Trajectory of Handgrip Strength Is Predictive of Worsening Physical Function: Application of Joint Functional Principal Components and Survival Analysis to Sparse Longitudinal Data

• Activity Number: 76
• Type: Contributed
• Date/Time: Sunday, August 9, 2015 : 4:00 PM to 5:50 PM
• Sponsor: Section on Statistics in Epidemiology
• Author(s): Qian-Li Xue* and Tong Tong Wu and Paulo Chaves
• Companies: The Johns Hopkins University and Rochester University and Florida International University
• Keywords: Functional Covariates ; Functional Data Analysis ; Functional Principal Components ; Longitudinal Data ; Partial Follow-up ; Survival Analysis

Abstract

Aging is associated with progressive loss of skeletal muscle mass and strength referred to as sarcopenia, a significant risk factor for late-life vulnerability and mortality. This study aims to evaluate the heterogeneity of short-term (6-month) trajectory of grip strength, and its impact on long-term (2-year) incidence of physical impairments and disability among older women. The analytic sample is comprised of 84 moderately to severely disabled women aged 65 years and over who were evaluated on a weekly basis over six months, followed by additional five semi-annual visits for a total follow-up of three years. The analytic model combines functional principal components analysis and survival analysis. Compared to the conventional functional data analysis, this approach has the advantage of handling sparse and irregularly spaced longitudinal data. Using this approach, we found that lower baseline grip strength, faster rate of decline, and greater intra-person variability in the short term were associated with greater risk of developing physical impairments in older age, suggesting that muscle strength trajectory provides a previously undiscovered window into late-life vulnerability.