Reduced neutrophil superoxide production among healthy older adults in response to acute psychological stress

Ageing is associated with higher morbidity and mortality, and declining immune function, termed immunesenescence. The present study examined the effects of an acute laboratory psychological stress task on innate immunity, specifically neutrophil function, among older adults. The two functional assays used were phagocytosis of Escherichia coli and stimulated superoxide production. Participants were 17 (11 female) older adults (mean age 75.7, SD=7.06 years). Blood samples to determine neutrophil function by flow cytometry were taken at the end of resting baseline, during an acute stress task and during recovery. The stress task was an 8-minute time-pressured mental arithmetic challenge with social evaluation. There was a significant reduction in neutrophil superoxide production, p=.017, η(2)(p)=.240, associated with the stress task relative to baseline, but no effect on phagocytosis. The results of this study could contribute to explaining the increased risk of infection in older adults, particularly those subject to frequent stress exposures. Future research is needed to explore the underlying mechanisms of acute stress effects on human neutrophil function in older adults in greater detail.