Prevalence of depression in patients with type 2 diabetes mellitus in Irish primary care and the impact of depression on the control of diabetes

As the Irish population ages, the management of chronic conditions in primary care is emerging as a challenge. The presence of co-morbid depression is common among such patients and may affect their response to treatment. This study sought to determine whether the prevalence of depression is higher in patients with type 2 diabetes mellitus than in the population aged > 50 in the West of Ireland, and whether depression is an independent predictor of diabetes control. We used a cross-sectional design to examine an anonymized database of 9,698 patients aged > 50 years whose medical data were collected as part of NUI Galway's CLARITY study. Glycosylated HbA1c levels were used to estimate type 2 DM control; depression was assessed using the Hospital Anxiety and Depression Scale. We found that while there is a higher prevalence of severe depression in patients with type 2 DM, there is no association between their diabetes control and depression after controlling for age, gender, comorbidity and GMS status. Multimorbidity is a significant predictor of depression in both diabetic and non-diabetic populations, with the odds of depression increasing as the number of co-morbidities increased. Patients with type 2 DM are more likely to suffer from severe depression than those without. Depression itself is not an independent predictor of diabetes control. However, it may be that the increased rates of depression observed in patients with type 2 DM are at least partially attributable to the burden of additional illnesses seen in these patients.