Post-menopausal Women Exhibit Greater Interleukin-6 Responses to Mental Stress Than Older Men

BACKGROUND: Acute stress triggers innate immune responses and elevation in circulating cytokines including interleukin-6 (IL-6). The effect of sex on IL-6 responses remains unclear due to important limitations of previous studies. PURPOSE: The purpose of this study was to examine sex differences in IL-6 responses to mental stress in a healthy, older (post-menopausal) sample accounting for several moderating factors. METHODS: Five hundred six participants (62.9 ± 5.60 years, 55 % male) underwent 10 min of mental stress consisting of mirror tracing and Stroop task. Blood was sampled at baseline, after stress, and 45 and 75 min post-stress, and assayed using a high sensitivity kit. IL-6 reactivity was computed as the mean difference between baseline and 45 min and between baseline and 75 min post-stress. Main effects and interactions were examined using ANCOVA models. RESULTS: There was a main effect of time for the IL-6 response (F(3,1512) = 201.57, p = <.0001) and a sex by time interaction (F(3,1512) = 17.07, p = <.001). In multivariate adjusted analyses, IL-6 reactivity was significantly greater in females at 45 min (M = 0.37 ± 0.04 vs. 0.20 ± 0.03 pg/mL, p = .01) and at 75 min (M = 0.57 ± 0.05 vs. 0.31 ± 0.05 pg/mL, p = .004) post-stress compared to males. Results were independent of age, adiposity, socioeconomic position, depression, smoking and alcohol consumption, physical activity, statin use, testing time, task appraisals, hormone replacement, and baseline IL-6. Other significant predictors of IL-6 reactivity were lower household wealth, afternoon testing, and baseline IL-6. CONCLUSIONS: Healthy, post-menopausal females exhibit substantially greater IL-6 responses to acute stress. Inflammatory responses if sustained over time may have clinical implications for the development and maintenance of inflammatory-related conditions prevalent in older women.