Reward-related functioning across diabetes subtypes: associations with glycaemic control

Insulin signaling has been implicated in reward processing and motivational regulation through its modulatory effects on mesolimbic pathways. However, reward-related behavioral functioning across different diabetes subtypes and insulin-related metabolic states remains poorly understood. This study aimed to compare motivational and reward-related behavioral measures among individuals with type 1 diabetes mellitus (T1DM), type 2 diabetes mellitus (T2DM), prediabetes, and healthy controls, and to investigate their associations with diabetes self-management and glycaemic control.

This cross-sectional study included 44 individuals with T1DM, 43 with T2DM, 28 with prediabetes, and 46 healthy controls. Participants completed measures assessing behavioral inhibition/activation (BIS/BAS), anhedonia, delay discounting, depressive symptoms, and diabetes self-management. Group differences were examined using analyses of covariance controlling for age, sex, education level, and depressive symptoms. Correlation and hierarchical regression analyses were conducted to evaluate associations with diabetes self-management and HbA1c levels.

Significant group differences were observed for BIS and BAS Reward Responsiveness scores after false discovery rate correction (p = .004). Post hoc analyses demonstrated that individuals with T1DM had significantly lower BIS and BAS Reward Responsiveness scores compared to T2DM, prediabetes, and healthy controls. No significant group differences were observed for anhedonia or delay discounting measures. Reward-related behavioral measures explained additional variance in HbA1c (ΔR² = .038, p = .035), with lower BAS Drive associated with higher HbA1c after adjustment for demographic and clinical covariates (β = -.162, p = .036).

Altered reward responsiveness and behavioral inhibition may be particularly associated with T1DM rather than T2DM or prediabetes. Reward-related behavioral functioning also showed a modest association with glycaemic control, with BAS Drive demonstrating the most consistent individual association with HbA1c. These findings highlight the potential clinical relevance of motivational and reward-related processes in diabetes and suggest that considering these behavioural dimensions may help inform more individualized approaches to diabetes management and glycaemic control.