Dynamic alterations of lymphocyte subsets following sepsis in octogenarian and elder patients

Sepsis is defined as a life-threatening organ dysfunction caused by dysregulated host responses to infections. This study aimed to investigate the early and dynamic changes in peripheral lymphocyte subsets following sepsis in octogenarian and elder patients and whether these changes were related to 28-day mortality.

A prospective cohort study of 3601 consecutive patients admitted to the intensive care unit (ICU) was performed between March 2017 and January 2023. Peripheral blood samples were collected on admission, Day 3, and Day 7 for patients with sepsis and on enrollment for patients without sepsis. Lymphocyte subsets were detected by flow cytometry. The 28-day mortality was determined using Kaplan-Meier analysis, while Cox regression identified prognostic factors.

All enrolled patients were divided into three groups: adult (18-64 years), elder (65-79 years), and octogenarian (≥80 years). Sepsis induced a numerical reduction in lymphocytes (median=0.653 [IQR: 0.500-1.038] vs. median=0.840 [IQR: 0.579-1.142] × 10⁹/L, P=0.043) and CD3⁺ T-cell counts (median=0.461 [IQR: 0.312-0.759] vs. median=0.590 [IQR: 0.417-0.789] × 10⁹/L, P=0.021) in octogenarian patients. Kaplan-Meier survival curves showed that in the elder (P [log-rank test] < 0.001) and octogenarian (P [log-rank test]=0.02) groups, patients with CD3⁺ T-cell nonrecovery on Day 3 and Day 7 had the highest mortality, followed by those with late recovery, and the lowest mortality was observed in the early recovery group. Multivariate Cox regression analysis demonstrated that age (hazard ratio [HR]=1.217, 95% confidence interval [CI]: 1.050 to 1.410, P=0.009) and CD3⁺T-cell counts (HR=0.999, 95% CI: 0.999 to 1.000, P < 0.001) were independent risk factors associated with 28-day mortality in patients with sepsis.

Sepsis induced a numerical reduction in lymphocytes and CD3⁺ T-cell counts in octogenarian patients (≥80 years). The persistent decrease of CD3⁺ T-cell counts on Day 3 and Day 7 following sepsis was associated with higher mortality in elder and octogenarian patients.Trial registration Chinese Clinical Trial Registry identifier: ChiCTR-ROC-17010750.