Nonlinear association between serum albumin levels and all-cause mortality in elderly patients with chronic aortic regurgitation

BACKGROUND  Low serum albumin levels are established predictors of adverse outcomes in various cardiovascular conditions. However, the role of serum albumin in mortality among elderly patients with chronic aortic regurgitation (AR) has not been thoroughly investigated. This study aims to assess the relationship between serum albumin levels and mortality in this specific patient population.

METHODS  Our analysis included 873 elderly AR patients from the China Valvular Heart Disease study, with baseline serum albumin measured at enrollment. Mortality outcomes were monitored for two years post-enrollment, employing a Cox proportional hazards model with a two-piecewise Cox proportional hazards framework to investigate the nonlinear relationship between serum albumin levels and all-cause mortality.

RESULTS  During the 2-year follow-up period, we observed 63 all-cause deaths. The association between serum albumin levels and all-cause mortality displayed an approximating L-shaped curve, indicating a mortality threshold at 35 g/L. For serum albumin levels below 35 g/L, each 1 g/L decrease was associated with a 25% higher risk of all-cause mortality (HR = 1.25, 95% CI: 1.07–1.45). In contrast, no significant change in mortality risk was observed when serum albumin levels were greater than or equal to 35 g/L. Moreover, when serum albumin is classified as hypoproteinemia (serum albumin < 35 g/L), the higher risks of all-cause death were observed in hypoproteinemic patients (HR = 2.93, 95% CI: 1.50–5.74). More importantly, the association between serum albumin and death was significantly stronger in overweight/obese patients (≥ 24 kg/m² vs. < 24 kg/m², P_interaction = 0.006).

CONCLUSIONS  In elderly patients with AR, serum albumin levels showed an approximating L-shaped relationship with all-cause death, with thresholds of 35 g/L. Body mass index was significant effect modifiers of the association. These results suggest that serum albumin, as an inexpensive and readily available biochemical marker, may further improve the stratified risk of mortality in older AR patients.