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A causal model for longitudinal randomised trials with time-dependent non-compliance.
Taeko Becque1, Ian R White, Mark Haggard
1York Trials Unit, Department of Health Sciences, University of York, York, YO10 5DD, U.K.
Statistics in Medicine
|March 18, 2015
Summary
This study introduces a new causal model for analyzing treatment efficacy with non-compliance over time. Surgery showed benefits for childhood ear disease at 6 months, though effects diminished by 12 months.
Area of Science:
- Biostatistics
- Epidemiology
- Clinical Trials
Background:
- Intention-to-treat analysis offers unbiased comparisons but can underestimate treatment efficacy with non-compliance.
- Complier-average causal effect (CACE) models efficacy based on adherence, assuming all-or-nothing compliance.
- Longitudinal data with time-dependent non-compliance requires advanced causal modeling approaches.
Purpose of the Study:
- To extend the CACE approach for modeling longitudinal data with time-dependent non-compliance.
- To develop a causal model accommodating treatment crossover in randomized controlled trials.
- To evaluate the efficacy of surgical intervention for childhood ear disease using this novel causal framework.
Main Methods:
- Developed a causal model for multivariate outcomes conditional on compliance type and randomized arm.
- Defined compliance type based on the timing of surgical intervention in the control group.
- Employed Markov chain Monte Carlo (MCMC) methods to estimate CACE over time.
Main Results:
- Over 50% of participants randomized to the control group eventually received surgical intervention.
- Surgical intervention demonstrated a statistically significant benefit compared to control at 6 months post-intervention.
- A small, non-significant beneficial effect of surgery was observed at 12 months.
Conclusions:
- The extended CACE model effectively handles time-dependent non-compliance in longitudinal studies.
- Surgical intervention is beneficial for childhood ear disease in the short term (6 months).
- Long-term benefits of surgical intervention require further investigation due to diminishing effects by 12 months.
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