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Table 1 Definitions and measures of key variables

From: Depressive symptoms and malnutrition are associated with other geriatric syndromes and increase risk for 30-Day readmission in hospitalized older adults: a prospective cohort study

Variable name Definition and Measure Used Variable classification in analysis
Frailty A clinical syndrome characterized by increased vulnerability to adverse health outcomes when exposed to acute stressors. Assessed using Clinical Frailty Scale (CFS, range 1–9) Analysed as a categorical variable: non-frail (CFS1-4), mild frailty (CFS 5), moderate frailty (CFS 6), severe frailty (CFS ≥ 7).
Depression Mood assessed using Patient Health Questionnaire-2 (PHQ-2) responses and medical records for prior history of depression PHQ-2 and history combined to derive 4 categories: PHQ-/ History-, PHQ-/History+, PHQ+/History±, uncommunicative
Malnutrition Nutritional status assessed using 3-minute Nutritional Screen (3MNS, range 0–9) Binary: malnutrition (3MNS ≥ 3) vs. non-malnourished
Cognitive impairment Operationalized as impaired performance on Abbreviated Mental Test (AMT, range 0–10), or established diagnosis of dementia from clinical records. Binary variable: AMT and history dichotomized as cognitive impaired (AMT < 8 or history of dementia) vs. unimpaired (AMT ≥ 8, no history)
Delirium An acute neuropsychiatric disorder characterized by inattention, global cognitive dysfunction, disturbance in consciousness, assessed using Confusion Assessment Method (CAM) with 2 core features and at least 1 of 2 other supportive features diagnostic of delirium; any 2 features not meeting diagnostic algorithm classified as subsyndromal Analysed as a binary variable: delirium (including subsyndromal) vs. no delirium
Functional decline Operationalized as the need for incremental assistance in activities of daily living (ADLs: feeding, toileting, dressing, bathing, walking) at discharge compared with patient’s baseline. Each ADL rated as independent, needing assistance or dependent Analysed as a binary variable: functional decline (any ADL registering higher level of assistance relative to baseline) versus no functional decline (stable or improved)
Oral intake Optimal intake was classified as consuming at least ¾ share of each meal ≥ 50% of all provided meals during the admission based on daily review of intake-output charts Analysed as a binary variable: poor oral intake versus optimal intake
Comorbidity burden Assessed using Charlson’s Comorbidity Index (CCI) with weighted CCI - low (0 points), medium (1–2 points), high (3–4 points) and very high (≥ 5 points) Analysed as a categorical variable: low, medium, high, very high
Severity of illness Severity of Illness Index (SII) with 4 levels provide a measure of the burden of illness and how sick a patient is while in hospital, to allow meaningful comparison across diagnostic groups. Binary variable: mild (Level 1 or 2) versus severe (Level 3) as patients in intensive care or high dependency (Level 4) excluded from study
Geriatric syndromes A range of multifactorial conditions that do not fit into discrete disease categories, share risk factors and commonly co-exist in older adults. Admission diagnoses categorized as geriatric syndromes include falls, delirium or cognitive impairment, and functional decline. Frailty and poor oral intake considered geriatric syndromes. Each syndrome analysed as a binary variable (present or absent)