Behavioral Adaptation and Late-Life Disability: A New Spectrum for Assessing Public Health Impacts

Abstract

OBJECTIVES

Promoting independent functioning of older adults requires attention to how older adults carry out basic activities. This paper provides the first national estimates of late-life disability that explicitly recognize behavioral adaptations to functioning.

METHODS

We analyzed the National Health and Aging Trends Study, a study of Medicare enrollees ages 65 and older (N=8,077). For seven mobility and self-care activities we identify five hierarchical stages—fully able, successful accommodation with devices, activity reduction, difficulty despite accommodations, and receipt of help—and explore disparities and associations with quality of life measures.

RESULTS

31% of older adults are fully able to complete self-care and mobility activities. The remaining groups successfully accommodate with devices (25%); reduce their activities (6%), report difficulty despite accommodations (18%), or receive help (21%). With successive stages physical and cognitive capacity decrease and symptoms and multi-morbidity increase. Successful accommodation is associated with maintaining participation in valued activities and high wellbeing, but substantial disparities by race, ethnicity and income exist.

CONCLUSION

Increased public health attention to behavioral adaptations to functional change can promote independence for older adults and may also enhance quality of life.

INTRODUCTION

An unprecedented number of adults in the US will reach late life over the next few decades. The Census Bureau projects that by 2030 the number of older Americans will exceed 70 million (20% of the population)¹ and the vast majority of these individuals will be living with multiple chronic conditions.² The risks of disability increase markedly with age and chronic illness, which in turn has consequences for older adults’ quality of life.³ Although late-life disability prevalence declined over the last quarter century, recent studies suggest such improvements have paused and may reverse course as the Baby Boom enters old age.^4–6 Significantly higher rates among disadvantaged groups also remain a concern.⁷

Consequently, late-life disability remains a prominent public health matter⁸ and maintaining the ability of older adults to function independently in the community an important goal.⁹ Self-care and mobility activities—although not the only targets of functional preservation—have long been recognized as essential to older adults’ well being and to their continued social and community participation and thus are of particular interest. Public health professionals play a unique role in addressing late-life disability by setting and monitoring population-level goals, designing needs assessments for communities, developing programs and policies to maximize functioning, providing information to older adults and their caregivers, and focusing on gaps for high risk groups (e.g., minority, low-income populations).¹⁰

With respect to public health monitoring, for example, Healthy People 2020 has targeted a 10% reduction nationally (from baseline level of 29%) in the proportion of older adults with moderate to severe limitations in daily functioning. Late-life disability is also tracked by the Federal Interagency Forum on Aging Statistics and the Center for Disease and Control and Prevention’s State of Health and Aging Report (at the state level) and has been incorporated into community needs assessments to promote aging preparedness.^11–13 Specific measurement approaches vary. Healthy People 2020, for instance, tracks the proportion of older adults who report having “difficulty by themselves and without special equipment” with basic activities of daily living (bathing or showering, dressing, eating, getting in or out of bed or chairs, walking, or using the toilet). CDC tracks those who either are limited in their activities or use special equipment because of a health problem, and other programs focus on needing help from another person with daily activities.

A common feature of these monitoring efforts is that they do not permit distinctions based on how older adults carry out daily activities. For instance, current approaches do not allow identification of individuals who have successfully accommodated difficulties by using aids such as walkers, grab bars, and other devices, which are increasingly being adopted by older adults to foster independent functioning.^14–15 They also miss altogether individuals who adjust their behavior without recognizing difficulty, for instance by dressing or walking less often (so-called “preclinical” disability^16–17), an at-risk group for whom intervention may delay or deter the need for hands-on care. Hence, current efforts overlook valuable opportunities for assessing public health needs and evaluating program impacts related to independent functioning.

To better address the extent to which the lives of older adults can be improved by public health efforts, a fuller spectrum of functional assessment is needed. Using a new national survey of Medicare beneficiaries, we introduce a five-category hierarchy of late-life mobility and self-care limitations — those who (1) are fully able; (2) have successfully accommodated declines by using assistive technology or environmental features; (3) have reduced their activity frequency but report no difficulty, (4) report difficulty doing activities by themselves, even when using any accommodations they may have in place; and (5) receive assistance from another person. We demonstrate how underlying physical and cognitive capacity and reports of multi-morbidity vary by each successive category. We then provide estimates of disparities for key demographic groups. Finally, recognizing the importance of integrating measures of participation and quality of life into studies of disability,¹⁸ we examine linkages of the new measures presented here to two such indicators: participation restrictions and subjective wellbeing. Discussion focuses on implications for public health practice and tracking population-level care needs.

METHODS

Data

Data are from the first (2011) round of the National Health and Aging Trends Study (NHATS). A sample of adults ages 65 and older was drawn from individuals in the Medicare enrollment file living in the contiguous United States on September 30, 2010, with oversamples by age and for Black, non-Hispanic individuals. The enrollment file represents 96% of all older adults in the United States; the 4% not represented include individuals who were born in another country and never qualified for Social Security benefits and those who remain on employer-based benefits (i.e. delayed enrollment, most of whom are ages 65–69).

Interviews were conducted from May through November 2011 (71% response rate). The sample size for this analysis is 8,077 persons, of whom 468 were nursing home residents. Analytic weights adjust for differential non-response and produce national prevalence estimates.¹⁹ Medicare population estimates are generated by applying estimates of age-specific prevalence to enrollment file totals by age when the sample was drawn.

In-person interviews, conducted in settings other than nursing homes (N=7,609), collected detailed self-reported information on participants’ physical capacity, how participants carry out activities of daily life, and their social, physical, and technological environment. Physical and cognitive performance batteries provided complementary measures of participants’ capacity, and additional survey questions elicited self-reported information on various topics including chronic health conditions, economic status, participation restrictions, and subjective well-being. Proxy respondents were interviewed when the sample person could not respond (N=583). For details see Kasper & Freedman.²⁰

Measures

Mobility and Self-care Disability

NHATS re-engineered the classic activities of daily living measures.²¹ For each activity (going outside, getting around inside, getting out of bed, eating, getting cleaned up, using the toilet, and dressing) participants were first asked about use of devices or environmental modifications (canes, walkers, wheelchairs, scooters, grab bars, bath/shower seat, eating and dressing devices) and help from another person during the previous month. Respondents who ever performed the activity without help were asked about difficulty in the last month when doing the activity alone (with the particular devices or environmental features named earlier, if used). For activities other than getting out of bed, toileting, and eating, participants were asked about changes in the last year in the frequency with which they performed the activity.

From these measures we created five hierarchical categories for each activity: (1) no device use, reduction in activities, difficulty, or assistance (fully able); (2) device use, but no reduction in activities, difficulty, or assistance (successful accommodation); (3) reductions in activities, but no difficulty or assistance (reduced activities) (4) difficulty performing activities (by oneself, when using devices, if used), but no assistance (difficulty); and (5) assistance from another person or, rarely, not doing the particular activity (assistance). We created a summary measure indicating the lowest level of functioning across all seven activities. For the summary measure, nursing home residents were combined with the assistance group and only non-missing cases (99.6% or more for each activity) were considered. All seven activities have statistical properties that suggest they belong in the scale (alpha=0.93) and a validation study conducted by NHATS investigators suggests good test-retest reliability for this type of hierarchical measure over a two-to-four-week period (kappa=0.6).

Physical and Cognitive Capacity Measures and Multi-morbidity

Physical capacity

The NHATS Physical Capacity scale (0–12; alpha=0.88) builds upon the traditional Nagi framework, but measures higher as well as more limited functioning.²² Questions assessed ability in the last month to carry out, without devices or help from another person, the following validated pairs: walk 6 blocks/3 blocks, walk up 20 stairs/10 stairs, lift and carry 20 pounds/10 pounds, kneel down /bend over (without holding on to anyone or anything), put a heavy object on a shelf overhead/reach up over head, open a sealed jar using hands only/grasp small objects.²² Persons who reported they were able to do the first (harder) activity in each pair were not asked the follow-up item. Individuals receive 1 point if they can carry out only the easier task and 2 points for the more challenging task.

We also developed a self-reported symptom scale (0–12; alpha=0.81), which measures pain; exhaustion; breathing problems; limited strength or movement in shoulders, arms, hands; limited strength or movement in hips, legs, knees, or feet; and balance/coordination.³ Individuals receive 1 point if they experienced the symptom in the last month and 2 points if it limited their activities.

NHATS also included several established physical performance measures: usual walking speed over 3m, five balance tests, rapid chair stands, grip strength using a hand held dynamometer, and peak air flow. Following prior studies,²³ usual walking speed, balance tests, and rapid chair stands were combined into the Short Physical Performance Battery (NHATS SPPB; range 0–12). For each test, quartiles were used to assign values 1–4 and 0 was assigned to individuals meeting exclusion criteria related to functioning, unable to complete a test, or not attempting it for safety reasons. Similar procedures were followed for coding grip strength (range 0–4) and peak air flow (0–4).²⁴

We imputed missing scores for the physical performance measures (5%–10% for components and 13% for the NHATS SPPB) multiple times (K=10) based on age, sex, race/ethnicity, proxy status, place of residence, physical capacity, and symptom scores.²⁵ Means reported here by disability level are nearly identical to those with missing cases omitted. Regression-based t-tests establishing the hierarchy of the disability spectrum take into account both sampling variation and imputation uncertainty.

Cognitive capacity

NHATS measured memory through a 10-word recall test. A randomly assigned list of nouns was read to respondents at 2-second intervals.²⁶ Participants were asked to recall as many words as possible, in any order, in up to 2 minutes (immediate recall) and again after a brief interval (delayed recall). For the 7% of participants with missing scores we performed multiple imputations using the previously described strategy.

Multi-morbidity

We created a count of chronic conditions (0–13) to reflect multi-morbidity. We included history of a heart attack, heart disease, high blood pressure, arthritis, osteoporosis, diabetes, lung disease, stroke, Alzheimer’s or dementia, cancer (excluding skin), or a broken or fractured hip, and current symptoms of depression and generalized anxiety (from the validated PHQ-4^27–28).

Race/ethnicity and income

Age and gender were confirmed with participants. Race was reported by respondents and/or proxies using 8 categories (White, Black, American Indian, Alaskan Native, Asian, Native Hawaiian, Pacific Islander, and other). Respondents giving multiple responses were asked to identify a primary race. NHATS also asked whether participants considered themselves Hispanic or Latino. For this study, we classified responses into: White non-Hispanic, Black non-Hispanic, Hispanic, and all other (including unknown). The latter category consists mainly of respondents identifying as Asian.

Information was obtained about the sampled person’s (and their spouse’s/partner’s) income from major sources including: Social Security, Supplemental Security Income, Veteran’s Administration, pension plans, earned income, interest/dividend income from mutual funds/stocks, bonds, bank accounts, or CDs, and retirement account withdrawals. After determining which sources of income the respondent (or spouse/partner) had, respondents were asked to report amounts, and bracketed ranges were provided to those who refused or did not know. A final item asked about total income from all sources with a bracketed range again offered as needed. We used the imputed total income value provided by NHATS, which filled in missing values for 13% of individuals within a reported bracketed value and 31% within an imputed bracketed value.²⁹ We constructed quartiles with cut points at $15,000, $30,000 and $60,000.

Participation restrictions and subjective wellbeing

We constructed a dichotomous indicator of participation restrictions that takes into account individual preferences for different types of activities. For visiting in person with friends or family; attending religious services; participating in clubs, classes or other organized activities; and going out for enjoyment, if the sample person valued the activity (a lot or somewhat) and their health or functioning kept them from doing the activity in the last month they were considered to have a participation restriction. Those who reported that their health or functioning kept them from working, volunteering, or carrying out their favorite activity also were considered to have a restriction.

For self-respondents (N=7,026) we created a scale of subjective wellbeing, (0–22; alpha=0.74) from 4 items reflecting positive and negative emotions (frequency from every day to never in the last month of feeling cheerful, bored, full of life, upset) and 3 reflecting self-realization (extent of disagreement with statements about purpose in life, self-acceptance and environmental mastery).³⁰ Factor analysis confirmed that these items formed one factor with loadings .47 or higher. (An additional item about personal growth did not scale with the others and was therefore omitted.) We imputed cases with missing values (<2%) according to the procedure described above and reverse coded items as necessary so that 0 indicates low wellbeing.

RESULTS

Among the 38 million older adults enrolled in Medicare, only 12 million (31%) are fully able (without accommodation, difficulty or help) to carry out all self-care and mobility activities (Table 1). Nine million (25%) have successfully accommodated and another 9 million either have reduced their activity level but do not report difficulty (2.1 million; 6%) or have difficulty carrying out activities alone (7 million; 18%). The remaining 7.7 million (21%) received assistance in the last month with at least one task (including 1.1 million nursing home residents).

Table 1.

Percentage (95% CI) and Number (in Millions) of Medicare Beneficiaries in Each Stage of the Late-Life Disability Spectrum, and Percentage by Activity

Level	Summary Across Activities			Going outside % (95% CI)		Getting around inside % (95% CI)		Getting out of bed % (95% CI)		Eating % (95% CI)		Bathing % (95% CI)		Toileting % (95% CI)		Dressing % (95% CI)
	% (95% CI)		Number (in Millions)
Fully able	31.0	(29.9,32.1)	12.0	64.1	(62.8,65.4)	69.0	(67.9,70.0)	74.2	(73.1,75.3)	90.0	(89.3,90.7)	53.8	(52.5,55.1)	57.2	(55.8,58.5)	77.5	(76.5,78.5)
Successful   accommodation	24.5	(23.5,25.5)	9.3	6.8	(6.2,7.4)	7.2	(6.6,7.9)	3.8	(3.2,4.3)	0.3	(0.2,0.4)	25.4	(24.3,26,6)	31.0	(29.5,32.6)	1.0	(0.8,1.2)
Activity reduction	5.6	(5.0,6.3)	2.1	7.0	(6.3,7.9)	2.8	(2.4,3.2)	-	-	-	-	2.4	(2.0,2.9)	-	-	1.2	(1.0,1.6)
Difficulty (by oneself,   with accommodations,   if used)	18.4	(17.4,19.5)	7.0	7.7	(6.9,8.5)	10.9	(10.2,11.6)	14.0	(13.3,14.9)	2.7	(2.3,3.1)	7.5	(6.8,8.2)	5.4	(4.8,6.0)	7.2	(6.6,7.8)
Assistance from others	20.5	(19.6,21.4)	7.7	11.3	(10.5,12.1)	6.7	(6.2,7.4)	4.8	(4.4,5.4)	4.0	(3.5,4.5)	7.6	(7.0,8.2)	3.1	(2.7,3.6)	9.9	(9.4,10.6)
Nursing home	-		-	3.0	(2.7,3.3)	3.0	(2.7,3.3)	3.0	(2.7,3.3)	3.0	(2.7,3.3)	3.0	(2.7,3.3)	3.0	(2.7,3.3)	3.0	(2.7,3.3)
Missing	-		-	0.1	(0.0, 0.2)	0.4	(0.3,0.6)	0.2	(0.1,0.3)	0.0	(0.0,0.2)	0.3	(0.2,0.5)	0.3	(0.2,0.6)	0.2	(0.0,0.3)
Total	100.0		38.1	100.0		100.0		100.0		100.0		100.0		100.0		100.0

The distribution of older adults across this spectrum varies by activity (remaining columns of Table 1). For instance, 90% of older adults are fully able to eat by themselves whereas this is true for only 54% for bathing. Successful accommodation is highest for bathing and toileting (most often using grab bars, bath seats, and raised toilet seats; not shown) and lowest for eating and dressing. Having reduced activity is most common for going outside (7.0%) whereas difficulty is highest for getting out of bed (14.0%) and assistance most common for going outside (11.2%) and dressing (9.9%).

The categories in the proposed spectrum are hierarchical and largely distinct (Table 2). Mean mobility performance (SPPB) scores, for instance, fall progressively with each successive category, ranging from nearly 9 (of 12) for those in the fully able category to under 3 for the group who receives assistance. SPPB components follow this pattern, as do grip strength, peak air flow, memory tests, and self-reported measures of physical capacity, symptoms and multi-morbidity. Within the intermediate categories, distinctions are statistically significant for the SPPB, walking speed, and self-reported measures. Moreover, those who limit their activities have similar balance and chair rise scores to those successfully accommodating and similar strength and cognitive capacity scores to those who report difficulty, suggesting the category is appropriately placed.

Table 2.

Physical and Cognitive Capacity Scores and Number of Chronic Conditions by Stage in the Late Life Disability Spectrum (Means; Non-nursing home based population)

	Test or Scale (Range):
	SPPBa (0–12)	Usual Walking Speed (0–4)	Rapid Chair Stands (0–4)	Balance Stands (0–4)	Grip Strength (0–4)	Peak Air Flow (0–4)	Immediate Word Recall (0–10)	Delayed Word Recall (0–10)	Physical Capacity (0–12)	Symptoms (12–0)	Chronic Conditions (0–13)
Fully able	8.6*	2.9*	2.7*	3.0*	2.8*	2.8*	5.2*	3.9*	11.3*	1.5*	1.9*
Successful accommodation	7.2*	2.5*	2.2	2.5	2.3*	2.5*	5.0*	3.6*	10.1*	2.2*	2.4*
Activity reduction	6.7*	2.2*	2.1*	2.4*	2.1	2.2	4.6	3.1	9.2*	3.3*	2.7*
Difficulty (by oneself, with accommodations, if used)	5.6*	2.0*	1.5*	2.1*	1.9*	2.2*	4.6*	3.3*	7.9*	5.3*	3.2*
Assistance from others	2.7	1.0	0.7	1.0	1.3	1.6	3.2	2.2	4.2	6.5	4.1
(N=7609)

^*p<.01 for test of difference from next (lower) functioning group

^aShort Physical Performance Battery

The proportion of the population that falls into each stage of the spectrum shifts dramatically with age (see Table 3; χ²=876.5, p<.001). For instance, about 45% of individuals ages 65–69 are fully able to carry out mobility and self-care activities independently whereas only 4% of those 90 or older do so, consistent with a linear decline. By contrast, the percentage receiving assistance increases exponentially from 11% at age 65–69 to nearly 62% by age 90. Two of the intermediate groups show a pattern of gradual increase with age, peaking at ages 75–84 for successful accommodation and 80–84 for difficulty despite accommodations, before declining at older ages. Reductions in activity are relatively rare across all age groups (4.5%–7%).

Table 3.

Stage in the Late-Life Disability Spectrum by Age, Gender, Race, Income Quartiles (%)

		(N)	Fully able	Successful accommodation	Activity reduction	Difficulty (by oneself, with accommodations if used)	Assistance from others	Total	X2, p
Age Group
65–69		764	44.6	22.4	4.9	17.1	11.0	100.0	876.5, <.001
70–74		882	39.0	24.4	6.0	17.7	12.9	100.0
75–79		897	27.4	29.2	6.2	19.1	18.1	100.0
80–84		963	19.7	27.1	5.3	21.8	26.1	100.0
85–89		674	10.2	21.8	7.0	19.2	41.8	100.0
90+		612	4.0	15.2	4.5	14.6	61.7	100.0
Gender
Male		3,285	40.0	22.5	4.8	18.0	14.7	100.0	271.9, <.001
Female		4,792	24.3	26.0	6.2	18.7	24.8	100.0
Race/ethnicity
White, non-Hispanic		5,498	31.4	26.4	5.1	18.3	18.9	100.0	146.5, <.001
Black, non-Hispanic		1,788	27.0	17.7	7.4	20.8	27.2	100.0
Hispanic		471	27.3	13.0	9.2	18.0	32.5	100.0
Other		320	37.3	20.5	6.3	16.9	19.0	100.0
Income Quartile
Lowest (<15k)		2,229	22.6	19.2	7.4	20.8	30.1	100.0	581.8, <.001
2nd (15–<30k)		1,968	25.2	23.4	7.4	22.5	21.6	100.0
3rd (30–<60k)		1,891	34.2	29.4	5.0	18.6	12.8	100.0
Highest (60k+)		1,521	45.0	28.3	3.7	14.3	8.8	100.0

Only 24% of older women, compared with 40% of men, are fully able to carry out activities. They are also more likely than men both to receive assistance (24.8% vs.14.7%) and to successfully accommodate (26% vs. 22.5%). Blacks and Hispanics, but not other minorities (who are mostly Asian), and those in the two lowest income quartiles are much less likely than others to be fully able or to successfully accommodate but are more likely to reduce their activity level, report difficulty (Blacks), and receive assistance.

As shown in the left panel of Figure 1, the proposed spectrum has a strong relationship with both participation restrictions (bars; p<.001) and mean wellbeing score (line; p<.001). For instance, only 9% of those fully able to carry out mobility and self care activities have a participation restriction and at the other end of the spectrum 64% of those who receive help with such tasks are restricted. These relationships are not simply due to age; to the contrary, patterns are much flatter when examined by 5-year age groups (right panel of Figure 1). Moreover, models including both limitation and age categories (not shown) demonstrate significant relationships with these outcomes only for limitations Note that those who have successfully accommodated report only slightly higher participation restrictions and similar wellbeing scores than those who are fully able (15% vs. 9% and 18.5 vs. 18.0, respectively).

Figure 1.

Percentage of Older Adults with Participation Restrictions and Mean Wellbeing Scores by Stage in the Late Life Disability Spectrum and Age

DISCUSSION

This study provides new national estimates of self-care and mobility limitations among older adults along a spectrum that incorporates adaptation to functional decline. Findings suggest that one-third of the population ages 65 and older are fully able to carry out self-care and mobility activities, half are managing without assistance to varying degrees of success, and the remaining fifth receive assistance from another person with mobility or some aspect of self-care. Importantly, for the first time with national data we have been able to distinguish 3 groups—amounting to nearly half the older population—who are not fully able but are managing without assistance. Previous national studies,⁴ which yield estimates of difficulty “without help or special equipment” of 20%–27% for older adults living in the community, and up to 29% if the institutional population is included, appear to miss a substantial fraction of this group. Moreover, we demonstrate associations with participation and wellbeing that are independent of age.

A limitation of the current study is its cross-sectional perspective. However, as future rounds of NHATS become available, investigation of individual pathways through the proposed spectrum as well as determinants and consequences of distinct pathways will be possible. In addition, although we demonstrated descriptive associations among disability, participation restrictions, and subjective wellbeing, further investigation into the extent and nature of causal linkages is needed.

Nevertheless, the proposed hierarchy may be helpful for developing, targeting and evaluating the effectiveness of public health policies and programs to curb disability and its negative consequences in late life. Two groups not previously discernible may be especially important targets for public health interventions – the 7 million older adults who have difficulty carrying out activities alone with whatever accommodations they have already made, and the additional 2.1 million who have reduced their activity level but do not experience or acknowledge difficulty. Identification of these individuals opens up the possibility of intervening to fortify individuals’ capacity to carry out these basic activities (e.g. through strength or endurance programs designed to avert deconditioning) and, in cases where restoration of capacity is not possible, to encourage safe and independent use of accommodations (e.g. through home environment or assistive technology programs).

The 9 million older individuals identified as successfully accommodating mobility or self-care activities are also a new group of special interest. Among the activities included here, toileting and bathing were most often successfully accommodated, typically through the use of grab bars and other simple environmental features such as raised toilet seats and bath/shower seats. Such features may accommodate underlying declines in capacity and also prevent progression if they avert, for example, debilitating falls.

Findings suggest that those who are Black or Hispanic and low income may be most important to target with interventions promoting successful accommodation. Communities where minority and low-income groups are prevalent may be especially fruitful targets for programs that promote home modification and identification of assistive devices suited to the individual’s needs and capacities. Notably the use of technological approaches to address functional decline is not associated with substantially reduced quality of life; to the contrary, adults who successfully accommodate seem on average to have levels of participation and subjective wellbeing close to those of persons who are fully able. Future research should investigate whether interventions that foster successful accommodation, particularly among minority groups and past the peak ages of 75–84, yield payoff not only for independent functioning but also for continued participation and wellbeing into very late life.

Finally, this analysis has implications for tracking and interpreting population-level trends in late-life disability prevalence. After many years of steady decline, the U.S. has experienced a plateau in late-life disability prevalence, and recent studies portend a possible reversal in direction.^4–6 Medical and public health advances are thought to be partly responsible for declines prior to 2000,³¹ but whether more older adults were reaching late life fully able to carry out daily activities or were better able than in the past to accommodate deficits in capacity could not be discerned, and reasons for the recent leveling off are equally unclear. As NHATS continues to track the self-care and mobility limitation spectrum introduced here, more nuanced investigations of factors driving trends can be undertaken and projections accordingly fine-tuned. Indeed, better characterizing the care needs of the growing older population is a critical step toward maximizing functioning—and quality of life—for all older adults.