This study investigated the prevalence of NPS among LLD patients in nursing homes and examined the relationship between depression severity, sleep quality, resilience, and NPS to provide a theoretical basis for future research to reduce the incidence of NPS. The findings showed that the relationship between depression severity and NPS in LLD patients was partially mediated by sleep quality, suggesting that depression severity may have both direct and indirect effects on NPS. In addition, the findings support that higher levels of resilience in nursing home patients with LLD may buffer the adverse effects of depression severity and sleep quality on NPS. These findings have important clinical implications and suggest that enhancing sleep quality and resilience in LLD patients is a key measure for reducing NPS in nursing homes. Not only do they theoretically enrich the understanding of the mental health of elderly depressed patients in nursing homes, but they also provide specific intervention pathways to improve the mental health status of this population in practice, which can effectively enhance the quality of life and well-being of the elderly.
In the present study, the prevalence of NPS among LLD patients in nursing homes was 33.33%, which was significantly higher than that(3.50%)of the elderly in psychiatric outpatient clinics [42] and those (10.00–15.00%) in the community [43]. Differences in study sites may explain some of the differences. The mean score for depression severity in this study was (7.70 ± 2.62), which was higher than in a Chinese study of community and hospital LLD patients (7.07 ± 3.33) [44]. Similarly, the sleep quality score of nursing home LLD patients (10.41 ± 4.86) was higher than that of Yunnan hospital LLD patients in China (6.88 ± 2.45) [45]. In contrast, the resilience score of LLD patients in nursing homes (20.24 ± 8.41) was higher than that of empty nesters in Huzhou, China (12.44 ± 3.63) [46]. A plausible explanation is that LLD patients living in nursing homes are more likely to face a variety of psychological burdens and have poorer sleep quality, which leads to an increased level of resilience [47, 48].
Our study demonstrated a significant positive correlation between depression severity and NPS in LLD patients in nursing homes, which is consistent with previous study [49–51]. In our study, LLD patients in nursing homes moving from a familiar home environment to a new, unfamiliar environment tended to show higher depression severity, affecting the expression of NPS [3]. Neurophysiological studies suggest that depression severity may influence the NPS by affecting neurotransmitter systems, inflammatory responses, and functional brain connectivity [52]. Although this association has been demonstrated in several studies, the specific neural mechanisms are unclear. Previous studies have demonstrated that better sleep quality and higher resilience level are protective factors for NPS in LLD patients [25, 53]. The protective effect of these factors was similarly demonstrated in our study.
The present study found that sleep quality mediated the relationship between depression severity and NPS to some extent, which may reveal a potential mechanism by which depression severity indirectly affects NPS. Previous studies have demonstrated that sleep quality has a mediating role in mediating the association between depressive symptoms and cognitive decline [54]. In our study, depression severity was directly related to NPS, depression severity was negatively related to sleep quality, and sleep quality was negatively related to NPS. Better sleep quality may help to reduce the association between depression severity and NPS[55, 56]. The results of a recent meta-analysis showed that greater improvements in sleep quality led to greater improvements in mental health, but there were differences in the effectiveness of interventions to improve sleep quality for different psychological problems [57]. Therefore, further research is necessary to improve understanding of the effectiveness of these interventions. In conclusion, interventions and management of sleep quality problems should be emphasized in the treatment and care of LLD patients.
According to our moderator-mediator analyses, resilience moderated the relationship between depression severity and NPS, as well as the second half of the mediated effect of sleep quality. This highlights the research and clinical relevance of resilience for understanding the impact of NPS, namely that resilience can reduce NPS to some extent. Resilience is a dynamic moderating process, and the experience of adversity modifies an individual's response to stress, which can be altered and learnt throughout the lifespan [58, 59]. Our study focused on NPS in LLD patients in nursing homes and found that they had higher severity of depression and poor sleep quality, but the effects of depression severity and sleep quality on NPS diminished with increasing resilience. Therefore, increasing resilience can be a key goal in improving NPS in patients with LLD [60, 61]. Targeted psychological interventions, supportive therapy, and rehabilitation programs can help patients improve their resilience, thereby reducing depressive symptoms and improving sleep quality. Future research and clinical practice should further explore and validate the effectiveness of different interventions.
Limitations
This study has some limitations in interpreting the results. Firstly, the cross-sectional data makes it challenging to make causal inferences between the identified variables and NPS. It does not allow for analysing causal relationships between variables. In the future, further longitudinal studies are needed to investigate causal relationships between depression severity and NPS, as well as more accurate mediating relationships. Secondly, the data in the study usually rely on self-reports or subjective evaluations by patients or subjects, which may be subjectively biased, and therefore in-depth interviews and behavior observations should be conducted. Thirdly, although we controlled for some possible confounding variables (e.g., age, gender), other uncontrolled variables (e.g., social support and functional limitations, etc.) may still have an impact on the results. Further future research needs to incorporate additional variables to gain a more complete understanding of this issue. Finally, this study was conducted only in nursing homes, and the limitations of the study site may limit the generalizability of the results. Therefore, future studies should be conducted in different settings and venues, including community and home care settings, to validate the generalizability of the results and to explore the potential impact of different settings on the study variables.