Muscle Strength and Muscle Mass as Predictors of Hospital Length of Stay in Patients with Moderate to Severe COVID-19: A Prospective Observational Study

AbstractImportanceStrength and muscle mass are predictors of relevant clinical outcomes in critically ill patients, but in hospitalized patients with COVID-19 remains to be determined.ObjectiveTo investigate whether muscle strength or muscle mass are predictive of hospital length of stay (LOS) in patients with moderate to severe COVID-19.DesignProspective observational study.SettingClinical Hospital of the School of Medicine of the University of Sao Paulo.ParticipantsOne hundred ninety-six patients were evaluated. Ten patients did not test positive for SARS-CoV-2 during hospitalization and were excluded from the analyses. The sample comprised patients of both sexes (50% male) with a mean age (SD) of 59 (±15) years, body mass index of 29.5 (±6.9) kg/m2. The prevalence of current smoking patients was 24.7%, and more prevalent coexisting conditions were hypertension (67.7%), obesity (40.9%), and type 2 diabetes (36.0%). Mean (SD) LOS was 8.6 days (7.7); 17.0% of the patients required intensive care; 3.8% used invasive mechanical ventilation; and 6.6% died during the hospitalization period.Main outcomeThe outcome was LOS, defined as time from hospital admission to medical discharge.ResultsThe crude Hazard Ratio (HR) for LOS was greatest for handgrip strength comparing the strongest vs. other patients (1.54 [95%CI: 1.12 – 2.12; p = 0.008]). Evidence of an association between increased handgrip strength and shorter hospital stay was also identified when handgrip strength was standardized according to the sex-specific mean and standard deviation (1.23 [95%CI: 1.06 – 1.19; p = 0.008]). The magnitude of these associations remained consistent and statistically significant after adjusting for other covariates. Mean LOS was shorter for the strongest patients (7.5 ± 6.1 days) vs. others (9.2 ± 8.4 days). Evidence of associations were also present for vastus lateralis cross-sectional area. The crude HR identified shorter hospital stay for patients with greater sex-specific standardized values (1.17 [95%CI: 1.01 – 1.36; p = 0.037]); however, we found increased uncertainty in the estimate with the addition of other covariates (1.18 [95%CI: 0.97 – 1.43; p = 0.092]). Evidence was also obtained associating longer hospital stays for patients with the lowest values for vastus lateralis cross-sectional area (0.69 [95%CI: 0.50 – 0.95; p = 0.025). Mean LOS for the patients with the lowest muscle cross-sectional area was longer (10.8 ± 8.8 days) vs. others (7.7 ± 7.2 days).Conclusions and RelevanceMuscle strength and mass assessed upon hospital admission are predictors of LOS in patients with moderate to severe COVID-19, which stresses the value of muscle health in prognosis of this disease.FundingThe authors acknowledge the support by the Brazilian National Council for Scientific and Technological Development (CNPq - grant 301571/2017-1). H.R. and B.G. are supported by grants from the Conselho Nacional de Pesquisa e Desenvolvimento (CNPq 428242/2018-9; 301571/2017-1; 301914/2017-6). B.G. is also supported by a grant from the Sao Paulo Research Foundation (FAPESP 2017/13552-2).Key pointsQuestionDo muscle strength and muscle mass predict hospital length of stay (LOS) in patients with moderate to severe COVID-19 patients?FindingsIn this prospective observational study that included 186 hospitalized patients with moderate to severe COVID-19, we observed that LOS was shorter among patients in the highest tertile of strength (assessed by handgrip) vs. those in the mid/lowest tertiles (crude Hazard Ratio [HR]: 1.54, 95%CI: 1.12-2.12). In addition, LOS was longer among patients in the lowest tertile of muscle cross-sectional area (assessed by ultrasound imaging) vs. those in the mid/highest tertiles (HR: 0.69, 95%CI: 0.50 – 0.95).MeaningMuscle strength and mass assessed on hospital admission are predictors of LOS in patients with moderate to severe COVID-19, suggesting that muscle health may be protective in this disease.