Can Aromatherapy Improve Cognitive Function in the Healthy Elderly Subjects?—A Randomized Double Blinded Placebo-Controlled Study (Japanese)

Background: Dementia places a severe and far-reaching burden on patients themselves and on their family members and communities. In dementia, olfactory function is known as likely to be antecedently impaired prior to memory. There is a hypothesis that effective stimulation of the olfactory nerve, as with aroma therapy, can improve cognitive function, but there was no evidence of this prior to this study among the elderly including dementia patients. We investigated whether the inhalation of natural fragrances ameliorates cognitive function among healthy elderly volunteers. Methods: The design was a randomized double blinded placebo-controlled trial. Participants were randomly allocated either to the aroma (essential oil) or the placebo (ethanol) groups. Participants prepared a fragrance patch and attached it to their clothing twice daily, for a minimum 2 hours. The primary outcome was PASAT, and participants were evaluated twice, at the baseline and the completion of interventions in Week 12, and the changes from baseline to Week12 were compared between groups using mixed-effects models for repeated measures. Results: A total of 119 were randomly assigned either to the aroma (n=60) or the placebo (n=59) groups. The mean age was 69.5 years and male rate was 49.6%. A total of more than 96% of participants achieved more than 80% of adherences. In PASAT-2, mean changes under 2-second condition from baseline were + 5.80 [95% CI; 3.76 to 7.84] in the aroma and +2.48 [95% CI; 0.48 to 4.47] in the placebo groups. The mean difference was 3.37 [95% CI; 0.47 to 6.17: P=0.0229] with the effect size of 0.44 (Hedges' g). No significant differences were observed in PASAT-1, RAVLT, SDMT or MMSE, while the placebo group was superior in well-being and olfactory function. Conclusions: Three months aroma therapy significantly improved "Attention" as assessed by PASAT-2 compared with the placebo. However, no significant differences were observed in other cognitive functions or psychological measures. "Attention" has been recognized as more important to maintain the independent life of the elderly than other cognitive functions including memory. Further research is considered to be required.