Physical Activities in Patients with β-Thalassemia As Measured By Fitbit in Association with Patient-Reported Outcomes

Background: Tiredness, weakness, and shortness of breath are the most commonly reported symptoms in patients with β-thalassemia, and they may also adversely affect the quality of life (QoL) of patients. We aimed to explore the associations between β-thalassemia symptom severity and QoL in relation to physical activities, as tracked by Fitbit wearable electronic devices (Fitbit, Inc., San Francisco, CA).

Method: Adult patients with β-thalassemia under routine clinical care were enrolled in a prospective observational study. All patients completed Short Form 36 Health Survey version 2 (SF-36v2) and Functional Assessment of Cancer Therapy (FACT)-Anemia (An) questionnaires at baseline and then once every 3 weeks using a hand-held electronic device. Patients with transfusion-dependent (TD) β-thalassemia also completed the Transfusion-dependent QoL (TranQoL) questionnaire, a disease-specific QoL instrument developed for TD patients, with the same scheduling. Transfusion dependent was defined as receiving ≥ 6 red blood cell units in the 24 weeks prior to study entry and no transfusion-free period for ≥ 35 days during that period. Patients with non-transfusion-dependent (NTD) β-thalassemia were instructed to complete the NTDT-PRO^© daily, a symptom diary developed specifically for patients with NTD β-thalassemia with 2 domains: tiredness/weakness (T/W; score range: 0-40) and shortness of breath (SoB; score range: 0-20) with higher scores indicating more severe symptoms. Physical activities were passively tracked by a Fitbit wearable electronic device in terms of steps taken and floors climbed. This analysis examined the association between physical activities at week 1 of the study with QoL measurements and β-thalassemia symptom severity at baseline. For this analysis, average daily steps taken and floors climbed were grouped into quartile categories for those patients who had 4 or more days of Fitbit data during week 1.

Results: A total of 102 patients with β-thalassemia (52 TD and 50 NTD) were enrolled; the mean age of patients was 31.2 years and 70 (68.6%) were females. A total of 91 patients had Fitbit data and, on average, they took 10,811 steps (median: 9,656) and climbed 16.0 floors (median: 10.0) daily. There were no associations observed between the number of steps taken and QoL measurements and β-thalassemia symptom severity. The floors climbed, however, were associated with SF-36v2 Physical Functioning and General Health domains. Patients in the lowest quartile for floors climbed had statistically significant lower Physical Functioning and General Health scores compared with patients in the highest quartile for floors climbed (47.0 vs 52.3; P < 0.01; and 42.1 vs 46.3; P= 0.01, respectively). Floors climbed were also associated with the NTDT-PRO^© symptom severity scores for T/W and SoB domains. Patients in the lowest quartile for floors climbed had T/W and SoB domain scores of 12.8 and 4.6, respectively, compared with those patients in the highest quartile for floors climbed who had scores of 4.9 and 0.8 (P < 0.01 and P= 0.02).

Conclusions: Steps taken tracked by Fitbit did not appear to be associated with QoL and symptom severity in patients with β-thalassemia. Floors climbed, however, were associated with SF-36v2 Physical Functioning and General Health domains, and β-thalassemia symptom severity. Floors climbed is likely to be a more sensitive endpoint as a measurement for physical activities in clinical studies.