Limited ability to walk 1/4 mile, reported by almost half of community-dwelling older adults, is a strong independent predictor not only of future disability in activities of daily living, but also of mortality, health care costs, and health care utilization. These data demonstrate the critical importance of mobility disability as a clear, conspicuous marker of high risk among older adults, including those whose capacity to manage their activities of daily living might otherwise conceal more precarious health. In an era of increasingly complex health care challenges, self-reported mobility offers providers a rare advantage: a powerful assessment tool that is simple, discrete, quick, unburdensome, and effectively free. Mobility disability can be easily assessed in any clinical setting, allowing providers to identify vulnerable older adults for preventive interventions or extra services.
Self-reported mobility provides short-term prognostic information above and beyond demographic factors, chronic diseases, and health behaviors. This information can identify Medicare beneficiaries for enrollment in demonstration projects designed to improve health outcomes or prevent recurrent hospitalizations. For example, older adults with chronic diseases and mobility limitations might benefit more from disease management programs than otherwise similar mobile patients. In addition, inability to walk 1/4 mile can help identify older adults at high risk of mortality and thus unlikely to benefit from selected screening or preventive therapies.
Ours is the first study of which we are aware to examine the relationship between ability to walk 1/4 mile and subsequent ADL difficulty and health care utilization and costs. In fact, relatively few prior studies of self-reported mobility disability have looked at subsequent outcomes. Inability to walk 1/2 mile (after adjustment for age and sex) has been associated with greater mortality in community-dwelling adults aged 70 years or older.11
Bowen and Gonzalez found that higher self-reported health care utilization predicted greater mobility disability.7
Although difficulty walking 1/4 mile is unlikely to directly cause mortality and increased health care utilization, mobility disability likely reflects a greater burden of underlying preclinical disease or physiologic abnormalities not captured by assessment of chronic diseases and other health risk factors. Cumulative burden of subclinical physiologic abnormalities12
, metabolic syndrome (without cardiovascular disease or diabetes),13
high levels of inflammatory markers,14,15
and limitations in peak expiratory flow16
have all been associated with incidence of mobility disability in large epidemiologic studies of older adults. Self-reported mobility may offer a simple proxy for clinically significant risk factors and conditions that providers usually lack the resources to assess.
Difficulty walking 1/4 mile may also be a simple way of monitoring changes over time in health and function, although further study would be needed to assess this measure’s sensitivity to change. Mobility disability is a dynamic condition and transitions between different levels of ability to walk 1/4 mile are common among older adults.17
Interventions can improve objective ability to walk 1/4 mile; further studies are needed to determine if improvements in self-reported walking ability are associated with corresponding decreases in mortality and health care utilization. In addition, future studies should compare the performance of walking difficulty with other methods of screening risk of disability, death, and future utilization.
The nationally representative sample and thorough data on health care utilization and costs are strengths of our study. However, several limitations should also be noted. First, due to sample size limitations, we collapsed ‘a little’, ‘some’, and ‘a lot’ of difficulty walking 1/4 mile into a single category. There are likely differences among those reporting different levels of difficulty, which should be further investigated. Second, the MCBS contains no standardized assessment of cognition; older adults with cognitive impairment may not be accurate in their assessment of their walking ability and other self-report items. Third, 12% of the interviews were completed by a proxy. However, despite the significant differences between respondents with or without a proxy in walking ability, exclusion of proxy responses did not substantively alter the results (data not shown). Finally, the data presented, with the exclusion of total costs and hospitalizations, are self-reported. We are unable to relate self-reported ability to walk 1/4 mile to any measures of physical performance. However, previous studies have shown that performance-based and self-report measures provide complementary information about function.18,19
In conclusion, older adults who report limited ability to walk 1/4 mile are at high risk for mortality, basic and instrumental ADL disability, high health care utilization, and high costs within the next year. This increased risk is not explained by age, socioeconomic status, chronic conditions, smoking, BMI, or self-rated health. Fortunately, self-reported limitation in walking 1/4 mile can be assessed easily, and therefore can be a potent tool to improve the targeting of care management and preventive interventions to the older adults who need them most.