The association of comorbid depression with mortality and amputation in veterans with peripheral artery disease

Objective: Peripheral artery disease (PAD) is an increasing health concern with rising incidence globally. Previous studies have shown an association between PAD incidence and depression. The objective of the study was to determine the association of comorbid depression with PAD outcomes (amputation and all-cause mortality rates) in veterans. Methods: An observational retrospective cohort of 155,647 patients with incident PAD (2003-2014) from nationwide U.S. Veterans Health Administration hospitals was conducted using the national Veterans Affairs Corporate Data Warehouse. Depression was measured using concurrent International Classification of Diseases, Ninth Revision diagnosis codes 6 months before or after PAD diagnosis. The main outcomes were incident major amputation and all-cause mortality. Crude associations were assessed with Kaplan-Meier plots. The effects of depression adjusted for covariates were analyzed using Cox proportional hazards models. Results: Depression was present in 16% of the cohort, with the occurrence of 9517 amputations and 63,287 deaths (median follow-up, 5.9 years). Unadjusted hazard ratios (HRs) of comorbid depression for amputations and all-cause mortality were 1.32 (95% confidence interval [CI], 1.25-1.39) and 1.02 (95% CI, 0.99-1.04), respectively. After adjustment for covariates in Cox regression models, a diagnosis of comorbid depression at the time of PAD diagnosis was associated with a 13% higher amputation (HR, 1.13; 95% CI, 1.07-1.19) and 17% higher mortality (HR, 1.17; 95% CI, 1.14-1.20) risk compared with patients with no depression. On stratification by use of antidepressants, depressed patients not taking antidepressants had a 42% higher risk of amputation (HR, 1.42; 95% CI, 1.27-1.58) compared with those without depression. Patients taking antidepressants for depression still had increased risk of amputation but only 10% higher compared with those without depression (HR, 1.10; 95% CI, 1.03-1.17). Interestingly, patients taking antidepressants for other indications also had a higher risk of amputation compared with those not having depression or not taking antidepressants (HR, 1.08; 95% CI, 1.03-1.14). Having any diagnosis of depression or the need for antidepressants increased the mortality risk by 18% to 25% in the PAD cohort compared with those without depression and not taking antidepressants for any other indication. Conclusions: PAD patients with comorbid depression have a significantly higher risk of amputation and mortality than PAD patients without depression. Furthermore, untreated depression was associated with an increased amputation risk in the PAD population, more so than depression or other mental illness being treated by antidepressants. The underlying mechanisms for causality, if any, remain to be determined. The association of antidepressant treatment use with amputation risk should prompt further investigations into possible mechanistic links between untreated depression and vascular dysfunction.