Effect of mindfulness intervention versus health education program on salivary All-42 levels in community-dwelling older adults with mild cognitive impairment: A randomized controlled trial

Background: Few randomized controlled trials have investigated the effects of mindfulness intervention on older adults diagnosed with mild cognitive impairment (MCI). Specifically, scarce literature exists on the potential benefits of mindfulness intervention on biomarkers representing AD hallmarks. Our previous studies showed the potential of Mindful Awareness Practice (MAP) in improving multiple biomarkers of gut microbiota, systemic inflammation, and synaptic functions. Extending these findings, in this study, we conducted analysis on bio-banked saliva samples, examining whether MAP improved salivary amyloid beta-42 (A beta-42) levels in community-dwelling older adults diagnosed with MCI. We also explored the moderating role of education level, an indicator of cognitive reserve, on intervention effect. Methods: A total of 55 community-dwelling older adults diagnosed with MCI were randomized into either the treatment arm, MAP, or the active control arm, the health education program (HEP). Interventions were performed for a total of nine months. Field and laboratory investigators who were blinded to the treatment allocations collected saliva samples at baseline, 3-month, and 9-month follow-ups. Salivary A beta-42 levels were quantified using a commercial assay. Linear-mixed models were used to examine the effect of MAP on salivary A beta-42 levels. Results: Compared to the HEP arm, MAP participants had no significantly modified A ss-42 levels throughout the 9-month intervention period, regardless of subgroup analyses stratified by either sex or MCI-subtypes (amnestic and non-amnestic). Exploring the moderating effect of education, participants in the HEP arm with higher education levels had significantly lower salivary A beta-42 at 3-month time-point. Discussion: Taken together with our previous findings and other mindfulness interventional studies failing to find a significant effect on peripheral A beta-42, we conclude the non-significant effects of mindfulness intervention on ameliorating peripheral A beta-42 levels. Conversely, participants in the HEP arm with higher cognitive reserve had significantly improved salivary A beta-42, highlighting the role of cognitive reserve in moderating treatment response in MCI.