Effect of Olfactory Stimulation by Fresh Rose Flowers on Autonomic Nervous Activity

Objective: To clarify the effect of olfactory stimulation by fresh rose flowers, which exude a strong fragrance, on heart rate variability. Settings: A chamber with an artificial climate maintained at 25 degrees C with 50% relative humidity and 230 lux illumination at the Center for Environment, Health, and Field Sciences, Chiba University, Japan. Participants: Nineteen female university and graduate students (mean age, 21.6 +/- 1.5 years; age range, 19.0-26.0 years). Interventions: Fresh rose flowers as an olfactory stimulant, with air as a control. Outcome measures: Heart rate variability and subjective evaluations. The power levels of the high-frequency (HF) (0.15-0.40 Hz) and low-frequency (LF) (0.04-0.15 Hz) components of heart rate variability were calculated by the maximum-entropy method. The HF power was considered to reflect parasympathetic nervous activity. The LF/HF power ratio was determined to reflect the sympathetic nervous activity. A modified semantic differential method was used to perform subjective evaluations. Results: Fresh rose flowers induced (1) a significant increase in parasympathetic nervous activities and (2) an increase in comfortable'' and natural'' feelings. Conclusion: The findings indicated that olfactory stimulation by fresh rose flowers induced physiological and psychological relaxation.