U.S. Department of Health and Human Services
A Framework for Identifying High-Impact Interventions to Promote Reductions in Late-Life Disability
Vicki A. Freedman, Nancy Hodgson, Joanne Lynn, Brenda Spillman, Timothy Waidmann, Anne Wilkinson, and Douglas A. Wolf
September 27, 2006
This report was prepared under contract #HHS-100-03-0011 between the U.S. Department of Health and Human Services (HHS), Office of Disability, Aging and Long-Term Care Policy (DALTCP) and the Urban Institute. For additional information about this subject, you can visit the DALTCP home page at http://aspe.hhs.gov/_/office_specific/daltcp.cfm or contact the ASPE Project Officers, William Marton and Hakan Aykan, at HHS/ASPE/DALTCP, Room 424E, H.H. Humphrey Building, 200 Independence Avenue, S.W., Washington, D.C. 20201. Their e-mail addresses are: William.Marton@hhs.gov and Hakan.Aykan@hhs.gov.
The Project Team (authors) are listed alphabetically. Jeannette Rogowski also served as a consultant to the project. The project team thanks Karen Kohn for her excellent assistance with identifying and tracking references. The opinions and views expressed in this report are those of the authors. They do not necessarily reflect the views of the Department of Health and Human Services, the contractor or any other funding organization.
Motivation and purpose. Considerable evidence now suggests that the prevalence of disability among older Americans is declining. This finding suggests that not only are older people living longer, but they may be enjoying more years of active life.
How best to implement intervention strategies to promote continued or accelerated declines in disability prevalence remains unstudied. Studies of disability trends among the population ages 65 and older have focused almost exclusively on establishing trends in disability prevalence and, to a lesser extent, potential explanations for those trends. Studies of individual interventions occasionally include projected effects at the population level, but in general such studies do not facilitate explicit comparisons among various types of interventions.
Identifying high-impact interventions to reduce disability prevalence requires reconceptualizing disability at the individual level and translating those ideas into population-level implications. The purpose of this report is to develop and begin to demonstrate a new framework for comparing the population-level effects of different types of interventions.
With the framework in mind, we reviewed the literature for seven illustrative interventions, seeking to learn how existing strategies compare. To focus the scope of this exercise, we purposefully limited our attention to interventions that were existing but not already widespread, had some published evidence demonstrating efficacy, and if implemented, could provide benefit within a few years. We selected the following interventions from a list of 12 by tabulating rankings provided by external reviewers with input from the Office of the Assistant Secretary for Planning and Evaluation and project team members:
- Implement smoking cessation programs for the older population.
- Improve exercise. The literature review focuses on exercise interventions in frail but otherwise healthy elderly people.
- Implement good chronic disease care. To narrow this set of interventions, we focus on chronic disease care for a commonly disabling condition: congestive heart failure (CHF).
- Implement depression screening, treatment, and follow-up.
- Implement fall prevention systems for frail elderly persons.
- Modify homes and provide assistive devices.
- Implement widespread care planning for seriously ill people.
We also reviewed the relatively limited literature evaluating multi-component interventions aimed at preventing or alleviating disability in late-life.
Conceptual underpinnings of framework. The proposed conceptual framework extends existing frameworks and models in several ways. First, building on the Institute of Medicines disablement process framework,1 the approach distinguishes among interventions designed to affect an individuals risk along different junctures of the disablement process from onset of disease to death. Second, building on Lunney and colleagues,2, 3 the proposed approach explicitly recognizes that interventions are often designed for and targeted at individuals with specific diseases and injuries, many of which conform to one of three prototypical trajectories: (1) a short period of evident decline (e.g., in patients with cancers); (2) moderate and slowly declining functioning with intermittent exacerbations and sudden dying (e.g., organ system failures); and (3) a prolonged period of disability before death (e.g., dementia, disabling strokes and frailty). Third, we extend well-established notions in the epidemiological literature about risk factors and health outcomes to explicitly address the effect of interventions aimed at altering distributions of risk factors for late-life disability.
Key factors to consider. The change in cross-sectional disability prevalence that would emerge in the presence and absence of an intervention(s), depends on three key factors:
- At which trajectory(ies) and at what point in the disablement process is the intervention targeted? What are the competing risks for other trajectories, causes of disability, and death?
- What is the size of the target population among the current older population and among future cross-sections? That is, how large a target population has the risk factor(s) targeted by the given intervention?
- What is the effect of the intervention on disability (either directly on disability or indirectly through shifts in functioning or illness trajectories) and mortality? The effect in the population will be influenced by:
- the risk factors influence on disability and mortality;
- the interventions efficacy in reducing the risk factor (how well it works in ideal circumstances) over time;
- the likely extent of adherence to the intervention in the target population (what percent maintain the protocol) in the short-run and longer-run; and
- the generalizability of study results (i.e., the difference between the composition of the at-risk population and those in clinical trials in factors related to the efficacy of the intervention).
In the proposed framework we consider disability to be the inability to carry out tasks independently, that is, without help from another person. Thus, in this framework, an environmental modification (e.g., addition of grab bars or ramp) that allows an individual to maintain independence would be considered an intervention that reduces the prevalence of disability. The approach we develop allows for a discussion of tradeoffs in both the short-term and long-term.
What is high-impact? Our interest is in identifying and comparing potentially high-impact interventions. We estimate that in a one-year period, it would take approximately 175,000 fewer people ages 65 and older with disability to generate a 1% decline in disability (e.g., from 20% to 19.8%). To gain a sense of what a high-impact intervention might achieve in the longer term, we created a very simple simulation to suggest what combinations of: (1) trajectory dynamics, (2) target population size, and (3) effects on disability and mortality, would be needed to sustain a 1% per year decline in disability. Our calculations suggest that a number of scenarios could move the age-adjusted disability rate, for instance, from 20% to 16% in 20 years. For example, one scenario would require interventions that would drastically reduce the expected years with a disability with no improvements in longevity for people in two trajectories--from 2.0 to 0.5 for people who die from cancer and from 3.0 to 1.0 for people who experience organ failure. A less drastic, but still sizeable, compression would be required for interventions aimed at the third trajectory (frailty/dementia). That is, the disability rate would be reduced by 1% per year from an intervention that reduced the expected years with a disability from 5.0 to 3.6 but did not alter life expectancy among people in this trajectory. Similar reductions could be achieved by postponing the onset of all three trajectories and adding four years of active life on average over the next 20 years.
Short-term comparisons. To compare short-run effects of the illustrative interventions, we compared interventions along three dimensions: size of the population with the targeted risk factor; short-term risk of disability associated with the targeted risk factor; and short-term effectiveness of the intervention in alleviating targeted risk factor. We found that comparisons across studies were particularly challenging because measures of disability, composition of study populations, and follow-up periods varied widely. Moreover, we were unable to identify a comprehensive study documenting either the relative importance of or co-occurrence of the environmental, physical, and psychological causes of disability. Nevertheless, we found:
Variation in the size of population with targeted risk factor. Interventions vary widely in the size of the population with the targeted risk factor. Three of the seven interventions we reviewed may be aimed at a large (10-18 million) target population: exercise, fall prevention, and depression screening and treatment; three other interventions--smoking cessation, management of CHF, and advanced care planning--target a substantially smaller population. Depending on how the target population is defined, assistive technology/home modifications fall somewhere in between.
Variation in short-term risk of disability associated with targeted risk factor. Interventions vary in effectiveness in part because they target fundamentally different kinds of risk factors for disability. One can, however, group risk factors (and intervention efforts) by the stage of the disablement process at which they are targeted. All else equal, secondary (CHF management, depression management, fall management) and tertiary prevention efforts (assistive technologies and environmental modifications) aimed at groups already experiencing disease or disability will have the greatest effect in the short run. Primary prevention strategies aimed at disease onset (exercise, smoking cessation) will have a weaker impact in the short-run.
Effects of intervention on risk factors and on disability. Of the seven interventions reviewed, there was evidence of a potentially modest effect on risk factors of interest for four of them: smoking cessation programs that combine counseling with pharmacologic treatment; exercise programs that increase strength, balance, and physical activity of older adults; depression screening, combined with referral and feedback, and combination therapy/pharmacologic treatment; and multi-factor fall prevention programs. Of those four, only three have been linked to reductions in risks of disability: exercise, depression screening and treatment, and fall prevention programs. The short-term effects of a population-based exercise intervention and of depression screening and treatment on disability risks are likely to be modest whereas multi-factor programs that successfully reduce the risk of falling could potentially have a large effect on the risks of disability.
Long-term comparisons. To compare long-term effects of the illustrative interventions, we considered three additional dimensions: How will the size and composition of the target population change in the future? At which trajectory is the intervention targeted and what are the competing risks? What are the effects of the intervention over the remaining lifetime? In particular, how will the intervention affect mortality as well as disability? We found:
Some targeted risk factors are already on the decline. Several well-known demographic trends have been identified which will influence the effectiveness of interventions--the aging of the population, its increasing racial and ethnic diversity, increases in obesity and related chronic conditions, and increases in educational attainment. In addition, for several of the interventions investigated here, we found evidence of ongoing trends. For instance, four of the seven risk factors of interest--inactivity, smoking, depression treatment, and assistive technology/home modification--appear to be moving already in a direction consistent with disability decline. There is also some evidence that injuries due to non-fatal falls have decreased and that advance care planning is increasing slowly. In contrast, CHF appears to be increasing. Limited information is available on trends in the joint distribution of these risk factors.
Variation in trajectories targeted and competing risks. Each of the illustrative interventions we reviewed may be targeted at one or more illness trajectories. Exercise and fall prevention, for example, are primarily targeted to older adults whose life experience is exemplified by a prolonged period of disability and frailty before death. CHF management is clearly targeted to a specific type of organ failure. Smoking cessation is likely to be geared toward people who go on to develop cancer or organ failure. Depression screening and treatment, assistive technology and environmental modifications, and advanced care planning are not unique to any one trajectory but may be targeted at all three. The issue of competing risks arises mainly for interventions targeted at the prevention of diseases with earlier ages of onset. That is, interventions designed to prevent cancer or organ failure, if successful, could allow people to experience the longer-lived frailty trajectory. Of the seven illustrative interventions reviewed here, consideration of competing risks is most important for smoking cessation.
Important relationships between lifetime disability and prevalence of disability. In longer-run comparisons it is important to understand the interventions effect not only on disability but also upon the length of life and whether (or what proportion of) additional years are free from disability. Intervention studies rarely examine effects beyond a year or two after the intervention, so we turned to life table analyses for insights into this issue. Using life table principles, we demonstrated the comparative effects on cross-sectional disability of hypothetical interventions affecting disease prevention (through shifts in trajectories), disease management (with and without mortality effects), and disability. We found that:
Disease prevention/trajectory shift: Interventions aimed at preventing disease or shifting people from cancer or organ failure trajectories to the longer-lived frailty trajectory resulted in no perceptible change in the population-level prevalence of disability, due to countervailing effects of reduced mortality and increased number of years lived with disability. For example, cutting the chances of eventually dying from cancer or organ failures by half has a negligible effect on the cross-sectional rate of disability.
Disease management: Interventions aimed at managing the course of disease will result in declines in disability prevalence only if: (a) the intervention does not alter the risk of mortality, or (b) resulting changes in disability-free life expectancy exceed changes in disabled life expectancy. For example, the exercise interventions discussed in the literature appear to be targeted at the frailty trajectory and have no apparent effect on mortality. If they delay disability onset by one year in this population (increasing disability-free life expectancy by one year), the estimated effect on disability prevalence is a reduction from 20.3% to 17.6%. Alternatively, suppose that smoking cessation interventions aimed at older people with a diagnosis of cancer or organ failure coincided with such diagnoses and resulted in an extension of life for both trajectories. In this case the disability rate would increase to 21.8%.
Shift in the disability threshold: Whether a limitation in functioning results in disability depends in part on the environment in which tasks take place. If home modifications or assistive technologies could reduce the amount of time spent living with a disability by 25%, disability prevalence would decline from 20.3% to 16.3%. Much smaller reductions (say of 5%) would still yield declines in disability (for example from 20.3% to 19.5%). The role of the environment as a component of late-life disability is not well understood, but merits further consideration.
Mortality-only interventions: An intervention to increase advance care planning may have the effect of reducing the period of disability at the end of life for frail individuals; but, as currently practiced, efforts to increase advance care planning would have practically no effect on the cross-sectional prevalence of disability.
Summary of key findings. Of the seven illustrative approaches we reviewed, evidence of reducing the risks of disability is strongest for exercise interventions, depression screening and treatment, and multi-factor fall prevention efforts. Because they can be targeted at potentially large populations, and may have modest or even potentially large effects on the risks of disability, widespread implementation of such interventions could potentially reduce the prevalence of disability in the short run if adherence issues could be addressed. Little evidence exists, however, about the long-term effects of such interventions on disability and its interplay with length of life.
This exercise has also provided several additional insights into how to reduce population-level disability prevalence among the elderly population. Our most striking finding is that efforts with the largest potential for success are those targeted at individuals whose life experience is exemplified by a prolonged period of disability and frailty before death. Multi-factor interventions that are targeted at frail individuals and that address individualized needs appear to be the most promising. However, both short and long-term effects are critical to consider when evaluating the population-level impact of such interventions.
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Lunney JR, Lynn J, Hogan C. Profiles of older Medicare decedents. Journal of the American Geriatrics Society. June 2002; 50(6):1108-1112.
Lunney JR, Lynn J, Foley DJ, Lipson S, Guralnik JM. Patterns of functional decline at the end of life. Journal of the American Medical Association. May 14, 2003; 289(18):2387-2392.
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