Association between fibrinogen and decline in cardiorespiratory fitness in patients undergoing cardiopulmonary exercise testing: a large cross-sectional study

BackgroundCardiorespiratory fitness (CRF) is critical cardiovascular risk predictor but unavailable for routine screening. Fibrinogen (FIB), a widely available biomarker, may be related to CRF through multiple mechanisms. However, evidence linking FIB to CRF decline is unclear. Therefore, we aimed to evaluate the relationship between FIB and CRF decline and to further examine its association with peak O2 pulse to provide physiological insight.MethodsIn this cross-sectional, retrospective study, 698 participants were included. FIB levels were categorized into tertiles: T1 (n = 238), T2 (n = 228), and T3 (n = 232). CRF status was divided into two groups based on CPET: normal-to-mild decline (n = 292) and moderate-to-severe decline (n = 406). Univariate and multivariate logistic regression, subgroup, sensitivity, and receiver operating characteristic (ROC) analyses were performed to evaluate the relationship between FIB and CRF decline. Multivariable linear regression was performed to examine the association between FIB and peak oxygen pulse (peak O2 pulse).ResultsThe prevalence of moderate-to-severe CRF decline increased across FIB tertiles (T1: 49.6%, T2: 60.1%, T3: 65.1%; P = 0.002). In the fully adjusted model of multivariate logistic regression, each 1-unit increase in FIB was associated with a 31.4% higher risk of moderate-to-severe CRF decline (OR = 1.314, 95% CI: 1.051–1.643, P = 0.016). Participants in theT3 had a 1.620-fold higher risk compared with those in T1 (OR = 1.620, 95% CI: 1.101–2.383, P = 0.014). The association remained consistent across all subgroups and was stronger in sensitivity analyses restricted to participants achieving maximal effort (P < 0.05). ROC analysis revealed a predictive value of FIB for moderate-to-severe CRF decline (AUC = 0.584, P < 0.001). In fully adjusted linear regression, each 1 g/L increase in FIB was associated with a 0.357 mL/beat lower peak O2 pulse (β = −0.357, P < 0.001), and T3 had a lower peak O2 pulse than T1 (β = −0.503, P = 0.012).ConclusionsAmong individuals undergoing CPET, higher FIB levels were associated with higher risk of moderate-to-severe CRF decline and lower peak O2 pulse, suggesting that FIB may serve as a potential biomarker for identifying CRF decline.