Percentage of missing values.

<div><p>Background</p><p>Previous studies have shown that both age and hemoglobin are closely associated with the prognosis of septic shock. A recent study found that hemoglobin may change with age. Hemoglobin-to-Age Ratio (HAR) takes both age and hemoglobin into consideration as essential factors. So far, the effect of HAR on the prognosis of septic shock is still unclear. This research aimed to investigate the association between the HAR and the prognosis of patients with septic shock.</p><p>Methods</p><p>Cox proportional hazards regression analysis, restricted cubic spline, Kaplan-Meier survivor analysis and stratified interaction analysis were used to elucidate the relationship between the HAR and prognosis of patients with septic shock.</p><p>Results</p><p>There is a nonlinear association between the HAR and mortality within 28 days after intensive care unit admission. When the HAR was lower than 0.13, mortality within 28 days after ICU admission decreased significantly as the HAR increased. When the HAR was higher than 0.13, the HAR was not a protective factor for mortality within 28 days after ICU admission. In patients with septic shock, the HAR was more effective in reducing the risk of death in patients with atrial fibrillation than in patients without atrial fibrillation.</p><p>Conclusion</p><p>There is a nonlinear association between the HAR and mortality within 28 days after intensive care unit admission. When the HAR was at a low level, mortality within 28 days after ICU admission decreased significantly as the HAR increased. When the HAR was at high levels, the HAR might not be a protective factor for mortality within 28 days after ICU admission. In patients with septic shock, the HAR was more effective in reducing the risk of death in patients with atrial fibrillation than in patients without atrial fibrillation.</p></div>