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

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. 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. 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. 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. A protocol of this systematic review was registered with PROSPERO (Registration No. CRD42023390236).