Effect of Japanese Cedar on Psychological and Physiological Factors Influencing Fatigue Recovery in an Indoor Environment

摘要

Background: In Japan, forest resources have not been used effectively, and much lumber from thinning has been left unused for a long time. These days, forest improvement has been reconsidered such that more wood will be used in public buildings and living spaces in Japan. Moreover, the arousing and/or sedative effects of fragrance from wood extracts have attracted increasing attention. Aims: This study was made to investigate how fatigue recovery can be psychologically and physiologically affected by the presence and emissions of cedar in an indoor environment. Methods: We carried out an experiment in November 2011. We assigned 15 healthy subjects (mean age 23 ± 3.8 years) to three groups. The crossover method was used in the experiment. In condition 1, room walls were covered with Japanese cedar, which was visually accessible to the subjects. In condition 2, a room was connected to the aforementioned room, allowing the circulation of air from it; hence, subjects were exposed to emissions from the cedar but could not see it. In condition 3, there was no circulation of air from the previous two rooms, and subjects could not see the cedar. The cedar, which was about 70 years old and grown in Kumamoto prefecture, was dried at 45°C before it was used for construction. Subjects moved to the rooms after spending two periods of 15 minutes each in a preparation room, and stayed in their rooms for 60 minutes. Results: Odor intensity in condition 1 and 2 was significantly higher than condition 3. Cedrol and β-eudesmol was specifically detected in condition 1 and 2 through an analysis of indoor air quality. Their fatigue and scores on the Total Mood Disturbance subscale of the Profile of Mood States decreased the fastest in Condition 1. This result indicates the effect of the odor and appearance of cedar. Physiological responses did not significantly differ between groups. Conclusions: These findings suggest that cedar has a larger psychological than physiological effect.