The purpose of this study was to clarify the relationship between PA and psychological and environmental factors in patients with pneumoconiosis. We were able to ascertain the comprehensive relationship between them by conducting a path analysis.
Regarding psychological factors, OE directly affected PA. SE and DB indirectly affected PA, with OE as a mediating factor.
The association between PA and psychological factors in patients with CRD has been reported to be associated with SE [26, 27]. SE represents confidence in performing an exercise . SE has been reported to be associated with PA not only in patients with CRD, but also in a variety of subjects, including healthy elderly persons and patients with diabetes. Therefore, it is assumed that behavior change is dependent on SE . In this study, SE was correlated and associated with PA. This result is similar to those in previous reports. However, the psychological factor that had a direct impact on PA was OE. OE is an understanding of the benefits of PA and the associated expectations. In TTM, it is considered a factor that mediates behavioral change . It has been reported that OE is related to PA in healthy elderly people and patients with chronic disease [28–31]. The lack of knowledge about the appropriate PA to perform may explain why OE had more impact on PA than SE. Most of the subjects in this study were in the action or maintenance stage of behavior change and reported that they exercised habitually. However, the PA determined by the IPAQ classified them in the low-activity group. In other words, there was a difference between subjective exercise and actual PA. Therefore, it is likely that OE, which represents the understanding of PA, was more influential than SE, which represents confidence in performing PA. One possible reason for the lack of knowledge about the required PA is the low implementation rate of pulmonary rehabilitation. The rate of implementation of pulmonary rehabilitation among the subjects in this study was lower than that reported for home-based patients with COPD in Japan . Thus, it is assumed that patients with CRD have few opportunities to be educated on the importance, the required amount, and the intensity of PA.
Dyspnea is the most common symptom of CRD . In patients with CRD, dyspnea is reported to be a fundamental symptom that limits PA because patients with dyspnea consciously or subconsciously avoid daily activities [34, 35]. In addition, dyspnea has been reported to affect a variety of symptoms which may be elicited using a question-prompt list such as symptoms of depression. It has been empirically reported that dyspnea causes a vicious cycle of decreased activity and decreased physical function, resulting in further increases in dyspnea . Recently, this vicious cycle has been demonstrated in patients with COPD using path analysis . The results of the present study indicate that dyspnea directly affects PA in patients with pneumoconiosis, as it does in patients with other CRDs. Furthermore, the results of the path analysis showed that dyspnea not only affected PA, but also impacted many other health-related items, such as depression and QOL. Hence, dyspnea was found to be a fundamental factor affecting PA and many other health-related items in patients with pneumoconiosis. Pulmonary rehabilitation has been reported to improve dyspnea in patients with CRD such as COPD and IP [18, 37]. The results of this study also show that pulmonary rehabilitation can improve dyspnea in pneumoconiosis patients, which may also improve QOL and other symptoms.
There was a significant correlation between LSA and PA when environmental factors were evaluated. LSA has been reported to be associated with PA in the elderly, and the results were similar to those of previous studies [38, 39]. However, the environment surrounding the home (IPAQ-E) was not associated with PA in this study.
The environment around the home has been reported to be associated with PA and the number of steps in healthy elderly people and patients with various diseases such as knee and hip Osteoarthritis (OA) [24, 40–42]. In this study, unlike in previous reports on elderly persons, there was no relationship between PA and the home environment. This may be a unique trend in patients with respiratory disease. This means that patients with respiratory diseases may decrease their PA if they have strong subjective symptoms (dyspnea), regardless of the environment around their home. In patients with OA of the knee or hip, PA has been reported to be associated with the environment surrounding the home, but the influence of physical factors such as pain was stronger . It was believed that subjective symptoms (dyspnea) may have an even stronger influence on PA in patients with respiratory diseases than in patients with other diseases.
We previously reported that elderly patients with pneumoconiosis have greater lower limb muscle strength than healthy elderly patients, even when PA is similar, and that pulmonary rehabilitation is necessary. The results of this study also suggest that pulmonary rehabilitation is necessary for patients with pneumoconiosis. Pulmonary rehabilitation has been reported to improve dyspnea . However, improvement of dyspnea alone is not sufficient to improve PA, and patient education on psychological factors is also important. Until now, patient education in pulmonary rehabilitation has often focused on SE. OE is a prerequisite for behavioral change, and it is believed that both SE and OE need to be improved in order for behavioral change to occur . Therefore, OE is a psychological factor that should be incorporated into intervention programs aimed at promoting physical activity [44, 45]. Therefore, in addition to conventional pulmonary rehabilitation, patient education is needed to improve OE and patient understanding of PA.