Anemia appears to be common and persistent in the first year following hospitalization for critical illness in adults, according to a recent study published in JAMA Network Open.

Though most survivors of critical illness are discharged from the hospital with anemia, the consequences associated with posthospitalization anemia remain understudied.

Matthew Warner, MD, of the department of anesthesiology and perioperative medicine at the Mayo Clinic in Rochester, Minnesota, and colleagues described the longitudinal changes in anemia status during and after critical illness in adults and assessed the associations between hemoglobin concentrations and postdischarge mortality.

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The study was conducted from January 1, 2010, to December 31, 2016, and participants who had been admitted for hospitalization (6901 patients) were from Olmsted County, Minnesota. Participants had been identified through the Rochester Epidemiology Project, a comprehensive epidemiologic database of population health information from Minnesota and Wisconsin.

Hemoglobin concentrations from the 12 months before hospitalization, during hospitalization, and in the 12 months after hospitalization were assessed. For analysis, patients were categorized according to the severity of anemia: mild (hemoglobin ≥10.0 to <12.0 g/dL in women or ≥10.0 to <13.5 g/dL in men), moderate (hemoglobin ≥8.0 to <10.0 g/dL), and severe (hemoglobin <8.0 g/dL). Complete recovery from anemia (nonanemic 12 months post hospitalization) and 12-month postdischarge mortality were also assessed.

For the 6901 patients (men/women, 55%/45%), the median age was 67 years (IQR, 52-79). For the 83% of patients who had prehospitalization hemoglobin values available, with median hemoglobin concentrations of 12.5 g/dL (IQR, 11.3-13.7) for women and 13.8 g/dL (IQR, 12.1-15.0) for men.

Overall, 41% of patients had anemia prior to hospitalization. Within 24 hours of hospital admission, 53% of patients had anemia; of those who were previously nonanemic, 40% developed incident anemia. At hospital discharge, 80% of patients (excluding those who died) had anemia: 58% of those cases were mild, 39% were moderate, and 3% were severe. Median hemoglobin values at discharge were 10.4 g/dL (IQR, 9.4-11.7) for women and 11.2 g/dL (IQR, 9.6-13.0) for men. In survivors who did not have anemia prior to hospitalization, 26% remained nonanemic while 74% became anemic by discharge.

After discharge, the prevalence of anemia among survivors was 56% (95% CI, 55-58) at 3 months, 52% (95% CI, 50-54) at 6 months, and 45% (95% CI, 43-47) at 12 months. Complete recovery rates for anemia at 12 months were 58% in mild cases (95% CI, 56-61), 39% in moderate cases (95% CI, 36-42), and 24% in severe cases (95% CI, 15-34). Higher hemoglobin values at hospital discharge were associated with lower postdischarge mortality in a multivariate model (hazard ratio, 0.95 per 1-g/dL increase; 95% CI, 0.90-0.99; P =.02).

Limitations of the study include the use of historical data and missing data for some patients. The investigators were not able to discern the causes of anemia, and the generalizability of the study is unclear due to differences in health care among locations and because most patients were of European descent.

“Further studies are necessary to more fully evaluate associations between posthospitalization anemia and patient-important clinical outcomes,” wrote the authors. “In addition, studies are warranted to distinguish patients likely to recover from anemia after hospitalization from those who may experience prolonged anemia; the latter group may benefit from close outpatient follow-up and/or targeted anemia management strategies.”


Warner MA, Hanson AC, Frank RD, et al. Prevalence of and recovery from anemia following hospitalization for critical illness among adults. JAMA Netw Open. 2020;3(9):e2017843. doi:10.1001/jamanetworkopen.2020.17843