Quality of life and self-regulatory fatigue in patients with type 2 diabetes mellitus: the mediating effects of personal mastery and health-promoting behaviors

Background Quality of life (QoL) is a key prognostic indicator in type 2 diabetes mellitus (T2DM). The interplay between psychological and behavioral determinants remains underexplored. Objectives To examine QoL and its associated factors in T2DM patients, and to test the mediating roles of personal mastery (PM) and health-promoting behaviors (HPB) between self-regulatory fatigue (SRF) and QoL. Methods A cross-sectional study recruited 432 T2DM patients from three Chinese tertiary hospitals (July 2025–February 2026). Data were collected using the Demographic Characteristics Questionnaire, Self-Regulatory Fatigue Scale, Personal Mastery Scale, Diabetes Health Promotion Scale, and Diabetes-Specific Quality of Life Scale. Pearson’s correlation, multiple linear regression, and structural equation modeling were employed for data analysis. The mediating effects were tested using the bootstrap method. Results The total scores for SRF, PM, HPB, and QoL were 38.63 ± 12.84, 26.12 ± 7.62, 97.69 ± 20.87, and 69.41 ± 20.89, respectively. QoL correlated positively with SRF ( r = 0.581) and negatively with PM ( r = −0.557) and HPB ( r = −0.613, all p < 0.01). Ten independent predictors of QoL were identified (age, educational level, medical insurance payment method, smoking status, glycemic control status, number of comorbidities, self-care ability, SRF, PM, HPB; R 2 = 0.418). SRF showed a total indirect effect on QoL via PM (28.7%) and HPB (44.6%), plus a chain mediation via PM→HPB (11.3%). Conclusion SRF is associated with lower QoL in T2DM patients, partly through reduced PM and HPB. Interventions targeting self-regulatory resources and PM may improve QoL. In parallel, strengthening personal mastery through empowerment-based education, goal setting, and individualized feedback can enhance patients’ confidence in diabetes self-management, which may promote sustained engagement in healthy behaviors and ultimately improve QoL in this population.