Predictors of change in physical function in older adults in response to long-term, structured physical activity: the LIFE study

Authors: LAYNE, ANDREW - University Of Florida; HSU, FANG-CHI - Wake Forest University; BLAIR, STEVEN - University Of South Carolina; CHEN, SHYH-HUEI - Wake Forest University; DUNGAN, JENNIFER - Duke University; FIELDING, ROGER - Jean Mayer Human Nutrition Research Center On Aging At Tufts University; GLYNN, NANCY - University Of Pittsburgh; HAJDUK, ALEXANDRA - Yale University; KING, ABBY - Stanford University; MANINI, TODD - University Of Florida; MARSH, ANTHONY - Wake Forest University; PAHOR, MARCO - Stanford University; PELLEGRINI, CHRISTINE - Northwestern University; BUFORD, THOMAS - University Of Florida

Submitted to: Physical Medicine and Rehabilitation Archives
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/15/2016
Publication Date: 8/25/2016
Citation: Layne, A.S., Hsu, F., Blair, S.N., Chen, S., Dungan, J., Fielding, R.A., Glynn, N.W., Hajduk, A.M., King, A.C., Manini, T., Marsh, A.P., Pahor, M., Pellegrini, C.A., Buford, T.W. 2016. Predictors of change in physical function in older adults in response to long-term, structured physical activity: the LIFE study. Physical Medicine and Rehabilitation Archives. 98(1):11-24. https://doi.org/10.1016/j.apmr.2016.07.019.
DOI: https://doi.org/10.1016/j.apmr.2016.07.019

Interpretive Summary: To evaluate the extent of variability in functional responses to exercise in older adults, and to identify the influence of intervention adherence, physical activity, and health characteristics to this variability, we performed a secondary analysis using data from The Lifestyle Interventions and Independence for Elders (LIFE) Study. LIFE was a multicenter single masked randomized controlled study that enrolled participants in 2010 and 2011 and followed them for an average of 2.6 years. 1,635 sedentary men and women aged 70-89 years who had functional limitations were randomized to a structured moderate intensity walking, resistance, and flexibility exercise program or a health education program. Study measures included walking speed over 400-m course (1/4 mile) and a composite measure of lower extremity function (the Short Physical Performance Battery (SPPB)) assessed at baseline. Higher levels of physical function (walking speed and SPPB score) were negatively associated with the change in gait speed and SPPB score, while greater number of steps recorded per day was positively associated with change in walking speed and SPPB score. Other baseline factors associated with positive change in walking speed and/or SPPB score include younger age, lower body mass index, and higher self-reported physical activity. This study demonstrated that demographic and physical activity-related factors were associated with the extent of change in functional outcomes and should be considered when designing interventions for improving mobility in older adults.

Technical Abstract: Objectives: To evaluate the extent of variability in functional responses in participants in the Lifestyle Interventions and Independence for Elders (LIFE) study and to identify the relative contributions of intervention adherence, physical activity, and demographic and health characteristics to this variability. Design: Secondary analysis. Setting: Multicenter institutions. Participants: A volunteer sample (N = 1635) of sedentary men and women aged 70 to 89 years who were able to walk 400m but had physical limitations, defined as a Short Physical Performance Battery (SPPB) score 9. Interventions: Moderate-intensity physical activity (n = 818) consisting of aerobic, resistance, and flexibility exercises performed both centerbased (2 times/wk) and home-based (3-4times/wk) sessions or health education program (n=817) consisting of weekly to monthly workshops covering relevant health information. Main Outcome Measures: Physical function (gait speed over 400m) and lower extremity function (SPPB score) assessed at baseline and 6, 12, and 24 months. Results: Greater baseline physical function (gait speed, SPPB score) was negatively associated with change in gait speed (regression coefficient beta = -.185; P<.001) and change in SPPB score (beta =-.365; P<.001), whereas higher number of steps per day measured by accelerometry was positively associated with change in gait speed (beta=.035; P<.001) and change in SPPB score (beta =.525; P<.001). Other baseline factors associated with positive change in gait speed and/or SPPB score include younger age (P<.001), lower body mass index (P<.001), and higher self-reported physical activity (P<.002). Conclusions: Several demographic and physical activity-related factors were associated with the extent of change in functional outcomes in participants in the LIFE study. These factors should be considered when designing interventions for improving physical function in older adults with limited mobility.