Science News: Relative Sit-to-Stand Muscle Power Predicts an Older Adult's Physical Independence at Age of 90 Yrs Beyond That of Relative Handgrip Strength, Physical Activity, and Sedentary Time: A Cross-sectional Analysis

Submitted by: Joshua M. Wilson, MD
Edited by: Nakul Katyal, MD

Hetherington-Rauth M, Magalhães JP, Alcazar J, et al. Relative Ssit-to-stand muscle power predicts an older adult's physical independence at age of 90 yrs beyond that of relative handgrip strength, physical activity, and sedentary time: A cross-sectional analysis. Am J Phys Med Rehabil. 2022;101(11):995-1000. doi:10.1097/PHM.0000000000001945

Summary: Functional decline associated with advanced age results in significant morbidity and mortality, in addition to increased demand on healthcare systems. Models and testing to predict functional decline help healthcare systems direct resources to vulnerable individuals that are at risk of future loss of independence.
 
The authors build on previous studies showing muscle power to be a greater predictor of age-related decline compared to evaluation using muscle strength or mass-based metrics. Using a cross-sectional study of 1,748 Portuguese adults over > 65 years old, they conducted multi-logistical regression analysis to compared standardized handgrip strength, sit-to-stand (STS) and sedentary time as predictors of moderate-high function at 90 years of age using the Composite Physical Functional (CPF) scale. Power analyses found that relative STS power assessment was a stronger predictor of anticipated independence at the age of 90 compared to sedentary time and commonly used handgrip testing.
 
They compared relative STS power quartiles demonstrating a graded response with prediction of a moderate-high functioning status at the age of 90. With an odds ratio up to 11.48 using the 4^th quartile of relative STS strength.
 
Using receiver operator characteristic curve analysis, they determined optimal cut-off values for relative STS power based on both sex and age that would predict independence at the age of 90. From this analysis, they derived an equation using individual age, gender, and relative STS power to predict the risk of losing independence later in life.

Comments: The authors cite that their findings were limited by being a cross-sectional study, and their reliance on using CPF self-reported scales. They believe that they have shown that relative STS strength out-performed handgrip as predictor for age associated functional decline. Furthermore, their analysis provided optimized cutoffs to screen individuals for future functional decline.
 
This study provided benefit by helping to establish a screening test that is easy to use and does not require the use of specialized equipment. Areas for further exploration would include the use of prospective studies to assess the outcomes of this predictive model once the individuals have reached the age 90. If use of relative STS power were to be shown to successfully predict independence in advanced age, then future studies should focus on modalities and timing of interventions to prevent such functional declines.

Article of similar interest: Alcazar J, Alegre LM, Van Roie E, et al. Relative sit-to-stand power: aging trajectories, functionally relevant cut-off points, and normative data in a large European cohort. J Cachexia Sarcopenia Muscle. 2021;12(4):921-932. doi:10.1002/jcsm.12737