Research into the Hinoki tree, or Japanese cypress, suggests that its root-derived aroma may aid sleep, particularly among middle-aged women who often experience sleep disturbances. A pilot study found that essential oil extracted from Hinoki roots could be beneficial for this demographic.
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In the study, 12 Japanese women aged 35 to 60 incorporated the essential oil into their bedtime routine over two weeks. When compared to a control group using an unscented product, participants reported fewer nighttime awakenings and felt more alert in the mornings. Brain-wave recordings indicated a smoother transition into deeper sleep when using the Hinoki oil.
Associate Professor Kuniyoshi Shimizu from Kyushu University explained the significance of the study's design. Previous work evaluated sleep quality over just one day in a controlled setting, but sleep is greatly influenced by daily life and home environments. This study provided insights from participants sleeping in their own bedrooms, utilizing both subjective reports and physiological measurements.
Published in the Journal of Wood Science, the study employed a single-blind crossover design, where each participant alternated between using the Hinoki oil and the unscented control. On nights with the oil, participants inhaled the scent from a paper cup prior to sleep.
After a week of using the Hinoki oil, participants demonstrated increased delta-wave activity—a type of brain wave associated with deep sleep—indicating a more effective transition into deeper sleep. Further improvements in morning alertness were noticed by day 13, along with objective evidence of reduced awakenings. Participants described the Hinoki scent as relaxing and pleasant compared to the control.
The research aims not only to enhance sleep through Hinoki essential oil but also to explore the untapped potential of forestry resources. Hinoki roots, often discarded after logging, contain compounds useful for producing essential oils. While oils from the tree's branches and leaves have previously been studied, the roots have not received much attention until now.
Potential future applications include developing aroma products from Hinoki roots for relaxation environments. This bedside setup could also serve as a model for testing aromatic materials in home settings, encouraging value-added uses for forestry byproducts. Further research is necessary to determine the best applications and dosage for these oils.
The study, titled “Sleep Improvement by Kagawa Hinoki Root Volatiles in Middle-Aged Women: A Home-Based Pilot Study,” is co-authored by Fadilla Zennifa, Akiko Isa, Erika Tomimatsu and others, and was supported by Kyushu University in collaboration with Ouken Co., Ltd.