Mild depressive symptoms are associated with amplified and prolonged inflammatory responses after influenza virus vaccination in older adults

Background: Depression is associated with enhanced production of proinflammatory cytokines that influence a spectrum of conditions associated with aging, including cardiovascular disease, osteoporosis, arthritis, type 2 diabetes mellitus, certain cancers, periodontal disease, frailty, and functional decline. In this prospective community study, we assessed the relationship between depressive symptoms and changes in inflammatory response after an influenza virus vaccination. Methods: To study the dynamics of interleukin (IL) 6 levels in plasma in response to an immunological challenge, we obtained blood samples in 119 older adults (mean age, 71.21 +/- 8.68 years [SD]) immediately before an annual influenza vaccination and again 2 weeks later. The short form of the Beck Depression Inventory, completed at these same times, provided information on depressive symptoms. Results: The number of depressive symptoms in this sample was low on average before vaccination (mean SD number of symptoms, 3.07 +/- 3.09) and did not change significantly after vaccination. Participants with more depressive symptoms had higher levels of IL-6 before and after vaccination than did those who reported fewer symptoms; moreover, individuals reporting more depressive symptoms also showed an increase in plasma IL-6 levels 2 weeks later, while there was little change in IL-6 levels among those reporting few or no symptoms. Conclusions: Even a modest number of depressive symptoms may sensitize the inflammatory response system in older adults and produce amplified and prolonged inflammatory responses after infection and other immunological challenges. Sustained and/or amplified inflammatory responses could accelerate a range of age-related diseases.