Functional Assessment: ADLs and IADLs

Functional assessment using Activities of Daily Living (ADLs) and Instrumental Activities of Daily Living (IADLs) is a structured clinical method for measuring how well an older adult can perform the tasks essential to independent life. These tools sit at the core of comprehensive geriatric assessment and directly influence care planning, eligibility determinations, and placement decisions. Understanding the distinction between ADLs and IADLs — and how each is scored and interpreted — is foundational to the geriatric evaluation process.

Definition and scope

ADLs and IADLs are standardized frameworks that classify an individual's functional capacity across two tiers of daily activity. The distinction between the two tiers is clinically significant: ADLs measure basic self-care functions, while IADLs measure the more complex cognitive and logistical tasks required for community living.

ADLs — commonly assessed using the Katz Index of Independence in Activities of Daily Living — cover 6 domains:
1. Bathing
2. Dressing
3. Toileting
4. Transferring (moving from bed to chair)
5. Continence
6. Feeding

Sidney Katz and colleagues at the Benjamin Rose Hospital in Cleveland developed the Katz Index in the 1960s; it remains among the most widely validated instruments in geriatric medicine (Katz et al., JAMA, 1963).

IADLs — assessed using the Lawton-Brody IADL Scale, published by M. Powell Lawton and Elaine Brody in 1969 — cover 8 domains:
1. Using the telephone
2. Shopping
3. Food preparation
4. Housekeeping
5. Laundry
6. Mode of transportation
7. Responsibility for own medications
8. Ability to handle finances

The Lawton-Brody scale scores each domain 0–1, yielding a maximum score of 8 for full independence. The Katz Index produces a summary score from 0 (complete dependence) to 6 (full independence).

Both instruments are recognized by the Centers for Medicare & Medicaid Services (CMS) in long-term care assessment requirements, including the Minimum Data Set (MDS) used in nursing facility resident assessments under 42 CFR Part 483.

The regulatory and clinical landscape governing these tools is explored in depth at /regulatory-context-for-geriatrics.

How it works

Functional assessment is conducted through clinician observation, structured interview, or proxy report (typically from a family caregiver). The choice of method affects reliability: direct observation is the gold standard, but structured interview with the patient and caregiver achieves acceptable inter-rater reliability in most validated studies.

Katz Index administration:

The clinician rates each of the 6 ADL domains as independent or dependent based on performance over the preceding 2 weeks. "Independent" requires no supervision, direction, or personal assistance. Partial assistance counts as dependent in the original binary scoring format. A score of 6 indicates full independence; a score of 0 indicates complete functional dependence across all basic self-care tasks.

Lawton-Brody IADL Scale administration:

Each of the 8 IADL domains is scored on a hierarchy of function (e.g., for telephoning: 1 = operates telephone on own initiative; 0 = does not use telephone at all). The original scale applied different scoring conventions to men and women for tasks like cooking and laundry, reflecting 1969-era assumptions; contemporary clinical practice typically scores all 8 domains for all patients regardless of sex.

Both assessments are brief — the Katz Index takes approximately 10–15 minutes; the Lawton-Brody scale takes 10–20 minutes — making them feasible within standard geriatric outpatient and inpatient workflows. The broader geriatric assessment process integrates these functional scores alongside cognitive screening, fall risk evaluation, and medication review.

Common scenarios

Post-hospitalization decline: Hospital-associated deconditioning is a recognized risk in adults over 70. A patient admitted with pneumonia and previously scoring 6/6 on the Katz Index may discharge with a score of 3 or 4, flagging the need for home health, physical therapy, or short-term rehabilitation. The /index of geriatric concerns addressed in this resource reflects how frequently functional decline follows acute illness.

Dementia staging: Progressive loss of IADLs typically precedes ADL loss in Alzheimer's disease and related dementias. A patient who can no longer manage finances or medications (IADL impairment) but still bathes and dresses independently represents an early-to-moderate functional stage. This pattern informs both safety planning and caregiver support intensity.

Long-term care eligibility: Medicaid personal care and nursing facility eligibility in most US states requires documented ADL dependency. Specific threshold requirements vary by state, but dependency in at least 2 of the 6 Katz ADL domains is a common benchmark used in level-of-care tools administered under state Medicaid plans, consistent with CMS guidance on functional criteria.

Caregiver burden assessment: IADL deficits often drive the invisible burden on family caregivers — managing medications, arranging transportation, and handling finances fall to informal caregivers when the older adult loses those capacities. Structured IADL scoring makes this burden visible and documentable, supporting referrals to palliative care and community support services.

Decision boundaries

The Katz and Lawton-Brody instruments have defined clinical boundaries that determine when and how their findings should be acted upon.

ADL vs. IADL priority: IADL deficits typically emerge first and signal the need for supportive services and safety monitoring. ADL deficits signal a higher level of functional impairment, often requiring personal care assistance or supervised living environments. Clinicians use the trajectory — stable, declining, or fluctuating — as much as the absolute score.

Acute vs. chronic functional loss: A sudden drop in ADL score (e.g., a 3-point decline within 2 weeks) warrants evaluation for reversible causes — delirium, new medication effects, infection, or orthopedic injury — before attributing the change to chronic disease progression. The delirium-sudden-confusion resource details the clinical overlap between acute cognitive and functional decline.

Screening vs. diagnostic use: ADL and IADL scores are screening and monitoring instruments, not diagnostic tests. A Katz score of 3/6 does not by itself establish a diagnosis; it documents a functional state that must be interpreted alongside cognitive screening (MMSE/MoCA), fall risk data (fall risk assessment), and medication review (polypharmacy evaluation).

Proxy reliability: When patients cannot self-report due to cognitive impairment, proxy respondents (caregivers, family members) tend to overestimate functional deficits compared to direct observation — a systematic bias documented in the gerontological literature. Clinicians weigh proxy reports accordingly, particularly when scores approach eligibility thresholds for care transitions.

Serial assessment: Single-point scores are less informative than longitudinal tracking. CMS requires quarterly MDS reassessment in certified nursing facilities, partly because functional trajectory over 90-day intervals is a stronger predictor of care needs and outcomes than any single measurement.

References

• Katz S, et al. "Studies of Illness in the Aged." JAMA, 1963. Abstract available via JAMA Network
• Lawton MP, Brody EM. "Assessment of Older People: Self-Maintaining and Instrumental Activities of Daily Living." The Gerontologist, 1969. Oxford Academic
• Centers for Medicare & Medicaid Services (CMS) — Minimum Data Set (MDS) 3.0 for Nursing Home Resident Assessment
• 42 CFR Part 483 — Requirements for States and Long Term Care Facilities (eCFR)
• Hartford Institute for Geriatric Nursing — Try This Series: Katz Index of Independence in ADLs
• Hartford Institute for Geriatric Nursing — Try This Series: Lawton IADL Scale

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