71 Changes in Muscle Strength in Older Patients During Hospitalisation: A Prospective Repeated Measures Cohort Study

Abstract Introduction Hospital associated deconditioning is a well-established phenomenon. Whilst mechanisms are not well understood, one is thought to be skeletal muscle wasting and/or loss of muscle strength. The primary aim of this study was to investigate changes in knee-extension muscle strength in older patients during and after an acute-hospital admission. We also aimed to explore the potential contributions of frailty, acute-illness severity and sedentary activity, with changes in knee-extension strength. Methods This was a prospective repeated-measures cohort study. Measurements of muscle strength and functional mobility were taken at recruitment, on day 7 of admission (or at discharge if earlier) and again 4-6 weeks post-hospitalisation. During the first 7 days of admission, daily measurements of muscle strength were taken. Results We recruited 70 participants, of which 65 had at least one repeated measure in hospital. Median age was 84 years, and participants participated in the study for a median of 6 days whilst in hospital, on average participants were ‘active’ for less than 4% of the day. Knee-extension strength significantly reduced by approximately 11% during hospitalisation, but no significant changes occurred post-hospitalisation. A repeated-measures mixed model included 292 observations from 62 participants and showed a significant decrease in the reduction in muscle strength as patients' sedentary time decreased on days 2 to 7 of the study. Additionally, the model showed that a higher frailty score, higher baseline knee-extension strength, lower baseline c-reactive protein levels were associated with greater loss in knee-extension strength during hospitalisation. Association between change in functional mobility after hospitalisation and change in knee-extension strength during hospitalisation was non-significant. Conclusion Our findings provide an important link in understanding the mechanisms and relative contributions of risk factors to hospital associated deconditioning. Further research is needed to confirm these findings and examine the impact of reducing sedentary time on muscle strength during and post-hospitalisation.