Our study showed that impaired PF in the acute post-transplant period of HSCT during hospitalization occurs in over a third of the recipients, mainly in the first week after HSCT. In our previous study with 41 participants, 24.40% of patients experienced a decline in PF after HSCT . Few studies have investigated PF changes after HSCT during the inpatient period. Hacker et al.  found that physical activity decreased and fatigue increased on the fifth day after HSCT compared to before HSCT. In line with these previous studies, our findings suggest that HSCT impairs the recipient’s PF within the first week post-transplant; thus, PF decline can be detected early in the hospitalization period. Relatively long-term follow-up studies also found that PF dropped to the lowest level at the time of discharge and recovered over several months [17, 22, 23]. Our study focused on the acute change in PF during the hospitalization period after HSCT, while other studies assessed PF mostly at the time of discharge, at 4–6 weeks, 2 months, 3 months, and 1 year.
One possible explanation for the decline in PF in the acute posttransplant period is physical inactivity or bed rest during HSCT. A preparative regimen of high-dose chemotherapy and sometimes total-body irradiation precedes HSCT to destroy the recipient’s immune system. As a result, the recipient becomes immunocompromised and prone to bleeding due to severe leukopenia and thrombocytopenia. Thus, the patient is required to stay in an isolated single bed with a working HEPA filter. Kortebein et. al reported that 10 days of bed rest in healthy older people (mean age: 67±5 years) resulted in marked loss of lean tissue from the lower extremity and showed significantly lower strength of the lower extremities and maximal aerobic capacity compared to baseline . Although our participants’ mean age was much younger (50.84±13.76 years), it is noteworthy that 10 days of physical inactivity could cause loss of leg muscle mass and strength and aerobic capacity, and this could provide a plausible explanation for the decline in PF at the first week after HSCT in our study.
Our research revealed several differences in self-reported QoL variables between low PF and good PF. The participants evaluated themselves using the EORTC QLQ-C30 scale at admission and discharge. Our study demonstrated that better cognitive function at baseline was associated with good PF, and better PF was associated with less depression at discharge. Numerous studies have shown similar findings that subjective cognitive impairment is related to QoL difficulties and psychological symptoms such as depression in HSCT recipients in the long term. A study conducted by Booth-Jones et al. reported that poorer cognitive function was associated with poorer PF and more severe depression at 6 months after HSCT . Our findings vary from these previous reports in that they found a link between low cognitive function, physical impairment, and QoL difficulty after HSCT. Our findings suggest that cognitive impairment may be a predictive factor for the decline in PF decline after HSCT, and there is evidence that cognitive function decline negatively affects PF in the elderly. Auyeung et al. reported that cognitive function decline in dementia might contribute to PF impairment independent of muscle mass . In our cohort, a decline in social function was detected in the physically impaired group at discharge. Social functioning is an essential skill for living with others outside the hospital and returning to work. Persoon et al. summarized the importance of returning to work for HSCT survivors and claimed that their return to work may improve the QoL of the patients . As low social functioning could further hinder the recovery of HSCT survivors, physicians should carefully consider social function as well as PF.
The importance of maintaining PF after HSCT can be suggested in that physical function is associated with other functioning and depression. Also, Wood WA et al. demonstrated decreases in physical component of patient-reported outcomes 100 days after HSCT were connected with higher overall mortality and treatment-related mortality . Physical rehabilitation interventions in HSCT patients have shown its potential to alleviate fatigue and enhance QoL . Our study revealed above a third of HSCT survivors encounter decreased PF as early as 1 week post-transplant. Impaired PF in acute post-HSCT period should always be of interest to physicians because physical rehabilitation may help recover or retain PF in an effective and timely manner.
Laboratory findings, including serum albumin, total protein, and hemoglobin, did not show any differences in relation to PF. Because mucositis and GVHD of the GI tract might have negative effects on nutrition absorption, the nutritional status of HSCT recipients has been of interest to researchers. Ferreira et al. compared laboratory data before and after HSCT and reported a significant decrease in serum albumin levels . Our research analyzed the laboratory changes within one month; therefore, it is possible that the follow-up period was too short to reflect systematic changes according to PF.
The main strength of this study was that we assessed objective PF changes via the DEMMI scores by rehabilitation therapists. The DEMMI score is a widely validated measuring system and consists of 15 hierarchical mobility items, including three beds, three chairs, four static balances, two walking, and three dynamic balance items . Many previous studies evaluated PF using the Eastern Cooperative Oncology Group performance, the Karnofsky Performance Scale, and the 6-minute walk test. These assessment have shortcomings in that they cannot point out the aspects that are lacking in the patients’ PF and cannot provide triage to rehabilitation, so further rehabilitation therapy targets are vague . Through the DEMMI scoring system, a proper rehabilitation program can be provided according to individual needs and weak points. There is no single standardized assessment tool for PF in HSCT recipients. Further research should validate the proper PF assessment tool and check the efficiency of physical rehabilitation in HSCT survivors.
This study had several limitations. First, this was a retrospective controlled cohort study conducted at a single center. Our study enrolled over 100 patients. To our knowledge, this cohort study is the largest among the studies that assessed PF repeatedly during the inpatient period. However, our study sample size was insufficient for multivariate analyses. Lastly, there are missing data of the DEMMI scores because we could not assess patients if their medical condition deteriorated after HSCT; for example, if the patients were transferred from the ward to the intensive care unit. We excluded patients if there were two or more missing exams; thus, our study had weaker generalizability.