In the present study, PCS and MCS scores decreased significantly during the follow-up period. The PCS score decreased significantly in both the non-rapid and rapid kidney function decline groups, and the MCS score decreased significantly only in the rapid kidney function decline group. The rapid decline in kidney function was a significant factor in the rapid deterioration of PCS and MCS scores. Even in propensity score-matched patients with similar basal renal function in the non-rapid and rapid kidney function decline groups, the rapid kidney function decline was significantly associated with the rapid deterioration of PCS and MCS.
In the present study, both the non-rapid and rapid kidney function decline groups showed a decrease in PCS during the follow-up period of patients before and after PSM. In addition, PCS components, including physical function, role-physical, and bodily pain, significantly decreased. According to national surveys in France, patients with CKD had lower HRQOL than the general population, including symptoms, burden, and effects of kidney disease2. Symptoms related to CKD often occur in clusters, and this symptom burden is a predictor of HRQOL decline8, 9. In patients with CKD, especially advanced CKD, symptoms such as lack of energy, drowsiness, fatigue, and pain are prominent7. This symptom burden can lead to negative physical, psychological, and emotional responses10. Therefore, when treating patients with CKD, the full range of symptoms should be assessed and applied to improve their QOL and the quality of care.
General health, which represents overall general health awareness, did not decrease significantly during the follow-up period in this study. However, the general health score was much lower at baseline compared with the other PCS components. The Heart and Soul Study showed that self-assessed overall health was reduced in earlier stages of renal function than mental health outcomes or QOL11. Another study also showed that as CKD progressed to general health, the SF-36 component decreased, whereas mental and physical HRQOL remained stable12. Therefore, it is necessary to pay attention to patients’ health awareness and educate them on improving their HRQOL. Since the patient's symptom burden affects the lowering of HRQOL, clarifying these symptoms and approaching treatment will help improve HRQOL. HRQOL is one of the many patient-centered outcomes that can be assessed using patient-reported outcome measures. Incorporating patient-reported outcomes into clinical care is crucial for providing patient-centered care and improving the QOL of patients13. Therefore, efforts are being made to pay attention to patient-reported results in patients with CKD, and studies in which symptom burden was relieved have also been reported14, 15.
MCS was significantly decreased in the rapid kidney function decline group but not in the non-rapid kidney function decline group of patients before and after PSM. MCS components also significantly decreased only in the rapid kidney function decline group. That is, when patients did not have rapidly decreasing kidney function, PCS decreased, but MCS did not decrease significantly. This suggests that the mental health composition of patients with CKD was better tolerated in the absence of rapid kidney function decline. Although not evaluated in patients with rapid decline in kidney function, a previous study showed that CKD stage 2-3b had no significant effect on mental HRQOL16. Another study showed that physical health is affected in patients with moderate CKD; however, mental health outcomes remain stable11. Therefore, physicians should be concerned with and supportive of patients’ mental health.
In advanced CKD (eGFR < 45 ml/min/1.73 m2), the rapid decline of kidney function was a significant risk factor for both rapid deterioration of PCS and MCS. This suggests that not only is HRQOL lower in advanced CKD, but the rate of deterioration is also faster. Although the criteria for GFR for decreased HRQOL vary from study to study (e.g., eGFR < 60 or < 45 ml/min/1.73 m2), decreased renal function is a risk factor for decreased HRQOL 11, 16. In advanced CKD, more attention is required for the deterioration of HRQOL, especially in patients with a rapid decline in kidney function.
The strength of our study was the large number of predialysis patients with CKD of all stages. The KNOW-CKD study used in the analysis is a well-designed protocol and a nationally representative cohort study. HRQOL was not cross-sectionally investigated once, but the results of follow-up results were also analyzed. In addition, this is a meaningful study because little is known about the deterioration of HRQOL due to rapid kidney function decline. However, this study has several limitations. HRQOL assessment is complex and difficult. There are geographic, cultural, linguistic, and generational variations in the HRQOL measurements. We used the Korean version 1.3 of the KDQOL-SF. In addition, the universal standard methods for assessing HRQOL are limited. We cannot rule out potential residual confounders although we considered various confounding factors in the multivariable analysis. Finally, the study participants belonged to a single ethnic group of Koreans; thus, caution is required when generalizing our findings to other ethnicities.
In conclusion, the rapid decline in kidney function was associated with the rapid deterioration of HRQOL in patients with predialyis CKD. Attention should be paid to the deterioration of HRQOL in patients with a rapid decline in kidney function. Furthermore, early assessment of HRQOL deterioration in high-risk patients and attempting to modify them may help improve HRQOL in patients with CKD.