Connecting Cognitive & Clinical Data

WRAP cognitive and clinical data can be merged together based on the variables "WRAPNo/wrapnum" and "VisNo" which represent the participant identifier and visit number for each participant, respectively. Some tables may not contain data for all visits, but the fqryStatisticalData table will list each visit and their respective details. VisNo = 1 is the initial/baseline visit.

Pairing Cognitive & Clinical Data with Images and/or Biofluids

The study structure of WRAP is unique. Imaging and other biomarkers have generally been obtained for WRAP participants as part of separately funded substudies. As such, there is not a single "Visit Number" that allows for appropriate pairing of cognitive & clinical visits with imaging or biofluids measures. Because of this, we provide information on the relative timing of all events to allow investigators to create the pairings that are most appropriate for their research question.

• In fqryStatisticalData, you will also find a field called Days_Since_Baseline. This establishes the timescale for joining the cognitive & clinical data with events that did not happen at a main study visit. For VisNo=1, Days_Since_Baseline should be 0.
• In the tabular data for both imaging and biofluids, you will find a Days_Since_Baseline field, which is on the same time scale as the same-named field in fqryStatisticalData. It does not include a VisNo field, as imaging/biofluid visits and cognitive/clinical visits are not the same. Frequently the first image will have been acquired many years after the initial study visit.
• Investigators will not usually want to perform a strict join between images and cognitive/clinical visits using WRAPNo/wrapnum and Days_Since_Baseline, as very few visits happen on the same day. Instead, it is better to think about an approach to joining the data that best supports your research question. Here are some examples of approaches that some in our group have taken:
  1. Select the first available image and pair with the full range of cognitive visits. Useful if your question is, "How do the earliest available brain biomarkers relate to cognition?"
  2. Select the first available image and pair only with the cognitive visits that happened at or after the image. Useful if your question is, "How does a biomarker at time t0 relate to subsequent cognition?"
  3. Select the last available image and pair with the full range of cognitive visits. Useful if your question is, "How does the best/most current information about biomarker phenotype relate to retrospective cognition?
  4. Select longitudinal pairs of images and cognitive/clinical visits, subject to some time constraint (e.g. visits must happen within 1 year of each other). If you select this option, you may want to consider what to do when a single visit of one type is the closest match to more than one visit of the other type.