This study evaluated the extent to which the underlying mechanisms of shoulder pain, shoulder disability, and depression mediate the relationship between stress and health-related quality of life in middle-aged women. Consistent with our conceptual framework, it was determined that: (1) stress negatively correlated with health-related quality of life, (2) shoulder pain, shoulder disability, and depression mediated the relationship between stress and health-related quality of life, and (3) these mediators had indirect effects of stress on health-related quality of life in a sequential manner.
Similar to previous studies, our data also showed a close relationship between stress and health-related quality of life [36, 37]; stress is a risk factor for poor physical and mental health . Middle-aged Korean women experience more stressful events than men, as they perform different social roles within their families, including those related to pregnancy, giving birth, and childcare, and experience events such as separation, divorce, job loss, and disease or death of family members. They often perform repetitive and unpaid household duties in addition to a fixed duration of working hours; therefore, compared to men, they are more vulnerable to stressors that threaten their social and daily lives . Social support at work and home can positively impact an individual’s physical and mental health and reduce stress [40, 41]. Therefore, systematic family and social support should be provided to improve health-related quality of life and reduce and control stress in middle-aged women.
In this study, stress had direct and indirect effects on health-related quality of life through shoulder pain and disability. Psychosocial factors, such as stress or anxiety, further activate pain perception [42, 43]. Shoulder pain often persists even after recovery  and, sometimes becomes a chronic condition (lasting for more than three months). It may occur in isolation or may be accompanied by neck or upper-back pain . Humans can perceive stress and can modify their responses to it. Therefore, to reduce shoulder pain or disability caused by stress, it is important to increase adjustment to stress and the threshold to endure it. As chronic pain and stress can be managed and controlled by proper exercise , it is necessary to conduct an intervention study in the future to control stress and pain by integrating exercise into the lives of middle-aged women.
This study showed that stress has direct and indirect effects on health-related quality of life mediated by shoulder pain, disability, and depression. These results are consistent with those of previous studies [43, 47], indicating that the higher the depression, the lower the health-related quality of life, and the higher the pain, the higher the depression and the lower the health-related quality of life . The results of this study suggest that stress directly affects health-related quality of life and causes shoulder pain, shoulder disability, and depression, all of which have direct and indirect effects on health-related quality of life. Therefore, controlling and managing stress is important for improving health-related quality of life. Stress has a secondary effect on physical symptoms, such as pain and disability, and mental symptoms, such as depression, as well as a negative effect on the quality of life.
Therefore, healthcare workers, such as nurses, need to implement nursing interventions that prevent and control stress caused by various complex factors experienced by middle-aged women. A previous study  reported that stress can be controlled through exercise and physical activity. Exercise has been reported to improve shoulder pain, shoulder disability, depression, and health-related quality of life [49, 50]. Therefore, future studies should develop an intervention program that includes various degrees and types of physical activity to reduce the stress experienced by women in their daily lives, restore their physical health if they have symptoms of physical health conditions and disabilities, and manage mental health conditions such as depression, thereby helping and supporting them in a healthy and happy life.
This study has several limitations. First, only participants living in Seoul, South Korea were included using convenience sampling. Therefore, the study results cannot necessarily be extrapolated to middle-aged women in other countries. Second, this study analyzed the relationship between stress, health-related quality of life, shoulder pain, shoulder disability, and depression based on a self-report survey. Therefore, the cause-and-effect interpretations of these variables cannot be established. Future studies should analyze and interpret data using tools to perform a more detailed and objective evaluation of various factors that affect health-related quality of life in middle-aged women. Despite these limitations, this study provides new insight into the relationship between stress and health-related quality of life and analyzes the degree of direct and indirect effects of shoulder pain, shoulder disability, and depression on stress. Furthermore, this study suggests that improving the health-related quality of life of middle-aged women and reducing stress necessitate the development of interventions to reduce and manage shoulder pain and disability and reduce the depression caused by these physical symptoms.