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Combining direct and proxy assessments to reduce attrition bias in a longitudinal study
Qiong Wu1, Eric J Tchetgen Tchetgen, Theresa L Osypuk
1Harvard Center for Population and Development Studies, Harvard University, Cambridge, MA, USA.
Alzheimer Disease and Associated Disorders
|September 21, 2012
Summary
Longitudinal dementia studies can now include proxy reports, improving dementia prevalence estimates and revealing faster memory decline. This method enhances data for memory loss research.
Area of Science:
- Gerontology
- Epidemiology
- Neuroscience
Background:
- Longitudinal studies tracking dementia and memory decline face challenges retaining severely impaired individuals.
- The Health and Retirement Study (HRS) uses direct assessments until impairment, then switches to proxy informants.
- Proxy reports are often excluded from analyses due to a lack of common scales with direct assessments.
Purpose of the Study:
- To develop and validate a method for estimating dementia probability and memory scores using both direct and proxy assessments.
- To integrate proxy data into longitudinal analyses of cognitive aging.
Main Methods:
- Utilized data from the Aging, Demographics, and Memory Study (ADAMS) on a subsample of HRS participants (n=856).
- Developed a prediction model for dementia probability and a composite memory score applicable to both direct and proxy assessments.
- Validated the model using DSM-diagnosed dementia, achieving a c-statistic of 94.3% in the ADAMS sample.
Main Results:
- Applied scoring rules to a larger HRS cohort (n=5483) born 1923 or earlier, assessing biennial data from 1995-2008.
- Incorporating proxy respondents increased estimated dementia prevalence by 12 percentage points in 2008 (average age 89).
- Analysis revealed accelerated rates of memory decline over time when proxy data was included.
Conclusions:
- The developed approach effectively integrates proxy informant data into longitudinal cognitive assessments.
- Including proxy reports significantly enhances the accuracy of dementia prevalence estimates and reveals more about the trajectory of memory decline.
- This method offers a valuable tool for improving the comprehensiveness of dementia and cognitive aging research.
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