Background: Fatigability describes how fatigued a patient is at any given level of activity, and is measured as the degree of fatigue a patient experiences after performing a specific amount of activity. The National Institute of Aging has suggested that fatigability is an important measure in patients with conditions where fatigue is a prominent symptom, such as hospitalized patients with anemia. This is because fatigue is the primary symptom of anemia, and both hospitalization and anemia-related fatigue are associated with declines in activity and functional capacity. As such, measuring fatigability in hospitalized patients with anemia could provide hospitalists information about the severity of patients’ fatigue, and how fatigue may be interfering with their functional capacity. Moreover, fatigability could be used to predict future functional decline or disability post hospitalization. However, fatigability has not been previously described in hospitalized patients with anemia. The purpose of our study was to establish the clinical reliability of fatigability, by characterizing the association between fatigability and patient’s clinical (i.e. Hb, comorbidities) and demographic characteristics.

Methods: From 6/2017-1/2018, hospitalized general medicine patients with a Hb<10g/dL were approached for an inpatient interview at hospital admission. Fatigability was measured using the Pittsburgh Fatigability Scale (PFS). The PFS contains 10 questions that measure fatigue in the context of specific activities. PFS scores range from 0-50, with higher scores indicating greater fatigability (higher fatigue at lower activity). Patients’ hemoglobin (Hb) values and clinical data were abstracted from hospital administrative data. Patients who received a transfusion prior to the PFS measurement were analyzed separately since transfusion affects Hb and could confound the association with fatigability. Linear regression was used to test the association between fatigability (PFS) as the dependent variable, and patient Hb and Charlson Comorbidity score (CCS) as predictor (independent) variables, controlling for age, race, and gender.

Results: 467 patients completed the inpatient PFS. The median age of the sample was 55 (IQR 39-68) years old, 61% (n=293) were female, 77% (n=360) were African American, with a median CCS of 2 (IQR 1-5). The median PFS score of the sample was 33 (IQR 25-38), and the median Hb was 8.9g/dL. In regression models, a Hb 7-8g/dL (=2.7, p=0.04) compared to Hb≥9-10, and higher CCS (=0. 8, P<0.001) were associated with increased fatigability.

Conclusions: Severity of anemia and number of comorbidities are predictive of higher fatigability (higher fatigue at lower activity) during hospitalization. This suggests that fatigability is reliably associated with expected clinical characteristics during hospitalization, and could be measured and used by hospitalists to clinically evaluate the severity of a patient’s fatigue, and how that fatigue may be affecting their functional capacity.