Sarcopenia in patients with hip fracture. A multicenter prospective study with one-year follow-up

Sarcopenia is a geriatric syndrome of reduced muscle mass and physical performance associated with falls, fractures, impairments in activities of daily living, and mortality. Hip fractures are fractures of the upper third of the femur and typically occur in older persons after a fall. They are associated with lifelong impairments of mobility, mortality and risk of institutionalization. Hip fractures are common, preventable and in many places receive suboptimal care. This thesis is based on the research project sarcopenia in patients with hip fracture. The project is a prospective study with oneyear follow-up on older acute hip fracture patients living in the community, admitted at three hospitals: Haraldsplass Deaconess Hospital and Haukeland University Hospital in Bergen and Diakonhjemmet Hospital in Oslo, Norway in the period of 2011-2013. The aim of this thesis is to investigate sarcopenia as a clinically useful risk factor for adverse clinical outcomes after hip fracture. Our findings are presented in four papers. In the first paper we studied anthropometry and bioelectrical impedance analysis for determining muscle mass in patients with hip fracture, using dual-energy X-ray absorptiometry as the reference method. We found that muscle mass measured by single frequency bioelectrical impedance and anthropometry can identify patients with low muscle mass, which is a necessary step in assessing sarcopenia at the bedside. In the second paper we investigated how hip fracture, surgical repair and surgical implants affected measurements by bioelectrical impedance analysis. Bioelectrical impedance analysis on the same side of the body as the fracture was affected in the days after surgery, but not after three months. Measurements by bioelectrical impedance analysis were not affected by type of surgical implant. Our findings support the use of bioelectrical impedance analysis in subjects who live with surgical implants and after surgery. We recommend measuring the unfractured side if bioelectrical impedance analysis is used to determine body composition in the days after hip fracture surgery. In the third paper, we assessed the feasibility of determining sarcopenia in postoperative patients with hip fracture, and the prevalence of sarcopenia. Sarcopenia status, estimated by anthropometry, grip strength and self-reported pre-fracture mobility, was assessed in 202 out of 282 participants. The prevalence of sarcopenia was 37% and associated with increasing age, comorbidities and malnutrition. There was no difference in the prevalence of sarcopenia by sex, but men with hip fracture had a higher prevalence of low muscle mass. Our findings support sarcopenia as a clinically relevant risk factor after hip fracture. In the fourth paper, we investigated how sarcopenia status predicted change in mobility and other clinical outcomes at one year after hip fracture. Sarcopenia did not predict change in mobility. Participants with sarcopenia had lower mobility and more impairments in activities of daily living and an increased risk of becoming a resident of a nursing home and death. Pre-fracture mobility predicted mobility at one year. Sarcopenia needs further validation in patients with hip fracture by exploring other definitions, techniques and cut-points in order to estimate future risk and provide personalized medicine. We recommend that all hip fracture patients have their prefracture mobility assessed to determine their risk of adverse outcomes and as a benchmark for successful rehabilitation. This thesis expands the knowledge about sarcopenia to a vulnerable group of patients. Our findings support sarcopenia as a clinically relevant risk factor in acute hip fracture patients. Determining sarcopenia is feasible, it is prevalent in patients with hip fracture and it is associated with comorbidities, malnutrition, mobility and becoming a resident of a nursing home