Biomarkers for length of hospital stay, changes in muscle mass, strength and physical function in older medical patients: protocol for the Copenhagen PROTECT study-a prospective cohort study.

INTRODUCTION: Sarcopenia is generally used to describe the age-related loss of muscle mass and strength believed to play a major role in the pathogenesis of physical frailty and functional impairment that may occur with old age. The knowledge surrounding the prevalence and determinants of sarcopenia in older medical patients is scarce, and it is unknown whether specific biomarkers can predict physical deconditioning during hospitalisation. We hypothesise that a combination of clinical, functional and circulating biomarkers can serve as a risk stratification tool and can (i) identify older acutely ill medical patients at risk of prolonged hospital stays and (ii) predict changes in muscle mass, muscle strength and function during hospitalisation. METHOD AND ANALYSIS: The Copenhagen PROTECT study is a prospective cohort study consisting of acutely ill older medical patients admitted to the acute medical ward at Copenhagen University Hospital, Bispebjerg and Frederiksberg, Denmark. Assessments are performed within 24 hours of admission and include blood samples, body composition, muscle strength, physical function and questionnaires. A subgroup of patients transferred to the Geriatric Department are included in a smaller geriatric cohort and have additional assessments at discharge to evaluate the relative change in circulating biomarker concentrations, body composition, muscle strength and physical function during hospitalisation. Enrolment commenced 4 November 2019, and proceeds until August 2021. ETHICS AND DISSEMINATION: The study protocol has been approved by the local ethics committee of Copenhagen and Frederiksberg (H-19039214) and the Danish Data Protection Agency (P-2019-239) and all experimental procedures were performed in accordance with the Declaration of Helsinki. Findings from the project, regardless of the outcome, will be published in relevant peer-reviewed scientific journals in online (www.clinicaltrials.gov). TRIAL REGISTRATION NUMBER: NCT04151108.

The Copenhagen Sarcopenia Study: lean mass, strength, power, and physical function in a Danish cohort aged 20-93 years.

BACKGROUND: Despite no international consensus on the diagnostic criteria for sarcopenia, low lean mass, muscle strength, and physical function are important risk factors for disability, frailty, and mortality in older individuals, as well as in a wide range of patients with muscle loss. Here, we provide a population-based reference material of total and regional lean body mass, muscle strength/power parameters, and physical function in a healthy cohort of Danish men and women across the lifespan. METHODS: Volunteers aged 20-93 years from the Copenhagen City Heart Study were invited to establish a Danish reference material (Copenhagen Sarcopenia Study) on lean mass characteristics [appendicular lean mass (ALM), iDXA, GE Lunar], muscle function [handgrip strength (HGS), Jamar dynamometer and leg extension power (LEP), Nottingham Power Rig], and physical function [30 s sit-to-stand test (STS), 10-m maximal and habitual gait speed (GS)]. RESULTS: A total of 1305 participants [729 women (age: 56.4 ± 18.9 years, height: 1.66 ± 0.01 m, body mass index: 24.6 ± 4.3 kg/m2 and 576 men, age: 57.0 ± 17.5 years, height: 1.80 ± 0.07 m, body mass index: 26.0 ± 3.9 kg/m2 ] completed all measurements and were included in the present analysis. Lean mass characteristics (TLM, ALM, and ALM/h2 ) decreased with increasing age in both men and women (P < 0.001). Men demonstrated larger absolute and relative total ALM and higher HGS and LEP compared with women at all age intervals (P < 0.001). HGS and LEP decreased progressively with age in both men and women (P < 0.01); 30 s STS performance, habitual GS, and maximal GS decreased at an accellerated rate of decline with increasing age in both men and women (P < 0.001). Habitual GS was reduced in men and women aged ≥70 years, while maximal GS was reduced from the age of ≥60 years compared with young adults (P < 0.001). Regardless of sex, 30 s STS was reduced from the age of ≥50 years compared with the young reference group (P < 0.001) CONCLUSIONS: While the power-based measurements (LEP and 30 s STS) started to decline already at age +50 years, less power-based parameters (GS and HGS) and lean mass characteristics (TLM, ALM, and ALM/h2 ) remained unaltered until after the age of +70 years. Notably, the cut-off thresholds derived in the present study differed from earlier reference data, which underlines the importance of obtaining updated and local reference materials.