NEW ORLEANS—Severe anemia increases a patient’s risk of dying in the hospital following a stroke by approximately three and a half times, researchers reported at the 2012 International Stroke Conference. After discharge following a stroke, a patient with severe anemia is about two and a half times more likely to die within a year than a healthy patient.
“Having a history of severe anemia is a potent predictor of dying anytime throughout the first year—more potent than having heart disease, and more potent than having cancer,” said Jason J. Sico, MD, Assistant Professor of Neurology and Internal Medicine at the Yale School of Medicine in New Haven, Connecticut.
Patients with moderate or mild anemia also have a higher risk of death at six months and one year after a stroke, noted Dr. Sico. In addition, a patient with a high hematocrit value is nearly three times more likely to die in the hospital after a stroke than one with a normal hematocrit level.
Stroke, Anemia, and Mortality
Previous studies revealed a link between anemia and mortality after a stroke, but most did not control for medical comorbidities and stroke severity. Dr. Sico and his colleagues sought to adjust for these variables to gain a clearer understanding of how anemia affects a stroke patient’s survival.
The team conducted a retrospective cohort study using data from more than 3,800 patients with stroke admitted to 131 Veterans’ Health Administration hospitals in 2007. The investigators defined the normal hematocrit range as 37% to 42%. Patients with a hematocrit level between 32% and 37% were considered to have mild anemia, those with a hematocrit value between 27% and 32% were considered to have moderate anemia, and those with a hematocrit level lower than 27% were considered to have severe anemia. A hematocrit value greater than 47% was defined as polycythemia. The researchers used multivariate logistic models to examine patients’ mortality during hospitalization, at 30 days, at six months, and at one year.
Patients With Anemia Should Be Monitored After Stroke
Anemia might reduce survival after a stroke in several ways, according to Dr. Sico. Low hematocrit levels decrease the amount of oxygen that the brain receives, increase heart rate, and sometimes cause high blood pressure. In addition, anemia “impairs the way the blood vessel to the brain can react to having a stroke,” observed Dr. Sico.
Although the large data set is one of the study’s strengths, the patient population included so few women that the investigators decided to exclude them from the analysis. “The results of this current study are applicable only to men. Studies examining how low and high hematocrits influence mortality in women with stroke are needed,” said Dr. Sico.
If a patient with stroke has anemia or polycythemia, a physician should determine whether the latter conditions are reversible and should be treated, said Dr. Sico. “Based on the study that we have available, we can’t say that you should give a blood transfusion to your patients,” he added. Physicians should monitor patients with anemia or polycythemia closely during the period after their strokes, Dr. Sico advised. “We want to be sure that they’re stroke survivors,” he concluded.
—Erik Greb