The Effects of Mindfulness-Based Interventions on Physiological Markers of Stress in Older Adults: A Systematic Review and Synthesis

Objectives: Given the rapid increase in population ageing and considering the great impact that mental disorders have on global disability, there is a critical need for mental health promotion in older adults. Mindfulness-based interventions (MBIs) have been widely used to improve mental health. However, a comprehensive understanding of their neurobiological effects is still missing. We therefore conducted a systematic review of controlled clinical trials evaluating the effects of MBIs on the physiological markers of stress in older adults. Method: A systematic literature search was conducted in five electronic databases and the ClinicalTrials.gov registry. Controlled trials of mindfulness-based stress reduction or mindfulness-based cognitive therapy programs for older adults measuring any physiological outcome were identified. The combined p-value analysis, following the Synthesis Without Meta-analysis reporting guidelines, was used for data synthesis. A sensitivity analysis and subgroup analysis by the study population were also conducted. Results: Based on 22 eligible studies, the synthesis shows a positive effect of MBIs on 43 physiological outcomes grouped by five stress-related systems, i.e., brain circuits and signalling (combined p-value < 0.001), the sympathetic-adrenomedullar axis (combined p-value = 0.004), the hypothalamus-pituitary-adrenal axis (combined p-value = 0.011), the immune system (combined p-value = 0.037), and gene expression and epigenetic mediators (combined p-value < 0.001). The effects on brain circuits and signalling were noticeable in both clinical and community populations. Conclusions: These findings preliminarily support the influence of MBIs on pathophysiological pathways related to chronic stress at a system level. Limitations of the included studies (e.g., outcome heterogeneity, small sample size, concern for risk of bias) and future perspectives are discussed. Preregistration: A protocol of this systematic review was registered with PROSPERO (Registration No. CRD42023390236).