Table 1. Summary of variables for study aims.
| Variable |
Method of Measurement |
Operational definition | Level of measurement |
|---|---|---|---|
| NVC | fNIRS | Change in relative HbO concentration in cortical small vessels during cognitive task | Continuous |
| Band-limited power | EEG | Amount of electrocortical activity in distinct frequency bands during cognitive task | Continuous |
| Retinal arteriolar function | DVA | Retinal arteriolar response to flickering light stimulus (NVC stimulus) | Continuous |
| Microvascular endothelial function | LSCI | Small vessel hand perfusion following the release of 5-minute occlusion | Continuous |
| Macrovascular endothelial function | FMD | Percent change in brachial artery diameter from baseline to release of 5-minute occlusion | Continuous |
| Pro-inflammatory cytokine levels | Magnetic bead-based multiplex assay | Quantified fluorescence intensity in pro-inflammatory cytokine levels | Continuous |
| Endothelial dysfunction biomarkers | Magnetic bead-based multiplex assay | Quantified fluorescence intensity in cardiovascular disease panel markers | Continuous |
| Antioxidant capacity | HORAC activity assay | Fluorescence decay curve: time until complete decay of fluorescent probe | Continuous |
| Fluid intelligence | NIH Toolbox | Individual and categorical T score based on cognitive test responses | Continuous |
| Crystalized Intelligence | NIH Toolbox | Individual and categorical T score based on cognitive test responses | Continuous |
| Emotion Score | NIH-Toolbox | Individual T-score based on normative population data | Continuous |
| n-back working memory performance | n-back | Percentage of correct responses and reaction time during n-back blocks | Continuous |
| Blood pressure | AD instruments | Blood pressure recorded during visits | Continuous |
| Time since SARS-CoV-2 Infection | Demographic | Duration from COVID-19 diagnosis to Visit 1 | Continuous |
| Age | Demographic | Age (in years) of participants at each visit | Discrete |
| Fazekas scale | MRI | WMH burden (0–3) periventricular and deep | Discrete |
| MoCA | Demographic | Montreal cognitive assessment score (0–30) | Discrete |
| ACE score | ACE questionnaire | Adverse childhood experience questionnaire, scored 1–10 with a score of 10 having high ACE | Discrete |
| Comorbidities | Demographic | Past medical history and/or ongoing medically controlled for conditions | Nominal |
| SARS-CoV-2 Variant | Demographic | Estimated variant based on time (month and year) patient was infected with SARS-CoV-2 | Nominal |
| Vaccination History | Demographic | Number of doses, vaccine manufacturer | Nominal |
| Education | Demographic | Highest level of education obtained | Ordinal |
| Progression of MCI to dementia | Clinical diagnosis | Use of neurocognitive screening (e.g., MoCA, clinical dementia rating) and final adjudication made through consensus management | Binary |
| COVID-19 status | *Previously confirmed COVID-19 history | COVID-19 positive or COVID-19 negative | Binary |
| Sex | Demographic | Male or female | Binary |
Note. Neurovascular coupling (NVC), Functional near-infrared spectroscopy (fNIRS), Oxy-hemoglobin (HbO), Electroencephalography (EEG), Dynamic retinal vessel analysis (DVA), Laser speckle contrast imaging (LSCI), Flow mediated dilation (FMD), Hydroxyl radical antioxidant capacity assay (HORAC), White mattery hyperintensity (WMH), Montreal cognitive assessment (MoCA), Mild cognitive impairment (MCI), Adverse childhood experience (ACE).
* Indicates COVID-19 was confirmed by PCR or serologic testing.