Studying psychosocial adaptation to end-stage renal disease: the proximal-distal model of health-related outcomes as a base model

Objective: Studying psychosocial adaptation in end-stage renal disease (ESRD) is increasingly important, as it may explain the variability in health outcomes unaccounted for by clinical factors. The Brenner et al. proximal-distal model of health-related outcomes provides a theoretical foundation for understanding psychosocial adaptation and integrating health outcomes, clinical, and psychosocial factors (Brenner MH, Curbow B, Legro MW. The proximal-distal continuum of multiple health outcome measures: the case of cataract surgery. Med Care. 1995;33(4 Suppl):AS236-44). This study aims to empirically validate the proximal-distal model in the dialysis population and examine the impact of psychosocial factors on the model. Methods: A cross-sectional observational study was conducted with a sample of long-term dialysis patients (n=201). Eleven factors: quality of life (QoL), depression, positive affect, comorbidity, symptoms, physical functioning, disease accommodation, loss, self-efficacy, illness acceptance, and social support were measured by standardized psychometric scales. A three-month average of hemoglobin was used. Latent composite structural equation modeling was used to examine the models. Results: The proximal-distal model with slight modification was supported by fit statistics [X²=16.04, df=13, P=25, root mean square error of approximation (RMSEA)=0.024], indicating that the impact of clinical factors on QoL is mediated through a range of functional and psychological factors, except for hemoglobin which impacts directly on QoL. The model with additional psychosocial factors was also supported by fit statistics (X²=43.59, df=41, P=36, RMSEA=0.018). These additional factors mainly impact on symptom status, psychological states, and QoL components of the model. Conclusion: The present study supported the proximal-distal model in the dialysis population and demonstrated the considerable impact of psychosocial factors on the model. The proximal-distal model plus psychosocial factors as a biopsychosocial model can be applied to studying psychosocial adaptation in ESRD.