NACC data: Who is represented over time and across centers, and implications for generalizability

Area of Science:

• Neuroscience
• Clinical Research
• Biostatistics

Background:

• Alzheimer's Disease Research Centers (ADRCs) have collected Uniform Data Set (UDS) data since 2005.
• Enrollment trends and center-specific variations within the UDS are not fully understood.
• Understanding these patterns is crucial for assessing the generalizability of UDS findings.

Purpose of the Study:

• To investigate temporal enrollment trends within the UDS.
• To examine heterogeneity in participant characteristics across different ADRCs.
• To assess the implications of these findings for the generalizability of UDS data.

Main Methods:

• Utilized data from the National Alzheimer's Coordinating Center (NACC).
• Analyzed baseline characteristics including demographics, clinical diagnosis, and family history.
• Assessed temporal trends and between-center variations in these characteristics.

Main Results:

• Most participant characteristics, excluding sex and family history, exhibited directional shifts over time.
• Significant heterogeneity was observed across centers for all examined variables.
• Participant profiles demonstrated both temporal evolution and substantial site-level variation.

Conclusions:

• Temporal changes and site variability in participant profiles present challenges and opportunities for generalizing UDS findings.
• While not nationally representative, UDS data can support generalization with appropriate analytical methods.
• Advanced statistical techniques, such as sensitivity analysis and meta-analysis, can enhance the transparency and robustness of inferences drawn from UDS data.