Mediators of medication adherence and glycaemic control and their implications for direct outpatient medical costs: a cross-sectional study

To investigate the effects of diabetes-related distress and perception of hyperglycaemia on self-reported medication adherence and glycaemic control, as measured by HbA_1c , and to compare the cost outcomes in patients with sub-optimally vs uncontrolled Type 2 diabetes mellitus.

We conducted a retrospective cross-sectional study that involved the review of a chronic disease database in Singapore. Data on clinical characteristics, diabetes-related distress, perception of hyperglycaemia, self-reported medication adherence and costs were obtained from the database. Mediation analyses were conducted using a linear regression-based approach. A final path model was built to illustrate the sequential mediating effects of diabetes-related distress and perception on the association of medication adherence and HbA_1c concentration.

Diabetes-related distress and perception of hyperglycaemia were significantly associated with medication adherence and HbA_1c concentration. Mediation analyses showed a significant indirect effect of diabetes-related distress and perception of hyperglycaemia on medication adherence and HbA_1c concentration. People with uncontrolled diabetes were found to incur significantly higher total direct medical costs than those with sub-optimally controlled diabetes (P = 0.034), with medication cost as the main cost driver (66.6%).

Identifying the influence of the sequential mediating effects of distress and perception was important in understanding the pathway between medication adherence and glycaemic control. This suggests the importance of a team-based approach to address these mediators and thus improve glycaemic control. Poor glycaemic control was also found to be associated with higher direct medical costs.