Anemia in hospitalized patients: an overlooked risk in medical care

BACKGROUND This study investigated the association between nadir anemia and mortality and length of stay (LOS) in a general population of hospitalized patients. STUDY DESIGN AND METHODS A retrospective cohort study of tertiary hospital admissions in Western Australia between July 2010 and June 2015. Outcome measures were in‐hospital mortality and LOS. RESULTS Of 80,765 inpatients, 45,675 (56.55%) had anemia during admission. Mild and moderate/severe anemia were independently associated with increased in‐hospital mortality (odds ratio [OR] 1.5, 95% confidence interval [CI] 1.36‐1.86, p = 0.001; OR 2.77, 95% CI 2.32‐3.30, p < 0.001, respectively). Anemia was also associated with increased LOS, demonstrating a larger effect in emergency (mild anemia—incident rate ratio [IRR] 1.52, 95% CI 1.48‐1.56, p < 0.001; moderate/severe anemia—IRR 2.18, 95% CI 2.11‐2.26, p < 0.001) compared to elective admissions (mild anemia—IRR 1.30, 95% CI 1.21‐1.41, p < 0.001; moderate/severe anemia—IRR 1.69, 95% CI 1.55‐1.83, p < 0.001). LOS was longer in patients who developed anemia during admission compared to those who had anemia on admission (IRR 1.13, 95% CI 1.10‐1.17, p < 0.001). Red cell transfusion was independently associated with 2.23 times higher odds of in‐hospital mortality (95% CI 1.89‐2.64, p < 0.001) and 1.31 times longer LOS (95% CI 1.25‐1.37, p < 0.001). CONCLUSION More than one‐third of patients not anemic on admission developed anemia during admission. Even mild anemia is independently associated with increased mortality and LOS; however, transfusion to treat anemia is an independent and additive risk factor.