Clinical methodsIntervention fidelity: Lessons learned from an unsuccessful pilot study
Introduction
To achieve internal validity in an experimental research design, nurse researchers routinely consider and control extraneous influences on outcomes of interest. In a pilot test of nurse-delivered motivational interviewing (MI) to support postpartum weight loss, we learned that the internal influences of intervention design, implementation, and group differentiation merit as much consideration as do external confounders.
Section snippets
A pilot study to reduce postpartum weight retention
The goal of our nurse-delivered intervention was to prevent or reduce long-term obesity in mothers by intervening soon after childbirth to facilitate loss of excess pregnancy weight. More than 25% of American women retain 9 lb or more over their pre-pregnant weight at 1 year after childbirth, and postpartum weight retention can lead to lifelong obesity (Gore, Brown, & West, 2003). Women who do not lose their excess weight in the early postpartum period can be up to 18 lb heavier 10 years later (
Results
The MI intervention produced no statistically detectable difference in weight, BMI, and weight retained at 8 months. Education, income level, breast-feeding, smoking, and weight loss programs did not affect weight retention.
Predictors of weight retained at 8 months postpartum were pre-pregnant BMI (Kendall's τ = .315; p = .049) and pregnancy weight gain (Kendall's τ = .492; p = 002). However, these two predictors were unrelated (Kendall's τ = .100; p = .516). Single minority women retained an
Lessons learned about intervention fidelity
Despite our efforts, our intervention was too weak to overcome other influences on study outcomes in this small sample. Was our failure a result of the nature of the intervention or the way we implemented it? A review of the principles of treatment integrity illuminates many weak links that may have contributed to our lack of effect.
Conclusions
Weight loss is a complex challenge affected by genetic, environmental, social, and cultural factors. Nonetheless, nurses and others are committed to designing and testing interventions to help women lose excess weight and maintain their weight loss. As these and other interventions are developed, it is important to recognize that intervention integrity is more complex than simply providing the same training to each interventionist and the same dose of intervention to each participant. This post
Acknowledgment
This research was supported by a Research Incentive Grant awarded by Boston College to Dr. Kearney.
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