Author
ESPELAND, MARK - WAKE FOREST UNIV | |
GILL, THOMAS - YALE UNIV | |
GURALNIK, JACK - NIA | |
MILLER, MIKE - WAKE FOREST UNIV | |
Fielding, Roger | |
NEWMAN, ANNE - UNIV PITTSBURGH | |
PAHOR, MARCO - UNIV FLORIDA |
Submitted to: Journal of Gerontology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 3/9/2007 Publication Date: 11/1/2007 Citation: Espeland, M.A., Gill, T.M., Guralnik, J., Miller, M.E., Fielding, R., Newman, A., Pahor, M. 2007. Designing Clinical Trials of Intervention for Mobility Disability: Results from the Lifestyle Interventions and Independence for Elders (LIFE) Pilot Trial. Journal of Gerontology. 62(11):1237-1243. Interpretive Summary: As the life expectancy in the United States has continued to rise, the maintenance of physical and cognitive independence of older Americans has emerged as a major clinical and public health priority. A critical factor in an older person’s ability to function independently is mobility, or the ability to move without assistance. Older people who lose mobility are less likely to remain in the community, have higher rates of morbidity, mortality, and hospitalizations and experience a poorer quality of life. Several studies suggest that regular physical activity may improve physical performance, but definitive evidence showing that mobility disability can be prevented is lacking. We conducted “Lifestyle Interventions and Independence For Elders-LIFE” pilot study. Clinical trials to assess interventions for mobility disability are critically needed, however data for efficiently designing such trials are lacking. Results are described from the LIFE pilot clinical trial, in which 424 volunteers aged 70-89 years were randomly assigned to one of two interventions -- physical activity or a healthy aging education program -- and followed for a planned minimum of 12 months. We evaluated the longitudinal distributions of four standardized outcomes to contrast how they may serve as primary outcomes of future clinical trials: ability to walk 400 meters, ability to walk 4 meters in <10 seconds, a physical performance battery, and a questionnaire focused on physical function. Changes in all four outcomes were related to each other statistically throughout the study. We found that one test, the ability to walk 400 meters, provided the smallest sample size projections (i.e. appeared to be the most efficient outcome). A four-year trial based on a primary outcome of 400 meter walk would require a sample size of 855 to 2,222 to detect an intervention effect. Future clinical trials of interventions designed to influence mobility disability may be most efficient if they adopt the ability to complete a 400 meter walk as their primary outcome. Technical Abstract: Clinical trials to assess interventions for mobility disability are critically needed, however data for efficiently designing such trials are lacking. Our results are described from the LIFE pilot clinical trial, in which 424 volunteers aged 70-89 years were randomly assigned to one of two interventions -- physical activity or a healthy aging education program -- and followed for a planned minimum of 12 months. We evaluated the longitudinal distributions of four standardized outcomes to contrast how they may serve as primary outcomes of future clinical trials: ability to walk 400 meters, ability to walk 4 meters in =10 seconds, a physical performance battery, and a questionnaire focused on physical function. Changes in all four outcomes were inter-related over time. The ability to walk 400 meters as a dichotomous outcome provided the smallest sample size projections (i.e. appeared to be the most efficient outcome). It loaded most heavily on the underlying latent variable in structural equation modeling (with a weight of 67.3%). A four-year trial based on the outcome of 400 meter walk is projected to require N=855 to 2,222 to detect an intervention effect of 30% to 20% with 90% power. Future clinical trials of interventions designed to influence mobility disability may be most efficient if they adopt the ability to complete a 400 meter walk as their primary outcome. As the life expectancy of older Americans increases, prevention of age-associated physical function decline and disabilities has emerged as a major clinical and public health priority. A critical factor in an older person’s ability to function independently is mobility, the ability to move without assistance. Older people who lose mobility are less likely to remain in the community, have higher rates of morbidity and mortality, have more hospitalizations, and experience a poorer quality of life. There is growing impetus for clinical trials to be conducted aimed at improving mobility outcomes. For major investments to be made, it is important that these trials are designed efficiently, which includes informed decisions on which outcomes have the best measurement characteristics, what effect sizes should be targeted, and how many participants are required. We use data collected by the Lifestyle Interventions and Independence for Elders Pilot (LIFE-P) trial to address these design issues. |