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Comparison Groups Matter in Traumatic Brain Injury Research: An Example with Dementia
Jennifer S Albrecht1, Raquel C Gardner2,3, Douglas Wiebe4
1Department of Epidemiology and Public Health, University of Maryland School of Medicine, Baltimore, Maryland, USA.
Journal of Neurotrauma
|May 25, 2022
Summary
Traumatic brain injury (TBI) significantly increases the risk for Alzheimer disease and related dementias (ADRD). The estimated risk varied based on the comparison group used in the study, highlighting the importance of careful selection for accurate TBI-ADRD association research.
Area of Science:
- Neuroscience
- Gerontology
- Epidemiology
Background:
- Traumatic brain injury (TBI) is a known risk factor for Alzheimer disease and related dementias (ADRD), but effect sizes vary across studies.
- Confounding factors and selection of comparison groups can influence the observed association between TBI and ADRD.
- Understanding the impact of comparison group selection is crucial for accurately estimating TBI's total associated risk for ADRD.
Purpose of the Study:
- To investigate how the choice of comparison group affects the estimated risk of developing ADRD after a traumatic brain injury (TBI).
- To analyze the association between TBI and ADRD in a veteran population using different control groups.
Main Methods:
- Utilized data from Veterans Health Administration (VA) from 1999-2019 for Veterans aged 55 years and older.
- Compared incident TBI cases (n=9440) against three distinct control groups: All VA (n=119,003), VA Emergency Department (VA ED) (n=111,342), and VA ED for non-TBI trauma (VA ED NTT) (n=65,710).
- Employed inverse probability of treatment weighted (IPTW) models to estimate hazard ratios (HR) and 95% confidence intervals (CI) for ADRD risk.
Main Results:
- TBI was associated with a significantly increased risk of ADRD across all comparison groups.
- The magnitude of the TBI-ADRD association varied substantially depending on the control group: HR 1.94 (All VA), HR 1.42 (VA ED), and HR 1.12 (VA ED NTT).
- The choice of comparison group critically impacted the estimated effect size of TBI on ADRD risk.
Conclusions:
- The selection of a comparison group is a critical determinant in estimating the association between TBI and the risk of ADRD.
- Findings underscore the need for careful consideration of control group selection in TBI research to avoid biased effect size estimates.
- This study emphasizes the significant impact of TBI on long-term dementia risk within the veteran population.
