Abstract
We conducted a within-subject study of 12 male students without a sleep disorder. Each subject has presented an odor [lavender, jasmine, or odorless air (control)] for 5 min while they were in a resting position, and the subjects then napped for 20 min. The heart rate during the nap was higher in the lavender condition than in the other conditions. These results showed that odor presentation before sleep onset prevented the subsequent enhancement of parasympathetic nervous activity. Odor preference should be considered as a factor that negatively influenced the results. Odors affect biological reactions based on their preference. Some fragrances affect mood based on individual preferences and the degree of preference, whereas some do not affect mood. In this study, the heart rate increased significantly due to the palatability of lavender. Therefore, in this study, we observed that odor preference had a significant influence on heart rate, which suggests that the sedative effects of lavender may be masked.
https://ror.org/01vvhy971 
