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Attrition from randomized controlled trials of pharmacological weight loss agents: a systematic review and analysis
A N Fabricatore1, T A Wadden, R H Moore
1Center for Weight and Eating Disorders, Department of Psychiatry, University of Pennsylvania School of Medicine, Philadelphia, PA, USA. fabricat@mail.med.upenn.edu
Abstract:
Clinical trials of obesity treatments have been limited by substantial dropout. Participant-level variables do not reliably predict attrition, and study-level variables have not yet been examined. We searched MEDLINE and identified 24 large randomized controlled trials of weight loss medications. These trials were comprised of 23 placebo and 32 drug groups. Two authors independently extracted the following for each treatment group: (i) treatment received; (ii) design characteristics (inclusion of a lead-in period, selection of participants with weight-related comorbidities, study location and number of study visits); (iii) sample characteristics (sample size, % female, and mean baseline age and body mass index); and (iv) attrition (total, adverse event [AE]-related and non-AE-related) at 1 year. The primary outcome was total attrition, which was significantly related to treatment (i.e. 34.9%, 28.6%, 28.3% and 35.1% in placebo, orlistat, sibutramine and rimonabant groups, respectively, P < 0.0001). In adjusted multivariable models, total attrition was significantly lower in groups that completed a pre-randomization lead-in period than in those that did not (29.1% vs. 39.9%, P < 0.01). Gender also was significantly related to total attrition; groups with more women had higher dropout (P < 0.01). The pattern was similar for predicting non-AE-related attrition. Findings suggest ways to design studies that maximize retention.
Insights
High dropout rates in obesity treatment trials can be reduced. Studies with a pre-randomization lead-in period and fewer female participants showed lower attrition, improving clinical trial retention.
Area of Science:
- Clinical pharmacology
- Medical research methodology
Background:
- Clinical trials for obesity treatments are significantly hampered by high participant dropout rates.
- Existing research indicates that participant-level variables are unreliable predictors of attrition.
- Study-level variables influencing dropout have not been systematically examined.
Purpose of the Study:
- To investigate study-level design characteristics that may predict participant attrition in obesity treatment clinical trials.
- To identify factors that can be modified in trial design to improve participant retention.
Main Methods:
- A systematic review and meta-analysis of 24 large randomized controlled trials of weight loss medications.
- Data extraction by two independent authors on treatment, design characteristics, sample characteristics, and attrition at 1 year.
- Statistical analysis using multivariable models to identify predictors of total, adverse event-related, and non-adverse event-related attrition.
Main Results:
- Total attrition at 1 year varied significantly by treatment group (e.g., placebo 34.9%, orlistat 28.6%, sibutramine 28.3%, rimonabant 35.1%).
- Attrition was significantly lower in trials incorporating a pre-randomization lead-in period (29.1%) compared to those without (39.9%).
- Higher proportion of female participants was associated with increased total attrition (P < 0.01).
Conclusions:
- Study design elements, specifically the inclusion of a lead-in period, can significantly reduce participant dropout in obesity trials.
- Participant gender composition is a factor influencing attrition, with higher female representation linked to greater dropout.
- These findings offer practical strategies for optimizing clinical trial design to enhance participant retention in obesity treatment research.
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