A Taxonomy to Characterize Stressor Variation in Studies of Physical Resilience and its Illustration in Total Knee Replacement

Abstract Background This study aimed to develop a conceptual framework and empirical measures to characterize stressor magnitude and type in the context of total knee replacement (TKR) and to investigate their relationship with resilience phenotypes. Methods A sequential elicitation process was used to identify key stressor characteristics, categorized as exogenous or endogenous. Resilience phenotypes were created as (postsurgery−[baseline or presurgery]) changes in 4 measures of physical function/symptoms selected based on their relevance to TKR outcomes. These measures included: the Short Physical Performance Battery score (SPPB), the Pittsburgh Fatigability Scale (PFS), the Short Form-36 physical component summary score, and the Knee Injury And Osteoarthritis Outcome Score quality of life subscale. Results Analyses revealed few associations between baseline phenotype measurements and stressor characteristics. Several consistent adjusted associations were observed between stressor characteristics and 6-month resilience phenotypes. All endogenous measurements analyzed exhibited the expected direction of association with PFS change from baseline to 6 months, indicating that higher stress levels predicted a diminished return of vigor postsurgery; intraoperative blood loss exhibited the strongest association. Outpatient versus inpatient procedures were associated with more beneficial change from baseline to 6 months of all resiliency phenotypes; SPPB score recovery exhibited the strongest association. Other individual strong associations were observed, but with less consistency across phenotypic trajectories or stressor characteristics. Conclusions The study highlights the importance of considering stressor variation in resilience research. The conceptual framework and empirical measures developed provide a foundation for future investigations into the factors influencing resilience to physical stressors in older adults.