Multi-systemic evaluation of biological and emotional responses to the Trier Social Stress Test: A meta-analysis and systematic review.

Humans experience multiple biological and emotional changes under acute stress. Adopting a multi-systemic approach, we summarized 61 studies on healthy people's endocrinological, physiological, immunological and emotional responses to the Trier Social Stress Test. We found salivary cortisol and negative mood states were the most sensitive markers to acute stress and recovery. Biomarkers such as heart rate and salivary alpha-amylase also showed sensitivity to acute stress, but the numbers of studies were small. Other endocrinological (e.g., dehydroepiandrosterone), inflammatory (C-Reactive Protein, Interleukin-6) and physiological (e.g., skin conductance level) measures received modest support as acute stress markers. Salivary cortisol showed some associations with mood measures (e.g., state anxiety) during acute stress and recovery, and heart rate showed preliminary positive relationship with calmness ratings during response to TSST, but the overall evidence was mixed. While further research is needed, these findings provide updated and comprehensive knowledge on the integrated psychobiological response profiles to TSST.

Qigong exercise enhances cognitive functions in the elderly via an interleukin-6-hippocampus pathway: A randomized active-controlled trial.

BACKGROUND: Evidence has suggested that exercise protects against cognitive decline in aging, but the recent lockdown measures associated with the COVID-19 pandemic have limited the opportunity for outdoor exercise. Herein we tested the effects of an indoor exercise, Qigong, on neurocognitive functioning as well as its potential neuro-immune pathway. METHODS: We conducted a 12-week randomized active-controlled trial with two study arms in cognitively healthy older people. We applied Wu Xing Ping Heng Gong (Qigong), which was designed by an experienced Daoist Qigong master, to the experimental group, whereas we applied the physical stretching exercise to the control group. The Qigong exercise consisted of a range of movements involving the stretching of arms and legs, the turning of the torso, and relaxing, which would follow the fundamental principles of Daoism and traditional Chinese medicine (e.g., Qi). We measured aging-sensitive neurocognitive abilities, serum interleukin-6 (IL-6) levels, and brain structural volumes in the experimental (Qigong, n = 22) and control groups (stretching, n = 26) before and after the 12-week training. RESULTS: We observed that Qigong caused significant improvement in processing speed (t (46) = 2.03, p = 0.048) and sustained attention (t (46) = -2.34, p = 0.023), increased hippocampal volume (t (41) = 3.94, p < 0.001), and reduced peripheral IL-6 levels (t (46) = -3.17, p = 0.003). Moreover, following Qigong training, greater reduction of peripheral IL-6 levels was associated with a greater increase of processing speed performance (bootstrapping CI: [0.16, 3.30]) and a more significant training-induced effect of hippocampal volume on the improvement in sustained attention (bootstrapping CI: [-0.35, -0.004]). CONCLUSION: Overall, these findings offer significant insight into the mechanistic role of peripheral IL-6-and its intricate interplay with neural processes-in the beneficial neurocognitive effects of Qigong. The findings have profound implications for early identification and intervention of older individuals vulnerable to cognitive decline, focusing on the neuro-immune pathway. The trial was registered at clinicaltrials.gov (identifier: NCT04641429).

Multi-Session Anodal Prefrontal Transcranial Direct Current Stimulation does not Improve Executive Functions among Older Adults.

OBJECTIVE: Findings from single-session online studies highlighted the potential of using anodal prefrontal transcranial direct current stimulation (tDCS) to enhance executive functions (EF) in the context of aging. However, tDCS must be executed as a multi-session offline intervention to ascertain its viability in this context. Relatedly, findings from multi-session studies remained inconclusive. To this end, we examined the effects of multi-session anodal prefrontal tDCS on EF in an intervention. METHOD: The intervention consisted of 15 sessions; in each, healthy older participants (Agemean = 66.7) received either 15 min of 1.5 mA tDCS (Ncompleted = 35) or sham stimulation (Ncompleted = 33) while performing EF training tasks. EF measures were assessed at baseline, post-intervention, and 1-month follow-up. Hierarchical linear models were used to examine the effect of tDCS on EF outcomes. RESULTS: Both groups of participants did not differ significantly in side effect ratings and attendance. There were no significant tDCS-associated gains in any EF outcomes in the intervention. CONCLUSIONS: Multi-session prefrontal tDCS did not lead to any significant gains in EF in the current intervention. More research is needed to optimize the use of tDCS before it can be effectively used to enhance EF among older adults.