The Inflammatory Indicator IL-6 and BDNF Levels in Male Fitness Athletes and Their Relationship with Acute Stress Disorder: A Case-Control Study

Abstract

Background: The responses of the inflammatory marker interleukin 6 (IL-6) and brain-derived neurotrophic factor (BDNF) to acute stress in fitness athletes are unknown. Objectives: This study aimed to investigate IL-6 and BDNF levels in male fitness athletes and their association with acute stress disorder using a case-control design. Methods: Ninety male fitness athletes were divided into a case group (individuals with acute stress disorder) and a control group (individuals without acute stress disorder) using a psychological diagnostic interview based on the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria, conducted by a clinical psychologist to reduce selection bias. Serum IL-6 and BDNF samples were collected at two time points, before and after muscular training. Data were analyzed using t tests and binary logistic regression. Results: After controlling for anxiety and depression, the association between IL-6 and acute stress disorder before muscular training was positive and significant (OR = 1.013; 95% CI, 1.003 to 1.022; P = 0.007). After muscular training, this association became negative and significant relative to the control group (OR = 0.975; 95% CI, 0.961 to 0.990; P = 0.001). Notably, after muscular training, there was a very strong positive association between BDNF and acute stress disorder (OR = 10.328; 95% CI, 1.585 to 67.318; p = 0.015). Muscular exercise increased serum IL-6 levels in the nonstressed group (mean change, 26.49 ± 39.18; P ≤ 0.001) but decreased IL-6 levels in the acute stress disorder group, which already had high serum levels (mean change, -56.87 ± 46.83; P ≤ 0.001). Conclusions: Muscular exercise increased BDNF levels in both groups. Acute stress disorder was significantly associated with increased IL-6 and BDNF levels in male fitness athletes. After physical exercise, IL-6 levels decreased, whereas BDNF levels increased. These findings are limited to male athletes.