U-shaped relationship between hemoglobin level and severity of ischemic stroke

We aimed to explore the relation between hemoglobin level and ischemic stroke severity and short-term improvement in patients admitted to hospital within 3 hours of stroke onset.

The relation between stroke severity and hemoglobin was explored by locally weighted scatterplot smoothing (lowess smoother) curves. The effect of hemoglobin on short-term outcome was determined by means of linear regression analyses with NIHSS score day 7 as dependent variable after adjusting for confounders including NIHSS score on admission. Analyses were performed to disclose clinical factor associated with hemoglobin level.

This study includes 905 ischemic stroke patients admitted within 3 hours of stroke onset. Lowess smoother curves showed a U-shaped relation between NIHSS score on admission and mRS score day 7 and hemoglobin level. Regression analysis showed low hemoglobin to be independently associated with females, high age, severe stroke, low systolic blood pressure, prior cerebral infarction, not smoking, not atrial fibrillation, and unknown etiology (all P < 0.05). Another regression analysis showed that high NIHSS score day 7 was independently associated with low hemoglobin after adjusting for confounders including NIHSS score on admission.

We found a U-shaped relationship between hemoglobin level on admission and stroke severity. There was no U-shaped relationship between improvement and hemoglobin level. Poor short-term improvement was associated with low hemoglobin levels.