The salience network, depression, and exercise dependence in middle-aged and older adults: A structural MRI study

BACKGROUND: Exercise guidelines encourage middle-aged and older adults to engage in physical activity for its health benefits. However, continuous excessive exercise can also lead to physiological and psychological symptoms, often called exercise dependence. The precise brain pathways underlying exercise dependence and depression in older individuals remain unclear. METHODS: This study included 79 participants exhibiting symptoms of exercise dependence and 54 healthy participants who engaged in regular exercise without symptoms. Initially, paper-based questionnaires were used to evaluate participants' overall health and symptoms of exercise dependence. Subsequently, non-negative matrix factorization and Kullback-Leibler divergence-based similarity analysis were employed to identify structural brain networks. At the same time, a two-sample T-test was conducted to assess group differences. Finally, partial correlation and mediation analyses were performed to explore the relationships between structural networks, exercise dependence, and depression. RESULTS: The findings revealed that the gray matter volume (GMV) and internal structural connectivity of the salience network were significantly increased in the group with exercise dependence symptoms. These changes were primarily associated with three key characteristics of exercise dependence: tolerance, conflict, and time commitment. Importantly, depression was found to mediate the relationship between the salience network and exercise dependence. CONCLUSIONS: In older adults, increased structural connectivity within the salience network may amplify impulsive and reward-driven cravings for exercise and the ability to perceive emotional states such as depression. These findings indicate that the salience network could serve as a potential target for preventing and treating exercise dependence in the elderly population.