Population Cohort Set-up for the Epidemiological Assessment of Balance Disorders in Elderly People

Static posturography measures the displacement of the center of pressure while standing on a force platform. Greater sway indicates poorer balance control. Also looks at dynamic stability.

The balance assessment is based on the comparison of the parameters that best discriminate the pathology of the general population with those obtained from patterns of normality segmented by age (database of the Institute of Biomechanics of Valencia). Ratings are displayed in percentages, so that results other than 100% reflect discrepancy with respect to normal values. It is considered pathological when the results are less than 95%, indicating that these subjects are more likely to present an alteration in the studied system. Pathological values for the limits of stability are considered to be below 85%.

The test measures whether the participant is able to stand on one leg without support for 5 seconds.

Time in seconds taken to rise from a chair, walk 3 meters, turn around, return, and sit down again. Shorter times indicate better functional mobility and lower fall risk.

The Tinetti assesses gait and balance. It consists of two components: balance (maximum 16 points) and gait (maximum 12 points), for a total score ranging from 0 to 28 points. Higher scores indicate better balance and gait performance, and lower risk of falls.

The Short Physical Performance Battery is an objective tool for measuring functional capacity, balance, and lower limb strength in adults over 65 years old. The test includes three different domains to assess functional mobility: gait, sit-to-stand, and balance. A score below 8 indicates mobility and physical exercise limitations and is associated with a higher risk of mobility disability and, consequently, a higher risk of falls. A score of 8 or higher is considered within the normal range.

This includes the test of the gimp leg and center of gravity assessment, as well as Romberg Test variants: Eyes Open (REO), Eyes Closed (REC), and on Foam Pad (RuFP), as performed in the posturography test. The Nintendo Wii provides accurate measures of body center of pressure (COP), an important metric for balance stability assessment approximating the body's center of mass. The Romberg test assesses gait disturbance caused by abnormal proprioception, disequilibrium from central vertigo, and peripheral vertigo. Patients is asked to stand with feet together, arms next to the body, first with eyes open and then closed. The patient tries to maintain his balance. The test is scored by counting the seconds the patient can stand with eyes closed.

Measurement of force in kilograms of the lower extremities using a hand-held dynamometer or similar device. Higher values indicate greater muscle strength

Measurement of usual walking speed (in seconds) over a distance of 6 meters. Higher speeds indicate better functional mobility.

The VREM is a short version in Spanish of the Minnesota Leisure Time Physical Activity Questionnaire (CAFM). It is a tool designed to assess the quality and quantity of physical activity performed during leisure time. It consists of 6 items that evaluate the physical activity performed in the last month, taking into account only the activities performed during free time.

The energy expenditure is quantified in MET-min/14 days by multiplying the METs of each physical activity by its duration (in minutes) by the frequency accumulated in the month prior to the interview and by the months of the year in which the activity was performed. Furthermore, it is divided by 365 days/year and multiplied by 14 days. Then, it is classified according to the energetic cast:

• Very active: Energy index higher than 5,000 METs-min/14 days.
• Active: Energy index between 3,000 and 4,999 METs-min/14 days.
• Moderately active: Energy index between 1,250 and 2,999 METs-min/14 days.
• Sedentary: Energy index

The scale evaluates complex daily activities (e.g., cooking, managing finances). Scores range from 0 (low function, dependent) to 8 (high function, independent). Higher scores indicate better functional capacity.

Assesses performance in basic activities such as bathing, dressing, and feeding. Scores range from 0 to 100. Higher scores indicate greater independence.

Health status will be assessed using the Health Assessment Tool (HAT), a composite measure integrating the following five health dimensions:

• Physical function, assessed by gait speed (measured over 4 meters);
• Cognitive function, assessed by the Mini-Mental State Examination (MMSE), ranging from 0 to 30, with higher scores indicating better cognitive function;
• Chronic morbidity, determined by the number of diagnosed chronic conditions recorded using the ICD-10 classification system;
• Mild disability, assessed using the Lawton-Brody Instrumental Activities of Daily Living (IADL) scale, excluding household tasks to reduce gender bias;
• Severe disability, assessed using the Barthel Index for basic activities of daily living (ADLs), focusing on five essential self-care tasks (bathing, toileting, transferring, eating, and dressing).

These dimensions will be combined to generate a composite health status profile, according to the HAT methodology.

Retinal images will be analyzed to assess microvascular parameters using two software tools:

• IMEDOS Vessel Map software (IMEDOS Systems UG, Germany) will be used to measure retinal vessel diameters and calculate central retinal arteriolar equivalent (CRAE), central retinal venular equivalent (CRVE), and arteriolar-to-venular ratio (AVR).
• SIRIUS software (University of A Coruña) will be used to calculate retinal vessel tortuosity and arteriovenous (A/V) ratio.

These parameters serve as non-invasive biomarkers of microvascular health.

Fear of falling will be assessed using the Short Falls Efficacy Scale - International (Short FES-I), a 7-item self-reported questionnaire that evaluates concern about falling during basic daily activities. Each item is rated from 1 (not at all concerned) to 4 (very concerned), yielding a total score from 7 to 28. Higher scores indicate greater fear of falling.

Participants will self-report the number of falls experienced in the 12 months preceding study enrollment, along with fall-related consequences (e.g., injuries, fractures, hospitalizations). The variable includes both quantitative (number of falls) and qualitative (presence of consequences) components.

Comorbidity will be assessed using the Charlson Comorbidity Index (CCI), a validated method for classifying prognostic comorbidity in longitudinal studies. The CCI assigns weighted scores based on the presence of 17 predefined chronic conditions.

Additionally, the total number of chronic conditions and specific ICD-10 diagnoses recorded in the patient's electronic health record will be documented.

Cognitive function will be assessed using the MMSE, a 30-item scale. Total scores range from 0 to 30, with higher scores indicating better cognitive function.

Cognitive impairment will be assessed using the SPMSQ, a 9-item scale. Scores range from 0 to 9 errors. Scores greater than 5 errors indicate moderate to severe cognitive impairment.

Perceived loneliness will be assessed using the 3-item UCLA Loneliness Scale (UCLA-3), which evaluates subjective feelings of social isolation and lack of companionship. Each item is scored from 1 (hardly ever) to 3 (often), for a total score ranging from 3 to 9. Higher scores indicate greater loneliness.

Loneliness will also be assessed using the De Jong Gierveld Loneliness Scale, a validated 6-item questionnaire that distinguishes between emotional and social loneliness. Items are scored and interpreted following the official scoring algorithm, with higher scores indicating greater loneliness.

Blood samples will be collected from participants for future analysis of biomarkers related to frailty and sarcopenia. The collected samples will be stored for use in subsequent studies aimed at identifying and validating relevant biomarkers.