Continuous quantitative variable: cm.

Continuous quantitative variable: kg/m².

Circumferences (arm and calf). Continuous quantitative variable. Unit of measurement: Millimeters (mm).

Body dynamometry measures the maximum voluntary isometric contraction (MVIC), which is the greatest force a muscle can generate without changing its length, or isokinetic strength, which is the force generated across a range of motion at a constant angular velocity. The primary variable is force, which reflects the muscle's ability to produce tension. Continuous quantitative variable. In general clinical practice using a handgrip dynamometer (a common and standardized measure), minimum values can be very low (e.g., under 10 kg for older, frail, or sarcopenic individuals). Very low values are often indicative of frailty or severe muscle wasting. Maximum values can reach or exceed 60 kg for strong, healthy, and athletic adult men.

Unit of measurement: kg.

Diet serves to classify subjects into distinct, non-ordered categories based on their primary eating patterns (omnivore, vegetarian, vegan, pescatarian, keto, mediterranean). Nominal qualitative variable.

Categorical qualitative variable: 25%, 50%, 75%, and 100%.

Dichotomous qualitative variable: SARC-F Questionnaire (Strength, Assistance in walking, Rise from a chair, Climb stairs, Falls). The SARC-F measures five key components related to muscle function and strength, which are reported by the individual being assessed. Each component is scored from 0 to 2 points. The total score is the sum of the points from the five components, resulting in a range from a minimum value of 0, which indicates the lowest risk for sarcopenia, to a maximum value of 10 (5 components x 2 points/component), which indicates the highest risk for sarcopenia. The SARC-F is primarily interpreted using a simple cut-off point for screening: a score of >4 points is considered positive and indicates a high risk for sarcopenia.

Discrete quantitative variable: Mini-Nutritional Assessment (MNA). It is designed to identify elderly individuals who are malnourished or at risk of malnutrition. It comprehensively evaluates several factors that influence nutritional status, including anthropometric measurements, general lifestyle and functional capacity, dietary changes, and self-perception of health and nutritional status. It is crucial for early intervention in geriatric care. The MNA produces a single score ranging from a minimum value of 0 (indicating severe malnutrition) to a maximum value of 30 (indicating satisfactory nutritional status). Scores are then grouped into categories: <17 (malnourished), 17.5 to 23.5 (at risk of malnutrition), and > 24 (well-nourished).

Categorical qualitative variable: Zarit Burden Interview (ZBI). The ZBI assesses the subjective stress, strain, and emotional distress felt by the caregiver. It consists of 22 items (in the full version) rated on a 5-point Likert scale ranging from 0 (Never) to 4 (Nearly always). The total score is the sum of the points from all 22 items, resulting in a range from a minimum value of 0, which indicates no burden is perceived by the caregiver, to a maximum value of 88 (22 items x 4 points/item), which indicates the highest level of perceived burden. The score is interpreted using established cut-off points to categorize the level of burden: scores typically ranging from 0 to 20 suggest no or minimal burden; scores between 21 and 40 indicate mild to moderate burden; scores from 41 to 60 suggest moderate to severe burden; and scores from 61 to 88 denote severe burden.

Discrete quantitative variable: Caregiver Strain Index. The CSI measures the caregiver's perception of strain across three main domains related to their caregiving role: Financial Strain, Physical Strain, and Emotional and Social Strain. The questionnaire consists of ten statements about common sources of strain. The caregiver responds to each item with a simple "yes" (strain is present) or "no" (strain is absent). The total score is calculated by summing the number of "yes" responses. The score ranges from a minimum value of 0, which indicates no strain is perceived by the caregiver, to a maximum value of 10 (10 items x 1 point/item), which indicates the highest level of perceived strain. The CSI is interpreted using a key cut-off point: a score of >7 points is generally considered clinically significant, indicating a high level of caregiver strain.

The total amount of stored fat in the body, including essential (vital for life and reproductive functions) and non-essential (storage) fat. It's a key component in assessing body composition, often used to determine the degree of obesity and related health risks. Continuous quantitative variable.

A healthy minimum body fat percentage for men is around 5%, and for women, around 10-13% (due to essential fat). Absolute minimum for survival is closer to 1-3% for men and 8-12% for women, but these are dangerously low values. Maximum value can exceed 50% of total body weight in cases of severe obesity. There is no biological maximum, but values over 40% often indicate high health risk.

Unit of measurement: Kilograms (kg or %).

The portion of the body that does not contain fat. It is composed primarily of muscle, bone, water, and internal organs (e.g., bone mineral mass, protein mass). It represents the metabolically active tissue and is a major determinant of Basal Metabolic Rate (BMR). Continuous quantitative variable. Minimum value varies widely based on height and body type, but generally represents a large proportion of total weight, typically over 50% of total body mass. Maximum value highly dependent on the individual's size, muscle mass, and hydration status. Unit of measurement: Kilograms (kg).

The total amount of water in the human body, encompassing both Intracellular Fluid (ICF) and Extracellular Fluid (ECF). Water is the largest component of Fat-Free Mass and is essential for nearly all physiological functions. It is a key indicator of hydration status. Continuous quantitative variable. Minimum value represents a large part of the body. Healthy adult men typically have 50-65% of their body mass as water, while healthy adult women typically have 45-60%. Values below this can indicate severe dehydration. Maximum value cannot biologically exceed the physiological upper limit (around 65-70% for the general population), as body water is homeostatically controlled. Excessively high values may indicate conditions like edema. Unit of measurement: Liters (L), Kilograms (kg), or Percentage (%) of total body weight.

A raw measure derived from Bioelectrical Impedance Analysis (BIA) that relates the resistance and reactance of body tissues. It is a non-invasive indicator of cellular health, integrity, and function. A higher phase angle is generally associated with greater cell membrane integrity, better nutritional status, and greater muscle mass. A lower angle may indicate cell breakdown, poor health, or malnutrition. Minimum value can be as low as 2º or 3º in severely malnourished, ill, or elderly patients. Maximum value typically ranges up to 9º or 10º in healthy, muscular, or athletic individuals. Unit of measurement: Degrees (º).

Dichotomous qualitative variable: Yes, No.

Categorical qualitative variable: Barthel Index. It is a foundational ordinal scale used primarily in rehabilitation and geriatric medicine to measure a person's level of independence in activities of daily living (ADLs) and functional mobility. It assesses ten essential areas: feeding, bathing, grooming, dressing, bowel control, bladder control, toilet use, transfers (bed to chair), mobility (walking or wheelchair), and climbing stairs. The total score reflects the individual's ability to perform these tasks with or without assistance, providing a clear indication of their care needs and the effectiveness of rehabilitation interventions. The Barthel Index ranges from a minimum value of 0, which signifies a totally dependent state requiring maximum assistance in all activities, to a maximum value of 100, which indicates complete independence in all ten functional areas.

Through Fried criteria. It is a widely recognized and simple clinical method used to identify and classify the physical frailty status of older adults. It specifically focuses on the physical decline associated with aging. The result of the Fried Criteria is a count of the deficits (criteria) met, ranging from 0 to 5. Minimum value: 0, which indicates the individual is considered Non-frail (or Robust). Maximum value: 5, which means the individual meets all five criteria, indicating Severe Frailty. The results are typically categorized into three clinical states: Robust/Non-frail (0 criteria met), Pre-frail (1 or 2 criteria met), Frail (3 or more criteria met).

Categorical qualitative variable: Falls Risk Detection Scale. It is a clinical screening tool used primarily in hospital and institutional settings to assess a patient's risk of falling. Its main purpose is to quickly identify individuals who require preventative measures to reduce their risk of falls during their stay. Minimum value: 0, indicating the lowest risk of falling. Maximum value: The maximum possible score can vary significantly, often up to 90 or more, indicating the highest risk of falling. Score Range: Low risk (0-24 points), moderate risk (25-50 points), high risk (>50 points).

Discrete quantitative variable: number of admissions.

Continuous quantitative variable: days.

Continuous quantitative variable: euros. Will be calculated by multiplying the days of admission or hospital stay by the daily cost of life.

Discrete quantitative variable: number of aspiration episodes.

Discrete quantitative variable: number of respiratory infection episodes.

Discrete quantitative variable: number of aspiration-derived pneumonia episodes.