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Dropouts and refusals in observational studies: lessons for prevention trials
Claudia Jacova1, Ging-Yuek R Hsiung, Howard H Feldman
1Division of Neurology, Department of Medicine, University of British Columbia, Vancouver, BC, Canada.
Neurology
|November 15, 2006
Summary
High refusal and dropout rates in Alzheimer disease (AD) prevention trials disproportionately affect at-risk individuals. Targeted retention strategies are crucial for study validity and power in dementia research.
Area of Science:
- Neuroscience
- Gerontology
- Clinical Trials
Background:
- Alzheimer disease (AD) and dementia prevention trials require robust recruitment and retention of at-risk populations.
- Participant attrition threatens statistical power and the validity of clinical trial findings.
- Observational cohort studies provide valuable insights into participant retention challenges.
Purpose of the Study:
- To investigate refusal and dropout rates in observational dementia cohort studies.
- To identify characteristics of participants who refuse or drop out.
- To evaluate the impact of attrition on study populations for AD/dementia prevention trials.
Main Methods:
- Analysis of data from the Canadian Cohort Study of Cognitive Impairment and Related Dementias (ACCORD).
- Comparison of subjects who refused baseline neuropsychological (NP) testing versus those who completed it.
- Comparison of subjects who dropped out versus those who attended 2-year follow-up.
Main Results:
- High rates of refusal (40%) and dropout (55%) were observed in the ACCORD study.
- Refusers were older, less educated, and, in the Cognitively Impaired Not Demented (CIND) group, had lower cognitive/functional scores.
- CIND dropouts also exhibited lower baseline cognitive and functional scores.
Conclusions:
- Refusal and dropout in dementia studies often involve individuals at higher risk of progression to AD/dementia.
- These attrition patterns can compromise the power and validity of prevention trials.
- Developing targeted strategies to retain high-risk participants is essential for successful AD/dementia prevention research.
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