Effects of Melissa officinalis Extract Containing Rosmarinic Acid on Cognition in Older Adults Without Dementia: A Randomized Controlled Trial

Background: Previous in vitro and in vivo studies on Alzheimer’s disease (AD) models have reported that rosmarinic acid (RA) can inhibit the formation of amyloid-β fibrils as well as the oligomerization and deposition of amyloid-β protein. Melissa officinalis (M. officinalis) extract containing 500 mg of RA is tolerable and safe in healthy individuals and patients with mild AD dementia. Objective: This randomized placebo-controlled double-blind trial aimed to assess the effects of M. officinalis extract on cognition in older adults without dementia. Methods: This study included individuals who were diagnosed with subjective or mild cognitive impairment (n = 323). The trial involved M. officinalis extract supplementation (500 mg of RA per day) period of 96 weeks followed by a washout period of 24 weeks. The primary endpoint was the Alzheimer’s Disease Assessment Scale-cognitive subscale score, and the secondary endpoints were other cognitive measure results as well as safety and tolerability. Results: There were no significant differences in cognitive measures between the placebo and M. officinalis groups from baseline to 96 weeks. However, based on the analysis of Clinical Dementia Rating Sum of Boxes scores in participants without hypertension, the score was found to be increased by 0.006 and decreased by 0.085 in the M. officinalis and placebo groups, respectively; this difference was statistically significant (p = 0.036). Furthermore, there were no differences in vital signs, physical and neurological measures, or hippocampal volume between the two groups. Conclusion: These results indicate that M. officinalis extract may help prevent cognitive decline in older adults without hypertension.