The aim of this study was to explore the relationship between SWB and survival time among three East Asian countries. We found that SWB was a significant factor correlated with survival in Taiwan, while it was insignificant in Japan and Korea. This study is the first of its kind to reveal the significant role of SWB in the survival time of patients with advanced cancer.
SWB was a significant factor associated with survival time in Taiwan in multivariate analysis. It was unexpected because we found an insignificant relationship between SWB and survival time in univariate analysis. There are two plausible explanations for this phenomenon from a statistical view point. Survival plots of Taiwanese patients suggested possible differences between groups with Lower and Better SWB. However, some outliers who had lived far longer narrowed the difference at the end of plots (Fig. 1). Second, the influence of SWB was contradictory in univariate analysis and thus it appeared significant after adjustment in multivariate analysis. The unique result may reflect intensive spiritual care in Taiwanese PCUs.
A previous study from Taiwan reported that spiritual care was an essential component of palliative care, especially at the very end of life in Taiwan and Clinical Buddhist Chaplains (CBC’s).
It is a mainstay of Taiwanese hospice care, and often spiritual care is provided to patients and families during life-limiting illness [
27–
28]. The shortest survival of 2 weeks in the Taiwanese group may be advantageous to show the relationship between SWB and survival time. SWB was insignificant in Japanese and Korean patients in the final model, and two groups had longer survival (around three weeks) compared with the Taiwanese group. Patients at the end of life are known to suffer from spiritual distress [
6]. It is common to see increasing levels of interest and concern among the families of patients under palliative care as death is nearer. Therefore, we assume that the influence of SWB on survival time may increase according to the shortened survival. Another biological plausibility is that SWB can affect survival time based on its link with physical symptoms [
2,
3]. Spirituality could be protective against physical symptoms [
29], while the intensity of physical symptoms is known to be associated with survival time of patients having advanced cancer [
30,
31]. Thus, better SWB may prolong survival time. Since the IPOS item for SWB assessed “peacefulness” of the patient, medical professionals may regard SWB as a part of overall QOL or “being free from suffering”. In fact, we observed a weak relationship between SWB and survival time in Japan based on the results of multivariate analysis (
p = 0.06). Therefore, SWB had a borderline significance on survival time in Japan. In univariate analysis, the median survival time of the Korean group with Worse SWB at admission was 22.0 days and it was longer than in Japanese and Taiwanese groups with Better SWB at admission (respectively, 22.0 days, 17.0 days). Therefore, we presume that SWB affects survival time significantly when death is near. Probably, Korean patients were not the population affected by SWB because of their longest survival time. Another possibility is that SWB is rated according to IPOS implicit overall well-being to some degree. The effect of SWB on survival time may overlap with that of physical distress. Especially in Japan, although SWB was significant in univariate analysis, its role in survival was diminished by other physical symptoms in multivariate analysis. A previous Korean study [
23] showed that SWB was not related to survival time. The median survival time of the study participants was about 20 days, which was comparable to our study. Hence, our results involving the Korean group are consistent with the previous study.
Previous studies reported that the intensity of physical symptoms such as dyspnea and anorexia were related to survival time of inpatients with advanced cancer [30, 31]. Notably, dyspnea has been reported to indicate psychosocial and spiritual distress [32, 33]. The lower KPS, fewer oral intakes and dyspnea at rest among Japanese patients were related to shorter survival time as in Korea and Taiwan. These variables have been consistently known to be poor prognostic factors for survival time [25]. Moreover, the intensity of anorexia and dyspnea play a predictive role in the survival time of inpatients with advanced cancer [30, 31]. Our results are consistent with previous studies. Korean patients showed similar results for lower KPS, decreased oral intake and dyspnea at rest, similar to Japanese cases described above. Taiwanese patients had significantly lower KPS, and decreased oral intake and dyspnea at rest with survival, similar to those of Japanese and Korean groups.
Surprisingly, married patients had shorter survival in Japan. Most of the married patients lived with their spouses and children, and their families could be caregivers at home. Therefore, married patients had many opportunities for caregiver support and stayed longer at home. In other words, the survival of married patients was shorter when they were admitted to PCUs. The survival of married Koreans was shorter similar to married Japanese patients. Similar assumptions as the Japanese group may be applied to the Korean group. Thus, unmarried, divorced or widowed patients might survive longer, thereby reflecting the Korean medical environment, where such patients tend to be admitted to PCUs earlier, thanks to the supportive nationwide health insurance coverage. The conditions were more favorable for cancer patients in hospice institutes, where half of all the patients received professional caregiver services at very affordable rates in Korea.
This study has several limitations. First, we used IPOS to evaluate SWB. In this study, IPOS was evaluated by physicians and/or nurses, which may lead to differences between patients’ subjective assessments and physicians’ and/or nurses’ objective assessments. Prior studies reported that the inter-class correlation of SWB for IPOS-Patient and IPOS-Staff was 0.581 in Japan [34] and 0.348 in Taiwan and the correlation ranged from fair to moderate. Therefore, we regard IPOS-Staff as an acceptable tool. Second, the evaluation by IPOS may not capture every domain of spirituality. For instance, IPOS cannot be used to measure “meaning of life”, “connectedness”, or “faith” simultaneously. Those concepts may play a role in prolonging survival time, and thus a further study via in-depth assessment of SWB will be meaningful. In addition, the IPOS SWB may be regarded by medical professionals as an assessment of psychological well-being including SWB, which can be affected by physical condition. Third, our patients do not represent a general population of patients with far advanced cancer, and thus our findings may differ from patients living at home or in a general ward. Therefore, it is required to evaluate the SWB of patients receiving care at home or general ward in near future.
In conclusion, SWB of far advanced cancer patients is related to survival time in Taiwan but not in Japan and Korea. We suggest that spiritual care may contribute to prolonged survival of patients with advanced cancer. A further study is needed to investigate the relationship between SWB of patients with far advanced cancer and survival time.