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A randomized trial of cardiovascular risk factor reduction: patterns of attrition after randomization and during
T J McCann1, M H Criqui, I A Kashani
1University of Washington, Department of Epidemiology, USA.
Insights
High attrition in cardiovascular disease (CVD) risk reduction trials is common. Early and late drop-outs differ significantly from participants, impacting study generalizability.
Area of Science:
- Preventive Cardiology
- Behavioral Science
- Public Health
Background:
- Investigated behavioral modification intensities for cardiovascular disease (CVD) risk factors.
- Compared characteristics of participants who dropped out versus those who completed a 6-month trial.
Purpose of the Study:
- To compare the characteristics of drop-outs with completers in a CVD risk reduction trial.
- To assess the impact of intervention intensity on participant retention.
Main Methods:
- 333 individuals were randomized into low-intensity (1 session) or high-intensity (5 sessions) behavioral interventions.
- Assessments included health questionnaires, nutritional surveys, and clinical measurements (blood pressure, lipids, height, weight).
Main Results:
- 28.3% were 'early drop-outs' (non-white, lower LDL cholesterol).
- 40.7% of intervention attendees were 'late drop-outs' (white, current smokers).
- Significant differences were observed between drop-outs and completers.
Conclusions:
- Participant attrition in CVD risk reduction trials is substantial.
- Drop-out characteristics vary (early vs. late) and differ from completers.
- Caution is advised when interpreting and generalizing findings from trials with high attrition.
Background:
The Preventive Cardiology Center compared two intensities of behavior modification for cardiovascular disease (CVD) risk factors in persons at risk and their families. Characteristics of drop-outs both before and after intervention were compared with subjects who completed the 6-month trial.
Methods:
A total of 333 individuals of all ages were enrolled in the study and randomly assigned by family to a single-session ('skills' group-low-intensity) or a five-session ('practice' group-high intensity) intervention. Baseline and follow-up assessments included a personal and family health questionnaire, nutritional intake survey, and clinic visit to obtain blood pressure, lipids, and height and weight data.
Results:
Two hundred and forty adults over 18 years of age were randomly assigned to one of the two intervention groups. Of these, 68 subjects (28.3%) did not participate in the intervention. Multivariate analysis revealed that these 'early drop-outs' were significantly more likely to be non-white and to have had a lower LDL cholesterol. Of the 172 subjects attending the intervention, 70 (40.7%) did not attend the 6-month follow-up ('late drop-outs'). Multivariate analysis revealed that, compared with follow-up attendees, non-attendees were significantly more likely to be white and to be current smokers.
Conclusions:
Both early and late drop-outs in a randomized trial of CVD risk reduction were significantly different than continuing participants in several key factors. These differences suggest the use of caution in both interpreting and making generalizations about behavioral trials of risk factor reduction when attrition is high.
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