MOBILITY AND FUNCTIONAL OUTCOMES FOR SARCOPENIA TRIALS

Abstract

Major mobility disability (MMD) (1, 2), defined as inability to walk ¼ mile or 400 m, is a relevant definite outcome in clinical trials. MMD is of major public health significance. Ability to walk ¼ mile is measured in the US census (3) and in most epidemiologic surveys (4). The MMD outcome based on the 400 m walk test is a feasible, objective, reliable (5), well-validated and important clinical and public health outcome in older people (1, 2, 6), which has been successfully implemented in the LIFE-Pilot and LIFE (7, 8). We have shown it to be a more efficient outcome for clinical trials than self-reported disability or the Short Physical Performance Battery (SPPB) (9). Public health agencies use ability to walk ¼ mile or 400 m to define need and policy impact of interventions (4). Finally, people reporting the inability to walk 400 m incur higher health care costs of $4,000 per person per year, compared with those not reporting inability to walk 400 m (4, 6, 10-12) MMD is operationalized as the inability to complete a 400 m walk test within 15 min without sitting or help of another person or walker (2). Completing the walk in >15 min would be in an extremely slow pace (<0.45 m/sec), which is of little utility in daily life (13). A higher cut point (30 or 60 min), makes the assessment impractical and does not add to the clinical significance of the outcome. The time to walk 400 meters and the ability to complete the test will provide data to test effects of the interventions resulting from both attenuation of decline and increase in walking speed.