Functional status is measured by the ability of people to perform basic and instrumental activities of daily living (ADLs). Basic activities of daily living (BADLs) consist of self-care tasks and include feeding, bathing, dressing, using the toilet, personal hygiene, ability to transfer from bed to chair and back again, and walking.  Instrumental activities of daily living (IADLs) allow a person to live independently in a community. They include the ability to use the telephone, perform housework and laundry, shop, prepare meals, manage finances, take medications, and arrange appropriate transportation.  More advanced ADLs include hobbies and leisure activities.
Information on functional status can be obtained during a patient interview and typically does not require a questionnaire. Screening for geriatric syndromes helps to identify risk factors for and causes of functional impairment. Identification of such syndromes and initiation of appropriate assessment and management strategies may also foster preservation of function. Several validated screening tools have been published to screen for many of these syndromes:
Delirium: Confusion Assessment Method (CAM), Richmond Agitation Sedation Scale (RASS)
Dementia: Short Portable Mental Status Questionnaire, AD8, Mini-Cog
Depression: Geriatric Depression Scale, PHQ-9, Cornell Scale for Depression in Dementia
Malnutrition: Mini Nutritional Assessment (MNA)
Pain: Verbal Pain Descriptors, Pain Thermometer, Faces Scale for Pain
Falls: Get-Up-and-Go (timed and modified), Single Limb Stance Test, Functional Reach. 
Functional decline in and of itself should not be considered a geriatric syndrome but rather an indicator of the negative impact that geriatric syndromes and acute/chronic medical conditions may have on an individual. Threats to functional independence arise from physical and cognitive limitations as a process of normal aging or the accumulation of chronic illness. Management of chronic illness is a key factor in preserving function. To optimize function as a result of the aging process, physical and cognitive interventions may be used when possible. Counseling patients regarding exercise and following up with them regularly has been shown to have a positive effect on mobility and helps preserve independence in community-dwelling elders.  In one meta-analysis, participation in exercise was shown to increase gait speed, balance, and performance in ADLs in frail older adults.  Physical interventions include regular exercise, balance training, participation in resistance training, and endurance training. Cognitive interventions include participating in leisure activities and in cognitively stimulating activities (cognitive training). Despite the focused nature of many of these activities, their benefits may overlap. For example, participating in cardiovascular physical activities may also benefit cognitive function. [ ] The evidence for many of the interventions remains unclear, and longitudinal studies are required. However, given the potential benefit of preserving and optimizing the functional status of older people, there appears to be limited risk in implementing these interventions. Guidelines supporting such interventions have been published. 
Cleveland Clinic Lerner College of Medicine of Case Western Reserve University
Geriatric Medicine Fellowship Program Director
Center for Geriatric Medicine, Medicine Institute
RF is a Pfizer stockholder.
Assistant Professor of Medicine
University of Florida
SRM declares that he has no competing interests.
Geriatric Medicine Fellowship
Department of Geriatrics
Boonshoft School of Medicine
Wright State University
SS declares that he has no competing interests.
Department of Medicine
Academic Medical Center
University of Amsterdam
ML declares that he has no competing interests.
Professor of Geriatrics (Emeritus)
St George's Hospital
University of London
PM declares that he has no competing interests.
Use of this content is subject to our disclaimer