We developed IADL stages as a companion to ADL stages4
and confirmed face validity according to hierarchies of difficulty reported in the literature.8,10,12,37
Together, these two domains comprise Activity Limitation Staging, which could provide a standard ICF-based disability monitoring system for describing self-care and domestic life limitations among older community-dwelling people. Recognizing problems distinguishing between the concepts,38
stages are intended to blend across activity and participation through different levels of measurement.1
Reported status in individual ADLs and IADLs detail activity limitation at the most granular level, specifying problems with individual tasks. ADL and IADL stages, each combining status across six activities, express tasks people are still able to perform across those domains. Combinations of ADL and IADL stages reflect patterns of participation relating to the co-occurrence of difficulties with self-care, and essential interactions with home and community environments (i.e., domestic life).19
Staging is not intended to replace descriptions of limitations across individual ADLs and IADLs or other approaches to measurement.27
Knowledge about difficulties with individual tasks is essential when establishing detailed care plans for an individual. Stages summarize this detailed information globally,22
which, although still specifying the activities individuals can perform, will logically be more beneficial for screening, population surveillance, and prediction.
As in ADL stages,4
construct validity of the IADL stages was supported by demonstration of expected associations. Although the prevalence of hypertension did not increase beyond IADL-I, the likelihood of stroke history increased progressively with stage of IADL limitation. Age, perception of poor health, and the need to use a proxy respondent because of Alzheimer disease or dementia all showed direct increases with higher stages of IADL limitation. The perception of unmet needs for environmental accessibility features increased steadily among those at IADL-I and IADL-II, leveling off at IADL-III and IADL-IV, suggesting thresholds at which the need for environmental adaptation is likely recognized.
Around 5% of older US community-dwelling persons can be expected to have activity limitations that follow the typical order of difficulty and thus are assigned stage III. Examples include people with difficulties eating or toileting but not dressing or bathing and those with difficulties telephoning or managing money but not preparing meals or shopping. Eating and toileting are essential to survival, and these limitations are a more immediate threat than limitations in more complex ADLs. Similarly, telephoning and managing money are more fundamental to life autonomy than the more challenging IADLs. We placed people with nonfitting limitations at a third “severe” stage. This positioning was empirically supported by our finding that people’s likelihood of poor health and disabling conditions increased progressively from stages 0, I, II, III, and IV in both the ADL and IADL dimen-tions.4
IADL and ADL tasks have distinct implication to individuals’ potential to live successfully in the community. Although ADL activities involve self-care and intimate management of body functions, IADL tasks are managed in interactions with places outside one’s self and are more naturally delegated to others. Therefore, they can be functionally irrelevant to those with others who normally do them. Nearly a quarter of older community-dwelling persons in our study were living in circumstances where IADLs were normally done by others.
Healthy People 2020 objectives include initiatives to encourage community life and reduce the number of people with disabilities living in nursing homes.39
Clinicians, health service researchers, and policy makers might use stages to establish and test alternative disability management strategies targeted at keeping people living at home longer. The success of such programs has implications to both the quality-of-life of older people and the overall economic solvency of society.
Staging is illustrated using the following hypothetical examples.
A 79-yr-old woman with insulin-dependent diabetes and right-sided stroke-related hemiparesis lives with her daughter (single working mother with 9-yr-old son). The home is accessible inside with 12 steps to exit.
She responds for ADLs, “I have no difficulty eating, toileting, dressing, or transferring from bed to chair. I have some difficulty bathing and walking.” For the IADLs, she indicates, “I have no difficulty telephoning or managing money but have some difficulty with meal preparation and a lot of difficulty with light housework. I am unable to shop or do heavy housework.”
Case 2 has the same living circumstances and diagnoses as case 1, but her activity limitations differ as follows: her daughter, serving as proxy, states for ADLs, “My mother has no difficulty eating but has some difficulty toileting. She has a lot of difficulty dressing and transferring from bed to chair. She is unable to bathe and has a lot of difficulty walking.” For IADLs, she indicates, “My mother has a lot of difficulty using the telephone; she is unable to manage money, prepare meals, do light or heavy housework, or shop.”
This man has the same living circumstances and diagnoses as case 2, but his activity limitations differ. His wife, serving as proxy, states that he is unable to eat and has some difficulty dressing and bathing but only some difficulty transferring and walking. She notes that none of the IADL activities are relevant because she normally does them.
To assign ADL and IADL stages, answer the clinical questions in using the ADL and IADL definitions from and . Beginning with stage 0, move down the stages until all answers are true.
- Case 1: ADL-I; IADL-II.
- Case 2: ADL-II; IADL-III.
- Case 3: ADL-III; IADL-NR.
Potential Clinical Applications for Screening and Population Surveillance
All cases had stroke and diabetes. The first two have identical histories showing distinctions between people with similar diagnoses and social and physical home environments but different stages. Capable of phoning for help, toileting herself, and walking (with difficulty), case 1 at ADL-1; IADL-II might be safely left alone for portions of the day. Case 2 at ADL-II; IADL-III, in comparison, would be at risk if left alone. Presumably needing to make tough choices between working vs. hiring care-givers, case 2’s daughter, compared with case 1’s daughter, will experience greater burden. Had case 2 been a 79-yr-old man living with his healthy 74-yr-old wife, the implication of the same disability could differ strikingly. If his wife is capable of being his primary caregiver and is normally home during the day, his daughter will be better able to attend to her child rearing and work responsibilities. Case 3’s disability at ADL-III falls outside the typical hierarchy. He experiences more difficulty eating (typically the easiest ADL) than walking (generally the most difficult). This pattern can occur with stroke or other conditions where swallowing or arm(s) are affected disproportionately to legs. Although we do not know about his IADL status, knowledge that he is at IADL-NR is valuable because it indicates the availability of someone to provide functional assistance.
It is important to recognize life contexts such as sex and available support networks when applying IADL stages because they make most sense for those for whom the performance of IADLs is relevant. Definition of the IADL-NR stage allowed us to capture the statistical weights of those for whom IADLs were not relevant. Alternatively, multiple imputation40
could be applied to predict what peoples’ IADL stages would have been from other information about them, assuming they were living in circumstances where they did not have someone normally doing the activities for them.
The stages provide a broad look at individual patients according to their aggregate self-care and domestic life functioning. Accordingly, activity limitation staging might be applied routinely for screening older people during outpatient or home visits by either the individual or family members answering simple questions about ADLs and IADLs ( and ). Using staging in this fashion becomes analogous to a functional review of systems informing areas needing more detailed needs assessment and treatment planning. In addition, integrated systems such as patient-centered medical homes or federally funded area agencies on aging41
might routinely stage persons at entry, applying stages as decision support for referral to preventive, rehabilitative, and supportive services. Broad assessment and management plans and guideline development might be targeted to particular ADL and IADL stages with population-level results continuously monitored through electronic medical records. Serial staging of individuals could monitor functional trajectories and facilitate communication within and across healthcare practitioner teams caring for populations of older community-dwelling people enhancing continuity of care. With declining proportions of younger persons in the US population potentially available to provide care, clinicians will be increasingly called upon to help match limited resources to the needs of people, their families, and their home environments.
Although empirical work in the future will be essential to confirm our assumptions, we believe that alternative combinations of ADL and IADL stages have distinct clinical implications to patients, families, and society. For example, at ADL-0; IADL-I, the most frequent limitation pattern in the elderly US population, there are no self-care difficulties and only limitations with the most complex domestic life chores of shopping and/or heavy housework. In contrast, at ADL-I; IADL-II people can be expected to have some difficulty dressing and/or transferring, and up to a lot of difficulty with the hardest ADL tasks i.e., bathing and/or walking. Able to manage money and use the telephone, these individuals can still exercise autonomy over their personal affairs, but will experience problems performing routine IADLs such as light housework. This suggests need for daily but not necessarily 24 hour assistance or supervision. With ADL-IV; IADL-IV, autonomy for independent living is lost and care burden is maximized with inability to perform all self-care and domestic life tasks.
Potential Research Applications
FI and Activity Limitation Staging were inspired by Tumor, Nodes, Metastases cancer staging,42
which led to revolutionary developments in therapeutic oncology. Tumor, Nodes, Metastases stages define explicit clinically meaningful physiologic states marking both the severity and nature of the tumor, nodes, and metastases. ADL and IADL stages, through defined thresholds of functioning, provide concise dichotomous indicators. These indicators could form functionally homogenous strata of people for studying the effects of various interventions in trials. Although in oncology, T1-N0-M0 indicates a small tumor with no evidence of nodal involvement or metastasis, Activity Limitation Staging defines explicit and clinically meaningful functional states that mark both the severity and nature of disability across domains of ADLs and IADLs. Counts of activity limitations or aggregated scores express the severity of disability. A person who has two IADL limitations has more severity than someone with one limitation, but this count says nothing about the individual’s retained function. Similarly, a person at IADL-II has more severe disabilities than someone at IADL-I, but in addition to expressing severity, the stages document different tasks people are still able to perform. When combining information across the Tumor, Nodes, Metastases domains, the oncologist gains insight about the overall status of the individual’s cancer. Likewise, combining information across the ADL and IADL stages can provide clinical insight into the overall status of the individual’s disability. The Tumor, Nodes, Metastases categorization has undergone extensive testing. In parallel, the predictive validity of ADL and IADL stages will need testing in support of its usefulness. In contrast to the extremes of cure or death typically addressed in oncology, Activity Limitation Stages might be applied to predict functional recovery or losses relevant to quality-of-life.
Potential Policy Applications
Anticipated exhaustion of the Medicare trust fund by 201943
and baby boomers’ needs for long-term care, coupled with the Supreme Court’s 1999 Olmstead decision to offer services in “the most integrated setting” appropriate to individuals’ needs, highlights the importance of establishing cost-effective home- and community-based services.44
Moreover, the National Strategy for Quality Improvement in Health Care includes a mandate to address gaps in data aggregation techniques to measure the results of efforts targeted to improving the delivery of health care, patient health outcomes, and population health.45
As illustrated by the clinical case scenarios, people at different stages can be expected to need different resources and supports. The weighted population prevalence estimates across the stages specify level and quality of demand for care in the older US community-dwelling population. and provide snapshots of the extent and types of expected care needed by the entire older community-dwelling US population at the stage and stage combination levels. Although 1994 prevalence estimates cannot be generalized to today’s population, knowledge of current stage distributions might be applied to project the broad needs of distinct groups of people today. There are millions of mildly limited people but only thousands at the most severe stages. Therefore, society’s total expenditures for care of the more mild could exceed expenditures for the more limited even though per-individual costs of the later might be higher. Functionally homogeneous strata might also serve to forecast need. For example, unmet population needs for home accessibility features accelerating at IADL-I and peaking at IADL-II suggest needs to screen people at these stages.
This study has limitations. It is not realistic to expect all older individuals to be able to answer questions about status. Although close family member proxies might not always reflect what the individual would have said, correlations between self-and proxy-rated function are high,46,47
and excluding people who do not report for themselves biases prevalence more than including information from proxies.48
Although the patient (or close proxy) voice is fundamental, self-report is distinct from functional measurements based on clinician-observed performances.13,26
Self-report measures cannot replace observational measures and vice-versa.
The age of the LSOA II data is concerning. We selected LSOA II data because of their linkage to the National Health Interview Disability Supplement. We could find no other source of national data that included such breadth and depth of information about disability, health conditions, and the physical and social environments within which people live. Field tested by the National Center for Health Statistics questionnaire design research laboratory before use, the ADL and IADL questions would be suitable for collection during outpatient clinical visits or for population surveys of older community-dwelling people.
Although Lazaridis et al., using data from the earlier LSOA I, confirmed that ADLs, as arranged within the Katz hierarchy and reflected in our stages, satisfied traditional requirements of scalability for forming a hierarchy,37
their analyses uncovered four additional hierarchies, suggesting heterogeneity. Moreover, in contrast with ADL and IADL stages for which mobility domains could not be psychometrically justified,4,14
FI stages having different questions include separate domains for mobility and self-care11
consistent with recent measures distinguishing lower limb function.49,50
Future research will undoubtedly identify condition-specific hierarchies or those reflecting dimensions of different functional status measures. The ADL and IADL dimensions were supported within the particular questions and data set applied in our study.48
Measures consisting of different questions or wordings will likely reflect alternative hierarchies or even dimensions. As an example, although persons responding to the English language version of the National Health and Retirement Survey reported walking difficulties most frequently, Hispanics responding to the Spanish-translated version reported dressing difficulty most frequently.51
This suggests that the translated version did not measure walking limitations the same way. Further studies on linguistic and cultural group differences will be essential.