Inflammatory Factors Associated with Late-Life Depressive Symptoms in Oldest-Old Patients with Type 2 Diabetes

While many studies indicate a bidirectional relationship between type 2 diabetes (T2DM) and depression, its precise nature remains unclear. The aim of the study was to determine the levels of inflammatory markers in oldest-old patients with diabetes and depressive symptoms and identify the risk factors associated with late-life depressive symptoms. In total, 195 participants with diabetes, aged 85 and above, were screened for depressive symptoms using the 30-item Geriatric Depression Scale (GDS-30). Clinical and biochemical data were also collected. Serum levels of inflammatory markers were measured via enzyme-linked immunosorbent assay (ELISA). Serum levels of TNF-α, IL-1β, and IL-6 were increased in individuals with depression and correlated with each other as well as with HbA_1c levels, GDS scores, FBG and BMI. The multivariable analysis confirmed that of the three studied biomarkers, only TNF-α is independently associated with depressive symptoms when adjusting for demographic factors (Model 1) and cardiovascular burden (Model 3); however, its significance disappeared when controlling for glycaemic parameters (Model 2). Only TNF-α is independently associated with depressive symptoms in oldest-old patients with T2DM, though this relationship is tightly dependent on glycaemic control. Future studies should clarify whether IL-1β and IL-6 contribute to depressive symptoms through distinct pathophysiological pathways.