The association of inflammatory markers with frailty and in-hospital mortality in older COVID-19 patients

Introduction: During the COVID19 pandemic, older patients hospitalized for COVID-19 exhibited an increased mortality risk compared to younger patients. While ageing is associated with compromised immune responses and frailty, their contributions and interplay remain understudied. This study investigated the association between inflammatory markers and mortality and potential modification by frailty among older patients hospitalized for COVID-19. Methods: Data were from three multicenter Dutch cohorts (COVID-OLD, CliniCo, Covid-Predict). Patients were 70 years or older, hospitalized for COVID-19and categorized into three frailty groups: fit (Clinical frailty score (CFS) 1-3), pre-frail (CFS 4-5), and frail (CFS 6-9). Immunological markers (lymphocyte count, neutrophil count, C-reactive protein, neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR) and systemic inflammation index (SII)) were measured at baseline. Associations with in hospital mortality were examined using logistic regression. Results: A total of 1697 patients were included from COVID-OLD, 656 from Covid-Predict, and 574 from CliniCo. The median age was 79, 77, and 78 years for each cohort. Hospital mortality rates were 33 %, 27 % and 39 % in the three cohorts, respectively. A lower CRP was associated with a higher frailty score in all three cohorts (all p < 0.01). Lymphocyte count, neutrophil count, NLR, PLR, or SII, were similar across frailty groups. Higher CRP levels were associated with increased in-hospital mortality risk across all frailty groups, across all cohorts (OR (95% CI), 2.88 (2.20-3.78), 3.15 (1.95-5.16), and 3.28 (1.87-5.92)), and frailty did not modify the association between inflammatory markers and in-hospital mortality (all p-interaction>0.05). Conclusion: While frailty is a significant factor in determining overall outcomes in older patients, our study suggests that the elevated risk of mortality in older patients with frailty compared to fit patients is likely not explained by difference in inflammatory responses.