Association of depressive symptoms with impaired glucose regulation, screen-detected, and previously known type 2 diabetes: findings from the Finnish D2D Survey

OBJECTIVE

To study the association between impaired glucose regulation (IGR), screen-detected type 2 diabetes, and previously known diabetes and depressive symptoms.

RESEARCH DESIGN AND METHODS

Altogether, 2,712 participants from three hospital districts in Finland attended a health examination. Cutoff scores ≥10 and ≥16 in the 21-item Beck Depression Inventory (BDI-21) were used for depressive symptoms. The participants were defined as having known diabetes if they reported diabetes. An oral glucose tolerance test was used to detect normal glucose regulation (NGR), impaired fasting glucose (IFG), impaired glucose tolerance (IGT), and screen-detected diabetes. The participants were defined as having IGR if they had IFG or IGT.

RESULTS

Prevalence of depressive symptoms, defined as a BDI-21 cutoff score ≥10, was 14.4% for those with NGR, 13.7% for those with IGR, 14.8% for those with screen-detected diabetes, and 26.4% for those with previously known diabetes. The corresponding prevalences for a cutoff score ≥16 were 3.4, 3.4, 4.2, and 7.5%, respectively. Compared with NGR and adjusted for demographic, lifestyle, and biological factors, the odds ratios for IGR, screen-detected diabetes, and previously known diabetes were 0.91 (95% CI 0.69–1.20), 0.70 (0.45–1.08), and 1.35 (0.84–2.15), respectively, for a cutoff score ≥10. For a cutoff score ≥16, the corresponding odds ratios were 1.05 (0.62–1.76), 0.87 (0.40–1.90), and 1.56 (0.69–3.50), respectively.

CONCLUSIONS

Participants with diagnosed diabetes had a higher prevalence of depressive symptoms than participants with NGR, IGR, and previously unknown diabetes. When potential confounding factors were included in the analysis, previously known diabetes was not significantly associated with depressive symptoms.It is widely recognized that depression is more common among people with diabetes than in the general population (1). However, previous studies (2–10) that have assessed the relationship between depressive symptoms and impaired glucose tolerance (IGT) or diabetes have been inconsistent. A German study (4) that included 4,597 subjects and a Dutch study (2) that included 4,747 participants found no association between type 2 diabetes and depressive symptoms. In a general-practice setting study that included 2,849 male and 3,160 female subjects, depression was not more prevalent in people with screen-detected diabetes or impaired glucose regulation (IGR) than in people with normal glucose regulation (NGR) (5). Contrary to these studies, within the Hertfordshire Cohort Study (6) there was a relationship between depression scores and diagnosed and previously undiagnosed diabetes. A U.S. study (8) including 4,293 U.S. veterans indicated that men with undiagnosed type 2 diabetes had nearly double the odds of major depression compared with those with normal fasting glucose.In 1992, it was stated about the relationship between depression and diabetes that “the etiology is unknown but is probably complex; and biological, genetic, and psychological factors remain as potential contributors. Several neuroendocrine and neurotransmitter abnormalities common to both depression and diabetes have been identified, adding to etiological speculations” (11). It has been suggested that stress-induced activation of the hypothalamic-pituitary-adrenal axis may result in the development of metabolic abnormalities and depression (12). In addition, possible neuroendocrine abnormalities associated with both diabetes and depressive symptoms may include abnormalities in vitamin B₁₂ and sex hormone–binding globulin (SHBG) levels. Low vitamin B₁₂ levels have been found to relate to type 2 diabetes (13) and depressive symptoms (14–16). Low levels of SHBG may predict diabetes (17). SHBG binds circulating sex hormones, which have been suggested to be associated with depressive symptoms (18). In addition to these biological factors, the observed association between diabetes and depressive symptoms could be a reflection of the burden of diabetes and comorbidities.In the present study, our aim was to analyze the prevalence of depressive symptoms in people with NGR, IGR (including impaired fasting glycemia and impaired glucose tolerance), screen-detected (previously unknown) diabetes, and previously known type 2 diabetes. Furthermore, our aim was to study the association between glucose tolerance and depressive symptoms, taking into account potential confounding demographic and biological factors as well as comorbidity.