Immersive Virtual Reality Training for Improving Cognition in Adults With Metabolic Syndrome

Global cognition is assessed with the Montreal Cognitive Assessment (MoCA) a screening tool designed to identify mild cognitive impairment (MCI) and other cognitive deficits. The MoCA takes around 10-15 minutes to complete and consists of 30 items (range=0-30). Higher scores mean a better outcome.

Sustained attention is measured with the Test of Word Accentuation. Scores range from 0-30, higher scores mean a better performance.

Verbal memory is measured with the Auditory Verbal Learning Test (AVLT). It is a word-learning test where five presentations of a 15-word list are given, each followed by an attempted recall. This is followed by a second 15-word interference list (list B), followed by recall of list A. Delayed recall and recognition are also tested. For each trial, the score ranges from 0 to 15, with higher scores indicating better memory performance. The total learning score (sum of the five List A trials) ranges from 0 to 75. Delayed recall and recognition scores also range from 0 to 15. Higher scores indicate better verbal memory performance.

Auditory attention is measured with Digit Span Forward (WAIS-IV). Participants are asked to repeat numbers in the same order as read aloud by the examiner. Scores range from 2 to 8, with higher scores indicating better attention span.

Working memory is assessed using Digit Span Backward (WAIS-IV), where participants repeat number sequences in reverse order. Scores range from 2 to 8, with higher scores indicating better working memory.

Processing speed is measured with the Digit Symbol Coding subtest from the WAIS-III. It consists of replacing symbols that lack verbal meaning with numbers based on a key. Scores range from 0 to 133, with higher scores indicating better processing speed.

Conners Continuous Performance Test - 3rd Edition (CPT-3) is task-oriented computerised assessment of attention-related problems. Participants are presented with a repetitive array of visual stimuli on a computer screen for 14 min. Participants are instructed to press the space bar every time a letter other than "X" appears and to not press the space bar when "X" appears. The rate of stimulus presentation varies according to 1, 2, and 4 s intervals throughout the task. Measures: Correct Detection (Higher rates indicate better outcome), Reaction times (Lower scores indicate better outcome), Omission errors (Lower rates indicate better outcome), and Commission errors (Lower rates indicate better outcome).

Visuospatial memory is assessed with the Brief Visuospatial Memory Test - Revised (BVMT-R). Immediate memory is evaluated through the total score of three learning trials, with scores ranging from 0 to 36. Delayed memory is assessed through free recall (score range: 0 to 12) and recognition (number of correctly identified figures, corrected for false positives). Higher scores indicate better visuospatial memory performance.

Verbal episodic memory is assessed with Logical Memory I and II (WMS-IV), evaluating immediate and delayed recall of short stories. Scores range from 0 to 25 for each story, with a maximum total score of 50 when two stories are administered. In addition, a recognition phase is included, with scores ranging from 0 to 30. Higher scores across all components indicate better verbal episodic memory.

Visual scanning and processing speed are measured with the Trail-Making Test-A version. Participants are asked to connect a series of numbered circles on a page in numerical order. Completion time is recorded in seconds, with lower scores indicating better performance.

Executive functioning and cognitive flexibility are measured with the Trail-Making Test-B version. Participants are asked to connect a series of circles that contain both numbers and letters in alternating numerical and alphabetical order. Completion time is recorded in seconds, with lower scores indicating better performance.

Executive functioning is assessed with the Modified Wisconsin Card Sorting Test (M-WCST), which evaluates abstract reasoning, cognitive flexibility, and the ability to shift problem-solving strategies. Performance is scored based on the number of categories completed, total errors, and perseverative errors. Higher scores in perseverative errors (range: 0 to >23) and total errors (range: 0 to >31) indicate worse performance, while more categories completed reflect better executive functioning (range: 0 to 8).

Selective attention, inhibition, and processing speed are measured with the Stroop Color and Word Test. Participants are asked to name the color of a series of color patches (Stroop Color Naming), read a series of color words (Stroop Word Reading), and name the color of a series of color words where the word and color do not match (e.g., the word "red" written in blue ink), Stroop Color-Word Interference. Higher scores mean a better outcome.

Phonemic verbal fluency is assessed using the PMR test, in which participants are asked to produce as many words as possible beginning with the letters P, M, and R, one minute per letter. The total score is the sum of all correct, non-repeated words across the three trials. Higher scores indicate better phonemic fluency and executive function.

Semantic verbal fluency is assessed with a category fluency task in which participants are asked to name as many words as possible belonging to a specific semantic category (e.g., animals, fruits) within one minute. The total score is the number of correct, non-repeated words produced. Higher scores indicate better semantic fluency and lexical access.

Body weight measured in kilograms, used as an indicator of metabolic status.

Waist circumference measured in centimeters at the midpoint between the lower margin of the last palpable rib and the top of the iliac crest. Indicator of abdominal fat.

Systolic and diastolic blood pressure measured in mmHg using an automated sphygmomanometer after 5 minutes of rest.

Fasting glucose levels obtained from a venous blood sample after 8-12 hours of fasting. Indicator of glycemic control.

Lipid profile including total cholesterol, HDL, LDL, and triglycerides measured via fasting blood samples (milligrams per deciliter (mg/dL)).

Serum insulin measured after overnight fasting using standardized immunoassay methods. Reflects insulin resistance.

Functionality is measured with a 12-item World Health Organization Disability Assessment Schedule-II (WHODAS-II). Patients are asked to state the level of difficulty experienced, considering how they usually do the activity. The scale scores each item as "none" (1) to "cannot do" (5). The total score is calculated with an SPSS syntax, and the range varies from 0 to 100, with higher scores reflecting more significant disability.

Quality of Life is measured with EuroQol a self-completion questionnaire, which consists of five questions: covering mobility, hygiene, activities, pain, and anxiety. The descriptive system divides each of the 5 dimensions into three levels of response: the absence of a problem, some problem, and extreme problem. Lower scores indicate better outcomes. In addition, the questionnaire has a plus scale where the participants rated their health state on a scale of 0-100. In this scale, higher scores indicate better outcome.

The WHOQOL-BREF assesses quality of life (QOL) within the context of an individual's culture, value systems, personal goals, standards and concerns.

Cognitive reserve is assessed with the Cognitive Reserve Questionnaire, which evaluates factors such as education, occupation, and engagement in cognitive and social activities. Scores range from 0 to 24, with higher scores indicating greater cognitive reserve.

Treatment expectations are assessed with the Expectation for Treatment Scale (ETS), a validated questionnaire that measures participants' beliefs and expectations about the potential benefits of the intervention. Total scores range from 5 to 25, with higher scores indicating more positive treatment expectations.

Subjective cognitive complaints are measured using the MiCog questionnaire, which evaluates participants' perceived difficulties in daily cognitive functioning. Total scores range from 0 to 24, with higher scores indicating more cognitive complaints.

General health is assessed using the Goldberg Health Questionnaire, a screening tool for psychological distress and general well-being. Higher scores indicating higher psychological distress.

Depression is measured with the Patient Health Questionnaire-9 (PHQ-9) which scores each of the 9 DSM-IV criteria as "not at all" (0 points) to "nearly every day" (3 points). Total scores range from 0 to 27, with higher scores indicating more severe depressive symptoms.

Anxiety is measured with the 7-item Generalized Anxiety Disorder Scale (GAD-7), a Likert-type scale with questions ranging from "not at all" (0 points) to "nearly every day" (3 points). The maximum score is 24. Higher scores mean a worse outcome.

Healthy lifestyle habits are evaluated using the Healthy Lifestyle Questionnaire, a validated Spanish-language instrument that evaluates physical activity, nutrition, and psychological well-being. Total scores range from 0 to 120, with higher scores indicating healthier lifestyle behaviors.

Sedentary behavior is measured with the short version of the Sedentary Behavior Questionnaire (SBQ-s), which asks about time spent in sedentary activities on weekdays and weekends. Total scores are reported in average hours per day, with higher values indicating greater sedentary behavior.

Sleep Quality is measured with The Pittsburgh Sleep Quality Index (PSQI). This test presents 24 items, although only 19 are taken into account for the correction. This test is divided into 7 dimensions, namely, sleep quality, sleep onset latency, sleep duration, sleep efficiency, sleep disturbances, hypnotic drugs, and daytime dysfunction. Total scores range from 0 to 21, with higher scores indicating worse sleep quality.

Physical performance is assessed using the Short Physical Performance Battery (SPPB), which includes balance, walking speed, and chair stand tests. Each component is scored from 0 to 4, and the total score ranges from 0 to 12, with higher scores indicating better physical function.

Intima-media thickness of the carotid arteries is measured using Doppler ultrasound to assess subclinical atherosclerosis.

Eye-tracking tasks will measure cognitive processing through saccades, fixations, and pupil response during attention and memory tasks.

Intraocular pressure (IOP) measured in both eyes using Goldmann applanation tonometry (millimeters of mercury (mmHg). Reflects ocular and cerebrovascular dynamics.

Retinal vascular density measured using Optical Coherence Tomography Angiography (OCTA). Reported as percentage of perfused area in superficial and deep retinal layers.

Peak systolic velocity (PSV) of the ophthalmic artery will be measured by Doppler ultrasound. Values are expressed in centimeters per second (cm/s). Higher values may reflect increased arterial flow.

End-diastolic velocity (EDV) of the ophthalmic artery will be measured by Doppler ultrasound. Values are expressed in centimeters per second (cm/s).

The resistive index (RI) of the ophthalmic artery will be calculated using Doppler ultrasound as (PSV - EDV) / PSV. The RI is a dimensionless value ranging from 0 to 1, with higher values typically indicating increased vascular resistance.

Gut microbiota is assessed using 16S rRNA sequencing. Permeability markers include zonulin (ZO-1) and lipopolysaccharide-binding protein (LBP).

Serum levels of total cholesterol, HDL-cholesterol, LDL-cholesterol, and triglycerides will be measured. Values will be reported in mg/dL. Lower LDL and triglycerides, and higher HDL, are considered more favourable cardiovascular risk profiles.

Apolipoprotein B (ApoB), apolipoprotein A1 (ApoA1), and lipoprotein(a) [Lp(a)] will be measured. Units will be reported as mg/dL or nmol/L, depending on the marker. Higher ApoB and Lp(a) levels indicate greater cardiovascular risk, while higher ApoA1 is considered protective.

Plasma activities of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and γ-glutamyl transferase (GGT) will be measured by standard kinetic assays. Results are expressed in U/L; lower values indicate better liver function.

Serum insulin concentration will be determined by chemiluminescent immunoassay and reported in µU/mL; lower values reflect better insulin sensitivity.

Plasma glucose will be measured by the hexokinase method and expressed in mg/dL.

Glycated haemoglobin will be analysed and reported as percentage of total haemoglobin (%); lower percentages indicate better long-term glycaemic control. Only for prediabetic and diabetic participants.

Serum urea, creatinine and uric acid will be measured by enzymatic assays and reported in mg/dL.

GFR will be calculated and expressed in mL/min/1.73 m²; higher values denote better kidney function.

Urinary albumin-to-creatinine ratio will be determined and reported in mg/g creatinine; lower values indicate better renal integrity.

Serum sodium, potassium and calcium will be quantified and expressed in mmol/L.

Serum leptin will be measured and reported in ng/mL.

Serum cortisol will be determined and expressed in µg/dL.

Serum TSH will be analysed by immunoassay and reported in mIU/L.

Serum CPK will be measured and expressed in U/L.

Serum BHB will be quantified and reported in mmol/L.

Plasma levels of IL-1β, IL-6, TNF-α and IL-10 will be determined using commercial ELISA kits. Values are expressed in pg/mL; lower pro-inflammatory (IL-1β, IL-6, TNF-α) and higher anti-inflammatory (IL-10) levels are considered favourable.

Serum BDNF will be quantified and reported in ng/mL; higher concentrations may reflect enhanced neuroplasticity.