HomeLarge Type Edition
HOME ARCHIVE SEARCH TABLE OF CONTENTS
This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Services
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
PubMed
Right arrow PubMed Citation
The Journals of Gerontology Series A: Biological Sciences and Medical Sciences 57:M217-M222 (2002)
© 2002 The Gerontological Society of America

Late Life Function and Disability Instrument

II. Development and Evaluation of the Function Component

Stephen M. Haleya, Alan M. Jettea, Wendy J. Costera, Jill T. Kooyoomjiana, Suzette Levensonb, Tim Heerenb and Jacqueline Ashbab

a Roybal Center for Enhancement of Late-Life Function, Sargent College of Health and Rehabilitation Sciences, Boston University, Massachusetts
b School of Public Health, Boston University, Massachusetts

Stephen M. Haley, Sargent College of Health and Rehabilitation Sciences, Boston University, Boston, MA 02215 E-mail: smhaley{at}bu.edu.


   Abstract
Top
 Abstract
Methods
 Results
 Discussion
 References
 
Background. Self-reported capability in physical functioning has long been considered an important focus of research for older persons. Current measures have been criticized, however, for conceptual confusion, lack of sensitivity to change, poor reproducibility, and inability to capture a wide range of upper and lower extremity functioning.

Methods. Using Nagi's disablement model, we wrote physical functioning questionnaire items that assessed difficulty in 48 common daily tasks. We constructed the instrument using factor analysis and Rasch analytic techniques and evaluated its validity and test-retest reliability with 150 ethnically and racially diverse adults aged 60 years and older who had a range of functional limitations.

Results. Our analyses resulted in a 32-item function component with three dimensions—upper extremity, basic lower extremity, and advanced lower extremity functions. Expected differences in summary scores of known-functional limitation groups support its validity. Test-retest stability over a 1- to 3-week period was extremely high (intraclass correlation coefficients = .91 to .98).

Conclusions. The Late-Life Function and Disability Instrument has potential to assess activity concepts related to upper and lower extremity functioning across a wide variety of daily physical tasks and individual levels of physical functioning.

PHYSICAL functioning refers to performance of a variety of activities that are expected for community-dwelling persons, including walking, climbing stairs, and handling objects (1). Physical functioning is important because it provides a foundation for many tasks required for living independently (2)(3). In this article, we use the term function to refer to the person's ability to perform specific activities that require gross or fine motor actions.

Self-report measures have been found to be a reliable and accurate methodology for obtaining information on functional status, describing the stages and severity of chronic diseases (4)(5), estimating demand for long-term care services (6)(7), and examining the impact of intervention programs (8)(9)(10). A wide variety of measures with function items have been published and are reviewed elsewhere (6)(11)(12)(13)(14)(15)(16). Yet, lack of sensitivity to change, reproducibility, and inability to capture the full spectrum of functioning have been common concerns regarding existing self-report measures of physical functioning (17)(18).

We have attempted to address two major concerns of current instruments. First, the structure and dimensionality of function items have been poorly defined, which has led to conceptual confusion. In accordance with Nagi and others (19)(20)(21)(22), our measure of physical function is focused specifically on discrete activities. Second, many of the current activity of daily living (ADL) measures focus too narrowly on basic physical skills, and thus are ineffective in capturing variations in function in the general population of community-dwelling elderly (23)(24).

The most widely used self-report measure of function is the 10-item Physical Functioning Scale (PF-10), a component of the Short-Form 36 Health Survey (SF-36) (25)(26). The scale was designed to be brief in order to minimize response burden yet comprehensive so that it would sample a core set of questions applicable for both general populations and those with acute or chronic conditions. However, it was not intended to be a general measure of change (27)(28)(29), in response to interventions.

In response to the continuing need for a comprehensive measure to examine functioning in older adults, we undertook the development of a new measure. This article reports on the conceptual basis and construction of the function component of the Late-Life Function and Disability Instrument (Late-Life FDI) and reports the results of an initial field test of the measure's reliability and validity. The development and evaluation of the disability component of the Late-Life FDI are reported elsewhere (30).


   Methods
Top
 Abstract
 Methods
Results
 Discussion
 References
 
Instrument Development
We constructed questionnaire items that encompass a wide variety of physical activities encountered in daily routines. After pilot-testing an initial draft of 54 items with 50 community-dwelling older adults, subsequent review by project staff, and consideration of suggestions from community focus groups, 48 physical functioning items were retained for the prototype instrument. The function items on the Late-Life FDI assess self-reported difficulty in performing a discrete physical activity. Questions are phrased, "how much difficulty do you have doing a particular activity without the help of someone else and without the use of assistive devices?" with response options of "none," "a little," "some," "quite a lot," and "cannot do." Factors that may influence difficulty in task performance (e.g., pain, fatigue, fear, weakness, soreness, ailments, health conditions, and disabilities) were identified for participants before the measure was administered.

Sampling Procedures
To develop a function scale designed to be sensitive across a wide range of ability levels, we recruited a convenience sample of adults who were 60 years of age and older, from diverse ethnic and racial backgrounds, with a range of functional limitations (30). A random subset of participants (n = 15) completed a second interview within 1 to 3 weeks after the initial interview to assess test-retest reliability of the function component.

Instrument Construction and Analyses
A series of factor analyses was used to identify the number and nature of latent factors that could be responsible for the covariation in the functioning data. A one-factor and a three-factor model were tested. A series of one-parameter Rasch rating scale analyses was performed to estimate item locations (calibrations) along a common scale (31). By our convention, the items on which most people express difficulty are associated with scores of increasing magnitude. Thus, the continuum of 0–100 reflects increasing function, with scores approaching 0 indicating poor ability and scores approaching 100 characterizing good function. The short-term stability of the Late-Life FDI was assessed by calculating intraclass correlation coefficients (32) between scores at the initial assessment and follow-up scores. We used the method of known-groups validity to test the ability of the overall measure and each identified dimension to discriminate between groups known to differ in functional status as measured by the physical functioning items (PF-10) of the SF-36 (33)(34). These methods are described in detail in a companion article (30).


   Results
Top
 Abstract
 Methods
 Results
Discussion
 References
 
Sample Characteristics
The final sample was composed of 150 community-dwelling older volunteers. See companion article (30) for a full description of the sample.

Questionnaire Content
Based on an initial item review consisting of a preliminary factor analysis, feedback from the participants, Rasch analysis to examine content redundancy and item fit, 16 of the original 48 items were deleted from further analyses. Six items were eliminated because they were not applicable to a significant number of participants, six were removed due to redundant content, one item was deleted due to respondent difficulty interpreting item content, and three items were removed because of ambiguous loadings on one or more factors.

Function Domains
Table 1 presents the factor loading estimates and Cronbach alpha values for the one- and three-factor analysis models for the function component. A maximum likelihood chi-square test showed that one factor was not sufficient to adequately explain the data ({chi}2 = 1579.1, p < .0001). Three factors were identified by Eigenvalues greater than 1.0. A three-factor solution explained 69.1% of the variance. We labeled the first factor advanced lower extremity functioning because it reflected physical activities that involve a high level of physical ability and endurance. A second factor was labeled basic lower extremity functioning because it is composed of activities that primarily involve standing, stooping, and fundamental walking activities. A third factor reflected activities of the hands and arms and was labeled upper extremity functioning. The correlation among factors for advanced versus basic lower extremity was r = .87 (p < .001), advanced lower extremity versus upper extremity was r = .64 (p < .001), and basic lower extremity versus upper extremity was r = .69 (p < .001); all indicating some overlap.


View this table:
[in this window]
[in a new window]
  		Table 1. Estimates of Factor Loading and Cronbach Alphas for Three- and One-Factor Models for Difficulty in Function

 
Function Instrument Scaling
The hierarchical order of items on the function component of the Late-Life FDI is graphically depicted in Fig. 1 and Fig. 2 for the one- and three-factor solutions, respectively. Item separation statistics for the overall function scale (item separation = 10.1) and its subscales [advanced lower extremity functioning (item separation = 8.6), basic lower extremity functioning (item separation = 5.2), and upper extremity functioning (item separation = 6.2)] all exceed a value of 3.0, which is a good indicator of spread of items along a scale.



View larger version (13K):
[in this window]
[in a new window]
  		Figure 1. Rasch model for one solution of functioning. *Identifies items with fit scores >= 2.0. See text for details.

 


View larger version (18K):
[in this window]
[in a new window]
  		Figure 2. Rasch models for three solutions of functioning. *Identifies items with fit scores >= 2.0. See text for details.

 
Five of the 32 items in the overall function component have item fit scores equal to or greater than 2.0; however, only one is quite large ("unscrew lid off jar"; infit = 6.2). Across the three-factor solution, only four items exceed the misfit cutoff score of equal to or greater than 2.0, and only one ("get up from the floor") approximated a value of 3.0. However, because the content was found to be central to the instrument, all were retained.

Instrument Reliability and Validity
Mean total function scores were significantly different on all comparisons between functional limitation categories, as indicated in Table 2 . In most cases, the separate scores were also significantly different between groups. The exceptions were the scores for basic lower extremity functioning and upper extremity functioning on which the slight functional limitation group and the nonfunctional limitation group did not differ significantly. Test-retest intraclass correlations from 15 individuals on each summary score (Table 3 ) were very high (Shrout-Fleiss random set ICC = .91–.98). There was an average of 12 days (SD 8.3) between test administrations.


View this table:
[in this window]
[in a new window]
  		Table 2. Average Function Summary Scores and Mean Differences Between Adjacent Functional Limitation Groups

 

View this table:
[in this window]
[in a new window]
  		Table 3. Test-Retest Reliability

 

   Discussion
Top
 Abstract
 Methods
 Results
 Discussion
References
 
Physical functioning can best be described as having one dimension (difficulty) and three separate domains (advanced lower extremity functioning, basic lower extremity functioning, and upper extremity functioning). However, both the one- and three-factor solutions are reasonable hierarchical scales, although fit problems are more evident in the one-factor solution. The choice of which model to use will be determined by the particular application intended. Domain scores may be most valuable in circumstances where it is expected that there will be significantly different degrees of change across the three domains.

Items on the function scales include daily activities that sample key indicators of functioning. We found that the items were not structured along basic ADL (BADL) or instrumental ADL (IADL) categories, but rather along dimensions that reflect different physical capabilities. For example, the advanced lower extremity dimension had a mixture of mobility items (e.g., "walk a brisk mile") and physical activities usually classified as IADLs such as shopping and carrying groceries (e.g., "carry objects while walking upstairs").

These results are in contrast to a previous questionnaire that yielded three functionally related dimensions: (i) basic ADLs (walk indoors, feed oneself), (ii) mobility (stairs, carry a heavy object), and (iii) instrumental ADLs (cooking, housework) (35). Analyses from instruments that measure dependency in goal-directed activities are often consistent with ADL and IADL factor structures (9). We surmise that these differences in structure between our data and the factor structure of ADL scales may be related to the discrete nature of the activities that are part of the function component of the Late-Life FDI. In addition, our items asked respondents to rate their experienced degree of difficulty performing these activities without help, whereas many other instruments have used dependency or assistance levels as the measure of function. Adults may report that they perform a particular functional activity without help, yet experience quite different degrees of difficulty. Our results are similar to the three major dimensions of function proposed by Avlund (upper limb function, lower limb function, and mobility) (36) from data analyses of an instrument that used a tiredness scale as the evaluative criterion.

Results of the known-groups analyses confirm the content spread of each scale and suggest that the scales will be able to discriminate among groups of older persons with different levels of functioning. These results are consistent with previous findings that self-reported difficulty in functional tasks identified distinct levels of functional ability (37). The results of the present analyses also suggest that the new measure has successfully avoided the difficulty with floor or ceiling effects identified on many self-report measures (21). Only one individual in our sample (less than 1%) reached a maximum score on the overall functioning scale, and no persons received the lowest score possible (summary score mean = 59.0, SD 13.2). In contrast, on the PF-10, 21 (14%) of our sample had a maximum score (ceiling effect), and one individual had the lowest possible score (floor effect).

Test-retest reliability correlations for self-report ADLs and IADLs generally have been reported to be high (r = .90 or above) (38). The total function summary scores and separate dimension scores on the Late-Life FDI showed equally high consistency, including the upper extremity functioning score (ICC= .91), which is derived from a small number of items (n = 7).

These findings indicate that the function component of the Late-Life FDI has potential to assess functioning across a wide variety of daily activities with a reasonable set of items and with stability over short periods of time. In subsequent field tests, we will evaluate the ability of the function component of the Late-Life FDI to detect meaningful changes in functional status across dimensions in a larger sample of community-dwelling older persons and compare its psychometric characteristics to those of other functional instruments commonly used in gerontological intervention research.


   Acknowledgments
 
This project was funded by the National Institutes of Health, National Institute on Aging, Grant AG11669. We thank all of the volunteers who participated in our study and New England Research Institute for recruiting 50 subjects for the pilot test of the initial instrument draft.

To obtain a copy of the Late-Life FDI, please access www.bu.edu/ roybal/products on the World Wide Web.

Received September 11, 2001

Accepted October 25, 2001


   References
Top
 Abstract
 Methods
 Results
 Discussion
 References
 

  1. Stewart A, Ware JE, Brook RH, 1977. The meaning of health: understanding functional limitations. Med Care. XV: (11) 939-952.
  2. Kaplan GA, Strawbridge WJ, Camacho T, Cohen RD, 1993. Factors associated with change in physical functioning in the elderly. J Aging Health. 5: (1) 140-153. [Abstract/Free Full Text]
  3. Gill T, Williams C, Tinetti M, 1995. Assessing risk for the onset of functional dependence among older adults: the role of physical performance. J Am Geriatr Soc. 43:603-609. [Medline]
  4. Siu A, Reuben D, Hays R, 1990. Hierarchical measures of physical function in ambulatory geriatrics. J Am Geriatr Soc. 38: (10) 1113-1119. [Medline]
  5. Spector WD, Katz S, Murphy JB, Fulton JP, 1987. The hierarchical relationship between activities of daily living and instrumental activities of daily living. J Chronic Dis. 40: (6) 481-489. [Medline]
  6. Rodgers W, Miller B, 1997. A comparative analysis of ADL questions in surveys of older people. J Gerontol Psychol Sci Soc Sci. 52B: (special issue) 21-36.
  7. Winograd C, Lindenberger E, Chavez C, Mauricio M, Shi H, Bloch D, 1997. Identifying hospitalized older patients at varying risks for physical performance decline: a new approach. J Am Geriatr Soc. 45:604-609. [Medline]
  8. Pols MA, Peeters PH, Ocke MC, Slimani N, Bueno-de-Mesquita HB, Collette HJ, 1997[1(su1)]. Estimation of reproducibility and relative validity of the questions included in the EPIC Physical Activity Questionnaire. Int J Epidemiology. 26:S181-S189. [1(su1)]. [Abstract/Free Full Text]
  9. Avlund K, Kreiner S, Schultz-Larsen K, 1996. Functional ability scales for the elderly: a validation study. Eur J Public Health. 6:35-42. [Abstract/Free Full Text]
  10. Avlund K, Davidsen M, Schroll M, Gause-Nilsson I, Laukkanen P, Heikkinen E, 1994. Self-reported functional ability in three Nordic localities: a comparative study of activities of daily living among 75-year-old men and women in Glostrup, Gothenburg and Jyvaskyla. Int J Health Sci. 5: (3) 119-128.
  11. Kempen GI, Suurmeijer TP, 1990. The development of a hierarchical polychotomous ADL-IADL scale for noninstitutionalized elders. Gerontologist 30:497-502. [Abstract]
  12. Ren X, Kazis L, Lee A, et al. 1998. Comparing generic and disease-specific measures of physical and role functioning. Results from the Veterans Health Study. Med Care. 36: (2) 155-166. [Medline]
  13. Thomas VS, Rockwood K, McDowell I, 1998. Multidimensionality in instrumental and basic activities of daily living. J Clin Epidemiol. 51: (4) 315-321. [Medline]
  14. Dencker K, Gottfries C, 1995. Activities of daily living ratings of elderly people using Katz's ADL Index and the GBS-M Scale. Scand J Caring Sci 9: (1) 35-40. [Medline]
  15. Kelly S, Jessop EG, 1996. A comparison of measures of disability and health status in people with physical disabilities undergoing vocational rehabilitation. J Public Health Med. 18: (2) 169-174. [Abstract/Free Full Text]
  16. Asberg K, Sonn U, 1988. The cumulative structure of personal and instrumental ADL: a study of elderly people in a health service district. Scand J Rehabil Med. 21:171-177.
  17. Reuben DB, 1995. What's wrong with ADLs?. J Am Geriatr Soc. 43: (8) 936-937. [Medline]
  18. Linn BS, Linn MW, 1980. Objective and self-assessed health in the old and very old. Soc Sci Med. 14A:311-315.
  19. Nagi SZ, 1965. Some conceptual issues in disability and rehabilitation. Sussman MB, , ed.Sociology and Rehabilitation 100-113. U.S. Department of Health, Education, and Welfare, Washington, DC.
  20. Nagi SZ, 1991. Disability concepts revisited: implications for prevention. Pope AM, Tarlov AR, , ed.Disability in America: Toward a National Agenda for Prevention 309-327. National Academy Press, Washington, DC.
  21. Sherman S, Reuben D, 1998. Measures of functional status in community-dwelling elders. J Gen Intern Med. 13:817-823. [Medline]
  22. Stewart A, Ware J. Measuring Functioning and Well-Being: The Medical Outcomes Approach. Durham, NC: Duke University Press; 1992.
  23. Jette A, Branch L, 1981. The Framingham Disability Study: II. Physical disability among the aging. Am J Public Health. 71: (11) 1211-1216. [Abstract/Free Full Text]
  24. Frederiks C, te Wierik M, Visser A, Sturmans F, 1991. A scale for functional status of the elderly living at home. J Adv Nurs. 16:287-292. [Medline]
  25. Ware J, Sherbourne C, 1992. The MOS 36-item Short Form Health Survey (SF-36). Med Care. 30: (6) 473-483. [Medline]
  26. Lyons RA, Perry HM, Littlepage BNC, 1994. Evidence for the validity of the Short-Form 36 questionnaire (SF-36) in an elderly population. Age Ageing. 23:182-184. [Abstract/Free Full Text]
  27. Prieto L, Alonso J, Ferrer M, Anto J, 1997. Are results of the SF-36 Health Survey and the Nottingham Health Profile similar? A comparison in COPD patients. J Clin Epidemiol. 50: (4) 463-473. [Medline]
  28. O'Mahony P, Rodgers H, Thomson R, Dobson R, James O, 1998. Is the SF-36 suitable for assessing health status of older stroke patients?. Age Ageing. 27: (1) 19-22. [Abstract/Free Full Text]
  29. Brazier J, Harper R, Jones N, et al. 1992. Validating the SF-36 Health Survey Questionnaire: new outcome measure for primary care. BMJ. 305:106-164.
  30. Jette A, Haley S, Coster W, et al. 2002. Late Life Function and Disability Instrument: I. Development and evaluation of the disability component. J Gerontol Med Sci. 57A:M209-M216. [Abstract/Free Full Text]
  31. Wright B, Masters G. Rating Scale Analysis. Chicago: MESA Press; 1982.
  32. Shrout PE, Fleiss JL, 1979. Intraclass correlations: uses in assessing rater reliability. Psychol Bull. 86:420-428. [Medline]
  33. Kerlinger F,; 1973. Foundations for Behavioral Research Holt, Rinehart, & Winston, New York.
  34. McHorney CA, 1994. Methodological and psychometric issues in health status assessment across populations and applications. Albrecht GL, Fitzpatrick R, , ed.Advances in Medical Sociology, Vol. 5: Quality of Life in Health Care JAI Press, LTD, Greenwich, CT.
  35. Hoeymans N, Feskens EJ, van den Bos GA, Kromhout D, 1996. Measuring functional status: cross-sectional and longitudinal associations between performance and self-report (Zutphen Elderly Study, 1990–1993). J Clin Epidemiol. 49: (10) 1103-1110. [Medline]
  36. Avlund K, Kreiner S, Schultz-Larsen K, 1993. Construct validation and the Rasch model: functional ability of health elderly people. Scand J Soc Med. 21: (4) 233-246. [Medline]
  37. Langlois J, Maggi S, Harris T, et al. 1996. Self-report of difficulty in performing functional activities identifies a broad range of disability in old age. J Am Geriatr Soc. 44:1421-1428. [Medline]
  38. Ottenbacher KJ, Mann WC, Granger CV, Tomita M, Hurren D, Charvat B, 1994. Inter-rater agreement and stability of functional assessment in the community-based elderly. Arch Phys Med Rehabil. 75: (12) 1297-1301. [Medline]



This article has been cited by other articles:


Home page
 Journals of Gerontology Series A: Biological Sciences and Medical SciencesHome page
A. M. Jette, S. M. Haley, P. Ni, S. Olarsch, and R. Moed
Creating a Computer Adaptive Test Version of the Late-Life Function and Disability Instrument
J. Gerontol. A Biol. Sci. Med. Sci., November 1, 2008; 63(11): 1246 - 1256.
[Abstract] [Full Text] [PDF]

Home page
 ptjournalHome page
M. L Puthoff and D. H Nielsen
Relationships Among Impairments in Lower-Extremity Strength and Power, Functional Limitations, and Disability in Older Adults
Physical Therapy, October 1, 2007; 87(10): 1334 - 1347.
[Abstract] [Full Text] [PDF]

Home page
 Age AgeingHome page
J. Rosie and D. Taylor
Sit-to-stand as home exercise for mobility-limited adults over 80 years of age GrandStand SystemTM may keep you standing?
Age Ageing, September 1, 2007; 36(5): 555 - 562.
[Abstract] [Full Text] [PDF]

Home page
 Journals of Gerontology Series B: Psychological Sciences and Social ScienceHome page
E. McAuley, J. F. Konopack, K. S. Morris, R. W. Motl, L. Hu, S. E. Doerksen, and K. Rosengren
Physical activity and functional limitations in older women: influence of self-efficacy.
J. Gerontol. B. Psychol. Sci. Soc. Sci., September 1, 2006; 61(5): P270 - P277.
[Abstract] [Full Text] [PDF]

Home page
 ptjournalHome page
A. M Jette
Toward a Common Language for Function, Disability, and Health
Physical Therapy, May 1, 2006; 86(5): 726 - 734.
[Abstract] [Full Text] [PDF]

Home page
 Journals of Gerontology Series A: Biological Sciences and Medical SciencesHome page
E. McAuley, J. F. Konopack, R. W. Motl, K. Rosengren, and K. S. Morris
Measuring Disability and Function in Older Women: Psychometric Properties of the Late-Life Function and Disability Instrument
J. Gerontol. A Biol. Sci. Med. Sci., June 1, 2005; 60(7): 901 - 909.
[Abstract] [Full Text] [PDF]

Home page
 Psychosom. Med.Home page
T. A. Glass, L. F. Berkman, E. F. Hiltunen, K. Furie, M. M. Glymour, M. E. Fay, and J. Ware
The Families In Recovery From Stroke Trial (FIRST): Primary Study Results
Psychosom Med, November 1, 2004; 66(6): 889 - 897.
[Abstract] [Full Text] [PDF]

Home page
 StrokeHome page
M. M. Ouellette, N. K. LeBrasseur, J. F. Bean, E. Phillips, J. Stein, W. R. Frontera, and R. A. Fielding
High-Intensity Resistance Training Improves Muscle Strength, Self-Reported Function, and Disability in Long-Term Stroke Survivors
Stroke, June 1, 2004; 35(6): 1404 - 1409.
[Abstract] [Full Text] [PDF]

Home page
 GerontologistHome page
M. Farkas, A. M. Jette, S. Tennstedt, S. M. Haley, and V. Quinn
Knowledge Dissemination and Utilization in Gerontology: An Organizing Framework
Gerontologist, March 1, 2003; 43(90001): 47 - 56.
[Abstract] [Full Text] [PDF]

Home page
 Journals of Gerontology Series A: Biological Sciences and Medical SciencesHome page
A. M. Jette, S. M. Haley, W. J. Coster, J. T. Kooyoomjian, S. Levenson, T. Heeren, and J. Ashba
Late Life Function and Disability Instrument: I. Development and Evaluation of the Disability Component
J. Gerontol. A Biol. Sci. Med. Sci., April 1, 2002; 57(4): M209 - 216.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Full Text (PDF)
Services
Right arrow Download to citation manager
Citing Articles
Right arrow Citing Articles via HighWire
PubMed
Right arrow PubMed Citation

HOME ARCHIVE SEARCH TABLE OF CONTENTS