Platelet count has a U-shaped association with all-cause mortality in COPD patients

Identifying reliable prognostic markers is crucial for the effective management of chronic obstructive pulmonary disease (COPD). The platelet count has emerged as a potential inflammatory marker associated with clinical outcomes. The aim of this study was to investigate the relationships of the platelet count with all-cause mortality and readmission rates among patients with acute exacerbations of COPD (AECOPD). Patients who were diagnosed with AECOPD between January 2019 and December 2023 at our institution were included. The platelet count was recorded on admission. The primary outcome was all-cause mortality. The secondary outcomes included readmission for AECOPD and a composite endpoint of readmission and mortality. Multivariate Cox proportional hazards models were constructed to examine the associations between the study endpoints and platelet counts categorized as low, normal, and high (< 150, ≥ 150 to < 300, and ≥ 300 × 10⁹/L, respectively). Additionally, restricted cubic spline (RCS) Cox regression was used to explore the dose‒response relationships of the platelet count with all-cause mortality and readmission. A total of 853 patients (mean age = 71.39 years; proportion of males = 58.7%) were ultimately included. After a follow-up of 48 (33-58) months, 163 deaths (19.1%) occurred among the cohort. The 5-year survival estimates were 67.5%, 81.2%, and 59.3% for the low, normal, and high platelet count groups, respectively (log-rank, P < 0.001). Similarly, the rate of readmission among patients with normal platelet counts was significantly lower than that in either the high or low platelet count groups (log-rank, P < 0.001). After adjusting for potential confounders, both low and high platelet counts in patients with AECOPD were found to be significantly associated with an increased risk of all-cause mortality and readmission. The RCS curves revealed U-shaped relationships of the platelet count with all-cause mortality and readmission in patients with AECOPD, with the lowest risk observed at a platelet count of approximately 200 × 10⁹/L for both outcomes. We observed U-shaped relationships of the platelet count with all-cause mortality and readmission in individuals with COPD. These findings may provide a simple approach for risk discrimination for adverse outcomes in patients with COPD.