Katz Index of Independence in Activities of Daily Living

The Katz Index measures basic, fundamental self-care — bathing, dressing, toileting, transferring, continence, and feeding — that nearly everyone must do for personal survival and that is lost relatively late in the disability process. Instrumental ADL scales, such as the Lawton-Brody scale, measure more complex skills needed to live independently in the community, such as using the telephone, shopping, cooking, housekeeping, managing transportation, medications, and finances. These higher-order functions tend to be lost earlier, so the two instruments capture different levels of disability and are typically used together for a fuller picture.

Katz observed that the activities are lost in a consistent order during decline and regained in the reverse order during recovery, with bathing usually impaired first and feeding preserved longest. This mirrors the developmental sequence in which children acquire these skills. The practical consequence is that the items behave like a cumulative scale: a person dependent in a later-lost activity such as feeding is almost always already dependent in the earlier-lost ones, so the count of preserved activities usually implies which specific abilities remain. This ordering gives the summary score more interpretive meaning than a simple checklist would.

Independence means performing the activity without supervision, direction, or active personal assistance, and it should be based on what the person actually does rather than what they might be able to do under ideal conditions. Refusal to perform an activity is scored as dependence even if the person is physically capable. The use of equipment or assistive devices by itself does not make someone dependent, since the question is whether another person's help is needed. Being explicit about these conventions is important because differences in how independence is interpreted are a common source of score variation between raters.