, Peter J.; Griffiths, Martin; Honary, Mahsa; Knowles, Dawn; Long, Rita; Morriss, Richard; Parker, Rob; Jones, Steven
    Background Interventions that teach people with bipolar disorder (BD) to recognize and respond to early warning signs (EWS) of relapse are recommended but implementation in clinical practice is poor. Objectives The objective of this study was to test the feasibility and acceptability of a randomized controlled trial (RCT) to evaluate a Web-based enhanced relapse prevention intervention (ERPonline) and to report preliminary evidence of effectiveness. Methods A single-blind, parallel, primarily online RCT (n=96) over 48 weeks comparing ERPonline plus usual treatment with ``waitlist (WL) control{''} plus usual treatment for people with BD recruited through National Health Services (NHSs), voluntary organizations, and media. Randomization was independent, minimized on number of previous episodes (<8, 8-20, 21+). Primary outcomes were recruitment and retention rates, levels of intervention use, adverse events, and participant feedback. Process and clinical outcomes were assessed by telephone and Web and compared using linear models with intention-to-treat analysis. Results A total of 280 people registered interest online, from which 96 met inclusion criteria, consented, and were randomized (49 to WL, 47 to ERPonline) over 17 months, with 80\% retention in telephone and online follow-up at all time points, except at week 48 (76\%). Acceptability was high for both ERPonline and trial methods. ERPonline cost approximately 19,340 to create, and 2176 per year to host and maintain the site. Qualitative data highlighted the importance of the relationship that the users have with Web-based interventions. Differences between the group means suggested that access to ERPonline was associated with: a more positive model of BD at 24 weeks (10.70, 95\% CI 0.90 to 20.5) and 48 weeks (13.1, 95\% CI 2.44 to 23.93)
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    Web-based integrated bipolar parenting intervention for parents with bipolar disorder: a randomised controlled pilot trial
    (WILEY, 2017-01-01) Jones, Steven H.; Jovanoska, Jelena; Calam, Rachel; Wainwright, Laura D.; Vincent, Helen; Asar, Ozgur; Diggle, Peter J.; Parker, Rob; Long, Rita; Sanders, Matthew; Lobban, Fiona
    Background: People with bipolar disorder (BD) experience additional parenting challenges associated with mood driven fluctuations in communication, impulse control and motivation. This paper describes a novel web-based self-management approach (Integrated Bipolar Parenting Intervention