Risk factors and precipitants of long-term disability in community mobility: A cohort study of older persons

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 precip-itants 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.