Aims:
Health-related quality of life (HRQoL) is a key patient-reported outcome in diabetes care, yet the extent to which somatic and psychological factors are associated with HRQoL remains unclear. This study examined how demographic, diabetes-related, medical, and psychological factors were independently associated with HRQoL in adults with diabetes.

Materials and Methods:
A cross-sectional online survey was conducted among adults with diabetes in Germany (September 2024–February 2025). HRQoL was assessed using the EuroQol 5-Dimension 5-Level questionnaire (EQ-5D-5L). Participants also completed the PHQ-8 for depressive symptoms, the problem areas in diabetes (PAID) scale, and the hypoglycaemia fear survey (HFS-II). Clinical variables were self-reported and included diabetes type, duration, HbA1c, body mass index (BMI), and complications. Tobit regression accounted for the censored EQ-5D distribution. Blockwise multivariable models evaluated incremental explained variance across demographic, diabetes-related, comorbidity, and mental-health domains.

Results:
Of 1581 invitees, 734 completed the EQ-5D (mean age 56 ± 14 years; 73% type I). In multivariable analyses, female sex (β = −0.045), higher BMI (β = −0.029), diabetic foot syndrome (β = −0.078), neuropathy (β = −0.123), and elevated depressive symptoms (β = −0.212), diabetes distress (β = −0.069), and fear of hypoglycaemia (β = −0.085) were all independently associated with lower EQ-5D utilities (p < 0.01). Mental-health variables explained a similar proportion of variance (≈22%) as diabetes-related complications (≈20%). Mental health factors like depression, diabetes distress, and fear of hypoglycaemia showed highly significant associations with reduced HRQoL by up to 27%.

Conclusions:
Both diabetes complications and mental health determine HRQoL in people with diabetes. Depression emerged as the strongest independent predictor reducing HRQoL by up to 21%. This underscores the importance of mental health for HRQoL. This findings highlight the relevance of integrating mental health assessment into diabetes management.