Background: Little information is available about the association of depression with long-term control of glycemia, blood pressure, or lipid levels in patients with diabetes.
Objective: To determine whether minor and major depression at study enrollment compared with no depression are associated with higher average HbA(1c), systolic blood pressure (SBP) and LDL cholesterol over the long term in patients with an indication for or receiving drug treatment.
Design: Cohort study.
Patients: A total of 3,762 patients with type 2 diabetes mellitus enrolled in the Pathways Epidemiologic Study in 2001-2002 and followed for 5 years.
Main measures: Depression was assessed at study enrollment using the Patient Health Questionnaire-9 (PHQ-9). SBP and information on cardiovascular co-morbidity were abstracted from medical records, and LDL cholesterol and HbA(1c) measured during clinical care were obtained from computerized laboratory data during a median of 4.8 years' follow-up.
Key results: Among those with an indication for or receiving drug treatment, after adjustment for demographic and clinical characteristics, average long-term HbA(1c), SBP, and LDL cholesterol did not differ in patients with comorbid diabetes and minor or major depression compared with those with diabetes alone.
Conclusions: The adverse effect of depression on outcomes in patients with diabetes may not be mediated in large part by poorer glycemic, blood pressure, or lipid control. Further study is needed of the biologic effects of depression on patients with diabetes and their relation to adverse outcomes.