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Placebo adherence and mortality in the Heart and Estrogen/Progestin Replacement Study
Amy M Padula1, Alice R Pressman, Eric Vittinghoff
1School of Public Health, University of California, Berkeley, CA, USA. ampadula@stanford.edu
The American Journal of Medicine
|July 31, 2012
Summary
Higher adherence to placebo medication in clinical trials is linked to significantly lower mortality rates. This unexpected finding in the Heart and Estrogen/Progestin Replacement Study (HERS) warrants further investigation into its underlying causes.
Area of Science:
- Cardiovascular disease research
- Clinical trial methodology
- Pharmacological adherence studies
Background:
- Observational data from randomized trials suggest improved outcomes with higher placebo adherence.
- The Heart and Estrogen/Progestin Replacement Study (HERS) provides a unique dataset to investigate this phenomenon.
- Postmenopausal women receiving hormone replacement therapy were studied in a placebo-controlled setting.
Purpose of the Study:
- To quantify the association between placebo adherence and all-cause mortality in HERS participants.
- To explore potential explanations for the observed link between placebo adherence and mortality.
- To assess the relationship between placebo adherence and cause-specific morbidity and mortality.
Main Methods:
- Participants were categorized into 'higher adherence' (≥75% medication intake) and 'lower adherence' (<75%).
- The primary endpoint was in-study all-cause mortality.
- Statistical analyses, including adjustments for confounders, were performed.
Main Results:
- Higher placebo adherence was associated with significantly reduced total mortality (Hazard Ratio: 0.52).
- Adjusting for confounders did not alter the significance of this association.
- Time-dependent confounding partially explained the observed relationship.
Conclusions:
- A strong association exists between adherence to placebo medication and mortality in the HERS trial.
- The mechanism behind this association is not fully understood and likely not due to simple lifestyle confounding.
- Further research is needed to elucidate the reasons for this observed phenomenon.
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