Our results revealed that rumination assumes a significant mediating role between fatigue and sleep quality. Thus, the more tired kidney transplant recipients become, the more likely they are to ruminate, which leads to a decline in sleep quality. This study discovered a lower incidence of sleep disorders; only 19.3% (defined as a PSQI score >7) in kidney transplant recipients than in the studies by Xie et al. (2018) (29.2%, poor sleeper defined as PSQI >7)(10) and Reilly-Spong, Park and Gross (2013) (41%, poor sleeper defined as PSQI >8)(33). Several factors may account for this difference, these include: these patients’ transplants occurred more than one year ago, their renal functions have had time to recover, their sleep difficulties might be relieved, the sample size may be too small, the sample populations differ, and the data were collected from different cultural settings. Nevertheless, this finding indicates that although the patients’ sleep difficulties have been alleviated to some extent after their kidney transplants, the overall poor sleep quality persists. Hasanzamani et al. (2020) also proved that renal transplants can improve patients’ sleep conditions after six months(11). Generally speaking, patients still have sleeping disorders more than a year after their kidney transplants, and the prevalence is high.
Furthermore, the study findings suggested that there was a significant positive correlation between fatigue scores and sleep disorder scores. This implies that higher fatigue scores lead to higher sleep disorder scores and poor sleep quality; Rodrigue et al. (2011) concurred with this conclusion(34). Studies also discovered that fatigue, hypertension, and hair loss are the three most common symptoms among renal transplant recipients in China(35). Additionally, since the patients cannot engage in heavy physical activities due to their transplanted kidneys, they become more sedentary and less active, which leads to fatigue. However, this type of fatigue is different from the fatigue caused by normal activities since it causes apathy and discomfort in patients’ limbs, which makes it difficult to fall asleep. However, fatigue not only affect quality of life, but also reduces patients’ tolerance to immunosuppressants, which increases their incidence of immune rejection and risk of death(36). Additionally, previous studies have pointed out that the severity of fatigue is closely related to sleeping disorders, and poor sleep quality will aggravate the fatigue of patients, which eventually lead to a decline in the quality of life(37).
The study results further indicate that, in addition to directly affecting patients sleep quality, fatigue also indirectly affects sleep quality through rumination. The research confirmed that fatigue is positively correlated with rumination, while rumination is positively correlated with sleeping disorders. Very few studies have explored the relationship between fatigue and rumination, and only explored the effects of work-related fatigue in employees(38–40).Nevertheless, previous studies revealed several correlations: physical fatigue can lead to a decline in athletic ability (i.e., lack of muscle strength); cognitive fatigue can lead to a decline in cognitive ability (i.e., poor attention and sensitivity); and mental fatigue can lead to negative emotions or stress disorders(41, 42). Thus, fatigue is a complex concept, and different performance of fatigue can enhance patients’ ruminant thinking levels, resulting in reduced sleep quality. Li et al. (2019) found that stressful life events can both directly and indirectly affect sleep quality through rumination(23). Furthermore, since stress can lead to the activation of the locus coeruleus noradrenaline (LC-NE) system and the hypothalamus pituitary adrenal (HPA) axis, it can increase excitability and aggravate existing difficulties in falling asleep(43, 44) According to Morin, Rodrgue, and Ivers’ (2003) insomnia-hyperactivity theory, cognitive arousal may play an important role in sleep disorders(45). Therefore, higher levels of rumination make people more prone to experiencing negative re-evaluations of the past, which increases their cognitive arousal and reduces sleep quality; thus supporting the “emotional flow” theory(46).
Diagnoses of renal failure and the subsequent kidney transplants are major life events that place strain on patients. Furthermore, since most patients will experience fear and then try to control their fear situation (anger), they may experience a “fight” response which will affect their sleep. Thus, the order of emotional change is fear—anger—happiness/sadness. Additionally, this result also supports the stress theory(47). Stress theory refers to the process of individual psychological adjustment and adaptation when faced with stress, whereas coping styles pertain to behavioral patterns that buffer and control an individual’s response to stress stimuli during the coping process; this is aimed at solving or mediating an individual's emotions(47, 48).Positive coping styles directly affect an individual’s compliance with disease treatment, which then affect their overall health status; negative coping styles are not conducive to patients’ health outcomes(47, 49).Rumination is a type of negative coping style that exacerbates the severe decline of sleep quality. When engaging in ruminant thinking, individuals easily become caught up in memories of negative events, this leads to excessive fantasizing during which they lose track of time(50).Self-accusatory thoughts are common while ruminating and are focused on the individual’s past mistakes and subsequent consequences. Individual’s then question why their problems are unique to themselves which further aggravates their negative thoughts and behaviors. Therefore, the cycle of rumination is characterized by a focus on negative emotions which then increases insomnia inducing factors, maintenance factors of insomnia, and finally persistent symptoms of insomnia(44).
This study demonstrated that rumination acts as a mediator between kidney transplant recipients’ fatigue and their sleep quality. However, given that the causes of fatigue are related to the source of transplanted kidney(51), graft dysfunctions(34), and the use of immunosuppressants(13), improving patients’ fatigue may not be very easy. Therefore, medical staff should employ effective measures that reduce patients’ levels of rumination. Furthermore, rumination causes individuals to fixate on the negative aspects of events and the possible negative effects; this induces negative emotional experiences (e.g., loneliness and depression) that cause adverse health consequences, such as impaired sleep quality(52, 53). Accordingly, nurses should pay close attention to the emotional states and psychological characteristics of their patients. This includes practically caring about patients during daily nursing work, such as encouraging their families to visit, to correct patients’ flawed perspectives over time. Meanwhile, the tendency of ruminating individuals to indulge in their own negative thought patterns and emotions increases their need for more social support to alleviate their inner pain. Therefore, nurses should provide the necessary social support for kidney transplant patients, such as strengthening communication with them and holding relevant informative lectures. Additionally, rumination interventions are very important. Previous studies have revealed that mindfulness therapy(54, 55), cognitive behavior interventions (56), and working memory training(57, 58)all play important roles in eliminating negative thinking and promoting positive thinking.
The study limitations relate to the use of a convenience sample of kidney transplant recipients located in one geographic area. This means that the representativeness and extrapolation efficiency of the conclusions are limited. Second, this study utilized a cross-sectional design to explore the effects of rumination on the relationship between fatigue and sleep quality of renal transplant patients. Consequently, this design cannot provide an accurate explanation for the causality between the two variables. Therefore, longitudinal studies or randomized controlled trials (RCTs) are necessary to confirm our results. Third, rumination was the only mediator considered in this study to determine the relationship between fatigue and sleep quality. However, other mediators may also affect the relationship between fatigue and sleep quality, including social support, family functions, anxiety, and depression. Future studies should include additional variables to comprehensively assess the impact of the results. Finally, the patients’ conditions were assessed with a self-reported questionnaire, which may be biased.