Instrumental Activities of Daily Living in Neurocognitive Disorders: Determinants and Clinical Implications for Health Promotion

<b>Background/Objectives</b>: Instrumental Activities of Daily Living (IADL) are the key indicators of the autonomy and functional ability in older adults with neurocognitive disorders (NCDs). However, the specific predictors of IADL performance across the NCD spectrum remains insufficiently characterized. This study aimed to identify the cognitive, motor, and caregiver-related determinants of the IADL in individuals with minor and major NCDs. <b>Methods</b>: A cross-sectional study was conducted involving 117 participants referred from a university-based dementia clinic. Standardized tools were administered to evaluate their IADL performance (Lawton IADL Scale), cognition [Addenbrooke's Cognitive Examination III (ACE-III)], Functional Cognitive Assessment Scale (FUCAS)], motor functions, balance, and mobility [Tinetti Test, Timed Up and Go (TUG)], emotional status [Geriatric Depression Scale (GDS)], neuropsychiatric symptoms [Neuropsychiatric Inventory (NPI)], and caregiver burden [Zarit Burden Interview (ZBI)]. Multiple regression analyses were performed to identify the significant predictors of IADL performance. <b>Results</b>: In the total sample (n = 117), the IADL performance was significantly predicted via ACE-III, FUCAS, and Tinetti-balance (adjusted R² = 0.729). In the minor NCD group (n = 41), the significant predictors included sex, FUCAS, GDS, Tinetti-balance, and TUG (adjusted R² = 0.725). In the major NCD group (n = 76), ACE-III, FUCAS, and Tinetti-balance remained the significant predictors (adjusted R² = 0.634). Female sex and a worse profile on the other variables were associated with lower IADL scores. <b>Conclusions</b>: Global cognitive decline, executive dysfunction in everyday problem-solving situations, and balance impairment are the key determinants of IADL performance across both minor and major NCDs. Female sex and depressive symptoms further predicted the IADL performance in the minor NCD group. These findings highlight the need for multidisciplinary assessment and intervention strategies to promote health and autonomy and preserve the functional independence in older adults with NCDs.