The Effect of Short-term Inhalation of Fir Essential Oil on Autonomic Nervous Activity in Middle-aged Women.

This study aimed to investigate the effect of short-term inhalation of fir essential oil on autonomic nervous activity in middle-aged women. Twenty-six women (mean age, 51.0 ± 2.9 years) participated in this study. The participants sat on a chair, closed their eyes, and inhaled fir essential oil and room air (control) for 3 min. A crossover trial was performed to eliminate the effect of the order of olfactory stimulation. Approximately half of the participants were administered stimuli in the following order: exposure to fir essential oil, then control. The remaining participants were administered control, followed by fir essential oil. Heart rate variability, heart rate, blood pressure, and pulse rate were used as indicators of the autonomic nervous system activity. The Semantic Differential method and Profile of Mood States were used as psychological indicators. The High Frequency (HF) value, an indicator of parasympathetic nerve activity reflecting a relaxed state, was significantly higher during stimulation with fir essential oil than during the control condition. The Low Frequency (LF)/(LF+HF) value, an indicator of sympathetic nerve activity reflecting awake state, was marginally lower during stimulation with fir essential oil than during the control condition. No significant differences were found in heart rate, blood pressure, and pulse rate. After inhaling fir essential oil, "comfortable," "relaxed," and "natural" feelings improved, negative moods decreased, and positive moods increased. In conclusion, inhalation of fir essential oil can help menopausal women in their physiological and psychological relaxation.