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Original Research |

Risk Factors and Precipitants of Long-Term Disability in Community Mobility: A Cohort Study of Older Persons

Thomas M. Gill, MD; Evelyne A. Gahbauer, MD, MPH; Terrence E. Murphy, PhD; Ling Han, MD, PhD; and Heather G. Allore, PhD
[+] Article and Author Information

From Yale University School of Medicine, New Haven, Connecticut.


Acknowledgment: The authors thank Denise Shepard, BSN, MBA, Andrea Benjamin, BSN, Barbara Foster, and Amy Shelton, MPH, for assistance with data collection; Wanda Carr and Geraldine Hawthorne, BS, for assistance with data entry and management; Linda Leo-Summers, MPH, for assistance with the figures; Peter Charpentier, MPH, for design and development of the study database and participant tracking system; and Joanne McGloin, MDiv, MBA, for her leadership and advice as the Project Director.

Grant Support: By grant R37AG17560 from the National Institute on Aging and Midcareer Investigator Award in Patient-Oriented Research K24AG021507 from the National Institute on Aging (Dr. Gill). The study was conducted at the Yale Claude D. Pepper Older Americans Independence Center (funded by National Institutes of Health grant P30AG21342).

Potential Conflicts of Interest: Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=M11-1227.

Reproducible Research Statement:Study protocol: Available from Dr. Gill (e-mail, thomas.gill@yale.edu). Statistical code: Available from Dr. Allore (e-mail, heather.allore@yale.edu). Data set: Not available.

Requests for Single Reprints: Thomas M. Gill, MD, Yale University School of Medicine, Adler Geriatric Assessment Center, 20 York Street, New Haven, CT 06504; e-mail, thomas.gill@yale.edu.

Current Author Addresses: Dr. Gill: Yale University School of Medicine, Adler Geriatric Assessment Center, 20 York Street, New Haven, CT 06504.

Drs. Gahbauer, Murphy, Han, and Allore: Yale Program on Aging, 300 George Street, Suite 775, New Haven, CT 06511.

Author Contributions: Conception and design: T.M. Gill, H.G. Allore.

Analysis and interpretation of the data: T.M. Gill, E.A. Gahbauer, T.E. Murphy, H.G. Allore.

Drafting of the article: T.M. Gill, T.E. Murphy, L. Han, H.G. Allore.

Critical revision of the article for important intellectual content: T.M. Gill, E.A. Gahbauer, T.E. Murphy, L. Han.

Final approval of the article: T.M. Gill, E.A. Gahbauer, T.E. Murphy, L. Han, H.G. Allore.

Statistical expertise: T.E. Murphy, L. Han, H.G. Allore.

Obtaining of funding: T.M. Gill.

Administrative, technical, or logistic support: T.M. Gill.

Collection and assembly of data: T.M. Gill, E.A. Gahbauer.


Ann Intern Med. 2012;156(2):131-140. doi:10.7326/0003-4819-156-2-201201170-00009
Text Size: A A A

Background: Relatively little is known about why older persons develop long-term disability in community mobility.

Objective: To identify the risk factors and precipitants for long-term disability in walking a quarter mile and driving a car.

Design: Prospective cohort study from March 1998 to December 2009.

Setting: Greater New Haven, Connecticut.

Participants: 641 persons, aged 70 years or older, who were active drivers or nondisabled in walking a quarter mile. Persons who were physically frail were oversampled.

Measurements: Candidate risk factors were assessed every 18 months. Disability in community mobility and exposure to potential precipitants, including illnesses or injuries leading to hospitalization or restricted activity, were assessed every month. Disability that lasted 6 or more consecutive months was considered long-term.

Results: 318 (56.0%) and 269 (53.1%) participants developed long-term disability in walking and driving, respectively. Seven risk factors were independently associated with walking disability and 8 were associated with driving disability; the strongest associations for each outcome were found for older age and lower score on the Short Physical Performance Battery. The precipitants had a large effect on long-term disability, with multivariate hazard ratios for each outcome greater than 6.2 for hospitalization and greater than 2.4 for restricted activity. The largest differences in absolute risk were generally observed in participants with a specific risk factor who were subsequently hospitalized.

Limitations: The observed associations may not be causal. The severity of precipitants was not assessed. The effect of the precipitants may have been underestimated because their exposure after the initial onset of disability was not evaluated.

Conclusion: Long-term disability in community mobility is common among older persons. Multiple risk factors, together with subsequent precipitants, greatly increase the likelihood of long-term mobility disability.

Primary Funding Source: National Institute on Aging, National Institutes of Health.

Figures

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Appendix Figure 2.
Participants in the 2 samples.

The first sample included 568 participants who were not disabled in walking a quarter mile at baseline, whereas the second included 507 participants who were driving a car at baseline. Of the 754 participants in the Precipitating Events Project, 434 (57.6%) were included in both samples and 113 (15.0%) were not included in either sample.

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Figure 1.
Absolute risk differences for precipitants and risk factors independently associated with long-term disability in walking a quarter mile.

Point estimates are accompanied by nonparametric 95% CIs. The absolute risk difference represents the absolute risk for the outcome when the risk factor is present minus the base risk (3.7%), which is the average probability of the outcome when all of the risk factors and precipitants in the final multivariate model are set to their reference levels, namely no precipitant, age 70 to 74 years, male sex, no chronic conditions, Mini-Mental State Examination score ≥24, functional self-efficacy score >27, Physical Activity Scale for the Elderly score ≥64 for men or ≥52 for women, and SPPB score ≥10. SPPB = Short Physical Performance Battery.

Grahic Jump Location
Grahic Jump Location
Figure 2.
Absolute risk differences for precipitants and risk factors independently associated with long-term disability in driving a car.

Point estimates are accompanied by nonparametric 95% CIs. The absolute risk difference represents the absolute risk for the outcome when the risk factor is present minus the base risk (4.1%), which is the average probability of the outcome when all of the risk factors and precipitants in the final multivariate model are set to their reference levels, namely no precipitant, age 70 to 74 years, male sex, mild or no visual impairment, no significant weight loss, Mini-Mental State Examination score ≥24, Physical Activity for the Elderly score ≥64 for men or ≥52 for women, SPPB score ≥10, and GMC time <8.8 s. GMC = gross motor coordination; SPPB = Short Physical Performance Battery.

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Summary for Patients

Why Do Many Older Persons Become Disabled in Walking and Driving?

The full report is titled “Risk Factors and Precipitants of Long-Term Disability in Community Mobility. A Cohort Study of Older Persons.” It is in the 17 January 2012 issue of Annals of Internal Medicine (volume 156, pages 131-140). The authors are T.M. Gill, E.A. Gahbauer, T.E. Murphy, L. Han, and H.G. Allore.

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