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Table of Contents
Vol. 54, No. 2, 2008
Issue release date: May 2008
Section title: Clinical Section
Free Access
Gerontology 2008;54:79–86
(DOI:10.1159/000115004)

Explaining the Effect of Gender on Functional Transitions in Older Persons

Hardy S.E.a · Allore H.G.b · Guo Z.b · Gill T.M.b
aDepartment of Internal Medicine, University of Pittsburgh School of Medicine, Pittsburgh, Pa., and bDepartment of Internal Medicine, Yale University School of Medicine, New Haven, Conn., USA
email Corresponding Author

Abstract

Background: Women live longer but experience greater disability than men. The reasons for this gender difference in disability are not well understood. Objective: Our objectives were to determine if the higher prevalence of disability in women is due to greater incidence of disability, longer duration of disability, or both, and to identify factors that potentially explain these gender differences. Methods: 754 community-living persons aged 70 and older who were non-disabled (required no personal assistance) in four essential activities of daily living (ADLs) were assessed monthly for disability for up to 6 years. A multi-state extension of the proportional hazards model was used to determine the effects of gender on transitions between states of no disability, mild disability, severe disability, and death, and to evaluate potential mediators of these effects. Results: Women were more likely to make the transition from no disability to mild disability and less likely to make the transitions from mild to no disability and from both mild and severe disability to death. The gender difference in the transitions between no disability and mild disability was largely explained by differences in gait speed and physical activity, but gender difference in transitions to death persisted despite adjustment for multiple potential mediators. Conclusion: The higher prevalence of disability in women versus men is due to a combination of higher incidence and longer duration, resulting from lower rates of recovery and mortality among disabled women.

© 2008 S. Karger AG, Basel


  

Key Words

  • Epidemiology
  • Gender differences
  • Activities of daily living
  • Disability

References

  1. Hoyert DL, Kung HC, Smith BL: Deaths: Preliminary Data for 2003. National Vital Statistics Reports, vol 53, No 15. Hyattsville, National Center for Health Statistics, 2005.
  2. Newman AB, Brach JS: Gender gap in longevity and disability in older persons. Epidemiol Rev 2001;23:343–350.
  3. Leveille SG, Resnick HE, Balfour J: Gender differences in disability: evidence and underlying reasons. Aging Clin Exp Res 2000;12:106–112.
  4. Dunlop DD, Hughes SL, Manheim LM: Disability in activities of daily living: patterns of change and a hierarchy of disability. Am J Public Health 1997;87:378–383.
  5. Beckett LA, Brock DB, Lemke JH, Mendes de Leon CF, Guralnik JM, Fillenbaum GG, Branch LG, Wetle TT, Evans DA: Analysis of change in self-reported physical function among older persons in four population studies. Am J Epidemiol 1996;143:766–778.
  6. Strawbridge WJ, Kaplan GA, Camacho T, Cohen RD: The dynamics of disability and functional change in an elderly cohort: results from the Alameda County Study. J Am Geriatr Soc 1992;40:799–806.
  7. Gill TM, Desai MM, Gahbauer EA, Holford TR, Williams CS: Restricted activity among community-living older persons: incidence, precipitants and health care utilization. Ann Intern Med 2001;135:313–321.
  8. Gill TM, Williams CS, Tinetti ME: Assessing risk for the onset of functional dependence among older adults: the role of physical performance. J Am Geriatr Soc 1995;43:603–609.
  9. Folstein MF, Folstein SE, McHugh PR: ‘Mini-mental state:’ a practical method for grading the cognitive state of patients for the clinician. J Psychiatr Res 1975;12:189–198.
  10. Kohout FJ, Berkman LF, Evans DA, Cornoni-Huntley J: Two shorter forms of the CES-D depression symptoms index. J Aging Health 1993;5:179–193.
  11. Washburn RA, Smith KW, Jette AM, Janney CA: The physical activity scale for the elderly (PASE): development and evaluation. J Clin Epidemiol 1993;46:153–162.
  12. Sherbourne CD, Stewart AL: The MOS social support survey. Soc Sci Med 1991;32:705–714.
  13. Gill TM, Hardy SE, Williams CS: Underestimation of disability among community-living older persons. J Am Geriatr Soc 2002;50:1492–1497.
  14. Hardy SE, Gill TM: Recovery from disability among community-dwelling older persons. JAMA 2004;291:1596–1602.
  15. Hardy SE, Dubin JA, Holford TR, Gill TM: Transitions between states of disability and independence among older persons. Am J Epidemiol 2005;161:575–584.
  16. Ferrucci L, Guralnik JM, Simonsick EM, Salive M, Corti MC, Langlois J: Progressive versus catastrophic disability: a longitudinal view of the disablement process. J Gerontol A Biol Sci Med Sci 1996;51:M123–M130.
  17. Allison PD: Missing Data. Thousand Oaks, Sage Publications, 2002.
  18. Therneau TM, Grambsch PM: Modeling Survival Data: Extending the Cox Model. New York, Springer, 2000.
  19. Prentice RL, Williams BJ, Peterson AV: On the regression analysis of multivariate failure time data. Biometrika 1981;68:373–379.

    External Resources

  20. Lin DY, Wei LJ: The robust inference for the proportional hazards model. J Am Stat Assoc 1989;84:1074–1078.

    External Resources

  21. Allison PD: Survival Analysis Using SAS: A Practical Guide. Cary, SAS Institute Inc, 1995.
  22. Kraemer HC, Stice E, Kazdin A, Offord D, Kupfer D: How do risk factors work together? Mediators, moderators, and independent, overlapping, and proxy risk factors. Am J Psychiatry 2001;158:848–856.
  23. Stuck AE, Walthert JM, Nikolaus T, Bula CJ, Hohmann C, Beck JC: Risk factors for functional status decline in community-living elderly people: a systematic literature review. Soc Sci Med 1999;48:445–469.
  24. Miller ME, Rejeski WJ, Reboussin BA, Ten Have TR, Ettinger WH: Physical activity, functional limitations, and disability in older adults. J Am Geriatr Soc 2000;48:1264–1272.
  25. Gill TM, Robison JT, Tinetti ME: Predictors of recovery in activities of daily living among disabled older persons living in the community. J Gen Intern Med 1997;12:757–762.
  26. Magaziner J, Simonsick EM, Kashner TM, Hebel JR, Kenzora JE: Predictors of functional recovery one year following hospital discharge for hip fracture: a prospective study. J Gerontol A Biol Sci Med Sci 1990;45:M101–M107.
  27. Mendes de Leon CF, Beckett LA, Fillenbaum GG, Brock DB, Branch LG, Evans DA, Berkman LF: Black-white differences in risk of becoming disabled and recovering from disability in old age: a longitudinal analysis of two EPESE populations. Am J Epidemiol 1997;145:488–497.
  28. Fried LP, Kronmal RA, Newman AB, Bild DE, Mittelmark MB, Polak JF, Robbins JA, Gardin JM: Risk factors for 5-year mortality in older adults: the Cardiovascular Health Study. JAMA 1998;279:585–592.
  29. Crimmins EM, Saito Y, Reynolds SL: Further evidence on recent trends in the prevalence and incidence of disability among older Americans from two sources: the LSOA and the NHIS. J Gerontol B Psychol Sci Soc Sci 1997;52:S59–S71.
  30. Von Strauss E, Aguero-Torres H, Kareholt I, Winblad B, Fratiglioni L: Women are more disabled in basic activities of daily living than men only in very advanced ages: a study on disability, morbidity, and mortality from the Kungsholmen Project. J Clin Epidemiol 2003;56:669–677.
  31. Guralnik JM, LaCroix AZ, Abbott RD, Berkman LF, Satterfield S, Evans DA, Wallace RB: Maintaining mobility in late life. I. Demographic characteristics and chronic conditions. Am J Epidemiol 1993;137:845–857.
  32. Oman D, Reed D, Ferrara A: Do elderly women have more physical disability than men do? Am J Epidemiol 1999;150:834–842.
  33. Hansen K, Mahoney J, Palta M: Risk factors for lack of recovery of ADL independence after hospital discharge. J Am Geriatr Soc 1999;47:360–365.
  34. Michel JP, Hoffmeyer P, Klopfenstein C, Bruchez M, Grab B, d’Epinay CL: Prognosis of functional recovery 1 year after hip fracture: typical patient profiles through cluster analysis. J Gerontol A Biol Sci Med Sci 2000;55:M508–M515.
  35. Kempen GI, Sanderman R, Scaf-Klomp W, Ormel J: The role of depressive symptoms in recovery from injuries to the extremities in older persons. A prospective study. Int J Geriatr Psychiatry 2003;18:14–22.
  36. Mor V, Wilcox V, Rakowski W, Hiris J: Functional transitions among the elderly: patterns, predictors, and related hospital use. Am J Public Health 1994;84:1274–1280.
  37. Leveille SG, Penninx BW, Melzer D, Izmirlian G, Guralnik JM: Sex differences in the prevalence of mobility disability in old age: the dynamics of incidence, recovery, and mortality. J Gerontol B Psychol Sci Soc Sci 2000;55:S41–S50.
  38. Dunlop DD, Manheim LM, Sohn MW, Liu X, Chang RW: Incidence of functional limitation in older adults: the impact of gender, race, and chronic conditions. Arch Phys Med Rehabil 2002;83:964–971.
  39. Peek MK, Coward RT: Gender differences in the risk of developing disability among older adults with arthritis. J Aging Health 1999;11:131–150.
  40. Arber S, Cooper H: Gender differences in health in later life: the new paradox? Soc Sci Med 1999;48:61–76.
  41. Murtagh KNMA, Hubert HBP: Gender differences in physical disability among an elderly cohort. Am J Public Health 2004;94:1406–1411.
  42. Mitnitski A, Song X, Skoog I, Broe GA, Cox JL, Grunfeld E, Rockwood K: Relative fitness and frailty of elderly men and women in developed countries and their relationship with mortality. J Am Geriatr Soc 2005;53:2184–2189.
  43. Liang J, Bennett JM, Sugisawa H, Kobayashi E, Fukaya T: Gender differences in old age mortality: roles of health behavior and baseline health status. J Clin Epidemiol 2003;56:572–582.
  44. Lopopolo RB, Greco M, Sullivan D, Craik RL, Mangione KK: Effect of therapeutic exercise on gait speed in community-dwelling elderly people: a meta-analysis. Phys Ther 2006;86:520–540.
  45. King AC, Rejeski WJ, Buchner DM: Physical activity interventions targeting older adults. A critical review and recommendations. Am J Prev Med 1998;15:316–333.
  46. Melzer D, Lan TY, Tom BD, Deeg DJ, Guralnik JM: Variation in thresholds for reporting mobility disability between national population subgroups and studies. J Gerontol A Biol Sci Med Sci 2004;59:1295–1303.
  47. Merrill SS, Seeman TE, Kasl SV, Berkman LF: Gender differences in the comparison of self-reported disability and performance measures. J Gerontol A Biol Sci Med Sci 1997;52:M19–M26.
  48. American FactFinder; in US Census Bureau, 2003.
  49. Gill TM, Kurland B: The prognostic effect of prior disability episodes among nondisabled community-living older persons. Am J Epidemiol 2003;158:1090–1096.
  50. Magaziner J, Zimmerman SI, Gruber-Baldini AL, Hebel JR, Fox KM: Proxy reporting in five areas of functional status. Comparison with self-reports and observations of performance. Am J Epidemiol 1997;146:418–428.
  51. Kane RL, Finch M, Blewett L, Chen Q, Burns R, Moskowitz M: Use of post-hospital care by Medicare patients. J Am Geriatr Soc 1996;44:242–250.

  

Author Contacts

Susan Hardy
University of Pittsburgh, 3471 Fifth Avenue, Suite 500
Pittsburgh, PA 15213 (USA)
Tel. +1 412 692 2360, Fax +1 412 692 2370
E-Mail hardys@dom.pitt.edu

  

Article Information

Received: July 23, 2007
Accepted: November 7, 2007
Published online: January 30, 2008
Number of Print Pages : 8
Number of Figures : 2, Number of Tables : 3, Number of References : 51

  

Publication Details

Gerontology (International Journal of Experimental, Clinical, Behavioural and Technological Gerontology)

Vol. 54, No. 2, Year 2008 (Cover Date: May 2008)

Journal Editor: Meier-Ruge W. (Basel)
ISSN: 0304–324X (Print), eISSN: 1423–0003 (Online)

For additional information: http://www.karger.com/GER


Copyright / Drug Dosage / Disclaimer

Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher or, in the case of photocopying, direct payment of a specified fee to the Copyright Clearance Center.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in goverment regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

Abstract

Background: Women live longer but experience greater disability than men. The reasons for this gender difference in disability are not well understood. Objective: Our objectives were to determine if the higher prevalence of disability in women is due to greater incidence of disability, longer duration of disability, or both, and to identify factors that potentially explain these gender differences. Methods: 754 community-living persons aged 70 and older who were non-disabled (required no personal assistance) in four essential activities of daily living (ADLs) were assessed monthly for disability for up to 6 years. A multi-state extension of the proportional hazards model was used to determine the effects of gender on transitions between states of no disability, mild disability, severe disability, and death, and to evaluate potential mediators of these effects. Results: Women were more likely to make the transition from no disability to mild disability and less likely to make the transitions from mild to no disability and from both mild and severe disability to death. The gender difference in the transitions between no disability and mild disability was largely explained by differences in gait speed and physical activity, but gender difference in transitions to death persisted despite adjustment for multiple potential mediators. Conclusion: The higher prevalence of disability in women versus men is due to a combination of higher incidence and longer duration, resulting from lower rates of recovery and mortality among disabled women.

© 2008 S. Karger AG, Basel


  

Author Contacts

Susan Hardy
University of Pittsburgh, 3471 Fifth Avenue, Suite 500
Pittsburgh, PA 15213 (USA)
Tel. +1 412 692 2360, Fax +1 412 692 2370
E-Mail hardys@dom.pitt.edu

  

Article Information

Received: July 23, 2007
Accepted: November 7, 2007
Published online: January 30, 2008
Number of Print Pages : 8
Number of Figures : 2, Number of Tables : 3, Number of References : 51

  

Publication Details

Gerontology (International Journal of Experimental, Clinical, Behavioural and Technological Gerontology)

Vol. 54, No. 2, Year 2008 (Cover Date: May 2008)

Journal Editor: Meier-Ruge W. (Basel)
ISSN: 0304–324X (Print), eISSN: 1423–0003 (Online)

For additional information: http://www.karger.com/GER


Article / Publication Details

First-Page Preview
Abstract of Clinical Section

Received: 7/23/2007
Accepted: 11/7/2007
Published online: 1/30/2008
Issue release date: May 2008

Number of Print Pages: 8
Number of Figures: 2
Number of Tables: 3

ISSN: 0304-324X (Print)
eISSN: 1423-0003 (Online)

For additional information: http://www.karger.com/GER


Copyright / Drug Dosage

Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher or, in the case of photocopying, direct payment of a specified fee to the Copyright Clearance Center.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in goverment regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

References

  1. Hoyert DL, Kung HC, Smith BL: Deaths: Preliminary Data for 2003. National Vital Statistics Reports, vol 53, No 15. Hyattsville, National Center for Health Statistics, 2005.
  2. Newman AB, Brach JS: Gender gap in longevity and disability in older persons. Epidemiol Rev 2001;23:343–350.
  3. Leveille SG, Resnick HE, Balfour J: Gender differences in disability: evidence and underlying reasons. Aging Clin Exp Res 2000;12:106–112.
  4. Dunlop DD, Hughes SL, Manheim LM: Disability in activities of daily living: patterns of change and a hierarchy of disability. Am J Public Health 1997;87:378–383.
  5. Beckett LA, Brock DB, Lemke JH, Mendes de Leon CF, Guralnik JM, Fillenbaum GG, Branch LG, Wetle TT, Evans DA: Analysis of change in self-reported physical function among older persons in four population studies. Am J Epidemiol 1996;143:766–778.
  6. Strawbridge WJ, Kaplan GA, Camacho T, Cohen RD: The dynamics of disability and functional change in an elderly cohort: results from the Alameda County Study. J Am Geriatr Soc 1992;40:799–806.
  7. Gill TM, Desai MM, Gahbauer EA, Holford TR, Williams CS: Restricted activity among community-living older persons: incidence, precipitants and health care utilization. Ann Intern Med 2001;135:313–321.
  8. Gill TM, Williams CS, Tinetti ME: Assessing risk for the onset of functional dependence among older adults: the role of physical performance. J Am Geriatr Soc 1995;43:603–609.
  9. Folstein MF, Folstein SE, McHugh PR: ‘Mini-mental state:’ a practical method for grading the cognitive state of patients for the clinician. J Psychiatr Res 1975;12:189–198.
  10. Kohout FJ, Berkman LF, Evans DA, Cornoni-Huntley J: Two shorter forms of the CES-D depression symptoms index. J Aging Health 1993;5:179–193.
  11. Washburn RA, Smith KW, Jette AM, Janney CA: The physical activity scale for the elderly (PASE): development and evaluation. J Clin Epidemiol 1993;46:153–162.
  12. Sherbourne CD, Stewart AL: The MOS social support survey. Soc Sci Med 1991;32:705–714.
  13. Gill TM, Hardy SE, Williams CS: Underestimation of disability among community-living older persons. J Am Geriatr Soc 2002;50:1492–1497.
  14. Hardy SE, Gill TM: Recovery from disability among community-dwelling older persons. JAMA 2004;291:1596–1602.
  15. Hardy SE, Dubin JA, Holford TR, Gill TM: Transitions between states of disability and independence among older persons. Am J Epidemiol 2005;161:575–584.
  16. Ferrucci L, Guralnik JM, Simonsick EM, Salive M, Corti MC, Langlois J: Progressive versus catastrophic disability: a longitudinal view of the disablement process. J Gerontol A Biol Sci Med Sci 1996;51:M123–M130.
  17. Allison PD: Missing Data. Thousand Oaks, Sage Publications, 2002.
  18. Therneau TM, Grambsch PM: Modeling Survival Data: Extending the Cox Model. New York, Springer, 2000.
  19. Prentice RL, Williams BJ, Peterson AV: On the regression analysis of multivariate failure time data. Biometrika 1981;68:373–379.

    External Resources

  20. Lin DY, Wei LJ: The robust inference for the proportional hazards model. J Am Stat Assoc 1989;84:1074–1078.

    External Resources

  21. Allison PD: Survival Analysis Using SAS: A Practical Guide. Cary, SAS Institute Inc, 1995.
  22. Kraemer HC, Stice E, Kazdin A, Offord D, Kupfer D: How do risk factors work together? Mediators, moderators, and independent, overlapping, and proxy risk factors. Am J Psychiatry 2001;158:848–856.
  23. Stuck AE, Walthert JM, Nikolaus T, Bula CJ, Hohmann C, Beck JC: Risk factors for functional status decline in community-living elderly people: a systematic literature review. Soc Sci Med 1999;48:445–469.
  24. Miller ME, Rejeski WJ, Reboussin BA, Ten Have TR, Ettinger WH: Physical activity, functional limitations, and disability in older adults. J Am Geriatr Soc 2000;48:1264–1272.
  25. Gill TM, Robison JT, Tinetti ME: Predictors of recovery in activities of daily living among disabled older persons living in the community. J Gen Intern Med 1997;12:757–762.
  26. Magaziner J, Simonsick EM, Kashner TM, Hebel JR, Kenzora JE: Predictors of functional recovery one year following hospital discharge for hip fracture: a prospective study. J Gerontol A Biol Sci Med Sci 1990;45:M101–M107.
  27. Mendes de Leon CF, Beckett LA, Fillenbaum GG, Brock DB, Branch LG, Evans DA, Berkman LF: Black-white differences in risk of becoming disabled and recovering from disability in old age: a longitudinal analysis of two EPESE populations. Am J Epidemiol 1997;145:488–497.
  28. Fried LP, Kronmal RA, Newman AB, Bild DE, Mittelmark MB, Polak JF, Robbins JA, Gardin JM: Risk factors for 5-year mortality in older adults: the Cardiovascular Health Study. JAMA 1998;279:585–592.
  29. Crimmins EM, Saito Y, Reynolds SL: Further evidence on recent trends in the prevalence and incidence of disability among older Americans from two sources: the LSOA and the NHIS. J Gerontol B Psychol Sci Soc Sci 1997;52:S59–S71.
  30. Von Strauss E, Aguero-Torres H, Kareholt I, Winblad B, Fratiglioni L: Women are more disabled in basic activities of daily living than men only in very advanced ages: a study on disability, morbidity, and mortality from the Kungsholmen Project. J Clin Epidemiol 2003;56:669–677.
  31. Guralnik JM, LaCroix AZ, Abbott RD, Berkman LF, Satterfield S, Evans DA, Wallace RB: Maintaining mobility in late life. I. Demographic characteristics and chronic conditions. Am J Epidemiol 1993;137:845–857.
  32. Oman D, Reed D, Ferrara A: Do elderly women have more physical disability than men do? Am J Epidemiol 1999;150:834–842.
  33. Hansen K, Mahoney J, Palta M: Risk factors for lack of recovery of ADL independence after hospital discharge. J Am Geriatr Soc 1999;47:360–365.
  34. Michel JP, Hoffmeyer P, Klopfenstein C, Bruchez M, Grab B, d’Epinay CL: Prognosis of functional recovery 1 year after hip fracture: typical patient profiles through cluster analysis. J Gerontol A Biol Sci Med Sci 2000;55:M508–M515.
  35. Kempen GI, Sanderman R, Scaf-Klomp W, Ormel J: The role of depressive symptoms in recovery from injuries to the extremities in older persons. A prospective study. Int J Geriatr Psychiatry 2003;18:14–22.
  36. Mor V, Wilcox V, Rakowski W, Hiris J: Functional transitions among the elderly: patterns, predictors, and related hospital use. Am J Public Health 1994;84:1274–1280.
  37. Leveille SG, Penninx BW, Melzer D, Izmirlian G, Guralnik JM: Sex differences in the prevalence of mobility disability in old age: the dynamics of incidence, recovery, and mortality. J Gerontol B Psychol Sci Soc Sci 2000;55:S41–S50.
  38. Dunlop DD, Manheim LM, Sohn MW, Liu X, Chang RW: Incidence of functional limitation in older adults: the impact of gender, race, and chronic conditions. Arch Phys Med Rehabil 2002;83:964–971.
  39. Peek MK, Coward RT: Gender differences in the risk of developing disability among older adults with arthritis. J Aging Health 1999;11:131–150.
  40. Arber S, Cooper H: Gender differences in health in later life: the new paradox? Soc Sci Med 1999;48:61–76.
  41. Murtagh KNMA, Hubert HBP: Gender differences in physical disability among an elderly cohort. Am J Public Health 2004;94:1406–1411.
  42. Mitnitski A, Song X, Skoog I, Broe GA, Cox JL, Grunfeld E, Rockwood K: Relative fitness and frailty of elderly men and women in developed countries and their relationship with mortality. J Am Geriatr Soc 2005;53:2184–2189.
  43. Liang J, Bennett JM, Sugisawa H, Kobayashi E, Fukaya T: Gender differences in old age mortality: roles of health behavior and baseline health status. J Clin Epidemiol 2003;56:572–582.
  44. Lopopolo RB, Greco M, Sullivan D, Craik RL, Mangione KK: Effect of therapeutic exercise on gait speed in community-dwelling elderly people: a meta-analysis. Phys Ther 2006;86:520–540.
  45. King AC, Rejeski WJ, Buchner DM: Physical activity interventions targeting older adults. A critical review and recommendations. Am J Prev Med 1998;15:316–333.
  46. Melzer D, Lan TY, Tom BD, Deeg DJ, Guralnik JM: Variation in thresholds for reporting mobility disability between national population subgroups and studies. J Gerontol A Biol Sci Med Sci 2004;59:1295–1303.
  47. Merrill SS, Seeman TE, Kasl SV, Berkman LF: Gender differences in the comparison of self-reported disability and performance measures. J Gerontol A Biol Sci Med Sci 1997;52:M19–M26.
  48. American FactFinder; in US Census Bureau, 2003.
  49. Gill TM, Kurland B: The prognostic effect of prior disability episodes among nondisabled community-living older persons. Am J Epidemiol 2003;158:1090–1096.
  50. Magaziner J, Zimmerman SI, Gruber-Baldini AL, Hebel JR, Fox KM: Proxy reporting in five areas of functional status. Comparison with self-reports and observations of performance. Am J Epidemiol 1997;146:418–428.
  51. Kane RL, Finch M, Blewett L, Chen Q, Burns R, Moskowitz M: Use of post-hospital care by Medicare patients. J Am Geriatr Soc 1996;44:242–250.