Choosing marginal or random-effects models for longitudinal binary responses: application to self-reported disability among older persons

BACKGROUND: Longitudinal studies with binary repeated outcomes are now widespread in epidemiology. The statistical analysis of these studies presents difficulties and standard methods are inadequate. METHODS: We consider strategies for modelling binary repeated responses and focus on two specific issues: the choice between marginal and random-effects models, and the choice of the time point origin. These issues are addressed using the example of self-reported disability in older women assessed annually for 6 years. The indicator of disability "needing help to go outdoors or home-confined" is used. RESULTS: In view of the observed associations between the responses for consecutive years, the baseline response was considered as a covariate. We compared the marginal and random-effects models first when only the influence of time and age is analysed and second when individual risk factors are studied in an aetiological perspective. There were substantial differences between the parameter estimates. They were due to differences between specific concepts related to the two models and the large between-individual heterogeneity revealed by the analysis. CONCLUSIONS: A random-effects model appears to be most suitable for the analysis of self-reported disability in older women

Adjectifs dérivés de noms : analyse en corpus médical et élaboration d'un modèle d'encodage terminologique

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal

Trauma and depressive symptomatology in middle-aged persons at high risk of dementia: the PREVENT Dementia Study

Objective: Depression and trauma are associated with changes in brain regions implicated in Alzheimer’s disease. The present study examined associations between childhood trauma, depression, adult cognitive functioning and risk of dementia. Methods: Data from 378 participants in the PREVENT Dementia Study aged 40–59 years. Linear and logistic models were used to assess associations between childhood trauma, depression, dementia risk, cognitive test scores and hippocampal volume. Results: Childhood trauma was associated with depression and reduced hippocampal volume but not current cognitive function or dementia risk. Poorer performance on a delayed face/name recall task was associated with depression. Childhood trauma was associated with lower hippocampal volume however poorer cognitive performance was mediated by depression rather than structural brain differences. Conclusion: Depressive symptomatology may be associated with dementia risk via multiple pathways, and future studies should consider subtypes of depressive symptomatology when examining its relationship to dementia

Statistical methods for dementia risk prediction and recommendations for future work: A systematic review

International audienceINTRODUCTION:Numerous dementia risk prediction models have been developed in the past decade. However, methodological limitations of the analytical tools used may hamper their ability to generate reliable dementia risk scores. We aim to review the used methodologies.METHODS:We systematically reviewed the literature from March 2014 to September 2018 for publications presenting a dementia risk prediction model. We critically discuss the analytical techniques used in the literature.RESULTS:In total 137 publications were included in the qualitative synthesis. Three techniques were identified as the most commonly used methodologies: machine learning, logistic regression, and Cox regression.DISCUSSION:We identified three major methodological weaknesses: (1) over-reliance on one data source, (2) poor verification of statistical assumptions of Cox and logistic regression, and (3) lack of validation. The use of larger and more diverse data sets is recommended. Assumptions should be tested thoroughly, and actions should be taken if deviations are detected

Sex-specific depressive symptoms as markers of pre-Alzheimer dementia: findings from the Three-City cohort study

International audienceLate-life depression, as a potential marker of pre-dementia, has seldom been explored by symptom dimension and sex, despite sexual dimorphic differences. This study aimed to examine whether specific depressive dimensions were associated with pre-Alzheimer's disease dementia (pre-AD), separately for women and men. Data were drawn from 5617 (58% women) community-dwellers aged 65+ recruited in 1999-2000 and followed at 2-year intervals for 12 years. We used Cox proportional hazard models to study associations between time-dependent Centre for Epidemiologic Studies-Depression Scale (CES-D) symptom dimensions (namely somatic, depressed, positive affect, and interpersonal challenge) and pre-AD, defined retrospectively from validated diagnoses established 3.5 (IQR: 3.2-4.0) years onwards. Analyses were performed according to overall depressive symptomatology (DS+: CES-D score ≥ 16) and antidepressant/anxiolytic medication use (AA). Results indicated that in DS+ women only, all four dimensions were significantly associated with pre-AD in the AA-group, in particular somatic item 'Mind' and depressed affect items 'Depressed' and 'Blues'. The most depression-specific dimension, depressed affect, was also significantly associated with pre-AD in the DS-AA-women (HR:1.28, 95%CI: 1.12;1.47). In both sexes, in the DS-groups somatic affect was the most robust pre-AD marker, irrespective of treatment (women: HR = 1.22, 95%CI: 1.08;1.38; men: HR = 1.30, 95%CI: 1.14;1.48). Our findings highlight sex-specific associations between depressive symptom dimensions and pre-AD, modulated by depressive symptomatology and treatment. Assessment of specific symptom dimensions taking into account overall symptomatology and treatment could help identify and target high-risk AD-dementia profiles for interventions

Lifetime exposure to ambient ultraviolet radiation and the risk for cataract extraction and age-related macular degeneration : the Alienor Study

While exposure to ultraviolet radiation (UVR) is a recognized risk factor for cataract, its association is more controversial with age-related macular degeneration (AMD). We report the associations of lifetime exposure to ambient UVR with cataract extraction and AMD. The Alienor Study is a population-based study of 963 residents of Bordeaux (France), aged 73 years or more. Lifetime exposure to ambient UVR was estimated from residential history and Eurosun satellite-based estimations of ground UVR. It was divided in three groups (lower quartile, intermediate quartiles, upper quartile), using the intermediate quartiles as the reference. Early and late AMD was classified from retinal color photographs. Cataract extraction was defined as absence of the natural lens at slit-lamp. After multivariate adjustment, subjects in the upper quartile of lifetime ambient UVR exposure were at increased risk for cataract extraction (odds ratio [OR] = 1.53; 95% confidence interval [CI], 1.04-2.26; P = 0.03) and for early AMD (OR = 1.59; 95% CI, 1.04-2.44; P = 0.03), by comparison with subjects in the intermediate quartiles. Subjects in the lower quartile of UVR exposure also were at increased risk for early AMD (OR = 1.69; 95% CI, 1.06-2.69; P = 0.03), by comparison with those with medium exposure. Associations of late AMD with UVR exposure was not statistically significant. This study further confirms the increased risk for cataract extraction in subjects exposed to high ambient UVR. Moreover, it suggests that risk for early AMD is increased in subjects exposed to high UVR, but also to low UVR, by comparison with medium exposures

Money for writing: Screenplay development and screenwriters earnings in French cinema

The funds allocated to developing screenplays currently constitute on average 2 to 3% of the overall budget of a film in France. Producers are more than ever dependent on presenting attractive draft screenplays to find their financial partners. As a result, screenwriters undoubtedly are active economic partners of production planning, but they do not seem to receive much professional recognition for this vital role. Moreover, their earnings often fail to reflect the amount of work produced and do not reward adequately the risks taken, including the possibility that production could stop after the screenplay is written. This article investigates the place of screenplay development within the economics of French cinema. Using recently published official reports and interviews, the author identifies different types of screenwriters – freestanding screenwriters, writing teams and screenwriters co-writing with the director – and addresses their working conditions. She surveys some of the contract modalities for the remuneration of professional screenwriters. Finally, she reviews the proposals made by different professional bodies to improve the remuneration of screenwriters and reform the financing of screenwriting

COSMIC (Cohort Studies of Memory in an International Consortium): An international consortium to identify risk and protective factors and biomarkers of cognitive ageing and dementia in diverse ethnic and sociocultural groups

BACKGROUND: A large number of longitudinal studies of population-based ageing cohorts are in progress internationally, but the insights from these studies into the risk and protective factors for cognitive ageing and conditions like mild cognitive impairment and dementia have been inconsistent. Some of the problems confounding this research can be reduced by harmonising and pooling data across studies. COSMIC (Cohort Studies of Memory in an International Consortium) aims to harmonise data from international cohort studies of cognitive ageing, in order to better understand the determinants of cognitive ageing and neurocognitive disorders. METHODS/DESIGN: Longitudinal studies of cognitive ageing and dementia with at least 500 individuals aged 60 years or over are eligible and invited to be members of COSMIC. There are currently 17 member studies, from regions that include Asia, Australia, Europe, and North America. A Research Steering Committee has been established, two meetings of study leaders held, and a website developed. The initial attempts at harmonising key variables like neuropsychological test scores are in progress. DISCUSSION: The challenges of international consortia like COSMIC include efficient communication among members, extended use of resources, and data harmonisation. Successful harmonisation will facilitate projects investigating rates of cognitive decline, risk and protective factors for mild cognitive impairment, and biomarkers of mild cognitive impairment and dementia. Extended implications of COSMIC could include standardised ways of collecting and reporting data, and a rich cognitive ageing database being made available to other researchers. COSMIC could potentially transform our understanding of the epidemiology of cognitive ageing, and have a world-wide impact on promoting successful ageing