Nagi Model of Disability

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Nagi used the term, pathology, pathophysiology, impairment, functional limitation and disability to describe health status. These term can be used to categorize clinical observations systematically.

Nagi Model


Disease is "a pathological condition of the body or abnormal entity with a characteristic group of signs and symptoms that affect the body". Aetiology can be known or unknown. Signs are direct observable or measurable evidence of physical abnormality while symptoms are the more subjective reactions to the physical abnormality.


Impairments (direct) are the result of pathology or disease states and include any loss or abnormality of physiologic, anatomic, or psychologic structure or function. For a patient with stroke, examples of impairments that are the direct result of pathology might include sensory loss, paresis and hemianopia. Impairments may or may not be permanent.

Secondary impairments (indirect) are the sequelae or complication (eg. Decubitus ulcer, DVT, UTI, Pneumonia, Depression)

Functional Limitation

“The restriction of the ability to perform at the level of the whole person, a physical action, task or activity in an efficient, typically expected or competent manner. BADL Basic ADL – Dressing, feeding, bathing IADL Instrumental ADL – House cleaning, preparing meals, shopping, managing finance, etc


The term disability refers to societal rather than individual functioning, it is defined as an inability to perform or a limitation in the performance of actions, tasks and activities usually expected in specific social roles that are customary for the individual or expected for the person’s status or role in a specific sociocultural context and physical environment. Categories of required roles included are self care, home management, work and community/ leisure.

Terminologies associated with disability

Activity - The nature and extent of functioning.

Function - Activities essential to support physical, social and psychological well being.

Health - State of complete physical, mental and social wellbeing.

Quality of life: The sense of total well-being that encompass both physical and psychosocial aspect of the patient's life.

Participation: The extent of a person’s involvement in life situations in relation to impairments, activities, health condition and contextual factors. Participation may be restricted in nature, duration and quality.

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