Rosemary (Salvia rosmarinus) and Cognitive function: evidence and sources

Patients with mild cognitive impairment eventually progress to Alzheimer's disease (AD) causing a strong impact on public health. Rosmarinus officinalis has long been known as the herb of remembrance and can be a potential cognition enhancer for AD. The aim of this review was to summarize the qualitative and quantitative aspects of R. officinalis and its active constituents in enhancing cognition. A structured search was conducted on Google Scholar and PubMed to find relevant studies that assessed the effect of R. officinalis extract or any of its active constituents on cognitive performance in animals. The following information was extracted from each study: 1) article information; 2) characteristics of study animals; 3) type of intervention: type, dose, duration, and frequency of administration of R. officinalis; and 4) type of outcome measure. Data were analyzed using Review Manager and meta-analysis was performed by computing the standardized mean difference. Twenty-three studies were selected for qualitative analysis and fifteen for meta-analysis. From the fifteen included papers, 22 with 35 comparisons were meta-analyzed. Effect sizes for intact and cognitively impaired animals were 1.19 (0.74, 1.64) and 0.57 (0.19, 0.96), indicating a positive effect on both groups. The subgroup analyses showed substantial unexplained heterogeneity among studies. Overall, R. officinalis improved cognitive outcomes in normal and impaired animals, and results were robust across species, type of extract, treatment duration, and type of memory. However, studies had a considerable amount of heterogeneity, and subgroup analyses failed to find any heterogeneity moderator.

This study was designed to assess the olfactory impact of the essential oils of lavender (Lavandula angustifolia) and rosemary (Rosmarlnus officinalis) on cognitive performance and mood in healthy volunteers. One hundred and forty-four participants were randomly assigned to one of three independent groups, and subsequently performed the Cognitive Drug Research (CDR) computerized cognitive assessment battery in a cubicle containing either one of the two odors or no odor (control). Visual analogue mood questionnaires were completed prior to exposure to the odor, and subsequently after completion of the test battery. The participants were deceived as to the genuine aim of the study until the completion of testing to prevent expectancy effects from possibly influencing the data. The outcome variables from the nine tasks that constitute the CDR core battery feed into six factors that represent different aspects of cognitive functioning. Analysis of performance revealed that lavender produced a significant decrement in performance of working memory, and impaired reaction times for both memory and attention based tasks compared to controls. In contrast, rosemary produced a significant enhancement of performance for overall quality of memory and secondary memory factors, but also produced an impairment of speed of memory compared to controls. With regard to mood, comparisons of the change in ratings from baseline to post-test revealed that following the completion of the cognitive assessment battery, both the control and lavender groups were significantly less alert than the rosemary condition; however, the control group was significantly less content than both rosemary and lavender conditions. These findings indicate that the olfactory properties of these essential oils can produce objective effects on cognitive performance, as well as subjective effects on mood.