Journal of Gerontology: SOCIAL SCIENCES
2001, Vol. 56B, No. 1, S10–S19
In the Public Domain
Severity of Upper and Lower Extremity Functional
Limitation: Scale Development and Validation
With Self-Report and Performance-Based
Measures of Physical Function
Eleanor M. Simonsick,1 Judith D. Kasper,2 Jack M. Guralnik,1 Karen Bandeen-Roche, 2
Luigi Ferrucci,3 Rosemarie Hirsch,4 Suzanne Leveille,1 Taina Rantanen,1 and Linda P. Fried2
for the WHAS Research Group
1Epidemiology,
Demography, and Biometry Program, National Institute on Aging, Bethesda, Maryland.
Johns Hopkins University Medical Institutions, Baltimore, Maryland.
3Geriatric Department “I Fraticini,” National Research Institute (INRCA), Florence, Italy.
4Centers for Disease Control, National Center for Health Statistics, Hyattsville, Maryland.
2The
Objectives. To better understand disablement and transitions from impairment to disability, discrete valid measures
of functional limitation are needed. This study reports the development and criterion-related validity of scales that quantify severity of upper and lower extremity functional limitation.
Methods. Data are from 3,635 cognitively intact community-dwelling women aged 65 years and older and 1,002
moderately to severely disabled participants in the Women’s Health and Aging Study. Scales assessing severity of upper
and lower extremity functional limitation were constructed from commonly available questions on functional difficulty.
Criterion-related validity was evaluated with self-report and performance-based measures.
Results. The upper and lower extremity scales range from 0 to 6 and 0 to 9, respectively. Scale scores were well distributed in the disabled group and discriminated limitations in the broader community. For both scales, rates of difficulty
for all ADL and IADL increased ( p ⬍ .001) with increasing severity score, and percent able and mean performance on
respective upper and lower extremity tasks decreased (p ⬍ .01).
Discussion. These scales, constructed from commonly used self-report measures of function, provide discrete measures of upper and lower functional limitation. Because these scales are distinct from measures of disability and impairment, their use should facilitate increased understanding of the disablement process.
I
NVESTIGATING the disabling process has become a
major focus of gerontological research; a conceptual
framework has been developed and several complementary
models of the pathway leading from pathophysiology to disability have been proposed (Fried, Herdman, Kuhn, Rubin,
& Turano, 1991; Lawrence & Jette, 1996; Nagi, 1965, 1976,
1991; Verbrugge & Jette, 1994). A common feature and key
component of these models is functional limitation, the state
between physical impairment and disability. Functional limitation is considered a state of high risk for disability (Fried
et al., 1991; Guralnik, Ferrucci, Simonsick, Salive, & Wallace, 1995; Harris, Kovar, Suzman, Kleinman, & Feldman,
1989), but also one in which the greatest benefit from intervention may occur (Pope & Tarlov, 1991). To more fully
understand the disabling process and transitions to and from
functional limitation, researchers need to (a) adopt a uniform definition of functional limitation, (b) consistently apply this definition in selecting and operationalizing measures, and (c) develop reliable and valid scales that
distinguish gradations of severity of functional limitation
(Clark, Stump, & Wolinsky, 1997; Johnson & Wolinsky,
S10
1993; Kelly-Hayes, Jette, Wolf, D’Agostino, & Odell,
1992; Pope & Tarlov, 1991).
Nagi (1965, 1976) developed a model of disablement
similar to the World Health Organization model (World
Health Organization, 1980) but that explicitly distinguishes
an interim state between impairment and disability, labeled
functional limitation (Nagi, 1991). This conceptualization
of functional limitation is accepted widely (Fried et al.,
1991; Lawrence & Jette, 1996; Schroll, 1994; Verbrugge &
Jette, 1994) and has been adopted by the Institute of Medicine (Pope & Tarlov, 1991). Functional limitation occurs at
the level of the organism and constitutes “restriction or lack
of ability to perform an action or activity in the manner or
within the range considered normal that results from impairment” (Pope & Tarlov, 1991, p. 79), such as lifting and carrying 25 lb; whereas disability, “inability or limitation in
performing socially defined activities and roles” (Pope &
Tarlov, 1991, p. 79), such as shopping for groceries, occurs
at the societal level. Rarely have these definitions been applied strictly in analyzing the state between physical impairment and disability. Although the term functional limitation
SEVERITY OF FUNCTIONAL LIMITATION
is used frequently, the measures to which it is applied often
include indicators of disability in the operational definition
(e.g., Boult, Kane, Louis, Boult, & McCaffrey, 1994; Ensrud et al., 1994), which prohibits examination of links between functional limitation and disability (Stuck et al.,
1999). Further, substantial variation in the measurement of
functional limitation restricts cross-study comparisons (Boult
et al., 1994) and can lead to inconsistent results and thereby
impede progress in understanding the disabling process
(Johnson & Wolinsky, 1993; Landerman & Fillenbaum, 1997).
Researchers have used both self-report and performancebased approaches to estimate prevalence and severity of
functional limitation (Guralnik, Ferrucci, et al., 1995; Harris
et al., 1989; Kelly-Hayes et al., 1992; Lawrence & Jette,
1996). Although performance-based measures have several
advantages (Guralnik, Branch, Cummings, & Curb, 1989),
they can be impractical in some settings because they are
time consuming, require face-to-face contact, and are seldom used exclusively. Thus, for developing summary indices of functional limitation, we have focused on self-report
measures, which are more widely available in large-scale,
longitudinal studies of older adults.
Self-report methods typically ascertain inability to perform, need for assistance, and/or the presence and sometimes amount of difficulty or tiredness associated with a variety of functions. These functions are distinct from basic
and instrumental activities of daily living (ADL and IADL)
and are typically represented by physical tasks such as
climbing stairs, walking, grasping and handling, and lifting
and carrying (Nagi, 1976; Rosow & Breslau, 1966). Even
though capacity to perform these functions has been ascertained in several large-scale epidemiologic studies and national surveys (e.g., Established Populations for Epidemiologic Studies of the Elderly, U.S. Bureau of the Census
Survey of Income and Program Participation, Longitudinal
Study on Aging), few researchers have published attempts
to develop and validate summary scales of severity of functional limitation using these or similar data (Avlund, Davidsen, & Schultz-Larsen, 1995; Clark et al., 1997). Although
several composite indices of physical function exist (Avlund et al., 1995; Feinstein, Josephy, & Wells, 1986; Langlois
et al., 1996; Laukkanen, Heikkinen, Schroll, & Kauppinen,
1997), most include ADL and IADL as well as functional
tasks involving both the upper and lower extremities and
thus are not distinct measures of functional limitation
(Johnson & Wolinsky, 1993). In addition, many scales simply sum the number of tasks that present difficulty (e.g.,
Clark, Stump, & Wolinsky, 1998; Lawrence & Jette, 1996;
Lichtenstein, Dhanda, Cornell, Escalante, & Hazuda,1998).
Rarely has degree of difficulty with individual functions
been utilized in scale construction, despite evidence that
amount of difficulty is associated with increasing age and
disability in ADL (Foley, Berkman, Branch, Farmer, &
Wallace, 1986; Guralnik, Fried, Simonsick, Kasper, & Lafferty, 1995) and decreased physical activity (Simonsick,
Guralnik, & Fried, 1999). Simple counts can pose limitations for tracking decline over time, because persons with
even minor difficulties may lie at the most severe end of the
scale (Feinstein et al., 1986). Moreover, because a lot of difficulty in one area may have similar if not greater implica-
S11
tions for function than minor difficulties in two areas, simple counts may misclassify severity of limitation.
Our primary objective in this article is to report the development of separate scales that quantify severity of functional limitation in the upper and lower extremities using
commonly available self-report measures of functional difficulty. These scales are intended to have a broad range in
order to detect small but potentially meaningful amounts of
change (Feinstein et al., 1986). Our second objective is to
establish the criterion-related validity of these scales using
self-report measures of disability and performance-based
measures of physical impairment, functional limitation, and
disability. Because the scales are intended to capture functional limitation, we expect the scales to show a stronger association with other measures of functional limitation than
with measures of disability and impairment.
METHODS
Study Population
The study population consisted of participants in the
Women’s Health and Aging Study (WHAS), a prospective
study of the causes and course of disability in women aged
65 years and older, conducted by the Johns Hopkins Medical Institutions and supported by the Epidemiology, Demography, and Biometry Program of the National Institute
on Aging. Participants were recruited from an age-stratified
random sample of Medicare beneficiaries residing in 12
contiguous zip code areas in the eastern part of Baltimore
City and a part of Baltimore County, Maryland. Study eligibility was determined from an in-person screening interview conducted in participants’ homes. Women who reported difficulty with one or more tasks in at least two out
of four domains of functioning and who were not severely
cognitively impaired (scored at least 18 on the Mini-Mental
State Examination; Folstein, Folstein, & McHugh, 1975)
were eligible to participate. Table 1 lists the functional domains and tasks representing each domain. More complete
details of the study objectives, design, and screening ap-
Table 1. Tasks and Functional Domains Used for
Eligibility Screening
Domain
Tasks
Mobility/exercise tolerance
Walking 1/4 mile
Walking up 10 steps without resting
Getting in and out of bed or chairs
Doing heavy housework
Upper extremity
Raising arms up over the head
Using fingers to grasp or handle
Lifting or carrying 10 lb
Higher functioning (instrumental
activities of daily living)
Self-care (activities of daily living)
Using the telephone
Doing light housework
Preparing meals
Shopping for personal items
Dressing
Bathing or showering
Using the toilet
Eating
S12
SIMONSICK ET AL.
proach have been published elsewhere (Guralnik, Fried, Simonsick, Kasper, & Lafferty, 1995; Kasper, Shapiro,
Guralnik, Bandeen-Roche, & Fried, 1999). In brief, of
5,316 women selected, 4,137 (78%) were contacted and
screened for eligibility. Of the screened population, 3,635
(88%) were cognitively intact and were administered the
physical functioning questions. Of the total population
screened, 1,409 (34%) were study eligible and 1,002 (71%
of those eligible) participated by completing an intervieweradministered questionnaire and physical assessment and
nurse-administered physical examination in the home.
Study Variables
Self-report measures of functional limitation.—In the
screening interview, for each of the items listed in Table 1,
participants were asked, “By yourself, that is, without help
from another person or special equipment, do you have any
difficulty . . . ?” If difficulty was present, the level of difficulty experienced—“a little” (1), “ some” (2), “a lot” (3), or
“unable to do” (4)—was ascertained. Those reporting no
difficulty were assigned a score of zero. The baseline interview, administered to study-eligible participants only, included three additional items—walking across a small
room; turning a key in a lock; and stooping, crouching and
kneeling. The items we used to construct the upper extremity functional limitation scale—using fingers to grasp or
handle, raising arms up over the head, and lifting and carrying something as heavy as 10 lb—are the same three items
that represent the upper extremity functional domain in the
screening interview (see Table 1). Although some have used
the lifting and carrying task to represent lower extremity
function (Lawrence & Jette, 1996; Wolinsky & Johnson,
1991), others have considered it, as we did here, to represent
upper extremity limitation (Bild et al., 1993; Lichtenstein et
al., 1998; Satariano & Ragland, 1996).
The lower extremity functional limitation scale uses two
items from the mobility/exercise tolerance domain—walking for 1/4 mile and walking up 10 steps without resting—
and two items from the baseline interview, which also represent this domain—walking across a small room and
stooping, crouching, and kneeling. Note that we excluded
two items in this domain from the lower extremity functional limitation scale—getting in and out of bed or chairs
and doing heavy housework—because they tap dimensions
of disability.
Self-report measures of disability.—As described previously, self-reported disability was ascertained in both the
screening and baseline interviews. Even though most activities involve both upper and lower extremity function, for
economy in analysis and presentation we categorized activities by their primary component, such that the upper extremity disability items include dressing, bathing, preparing
meals, turning a key in a lock, and eating; items representing lower extremity disability include doing heavy housework, getting in and out of bed or chairs, and using the toilet; and two items represent both upper and lower extremity
disability—doing light housework and shopping. To examine the criterion-related validity of the functional limitation
scales, we used the disability items individually and dichotomized them as any versus no difficulty. Even though using
the telephone was a screening item, we did not include it in
these analyses, because it is primarily an indicator of cognitive function (Wolinsky & Johnson, 1991). Because only 10
of the 1,002 WHAS participants would not have qualified
for the study if using the telephone were not a screening
item and 8 of these women had vision problems, we saw no
need to exclude them from the analyses.
Performance-based measures of impairment, functional limitation, and disability.—The interviewer-administered physical assessment and nurse-administered clinical
examination included several performance-based measures
of strength-related impairment, functional limitation, and
disability. Detailed measurement procedures can be found
in Simonsick and colleagues (1997). The upper extremity
impairment measures included grip (Jamar adjustable grip
hand dynamometer, model BK-7498, Fred Sammons, Inc.,
Burr Ridge, IL) and pinch strength (0–60-kg pinch gauge,
model 81441, Adaptability, Colchester, CT). Three tests assessed participants’ upper extremity functional limitation:
(a) ability to lift a 10-lb water jug using both arms from the
lap to eye level to up over the head, (b) capacity to fully internally and externally rotate the left and right shoulders,
and (c) time needed to pick up and place 10 pegs in a pegboard with the dominant hand. Two tests captured upper extremity disability: ability and time to (a) put on and button a
blouse and (b) pick up a key and open a lock. Lower extremity impairment measures included knee extensor and
hip flexor strength determined from hand-held dynamometry (Nicholas Manual Muscle Tester, model BK-7454, Fred
Sammons, Inc., Burr Ridge, IL). A standardized battery,
consisting of measured walks, a standing balance test, and
five repeated chair stands (Guralnik et al., 1994) tapped
lower extremity functional limitation.
For all performance measures, participants too weak or
functionally limited to perform the test safely were excluded
from testing. For example, for both knee extensor and hip
flexor strength measurement, participants who had undergone knee or hip surgery within the preceding 3 months and
those who did not have sufficient range of motion to do the
strength measures were not tested. Thus, for the strength and
some of the performance measures, we report both the percentage of participants able to do the component and the
mean performance of those tested. The values for grip,
pinch, knee extensor, and hip flexor strength represent the
average of the best trials for the right and left sides.
Scale Construction
Our objective was to create scales with good face validity
as indicators of severity and a scoring range of at least 6 up
to 10 points (Krosnick & Fabrigar, 1997), with the scores
well distributed in a disabled population. For upper extremity, we gave equal weight to the three representative functions—using fingers to grasp and handle, raising arms up
over the head, and lifting and carrying 10 lb—because they
bear similar importance to independent functioning and have
little overlap in terms of underlying impairments. For the
first step of scale construction, we used the full range of dif-
SEVERITY OF FUNCTIONAL LIMITATION
ficulty scoring (0–4) for each item and created a simple sum
of the amount of difficulty reported for each task, resulting
in a scale ranging from 0 to 12. Because less than 20% of the
disabled women had scores above 4, in the second step we
collapsed categories to yield a 7-point scale ranging from 0
to 6: (a) scores from 0 to 5 were retained, (b) scores of 6 and
7 were recoded to 5, and (c) scores from 8 to 12 were recoded to 6. In the third step, we reviewed the patterns of difficulty across the items at each severity level, then adjusted
scale scoring to improve face validity. Specifically, we recoded (a) scores from 5 to 4, when difficulty was no greater
than “some” on any item; (b) scores from 5 to 6, when “unable” was reported for one item and “a lot of difficulty” was
reported for another; and (c) scores from 6 to 5, when “unable” was reported for one item and “some difficulty” was
reported for the others. In this way, a slightly higher weight
was given to a lot of difficulty or inability to do a task than to
a little or some difficulty. Table 3 describes the categories in
detail; the scoring algorithm is available on request.
Construction of the lower extremity functional limitation
scale entailed three steps. First, we created a hierarchical
scale using walking for 1/4 mile and walking across a small
room. Persons with no difficulty walking across a small
room were assigned a score from 0 to 4 based on their reported difficulty walking for 1/4 mile. Those who had a little
or some difficulty walking across a room were assigned a
score of 5, and participants with a lot of difficulty or who
were unable to walk across a room received a score of 6. In
the next step we added difficulty walking up 10 steps without resting, with difficulty level trichotomized as “none” (0),
“a little or some” (1), and “a lot or unable to do” (2). Climbing stairs was given less weight because this activity involves walking. Difficulty level when climbing stairs was
highly correlated with difficulty level when walking a distance in both the screened and disabled samples (0.67 and
0.51, respectively). Lastly, we added difficulty stooping,
crouching, and kneeling, dichotomized as “able, with or
without difficulty” (0), and “unable to do” (1). Because diffi-
S13
culty stooping is commonly reported in old age (50% of persons aged 65 years and older; Foley et al., 1986) even among
well-functioning elderly persons (Berkman et al., 1993) and
is not critical to daily functioning, we counted only inability
as indicative of limitation. Table 6 describes the categories
in detail; the scoring algorithm is available on request.
Data Analysis
To determine criterion-related validity of the upper and
lower extremity functional limitation scales, we examined
the prevalence of self-reported difficulty with the respective
upper and lower extremity-related activities at each level of
functional limitation. We used both the screened population
and the 1,002 study participants for these analyses to allow
examination of scale distributions within cognitively intact,
urban, community-dwelling women as well as the subgroup
with moderate to severe disability. The remaining analyses
included only the WHAS participants, because the performance and strength measures were not part of the screening
interview. For the timed tests and strength measures, we examined the percentage of participants able to do the test and
the mean completion time or kilograms of force generated,
as appropriate. In the analyses, lower extremity strength
was adjusted for body weight. For the lower extremity performance battery items—standing balance, repeated chair
stands, and usual gait speed—we used an established categorical scoring approach (Guralnik et al., 1994) because it
takes into account inability to do the test. We present the
mean scores on the individual components, each ranging
from 0 to 4, and the summary score, which ranges from 0 to
12. For the statistical analysis, we used the chi-square test
for trend for dichotomous variables, for example, ADL difficulty or not and able to do test or not. Pearson correlation
coefficients were calculated for all continuous measures,
such as strength and timed performance, and Spearman correlation coefficients were calculated for ordinal variables.
All analyses were performed using SASpc version 6.12
(SAS Institute, 1988).
Table 2. Percentage of the Screened Populationa With Difficulty Performing Activities Involving Upper Extremity Function by Severity of
Upper Extremity Functional Limitationb
Upper Extremity Activities
Severity Score
0
1
2
3
4
5
6
Percent Distribution
Dressing
Bathing
Preparing Meals
Light Housework
Shopping
Eating
64.4
9.7
5.9
5.2
7.0
4.9
3.0
0.5
6.0
15.1
16.8
22.4
40.0
58.3
5.7
23.8
28.0
44.3
53.2
65.2
73.8
1.4
4.9
10.9
13.0
30.9
38.4
60.3
1.6
10.1
14.4
23.8
32.8
43.9
68.2
6.2
20.5
27.7
33.8
58.6
61.9
71.1
0.4
1.9
3.9
8.0
8.1
20.5
30.7
an ⫽ 3,635 women screened for participation in the Women’s Health and Aging Study. Data are weighted to account for sample stratification and differential nonresponse.
bSeverity score was determined from difficulty using fingers to grasp or handle, lifting and carrying 10 lbs., and raising arms up over the head. Scores are defined
as follows: 0 ⫽ no difficulty on any task; 1 ⫽ a little difficulty with one activity; 2 ⫽ a little difficult with two activities or some difficulty with one activity; 3 ⫽ a little difficulty in all three activities, a little difficulty with one and some difficulty with a second, or a lot of difficulty with one activity; 4 ⫽ some difficulty with one activity and a little or some difficulty on the other two, some difficulty with two activities, a little difficulty with one activity and a lot of difficulty with a second, or unable to do one activity; 5 ⫽ difficulty in all three activities and a lot of difficulty or unable to do one activity, a lot difficulty with one activity and some or a lot of
difficulty with a second, or unable to do one activity and a little or some difficulty with a second; 6 ⫽ difficulty in all three activities and at least a lot of difficulty with
two of them. (See text for scoring rules.)
S14
SIMONSICK ET AL.
Table 3. Percentage of Moderately to Severely Disabled Womena With Difficulty Performing Activities Involving Upper Extremity
Function by Severity of Upper Extremity Functional Limitationb
Upper Extremity Activities
Severity Score
Percent Distribution
Dressing
Bathing
Preparing Meals
Light Housework
Shopping
Turning Key in Lock
Eating
18.1
18.4
14.3
13.0
16.4
12.2
7.8
6.7
8.7
16.1
20.8
24.5
43.4
56.4
44.4
31.5
31.5
46.5
49.4
68.8
73.1
13.3
5.4
9.9
14.6
27.6
35.2
59.0
8.3
13.0
20.3
22.3
31.1
42.6
65.4
51.4
24.5
27.3
40.0
58.5
60.3
71.8
1.7
5.0
7.7
9.2
11.2
26.4
39.2
4.4
2.7
3.5
8.5
6.7
20.5
30.8
0c
1
2
3
4
5
6
⫽ 1,002 participants in the Women’s Health and Aging Study.
score was determined from difficulty using fingers to grasp or handle, lifting and carrying 10 lbs., and raising arms up over the head. Scores are defined as
follows: 0 ⫽ no difficulty on any task; 1 ⫽ a little difficulty with one activity; 2 ⫽ a little difficult with two activities or some difficulty with one activity; 3 ⫽ a little
difficulty in all three activities, a little difficulty with one and some difficulty with a second, or a lot of difficulty with one activity; 4 ⫽ some difficulty with one activity and a little or some difficulty on the other two, some difficulty with two activities, a little difficulty with one activity and a lot of difficulty with a second, or unable
to do one activity; 5 ⫽ difficulty in all three activities and a lot of difficulty or unable to do one activity, a lot difficulty with one activity and some or a lot of difficulty
with a second, or unable to do one activity and a little or some difficulty with a second; 6 ⫽ difficulty in all three activities and at least a lot of difficulty with two of
them. (See text for scoring rules.)
cIn some cases, as a function of study eligibility criteria (difficulty with at least one task in each of two functional domains), participants with a score of 0 had a
higher prevalence of difficulty on instrumental and self-care tasks than those with a severity score of 1.
an
bSeverity
RESULTS
Table 2 shows the distribution of the upper extremity
functional limitation scale in the screened population. Although nearly two thirds of these cognitively intact community-dwelling women had a score of zero, among the 36%
with some upper extremity limitation, scale scores were
evenly distributed with about 5–10% in each severity category, with the exception of the most severe. With increasing
severity score, for each upper extremity activity, prevalence
of difficulty increased significantly ( p ⬍ .001). In the moderately to severely disabled women, the upper extremity severity scale is well distributed with 12–18% in each category from 0 to 5 and 8% at the most severe level (see Table
3). As in the screened population, with increasing severity
of upper extremity functional limitation, prevalence of diffi-
culty in activities increased significantly ( p ⬍ .001). Even
at the higher severity levels, a 1-point increase showed a
substantial increase ( p ⬍ .01) in the percentage with difficulty for each activity. In the moderately to severely disabled subgroup, for some items—most notably shopping,
bathing, and preparing meals—those with a severity score
of zero had a higher prevalence of difficulty than those with
a higher severity score. This apparent anomaly in the
WHAS population is an artifact of study eligibility criteria,
because women with no upper extremity difficulty (i.e.,
scale score of 0) by definition had to have difficulty in at
least two of three other domains—mobility/exercise tolerance, higher functioning, and self-care. Higher functioning
tasks included light housework, shopping, and preparing
meals, and self-care included dressing, bathing, and eating
Table 4. Upper Extremity Performance and Strength of Moderately to Severely Disabled Womena by Severity of Upper Extremity
Functional Limitationb
Upper Extremity Performance and Strength Measures
Severity Score
0
1
2
3
4
5
6
Put on Blouse
Lock and Key
% Able M, s
% Able
M, s
94.9
96.1
97.2
94.4
93.8
92.4
85.5
11.7
10.1
10.5
11.3
11.9
12.2
13.4
91.6
93.3
92.0
88.9
82.5
79.7
56.0
78.3
80.0
77.3
83.7
99.0
103.6
103.3
Pegboard
Pinch Strength
Grip Strength
% Able M, s
% Able M, kg
% Able M, kg
94.3
93.4
95.0
90.5
86.2
84.8
61.3
29.5
29.2
29.7
29.0
31.3
31.1
33.8
99.4
98.4
97.9
99.2
98.8
96.7
87.0
4.9
4.9
5.1
4.9
4.7
4.5
4.5
98.8
97.1
94.7
96.7
95.4
89.5
73.0
21.3
20.7
21.7
20.9
19.7
19.2
17.9
10-lb Lift, % Able
Eye
Overhead
Shoulder Rotation, % Able
87.8
83.4
82.5
71.4
65.6
57.5
32.9
60.6
58.6
55.5
45.2
37.6
25.0
15.8
71.3
75.0
72.0
61.5
61.0
43.4
33.8
⫽ 1,002 participants in the Women’s Health and Aging Study.
score was determined from difficulty using fingers to grasp or handle, lifting and carrying 10 lbs., and raising arms up over the head. Scores are defined as
follows: 0 ⫽ no difficulty on any task; 1 ⫽ a little difficulty with one activity; 2 ⫽ a little difficult with two activities or some difficulty with one activity; 3 ⫽ a little
difficulty in all three activities, a little difficulty with one and some difficulty with a second, or a lot of difficulty with one activity; 4 ⫽ some difficulty with one activity and a little or some difficulty on the other two, some difficulty with two activities, a little difficulty with one activity and a lot of difficulty with a second, or unable
to do one activity; 5 ⫽ difficulty in all three activities and a lot of difficulty or unable to do one activity, a lot difficulty with one activity and some or a lot of difficulty
with a second, or unable to do one activity and a little or some difficulty with a second; 6 ⫽ difficulty in all three activities and at least a lot of difficulty with two of
them. (See text for scoring rules.)
an
bSeverity
SEVERITY OF FUNCTIONAL LIMITATION
S15
Table 5. Percentage of the Screened Populationa With Difficulty Performing Activities Involving Lower Extremity Function by Severity of
Lower Extremity Functional Limitationb
Lower Extremity Activities
Severity Score
0
1
2
3
4
5
6
Percent Distribution
Heavy Housework
Transfer
Shopping
Light Housework
Using the Toilet
59.2
10.8
7.4
5.8
5.5
4.6
6.8
15.6
51.0
62.4
75.2
90.2
90.0
93.7
3.8
13.2
20.7
23.5
30.0
47.6
62.3
2.5
15.0
24.7
28.7
55.2
66.0
86.9
1.1
6.7
12.1
12.4
28.8
42.2
60.9
0.6
3.4
8.5
11.4
16.3
25.5
57.6
an ⫽ 3,635 women screened for participation in the Women’s Health and Aging Study. Data are weighted to account for sample stratification and differential nonresponse.
bDifficulty walking across a small room and stooping, crouching, and kneeling were not ascertained in the screening interview; thus an alternate measure of severity
of lower extremity functional limitation was constructed with difficulty walking for a 1/4 mile and climbing 10 steps without resting, with the same scoring conventions as the full scale. Severity of lower extremity functional limitation consists of the sum of (a) severity of walking difficulty, with scores of 0 to 4 representing the
category of difficulty walking for a 1/4 mile (0 ⫽ “none,” 1 ⫽ “a little,” 2 ⫽ “some,” 3 ⫽ “a lot,” and 4 ⫽ “unable”) among those with no difficulty walking across a
small room, and with a score of 5 assigned to those reporting a little or some difficulty walking across a room and 6 assigned to those with a lot of difficulty or unable
to walk across a room; (b) level of difficulty climbing 10 steps with resting (0 ⫽ “none,” 1 ⫽ “a little or some,” and 2 ⫽ “a lot or unable”); and (c) whether “able” (0)
or “unable” (1) to stoop, crouch, or kneel.
(see Table 1). In addition, these activities that are used to reflect the disabling effects of upper extremity limitations (see
Table 3) are also affected by lower extremity functioning, as
noted earlier. This pattern does not occur in the screened
population, which includes women across the entire spectrum of functioning (see Table 2).
Table 4 gives the percentage of participants able to do
each of the performance and strength tests and the mean time
to complete each task or kilograms of force generated, where
applicable, by severity of upper extremity functional limitation among the 1,002 disabled women in the WHAS. For the
10-lb lift, the first and second columns show the percentage
who could lift the weight to eye level and over their head, respectively. In general, with increasing severity score, the
percentage able to do each test decreased and the perfor-
mance level declined (e.g., mean time increased and force
generated decreased). The overall trend was statistically significant in all cases ( p ⬍ .01), with shoulder rotation and the
10-lb lift showing the strongest correlations with functional
limitation score, ⫺.26 and ⫺.34, respectively.
To examine the distribution of lower extremity functional
limitation in the screened population, we created an alternate version of the scale, because difficulty walking across a
small room and stooping, crouching, and kneeling were not
part of the screening interview. This modified scale ranges
from 0 to 6 and uses the same scoring conventions for walking 1/4 mile and up 10 steps as used for the 10-point scale.
Table 5 shows the scale distribution in the screened population. Nearly 60% scored zero, but among the remaining
40%, severity was well distributed across the full range of
Table 6. Percentage of Moderately to Severely Disabled Womena With Difficulty Performing Activities Involving Lower Extremity
Function by Severity of Lower Extremity Functional Limitationb
Lower Extremity Activities
Severity Score
0c
1
2
3
4
5
6
7
8
9
Percent Distribution
Heavy Housework
Transfer
Shopping
Light Housework
Using the Toilet
14.7
12.4
11.3
10.3
8.1
9.3
9.9
8.7
7.2
8.3
76.9
65.3
69.0
80.4
87.3
92.4
86.8
93.1
93.1
95.2
18.5
17.7
20.5
25.2
28.4
35.9
37.8
46.0
77.8
74.7
13.6
12.1
22.1
33.0
32.1
58.7
70.7
75.9
88.9
96.4
4.8
7.3
8.0
13.6
22.2
29.0
29.3
42.5
56.9
72.3
5.4
5.7
3.6
15.5
11.1
15.0
22.2
38.4
53.5
74.7
⫽ 1,002 participants in the Women’s Health and Aging Study.
of lower extremity functional limitation consists of the sum of (a) severity of walking difficulty, with scores of 0 to 4 representing the category of difficulty walking for a 1/4 mile (0 ⫽ “none,” 1 ⫽ “a little,” 2 ⫽ “some,” 3 ⫽ “a lot,” and 4 ⫽ “unable”) among those with no difficulty walking across a small room, and
with a score of 5 assigned to those reporting a little or some difficulty walking across a room and 6 assigned to those with a lot of difficulty or unable to walk across a
room; (b) level of difficulty climbing 10 steps without resting (0 ⫽ “none,” 1 ⫽ “a little or some,” and 2 ⫽ “a lot or unable”); and (c) whether “able” (0) or “unable”
(1) to stoop, crouch, or kneel.
cIn some cases, as a function of study eligibility criteria (difficulty with at least one task in each of two functional domains), participants with a score of 0 had a
higher prevalence of difficulty on mobility, instrumental, and self-care tasks than those with a severity score of 1.
an
bSeverity
S16
SIMONSICK ET AL.
scores with 5–11% in each category. Prevalence of difficulty in the lower extremity activities increased with increasing severity score ( p ⬍ .001). Table 6 gives the distribution of the full 10-point scale of lower extremity functional
limitation in the disabled subgroup. The scale was well distributed in this group with 7–15% in each category and the
prevalence of difficulty in activities increasing with severity
score for all activities ( p ⬍ .001).
The relationship of lower extremity strength and performance to severity of lower extremity functional limitation is
shown in Table 7. The percentage able to do the strength
measures and the fast 4-m walk, the kilograms of force generated by knee extension and hip flexion, and the speed of
the 4-m walk all decreased with increasing severity score ( p ⬍
.001). The Spearman correlation coefficients between the
lower extremity functional limitation scale and each of the
individual performance test scores, as well as the total performance score, were moderate to high, ranging from ⫺.49
to ⫺.64. For the strength measures, the correlations were
also significant ( p ⬍ .001), but somewhat smaller (⫺.20
and ⫺.30 for hip flexion and knee extension, respectively).
DISCUSSION
Our primary objective—to develop valid summary scales
that capture severity of upper and lower extremity functional
limitation using commonly available self-report measures of
difficulty performing routine functions—appears to be satisfied. Both scales are well distributed in moderately to severely disabled community-resident women, the primary focus of the WHAS, and also differentiate gradations of
limitation in the broader community of cognitively intact
older women. The strong associations between the functional limitation scales and disability, as measured by the
prevalence of self-reported difficulty in ADL and IADL and
tests of strength and performance, provide support for the
criterion-related validity of the scales. The good, but not per-
fect, correspondence of the severity of limitation scales with
self-reported difficulty with ADL and IADL and the performance-based measures of physical impairment and disability
is consistent with Nagi’s theory that not all impairment leads
to functional limitation and not all functional limitations lead
to disability (Nagi, 1991). These associations are also consonant with findings from an empirical analysis of the disablement pathway (Lawrence & Jette, 1996). The relatively
weak relationship between scale scores and strength is supported by reports that the association between strength and
functional limitation exists only below a specific threshold
of weakness (Buchner, Larson, Wagner, Koepsell, & De
Lateur, 1996; Ferrucci et al., 1997; Rantanen et al., 1998).
Severity of limitation scale scores are most strongly associated with the performance-based measures of functional limitation, as expected. For the upper extremity, the correlations
are weaker (⫺.26 to ⫺.34), but the actual tasks, lifting 10 lb
while seated to eye level and then up over the head, full internal and external rotation of both shoulders, and placing 10
pins in a pegboard in less than 60 s, are more difficult to perform than the functions to which the self-report items refer
(i.e., lifting and carrying 10 lb, raising arms up over the head,
and using fingers to grasp and handle). Also, because the upper extremity scale assesses global upper extremity limitation,
measures that assess hand function (e.g., grip strength and
pegboard) show a less consistent decrease in performance
with increasing scale score, particularly at the lower range of
the scale, where severe difficulty using the fingers is rare. The
magnitude of association is greatest between the lower extremity functional limitation scale and the lower extremity
performance battery, with the self-report scale explaining
more than 42% of the variance in the performance-based measure. Thus, it appears that self-report of functioning that uses
several levels of difficulty with basic functions may be a viable substitute measure of lower extremity functional limitation
when performance-based testing is not possible.
Table 7. Lower Extremity Strength and Performance of Moderately to Severely Disabled Womena by Severity of Lower Extremity
Functional Limitationb
Lower Extremity Strength and Performance Measures
Knee Extensor
Severity Score
0
1
2
3
4
5
6
7
8
9
% Able M,
96.6
95.2
90.3
93.2
90.1
94.6
86.9
87.4
81.9
73.5
kgc
15.3
14.4
13.7
13.0
13.3
12.5
12.1
11.1
10.5
10.5
Hip Flexor
% Able M,
95.2
93.5
86.7
92.2
87.7
91.4
79.8
86.2
80.6
66.3
kgc
13.2
11.9
12.0
11.6
11.8
11.1
10.3
10.2
9.7
9.8
Fast 4-m Walk
% Able M, m/s
99.3
98.4
99.1
98.1
98.8
97.8
92.9
83.9
83.3
50.0
1.20
1.08
1.02
0.99
0.90
0.81
0.74
0.58
0.46
0.42
Usual 4-m Walk,
M Score
5 Chair Stands,
M Score
Standing Balance,
M Score
Total Performance,
M Score
3.22
3.00
2.76
2.72
2.53
2.25
1.95
1.49
1.30
0.78
2.48
2.33
1.96
2.00
1.81
1.53
1.26
0.67
0.61
0.17
2.84
2.57
2.53
2.34
2.05
1.65
1.73
1.42
1.18
0.41
8.52
7.91
7.26
7.06
6.43
5.45
5.01
3.61
3.10
1.36
⫽ 1,002 participants in the Women’s Health and Aging Study.
of lower extremity functional limitation consists of the sum of (a) severity of walking difficulty, with scores of 0 to 4 representing the category of difficulty walking for a 1/4 mile (0 ⫽ “none,” 1 ⫽ “a little,” 2 ⫽ “some,” 3 ⫽ “a lot,” and 4 ⫽ “unable”) among those with no difficulty walking across a small room, and
with a score of 5 assigned to those reporting a little or some difficulty walking across a room and 6 assigned to those with a lot of difficulty or unable to walk across a
room; (b) level of difficulty climbing 10 steps without resting (0 ⫽ “none,” 1 ⫽ “a little or some,” and 2 ⫽ “a lot or unable”); and (c) whether “able” (0) or “unable”
(1) to stoop, crouch, or kneel.
cAdjusted for total body weight.
an
bSeverity
SEVERITY OF FUNCTIONAL LIMITATION
As another check on scale validity, we examined associations between the functional limitation scales and the opposing performance measures of functional limitation. Despite the fact that 70% of the disabled cohort had both an
upper and a lower extremity limitation, these analyses provide moderate support for the specificity of the scales, in
that (a) correlations between the upper extremity scale and
lower extremity performance tests are substantially weaker
than those between the lower extremity scale and lower extremity performance: ⫺.17 versus ⫺.49, ⫺.18 versus ⫺.54,
and ⫺.27 versus ⫺.60 for standing balance, repeat chair
stands, and walking speed, respectively; (b) correlations between the lower extremity scale and upper extremity performance items are weaker than those between the lower extremity scale and lower extremity performance; and (c)
correlations between the upper extremity scale and upper
extremity performance are generally stronger than the correlations between the upper extremity scale and lower extremity performance. However, correlations between the
lower extremity scale and upper extremity performance
tests, although weak, are similar to those between the upper
extremity scale and upper extremity tests: .33 versus .20,
⫺.25 versus ⫺.26, and ⫺.34 versus ⫺.34 for pegboard,
shoulder rotation, and 10-lb lift, respectively.
Comments on Scale Construction
The scales described in this report represent a compromise between simplicity and comprehensiveness. Although
aspects of scale construction were complex, more simplistic
approaches did not produce satisfactory results. For example, for the upper extremity scale, we first grouped the response options of “a little and some” (1) and “a lot and unable” (2) to produce a scale ranging from 0 to 6, the same
range of the more complex scale presented in this article.
The distribution of the simple scale, however, was skewed,
because more than 75% of the disabled women had scores
between 0 and 2 and only 5% had scores of 5 or 6. Furthermore, we found that the prevalence of difficulty in most of
the ADL and IADL items more than doubled between
scores of 1 and 2, using the more simplified approach to
scale construction (data available on request).
As noted in the Methods section, some studies consider
the lifting and carrying item as a measure of lower extremity function (Lawrence & Jette, 1996; Wolinsky & Johnson,
1991) and others use it to indicate upper extremity limitation (Bild et al., 1993; Lichtenstein et al., 1998; Satariano &
Ragland, 1996). This item is problematic because it combines activities that involve both the upper and lower extremities and it is unknown whether difficulty lifting and
carrying implies difficulty with the lifting and/or holding
aspect of carrying or with the walking component of carrying or both. Because factor analyses have yielded inconsistent findings (e.g., Fried, Ettinger, Lind, Newman, & Gardin, 1994; Lichtenstein et al., 1998; Wolinsky & Johnson,
1991), we conducted our own analysis in the disabled sample. Using principal component analysis with a varimax rotation, we identified two factors. On the first, walking 1/4
mile plus across a room; walking up 10 steps; and stooping,
crouching, and kneeling loaded between .66 and .82, and
lifting and carrying loaded .63. On the second factor, using
S17
fingers to grasp and handle loaded .82, raising arms up over
the head loaded .75, and lifting and carrying loaded .22.
However, given that factor analysis tends to group items according to their frequency distributions and not necessarily
by their underlying constructs, it is unclear whether Factor 1
represents lower extremity function and Factor 2 upper extremity function or whether they represent more frequent
and less frequent functional limitations, respectively. The
distribution of difficulty on the upper extremity items supports the latter possibility, because 65% report difficulty
lifting or carrying, in contrast to 35% for using fingers to
grasp or handle and 28% for raising arms up over the head.
On the lower extremity tasks, 77% report difficulty walking
1/4 mile; 52% have difficulty walking up 10 steps; and 88%
have trouble stooping, crouching, and kneeling.
The WHAS has used the lifting and carrying item to represent upper extremity function in both the screening process and
analyses of data for the main study. Because lower extremity
function, including walking, is adequately assessed using multiple items, we also chose to use lifting and carrying as a measure
of upper extremity function to reduce the likelihood of overlooking limitations in this dimension. In support of this decision, among women aged 70–79 with no difficulty walking for
1/4 mile or up 10 steps without resting, 10% report difficulty
lifting or carrying 10 lb and 36% report difficulty with 20 lb.
There are three important points to make regarding the lower
extremity functional limitation scale. First, the alternate scale
constructed for the screened population that included only two
items—walking 1/4 mile and up 10 steps—performed well in
the disabled women. From 11 to 18% fell into each category
from 0 to 6, with more than 17% having a score of 6. There
was a steady increase in the prevalence of difficulty for each of
the ADL and IADL items between 0 and 5, with a large jump
in prevalence for some activities, including transferring, shopping, doing light housework, and using the toilet, between
scores of 5 and 6. In terms of the performance battery, mean
scores for each individual test as well as the summary scale declined steadily, as the severity of lower extremity functional
limitation increased from 0 to 4, then showed a dramatic decrease between 5 and 6 (e.g., from 5.0 to 2.7 for the summary
performance scale score; data available on request).
Although the alternate scale showed promise, it did not
adequately discriminate severity in the most functionally
limited women. A major difference between the two scales
was the inclusion of “walking across a small room” in the
10-point scale. Although inability to walk across a room is
typically used to indicate disability (Branch, Katz, Kniepmann, & Papsidero, 1984; Jette, Branch, & Berlin, 1990),
Nagi (1991) considered even severe mobility restrictions to
be a functional limitation. Moreover, we found this item critical for discriminating severity level among those with more
severe limitations in lower extremity function. Many women
with difficulty walking 1/4 mile also reported difficulty
walking across a room. For example, of the 187 women with
a lot of difficulty walking 1/4 mile, 52 (28%) also reported
some level of difficulty walking across a room; of the 278
unable to walk for 1/4 mile, 62% had difficulty walking
across a room. Clearly there exists a range of walking ability
among those reporting the same level of difficulty in walking
1/4 mile. Even though the likelihood of difficulty walking
S18
SIMONSICK ET AL.
across a room increased with increasing difficulty walking 1/4
mile, the correspondence was not perfect; therefore, including walking across a room is necessary to improve discrimination of functional limitation at the upper, most severe end
of the scale. Lastly, stooping, crouching, and kneeling, although used only as a dichotomous measure—“able with or
without difficulty” (0) and “unable” (1)—serves to disaggregate women at the least severe end of the scale. Without this
item, 17.5% of the disabled women scored zero versus
14.7%. This difference is small but nonetheless provides further assurance that persons who score zero on the scale have
no major functional limitations.
The questions we used to derive the severity of functional
limitation scales include “unable” as a response option.
Some have used inability to walk a distance or climb stairs
to indicate mobility-related disability (Guralnik, Ferrucci et
al., 1995). Even though this is a useful construct for understanding pathways to disablement, under a strict interpretation of Nagi’s conceptual framework (1991) inability to
walk is more appropriately considered a measure of functioning. Classification of those unable to perform a function
can vary with analytic objectives, however. Persons unable
to walk can be contrasted with those who are able when the
focus is on the threshold between the two, and interpretation
of these analyses may be framed in terms of disabled and
not disabled. For evaluating heterogeneity of function with
a single scale that captures the full continuum of functional
limitation, those who are unable, represent the lowest level
of functioning, and should be assigned the poorest score, as
was done here. This is analogous to performance-based
measures of functional limitation, in which persons unable
to do a test are assigned the lowest performance score
(Guralnik et al., 1994; Seeman et al., 1994).
In the introduction we argued that to more fully understand disablement, researchers must define and measure
functional limitation more consistently. This is a challenging objective because model specification from diverse perspectives—medical, rehabilitative, and social science—
results in different, although often complementary, interpretations of Nagi’s theoretical perspective. For example, Fried
and colleagues (1991, 1996) have used the term preclinical
disability to describe a state of diminished or altered function that falls between impairment and disability, similar to
functional limitation. Preclinical disability, however, is operationalized as no report of difficulty with task performance, but self-perceived reduction in frequency of and/or
alteration in approach to performing ADL, IADL, mobility,
and upper extremity tasks. Similarly, Schultz-Larsen, Avlund, and Kreiner (1992) have examined ability to do activities with or without reduced speed and/or tiredness as a precursor to disability. We focused here on reported level of
difficulty in functioning, because questions about difficulty
are more widely available in studies of older adults.
Future Directions
We developed the scales described in this article to investigate the causes and course of disability in a cohort of older,
moderately to severely disabled women. Although the scales
are well distributed and have good criterion-related validity,
the findings are limited to, primarily, disabled older women. It
is unknown how the scales would (a) distribute in men, (b) relate to self-reported difficulty in ADL and IADL in men, and
(c) relate to strength and performance-based measures in both
men and women in the broader community. Even though the
individual items have good test-retest reliability (Rathouz et
al., 1998; Tager, Swanson, & Satariano, 1998), reproducibility
of the complete scales should also be considered to determine
how much change in score constitutes true change.
Despite these caveats, we believe these scales can be useful research tools for understanding (a) how impairments,
such as pain and weakness, lead to functional limitation; (b)
the conditions (e.g., social, psychological, cognitive, and
environmental) under which functional limitations promote
disability; and (c) the unique contribution of upper and
lower extremity functional limitations to difficulty in activities and tasks that involve both the upper and lower extremities. Because the items we used to construct these scales
were included in many large studies and databases, comparable investigations of varied populations addressing several of the issues outlined previously could be undertaken
with current data. Lastly, in terms of public health and primary prevention of disability, the availability of self-reportbased assessments of severity of functional limitation permits cost-effective screening of persons at risk of disability.
Acknowledgments
The Women’s Health and Aging Study was supported by Contract Number NO1-AG-1-2112 from the National Institute on Aging.
Address correspondence to Dr. Eleanor M. Simonsick, Epidemiology,
Demography, and Biometry Program, National Institute on Aging, 7201
Wisconsin Avenue, Suite 3C-309, Bethesda, MD 20892. E-mail: simonsie@
gw.nia.nih.gov
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Received February 16, 2000
Accepted August 4, 2000