Functional Status

Functional status is a common health measure used in both clinical care and research. The general domains of functional status are physical, mental, and sometimes social. Numerous self-report and clinician-rated instruments for measuring functional status exist in the public health literature. Poor functional status has been shown to be associated with chronic medical conditions, comorbidities, age, and mortality. Functional status is a broad term that has come to encompass a number of concepts that can vary with the many different instruments developed for its measurement. Although sometimes used interchangeably, functional status can differ conceptually from health status or quality of life.

Functional status originated as a measure of disability status, but it has come to be commonly used as a health research measure. Some make a distinction between functional status (how one does something) and functional ability (the capacity to do something). Functional status is often based on assessment of individuals’ performance of activities without assistance from other people or assistive technology. In addition, functional status measures can be specific to different conditions or generic. Condition-specific measures are intended to assess functional limitations caused by the specific disease/disorder of interest. Generic measures are designed to assess functional status outside of a specific medical context.

Among the most commonly used measures of physical functioning are those that assess activities of daily living (ADL) and instrumental activities of daily living (IADL). ADL are activities related to personal care and include bathing or showering, dressing, getting in or out of bed or a chair, using the toilet, and eating. IADL are activities related to independent living and include preparing meals, managing money, shopping for groceries, performing housework, and using a telephone.

Mental functional status is often based on cognitive function, psychological symptom severity, or social role function such as ability to engage in social activities or in work. Cognitive activities assessed include orientation to date and place, recall, language skills, attention span, ability to calculate, and to identify objects. Commonly assessed psychological symptomatology include feelings of depression, anxiety, phobias, stress, confusion, problems concentrating, problems making or keeping friends, and interacting with others.

Toward the end of the 20th century, and influenced by the social model of disability, assessment of functional status developed to include contextual considerations as in the World Health Organization's (WHO) International Classification of Functioning, Disability, and Health (ICIDH-2, hereafter ICF). The purpose of the ICF classification is to allow a unified and standard language for assessing health and health-related components of well-being. It allows a person's functioning and disability to be viewed as a dynamic interaction between health conditions and contextual factors. By integrating multiple dimensions of disability (i.e., structural and functional impairments, activity limitations, participation restrictions, and environmental factors), the ICF is intended to characterize functional status in terms of the interaction between intrinsic individual characteristics and extrinsic social phenomena. The ICF approach is considered by some to be more empowering to individuals because it does not classify people but rather the situations in which they live and experience health and health-related concerns.