Relation of Depression, Natural Killer Cell Function, and Infections after Coronary Artery Bypass in Women

Abstract

After hospital discharge for coronary artery bypass grafting (CABG), infection is a common cause of morbidity. Although depression has been associated with immune dysfunction, its role in post-CABG infection is unknown. The purpose of this study was to: 1) compare natural killer cell cytotoxicity (NKCC) and post-hospitalization infections in depressed and non-depressed women after CABG; and 2) test whether NKCC mediated the relationship between post-discharge depression and infections. Sixty-seven women recovering from CABG were assessed for depression prior to hospital discharge and followed for six months. Major depression was identified by a structured clinical interview. Infections were identified by patient report using the Modified Health Review and by medical chart audit. Compared to non-depressed women after CABG, women with major depression had reduced NKCC, more all-cause infections, and more self-reported illnesses. Although NKCC did not mediate the relationship between depression and wound (i.e. incisional) infections after CABG, it did mediate the relationship between depression and non-wound infections, including pneumonias and upper respiratory infections. For the first six months after CABG, women with major depression are at increased risk for infections. Natural killer cell cytotoxicity may be related to this phenomenon, particularly to non-wound infections.