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For time-to-event outcomes, the difference in restricted mean survival time is a measure of the intervention effect, an alternative to the hazard ratio, corresponding to the expected survival duration gain due to the intervention up to a predefined time t*. We extended two existing approaches of restricted mean survival time estimation for independent data to clustered data in the framework of cluster randomized trials: one based on the direct integration of Kaplan-Meier curves and the other based on pseudo-values regression. Then, we conducted a simulation study to assess and compare the statistical performance of the proposed methods, varying the number and size of clusters, the degree of clustering, and the magnitude of the intervention effect under proportional and non-proportional hazards assumption.

The 2020-2022 thesis prize «Daniel Schwartz», founder of the French Society of Biometrics, French component of the International Biometric Society (IBS), was awarded to two spherian doctoral students: Arthur CHATTON and Marion KERIOUI

They were invited to present their research at the Journée Jeunes Chercheur.e.s of the Société Française de Biométrie, held in Rennes on 19 January 2023.

Congratulations to both of you!

Aims. To estimate whether the use of wagering inducements has a significant impact on the gambling behaviors of online gamblers and describe this temporal relation under naturalistic conditions. Design. This longitudinal observational study is part of the second stage of the Screening for Excessive Gambling Behaviors on the Internet (EDEIN) research program. Setting. Gambling tracking data from the French national online gambling authority (poker, horse race betting and sports betting) and from the French national lottery operator (lotteries and scratch games). Participants. A total of 9306 gamblers who played poker, horse race or sports betting and 5682 gamblers who played lotteries and scratch games completed an online survey. The gender ratio was largely male (around 90% for poker, horse race betting and sports betting and 65% for lotteries). Median age ranged from 35 (sports betting) to 53 (horse race betting and lotteries). Measurements. The survey used the Problem Gambling Severity Index (PGSI) to determine the status of the gamblers (at-risk or not). Gambling tracking data included weekly gambling intensity (wagers, deposits), gambling frequency (number of gambling days), proxies of at-risk gambling behaviors (chasing and breadth of involvement), and use of wagering inducements. Findings Use of wagering inducements was associated with an increase of gambling intensity (β between -0.06 [-0.08;-0.05] and 0.57 [0.54;0.60]), gambling frequency (β between 0.12 [0.10;0.18] and 0.29 [0.28;0.31]), and at-risk gambling behaviors (odds ratio between 1.32 [1.16;1.50] and 4.82 [4.61;5.05]) at the same week of their use. This effect was stronger for at-risk gambling behaviors and at-risk gamblers. Conclusions. Wagering inducements may represent a risk factor for developing or exacerbating gambling problems.

Both in France and Sweden, global changes in online gambling activities due to the COVID-19 pandemic, and their potential for gambling problems, are a source of concerns for public health authorities. The CONGA project aims to measuring the impact of the COVID-19 pandemic on the online gambling activity, both in France and Sweden. The use of gambling tracking data, widely acclaimed in recent years in research on online gambling given its ecological nature, could allow observing longitudinally changes in online gambling activities due to the pandemic. Moreover, the combination of French and Swedish data will allow comparing two countries with very distinct politics regarding the pandemics, i.e. a lockdown in France compared to no lockdown in Sweden. The CONGA study will provide a better understanding of the impact of restriction measures in the context of the health crisis on online gambling activities. Moreover, the identification of sub-populations particularly at risk of increasing their gambling activity in response to the health crisis will have both clinical and epidemiological perspectives, even beyond the current period of crisis.

Principal investigator: Gaëlle Challet-Bouju

Behavioural addictions (BAs) [gambling disorder (GD), food addiction (FA), sexual addiction (SA)] may lead to disastrous consequences. They are often associated with other addictive or psychiatric disorders, and high rates of suicide attempts. Epidemiological studies report prevalence reaching 2.7% for GD, 5% for SA, and up to 7.9% for FA.
Many similarities have been highlighted between BAs, as well as with substance use disorders. One core clinical similarity between those disorders is craving (uncontrollable urge to engage in rewarding behaviours), which has been consistently associated with diminished control over the behaviour and relapse.
Whereas cognitive behavioural therapies have demonstrated their efficacy for the management of BAs in the short-term, the extent and durability of their effects are still unknown. Drop-outs are frequent, as well as relapses, with for example more than 70% of patients presenting recurrence of gambling behaviour at 12-months follow-up.
At present, no pharmacological treatment has been approved for BAs, but several medications have been tested. Among them, two opioid receptor antagonists - naltrexone and nalmefene - appear the most promising. By decreasing dopamine neurotransmission in the reward circuitry, they reduce both excitement for rewarding behaviours and craving.
Compared to naltrexone, nalmefene seems to have a better safety. To date, no study investigated the efficacy of nalmefene as a pan-addiction treatment for BAs. Two clinical trials have demonstrated its efficacy for the treatment of GD, but no clinical trial was conducted for FA and SA.
We hypothesise that nalmefene (36 mg/d), compared to a placebo, can have a therapeutic effect as an add-on to usual treatment for decreasing craving in several BAs. The NABAB study could therefore lead to the development of guidelines incorporating a drug option for treating BAs. The project will also investigate the genetic predictors of therapeutic success, which may improve knowledge on the genetic determinants of the nalmefene action.
Nalmefene holds a marketing authorization at the dosage of 18 mg/d in France for alcohol use disorder only. The choice of the dosage tested in this study (36 mg/d) results of a balanced decision between efficacy (demonstrated at 40 mg/d) and safety (poor from 50 mg/d), as observed in the two trials on GD. Moreover, our study will comprise “real-life” conditions: (i) patients who are often excluded from clinical trials on addiction, i.e. females, patients with psychiatric/addictive comorbidities and concomitant substance consumption, or treated with concomitant psychotropic medications, provided that nalmefene is not contraindicated; (ii) all therapeutic goals, either regaining control over the addictive behaviour or achieving abstinence. This may favour the applicability of the treatment in real-life and the generalizability for all patients that could benefit from it.
The provision of well-tolerated and inexpensive drug treatment would allow easier accessibility to care, for example in primary care such as general practice, and in the management of patients who have difficulty engaging in specialized care.

Principal investigator: Marie Grall-Bronnec