Fasting Glucose, Diagnosis of Type 2 Diabetes, and Depression: The Vietnam Experience Study

Background: Recent findings suggest that both low and very high fasting blood glucose concentrations may be linked with depression, though whether type 2 diabetes is associated with depression may depend on awareness of the diagnosis. We explored the association between fasting glucose and type 2 diabetes (undiagnosed and diagnosed) and depression in middle-aged men.
Methods: Participants were 4293 US veterans who underwent an examination during which fasting blood glucose was measured, major depression diagnosed using DSM-III criteria, and depressive symptoms assessed with Minnesota Multiphasic Personality Inventory (MMPI) Clinical Scale for Depression.
Results: Compared to those with normal fasting glucose, men with undiagnosed type 2 diabetes had nearly double the prevalence of major depression, odds ratio (95% confidence interval 1.80 (1.01, 3.22), and men with diagnosed diabetes had triple the prevalence of major depression, 3.82 (1.68, 8.70), after adjustment for confounding variables. Men with undiagnosed or diagnosed diabetes had higher MMPI depression scores. There was no curvilinear association between fasting glucose and depression (p>0.45).
Conclusions: These findings do not support a ‘U’-shaped association between fasting glucose and depression. They suggest that the positive association between type 2 diabetes and depression extends beyond those who are aware they have the disease.