Novel cardiovascular risk markers in depression: no association between depressive symptoms and osteoprotegerin or adiponectin in persons at high risk for sleep apnea.

Background: Inflammation is believed to play a role in the pathogenesis of both cardiovascular disease and depressive disorders. We hypothesized that circulating concentrations of the novel inflammatory and cardiovascular biomarkers osteoprotegerin (OPG) and adiponectin as well as high sensitivity C-reactive protein (hsCRP) are associated with the severity of depressive symptoms and presence of major depressive disorder (MDD).

Methods: In a cross-sectional population-derived study (Akershus Sleep Apnea Project) 520 persons underwent clinical examination and venous blood sampling. Medical history was obtained and the participants completed the Beck Depression Inventory (BDI). Structured clinical interviews for axis-I disorders including MDD were performed in a subgroup of 288 participants. OPG and adiponectin concentrations were determined by in-house time-resolved immunofluorometric assays.

Results: Despite significant correlation with hsCRP (r=0.162, p<0.001), the sum-score of BDI did not correlate with OPG or adiponectin levels (r=0.011, p=0.811 and r=0.055, p=0.210, respectively). Neither circulating OPG nor adiponectin differed between persons with (n=34) and without (n=246) MDD (median±interquartile range: 1.18 (0.96-1.49) vs. 1.17 (0.93-1.57) ug/l and 7.26 (5.13-9.91) vs. 7.39 (5.23-11.37) mg/l, respectively).

Limitations: Causal considerations are not possible, and results in the sub-group of diagnosed participants need careful interpretation due to small sample size.

Conclusions: hsCRP was independently associated with depressive symptoms, but no association between depression severity or presence of MDD and OPG- or adiponectin concentrations was observed in community-residing persons at high risk for obstructive sleep apnea.