Functional Status and Activities of Daily Living

Functional status describes a person's ability to carry out the activities required for independent living, and activities of daily living (ADL) are the standardised tasks used to measure it. In older adults, function is a core outcome and organising concept of geriatric assessment, often more informative than diagnosis alone for capturing health and care needs.

Definition

Functional status is the degree to which a person can independently perform the tasks of everyday life; activities of daily living are the standardised set of such tasks — typically divided into basic self-care activities and instrumental activities — used to operationalise and measure that ability.

Scope

This entry covers the distinction between basic activities of daily living and instrumental activities of daily living, the classic instruments used to measure them, and the role of functional status as an outcome in geriatric assessment. It treats functional assessment as a methodological topic, not as treatment guidance.

Core questions

• What distinguishes basic from instrumental activities of daily living?
• Why is functional status often more informative in older adults than diagnosis alone?
• How do standardised ADL and IADL instruments operationalise independence?

Key concepts

• Basic activities of daily living (ADL)
• Instrumental activities of daily living (IADL)
• Katz Index of ADL
• Lawton-Brody IADL scale
• Functional independence and dependence
• Function as a geriatric outcome

Mechanisms

Functional assessment operationalises independence by scoring performance on defined tasks. Basic activities of daily living cover self-care such as bathing, dressing, toileting, transferring, continence, and feeding, captured by the Katz Index, while instrumental activities such as managing finances, medications, transportation, shopping, and meal preparation are captured by the Lawton-Brody scale and reflect the more complex skills needed to live independently in the community. Loss often follows a graded pattern, with more complex instrumental tasks affected before basic self-care, so the two scales together describe a spectrum of independence and are widely used as outcomes in geriatric assessment.

Clinical relevance

Functional status is a core descriptor in geriatric medicine and a frequently used outcome in comprehensive geriatric assessment and its evidence base. This entry explains how function is conceptualised and measured and how it is used as an outcome; it is reference-educational and is not a basis for individual diagnostic or treatment decisions.

Epidemiology

Functional limitation in basic and instrumental activities becomes more common with advancing age and is associated with adverse outcomes in older populations. Because functional decline frequently precedes or accompanies disease in later life, ADL and IADL measures are routinely used to characterise older cohorts and as endpoints in geriatric trials.

History

The systematic measurement of everyday function in older adults was established in the 1960s. Katz and colleagues introduced the Index of ADL in 1963 to standardise the assessment of basic self-care, and Lawton and Brody extended the approach in 1969 to instrumental activities needed for community living. These instruments became foundational to functional assessment and were incorporated into the comprehensive geriatric assessment frameworks consolidated in later decades.

Debates

Self-report versus performance-based measurement of function

ADL and IADL instruments often rely on self- or proxy report, which can diverge from directly observed performance; how best to measure function, and whether performance-based measures should supplement scales, remains a methodological question.

Key figures

• Sidney Katz
• M. Powell Lawton
• Elaine M. Brody
• Laurence Z. Rubenstein

Seminal works

• katz-1963
• lawton-1969

Frequently asked questions

What is the difference between ADL and IADL?

Basic activities of daily living (ADL) are self-care tasks such as bathing, dressing, and feeding, measured by instruments like the Katz Index; instrumental activities of daily living (IADL) are more complex tasks needed to live independently, such as managing finances and medications, measured by scales like the Lawton-Brody IADL scale.

Why is functional status emphasised in older adults?

Because function captures the practical consequences of disease, frailty, and cognitive change for everyday independence, it often describes an older person's health and care needs more fully than a list of diagnoses, and it is a common outcome in geriatric assessment.