Depression severity is associated with increased inflammation in veterans with peripheral artery disease

The present study examines the association between depressive symptoms and inflammatory markers in peripheral artery disease (PAD) to better understand the mechanistic relationship between depression and PAD. A cross-sectional sample of 117 patients with PAD (97% male, 76% Caucasian) was recruited from the San Francisco Veterans Affairs Medical Center. Patients were categorized into three subgroups based upon current depressive symptom severity, as defined by Patient Health Questionnaire-8 scores: no symptoms (score of 0-4, n = 62), mild symptoms (score of 5-9, n = 33), and moderate/severe symptoms (score 10, n = 22). Serum levels of high-sensitivity C-reactive protein (hs-CRP), interleukin-6 (IL-6), soluble intercellular adhesion molecule-1 (ICAM-1), and tumor necrosis factor-alpha (TNF-) were assayed and log-transformed for multivariable analysis. To decrease the possibility of Type 1 errors, inflammatory markers were standardized and summed to create a total inflammatory score. In a multivariable analysis controlling for demographics, PAD severity, and atherosclerotic risk factors, mild and moderate/severe depressive symptoms were predictive of a higher total inflammatory score when compared to the group with no symptoms (mild symptoms p = 0.04, moderate/severe symptoms p = 0.007). Exploratory multivariable analyses of individual inflammatory markers found IL-6 levels were significantly higher in the moderate/severe symptoms group (p = 0.006) than in the no symptoms group. Moreover, hs-CRP and ICAM-1 trended upwards with increasing depression severity. TNF- was not associated with depression severity. We conclude that depressive symptom severity was independently associated with greater inflammation in PAD. Future research should examine the strength and directionality of this association through larger prospective cohort studies, as well as investigate the pathophysiological mechanisms responsible.