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Abstract

Introduction:

Essential oil preferences, which vary depending on an individual's physical and mental conditions, may trigger various emotions and affect autonomic nervous system (ANS) function and cerebral blood flow. This study aimed to investigate the relationship between essential oil preference during the menstrual cycle, ANS activity, and cerebral blood flow during a sniffing exercise.

Methods:

An observational study integrating aromatherapy with slow-paced breathing was conducted. Eighteen women (aged 20–22 years) without olfactory impairments were categorized into two groups: those with strong symptoms perceived in the late luteal phase (n = 10) and those with mild symptoms (n = 8). The study assessed responses during the early follicular and late luteal phases and recorded preferences for the following four essential oils: pine sylvestre (Pinus sylvestris), geranium bourbon (Pelargonium X asperum), lemongrass (Cymbopogon flexuosus), and lavender vera (Lavandula angustifolia). The autonomic nervous activity and cerebral blood flow were assessed in the early follicular and late luteal phases using the essential oils most and least preferred by each participant.

Results:

Participants with stronger symptoms in the late luteal phase appeared to prefer lemongrass and dislike pine sylvestre, whereas those with milder symptoms in the late luteal phase preferred lavender vera and disliked lemongrass. Changes in ANS activity, marked by an increase in sympathetic function and a decrease in parasympathetic function during the sniffing exercise, persisted regardless of the menstrual cycle stage or essential oil preference. The inhalation of preferred essential oils stimulated cerebral blood flow, whereas less-preferred oils led to a reduction.

Conclusion:

Essential oil preference in young women may be influenced by subjective symptoms during the menstrual cycle. Furthermore, essential oil preference affects cerebral blood flow. These findings have potential implications for aromatherapy practice.

Introduction

Numerous studies have investigated the impacts of essential oils. Geranium essential oil reportedly augments estrogen levels in menopausal women.¹ Lavender essential oil is recognized for its potential to enhance autonomic nervous system (ANS) functioning, cerebral blood flow, and psychological symptoms.² Shiotani et al. reported that ANS activity varies considerably even when the same essential oil is inhaled, depending on individual preference.³ During the luteal phase, many physical and mental symptoms may arise and sometimes culminate in the diagnosis of premenstrual syndrome (PMS).

Matsumoto et al. used heart rate variability (HRV) in their study on the effects of lavender essential oil and concluded that inhalation augmented the high-frequency (HF) index of the parasympathetic nervous system.⁴

Kunihiro et al. revealed that nasal exposure to yomogi oil could alter cerebral oxygenated hemoglobin concentrations, inducing sedative effects.⁵ Igarashi et al. proposed that olfactory stimulation with rose and orange oils reduces oxygenated hemoglobin levels in the right prefrontal cortex.⁶ Thus, performing further studies using HRV and NIRS could establish aromatherapy as a well-founded complementary and alternative therapy.

Vierra et al. demonstrated that the 4-7-8 breathing technique could amplify parasympathetic activity and diminish sympathetic activity in young adults without sleep disturbances.⁷ Fumoto et al. demonstrated that 20 min of voluntary abdominal breathing activated serotonergic nerves in the brain and fostered cortical alertness.⁸ Yamakawa's sniffing exercise, combining aromatherapy and deep breathing, is simple and effective. Before reaching the cortical olfactory cortex, inhaled smell stimulates the amygdala and hypothalamus, which control emotional response and the ANS. Smell is closely related to memory, and a favorite smell often evokes a “pleasant” memory. Many people choose their favorite essential oils and incorporate them into their daily lives. Even if an essential oil has an effective pharmacological action, an odor they do not like is unacceptable. In other words, a favorite essential oil is an important factor for continuing aromatherapy.

In our study, we first tracked essential oil preferences during the menstrual cycle, then examined how these preferences correlated with autonomic system activity and cerebral blood flow during the sniffing exercise. Our study could substantiate the efficacy of personalized aromatherapy in therapeutic settings.

Materials and Methods

Study sample

We recruited 28 young Japanese women; personal circumstances or sickness prevented 10 individuals from participating. Hence, 18 women aged 20–22 years, characterized by menstrual cycles of 24–35 days and menstrual periods of 3–7 days, participated in this study. All participants reported normal olfactory functioning. The exclusion criteria were underlying conditions such as thyroid disease, diabetes mellitus, malignant neoplasms, and manic depression and medication with hormones, ANS-affecting drugs, or antidepressants within 2 months of the study. All participants provided written informed consent.

Experimental setting and duration

The experiments were performed between December 2021 and October 2022 within a 4.6 × 4.0 m private chamber in the Kyushu University of Nursing and Social Welfare, climate controlled to maintain a temperature range of 24–28°C.

Procedure

Each participant underwent two sessions: during the early follicular (3–5 days postmenstruation) and late luteal phases (3–5 days premenstruation). During each cycle, we assessed essential oil preferences and the degree of symptoms. After 5 min’ rest, a sniffing exercise was performed, followed by a language task using an aroma sticker (TREE OF LIFE Co., Ltd., Tokyo, Japan) immersed in essential oil and positioned ∼15 cm beneath the nasal cavity. During a 3-min exercise, participants inhaled for 4 sec and exhaled for 8 sec while smelling an aroma sticker. The language task recalled words for 3 min. Each participant selected the preferred and nonpreferred essential oils during the menstrual cycle and measured cerebral blood flow, ANS activity, and salivary amylase levels.

Essential oil preference evaluation

The essential oils used were pine sylvestre (Pinus sylvestris), geranium bourbon (Pelargonium X asperum), lemongrass (Cymbopogon flexuosus), and lavender vera (Lavandula angustifolia) (FLORIHANA Co., Ltd., Tokyo, Japan). Participants, unaware of the name of the essential oil, sniffed each essential oil for 5 sec at 90-sec intervals to combat olfactory fatigue. Essential oils with the highest and lowest preference ratings served as the preferred and nonpreferred oils, respectively, during each participant's menstrual cycle.

HRV analysis

The interval between the R and R’ waves was captured from lead II of the electrocardiogram using an Active Tracer AC-301A^® (Arm Electronics Co., Ltd., Tokyo, Japan). For HRV analysis, a fast Fourier transform was used to obtain the power spectrum (MemCalc/Tarawa GMS Co., Ltd., Tokyo, Japan). The analyzed HRV spectrum spanned a frequency range of 0.04–0.4 Hz, with a low-frequency (LF) component at 0.04–0.15 Hz and an HF component at 0.15–0.4 Hz. The LF/HF power ratio measured sympathetic nervous activity.^9–11 The HF value divided by the sum of the HF and LF values (HF nu) was used as an index of parasympathetic activity.³

Salivary amylase level analysis

Salivary amylase levels were evaluated using a salivary amylase monitor (NIPRO Co., Ltd., Osaka, Japan) after 5 min of rest and subsequent sniffing exercises and language tasks.

NIRS analysis

Cerebral blood flow was assessed using the HOT Measure Ver. 3.0 (NeU Co., Ltd., Tokyo, Japan) with a HOT-2000^® headset (NeU Co., Ltd.) affixed to the forehead. The lightweight headset (∼129 g) minimized physical intrusion during extended wear. Near-infrared light of ∼800 nm, absorbed readily by hemoglobin, was projected from a two-channel sensor in the headset, and modifications in the total hemoglobin levels in the left and right prefrontal cortexes were analyzed every 0.2 sec.

Menstrual cycle symptoms

Physical and psychological symptoms accompanying the menstrual cycle were assessed using the Japanese version of the menstrual distress questionnaire (MDQ).¹² MDQ, developed by Kayashima et al., features 47 items across 8 domains: moisture storage, concentration force, negative feelings, behavioral changes, pain, control, mood elevation, and autonomic dysregulation. Each item received a score of 0 (none) to 3 (severe). MDQ scores were totaled for each domain during the early follicular and late luteal phases.

Statistical analyses

Participants were divided into two groups: those with an MDQ score exceeding 40 points during the late luteal phase relative to the early follicular phase (PMS group [P group]) and those scoring less than 40 points (non-PMS group [N group]). We compared salivary amylase, autonomic activity, cerebral blood flow and MDQ scores between menstrual cycles, between groups, and between essential oil types using t-test, analysis of variance (ANOVA), Mann–Whitney U and signed-ranks tests, and Dunnett's test. All analyses were performed using Statistical Package for the Social Sciences (version 25; IBM, Armonk, NY). Statistical significance was set at p < 0.05.

Ethical considerations

This study was approved by the Ethics Committee of Kyushu University of Nursing and Social Welfare (Approval No. 02-029) and conducted in accordance with the Declaration of Helsinki.

Results

Essential oil preferences

Irrespective of menstrual cycle stage, participants selected lemongrass and lavender vera essential oils more than geranium bourbon and pine sylvestre. However, lemongrass was the least-liked essential oil in the N group and the most preferred in the P group. Lavender vera was popular in the N group, whereas pine sylvestre was disliked in the P group (Table 1).

Table 1.

Frequency of Use Associated with Preference for Essential Oils During Each Menstrual Cycle (n = 18)

Menstrual cycle	Preference for essential oil	Pine sylvestre	Geranium bourbon	Lemongrass	Lavender vera
Early follicular phase	Favorite	3 (2)	3 (2)	5 (4)	7 (2)
Early follicular phase	Dislike	4 (4)	1 (1)	8 (2)	5 (3)
Late luteal phase	Favorite	3 (1)	3 (2)	6 (5)	6 (2)
Late luteal phase	Dislike	6 (4)	1 (1)	7 (2)	4 (3)

Numbers in parentheses indicate the frequency used in the P group.

P group, PMS group; PMS, premenstrual syndrome.

Salivary amylase levels

The salivary amylase levels did not show any significant variation after the sniffing exercise and language task compared with the preexercise levels across all groups. Notably, during the early follicular phase in the P group, salivary amylase levels after the sniffing exercise and language task were significantly higher than those before the sniffing exercise (p = 0.056 and 0.009, respectively) (Table 2).

Table 2.

Salivary Amylase Levels Associated with Essential Oil Preference During the Menstrual Cycle of Each Group

Menstrual cycle	Group	Favorite essential oil					Disliked essential oil
		Before sniffing exercise	After sniffing exercise	After language task	Within-group comparison		Before sniffing exercise	After sniffing exercise	After language task	Within-group comparison
		Mean ± SE	Mean ± SE	Mean ± SE	F -value	p	Mean ± SE	Mean ± SE	Mean ± SE	F -value	p
Early follicular phase	N group (n = 8)	6.38 ± 1.78	7.88 ± 2.50	13.13 ± 4.71	2.015	0.170	8.88 ± 2.14	7.38 ± 1.97	11.63 ± 3.57	1.373	0.285
Early follicular phase	P group (n = 10)	10.50 ± 2.74	12.20 ± 3.39	12.50 ± 1.59	0.317	0.732	6.80 ± 1.34	10.70 ± 1.90	12.20 ± 1.47	5.596	0.013^*
Late luteal phase	N group (n = 8)	8.25 ± 3.10	7.50 ± 2.44	9.38 ± 2.65	0.446	0.649	10.50 ± 3.33	6.38 ± 1.84	9.25 ± 3.29	2.404	0.127
Late luteal phase	P group (n = 10)	13.70 ± 3.34	11.40 ± 3.49	11.80 ± 2.30	0.137	0.873	12.30 ± 2.60	14.30 ± 4.50	9.30 ± 1.33	0.857	0.441

No significant difference between the N and P groups.

No significant difference between early follicular and late luteal phases.

p < 0.05, Dunnett's test.

N group, non-PMS group; SE, standard error.

Heart rate variability

The HF nu values before the sniffing exercise with the preferred essential oil during the late luteal phase were significantly lower in the P group (p = 0.021). Early follicular phase observations mirrored these, both with the nonpreferred essential oil before the sniffing exercise (p = 0.040) and language task (p = 0.048). In both groups, the HF nu values during the sniffing exercise were significantly lower than those before the sniffing exercise, regardless of the menstrual cycle phase or essential oil preference (p < 0.01) (Table 3).

Table 3.

Changes in Autonomic Nervous Activity Associated with Essential Oil Preference During the Menstrual Cycle of Each Group

	Menstrual cycle	Group	Favorite essential oil								Disliked essential oil
			Before sniffing exercise		During sniffing exercise		During language task		Within-group comparison		Before sniffing exercise		During sniffing exercise		During language task		Within-group comparison
			Mean ± SE	p	Mean ± SE	p	Mean ± SE	p	F-value	p	Mean ± SE	p	Mean ± SE	p	Mean ± SE	p	F-value	p
HR	Early follicular phase	N group (n = 8)	79.62 ± 3.88	0.299	79.23 ± 3.54	0.429	80.30 ± 3.01	0.245	0.354	0.708	77.70 ± 3.76	0.172	77.55 ± 3.53	0.141	79.48 ± 3.54	0.255	3.193	0.072
	Early follicular phase	P group (n = 10)	85.33 ± 3.60	0.299	83.10 ± 3.23	0.429	85.97 ± 3.46	0.245	2.073	0.155	85.33 ± 3.69	0.172	85.08 ± 3.30	0.141	85.50 ± 3.55	0.255	0.020	0.980
	Late luteal phase	N group (n = 8)	80.14 ± 5.08	0.302	80.00 ± 4.45	0.332	81.47 ± 4.38	0.191	0.773	0.481	79.28 ± 4.64	0.419	78.84 ± 4.05	0.255	80.23 ± 3.92	0.204	1.415	0.276
	Late luteal phase	P group (n = 10)	85.89 ± 2.65	0.302	86.10 ± 2.48	0.332	88.60 ± 3.09	0.191	2.000	0.164	83.77 ± 3.11	0.419	84.21 ± 2.48	0.255	88.54 ± 2.90	0.204	2.109	0.150
HF nu	Early follicular phase	N group (n = 8)	53.02 ± 4.86	0.165	12.27 ± 1.62	0.875	41.26 ± 3.78	0.156	58.202	0.000⁺⁺	49.17 ± 6.10	0.040^*	12.33 ± 3.13	0.830	35.03 ± 1.92	0.048^*	24.203	0.000⁺⁺
	Early follicular phase	P group (n = 10)	40.26 ± 6.78	0.165	11.66 ± 3.18	0.875	32.80 ± 4.07	0.156	9.797	0.001⁺⁺	32.73 ± 4.39	0.040^*	13.20 ± 2.55	0.830	27.18 ± 2.88	0.048^*	11.041	0.001⁺⁺
	Late luteal phase	N group (n = 8)	56.01 ± 6.34	0.021^*	14.11 ± 4.06	0.894	39.97 ± 4.74	0.289	16.917	0.000⁺⁺	45.73 ± 7.30	0.393	18.79 ± 5.83	0.246	37.84 ± 3.44	0.206	6.119	0.012⁺
	Late luteal phase	P group (n = 10)	35.37 ± 5.16	0.021^*	15.06 ± 5.35	0.894	34.33 ± 2.63	0.289	6.682	0.007⁺⁺	37.01 ± 6.70	0.393	11.25 ± 3.14	0.246	31.57 ± 3.25	0.206	7.550	0.004⁺⁺
LF/HF	Early follicular phase	N group (n = 8)	1.54 ± 0.48	0.233	20.01 ± 7.61	0.507	1.82 ± 0.22	0.136	5.943	0.014⁺	1.64 ± 0.43	0.250	23.68 ± 9.30	0.811	2.39 ± 0.41	0.021^*	5.457	0.018⁺
	Early follicular phase	P group (n = 10)	3.11 ± 1.06	0.233	28.26 ± 8.97	0.507	3.44 ± 0.97	0.136	6.933	0.006⁺⁺	5.89 ± 3.15	0.250	21.03 ± 6.35	0.811	4.11 ± 0.51	0.021^*	4.696	0.023⁺
	Late luteal phase	N group (n = 8)	1.42 ± 0.51	0.092	12.98 ± 2.82	0.152	2.28 ± 0.43	0.520	13.506	0.001⁺⁺	2.19 ± 0.56	0.366	12.53 ± 4.11	0.296	2.43 ± 0.31	0.122	6.304	0.011⁺
	Late luteal phase	P group (n = 10)	3.57 ± 0.99	0.092	20.92 ± 4.13	0.152	2.76 ± 0.54	0.520	18.642	0.000⁺⁺	4.47 ± 2.14	0.366	17.99 ± 3.10	0.296	3.32 ± 0.42	0.122	13.130	0.000⁺⁺

p < 0.05, Student's t-test.

p < 0.05, ⁺⁺p < 0.01, Dunnett's test.

HF nu, high-frequency normalized unit; HR, heart rate; LF/HF, low frequency/high-frequency ratio.

The LF/HF values before the sniffing exercise with the preferred essential oil during the late luteal phase in the P group tended to be higher (p = 0.092). The LF/HF values during the language task with the disliked essential oil during the early follicular phase were significantly higher in the P group (p = 0.021). In both groups, the LF/HF values during the sniffing exercise were significantly higher than those before the sniffing exercise, regardless of the menstrual cycle phase or essential oil preference (p < 0.05) (Table 3).

Prefrontal cerebral blood flow (changes in total hemoglobin levels)

The changes in total hemoglobin at the 1-cm depth during the sniffing exercise and language task with the preferred essential oil increased significantly compared with those of the resting state across all groups on the left side and three groups except for the N group during the late luteal phase on the right side (p < 0.05). In the P group, the changes in total hemoglobin at the 3-cm depth area on the right and left sides during the language task during the late luteal phase were significantly increased compared with those during the resting state (p < 0.05).

However, the changes in total hemoglobin at the 3-cm depth area on the left side during the sniffing exercise and language task with the disliked essential oil were significantly decreased compared with those during the resting state in the P group (p < 0.05). The sniffing exercise and language task with the disliked essential oil revealed significantly decreased total hemoglobin at the 3-cm depth area on the right side compared with that of the resting state in both groups during the early follicular phase (p < 0.05). Both groups had a similar trend during the late luteal phase (Table 4).

Table 4.

Changes in the Total Hemoglobin in the Prefrontal Cortex Associated with Essential Oil Preference During the Menstrual Cycle of Each Group

Prefrontal cortex area		Menstrual cycle	Group	Favorite essential oil					Disliked essential oil
				Before sniffing exercise	During sniffing exercise	During language task	Within-group comparison		Before sniffing exercise	During sniffing exercise	During language task	Within-group comparison
				Mean ± SE	Mean ± SE	Mean ± SE	F -value	p	Mean ± SE	Mean ± SE	Mean ± SE	F -value	p
Left	SD 1 cm	Early follicular phase	N group (n = 8)	0.27 ± 0.88	0.37 ± 0.11	0.44 ± 0.12	5.776	0.015^*	0.59 ± 0.15	0.55 ± 0.17	0.61 ± 0.20	0.702	0.512
		Early follicular phase	P group (n = 10)	0.40 ± 0.04	0.57 ± 0.07	0.67 ± 0.09	12.366	0.000^**	0.86 ± 0.09	0.82 ± 0.10	0.84 ± 0.11	0.630	0.544
		Late luteal phase	N group (n = 8)	0.38 ± 0.13	0.49 ± 0.13	0.53 ± 0.15	6.942	0.008^**	0.63 ± 0.13	0.60 ± 0.16	0.61 ± 0.15	0.660	0.532
		Late luteal phase	P group (n = 10)	0.35 ± 0.09	0.49 ± 0.12	0.68 ± 0.15	10.134	0.001^**	0.76 ± 0.16	0.76 ± 0.17	0.86 ± 0.19	2.745	0.091
	SD 3 cm	Early follicular phase	N group (n = 8)	0.37 ± 0.15	0.39 ± 0.14	0.43 ± 0.16	0.106	0.900	0.66 ± 0.14	0.53 ± 0.18	0.59 ± 0.19	1.300	0.303
		Early follicular phase	P group (n = 10)	0.37 ± 0.11	0.32 ± 0.12	0.49 ± 0.14	2.147	0.146	0.73 ± 0.16	0.55 ± 0.16	0.57 ± 0.15	5.862	0.011^*
		Late luteal phase	N group (n = 8)	0.35 ± 0.13	0.22 ± 0.10	0.34 ± 0.17	0.899	0.429	0.53 ± 0.11	0.33 ± 0.12	0.44 ± 0.14	3.554	0.056
		Late luteal phase	P group (n = 10)	0.34 ± 0.12	0.21 ± 0.16	0.62 ± 0.24	6.948	0.006^**	0.68 ± 0.18	0.44 ± 0.21	0.65 ± 0.26	3.681	0.046^*
Right	SD 1 cm	Early follicular phase	N group (n = 8)	0.31 ± 0.11	0.36 ± 0.13	0.48 ± 0.14	5.019	0.023^*	0.62 ± 0.15	0.55 ± 0.16	0.62 ± 0.17	3.236	0.070
		Early follicular phase	P group (n = 10)	0.31 ± 0.08	0.49 ± 0.08	0.60 ± 0.10	15.442	0.000^**	0.79 ± 0.12	0.75 ± 0.12	0.75 ± 0.13	0.740	0.491
		Late luteal phase	N group (n = 8)	0.19 ± 0.09	0.20 ± 0.15	0.24 ± 0.17	0.168	0.847	0.36 ± 0.21	0.14 ± 0.17	0.20 ± 0.18	1.811	0.200
		Late luteal phase	P group (n = 10)	0.34 ± 0.07	0.40 ± 0.08	0.60 ± 0.16	5.944	0.010^*	0.66 ± 0.12	0.58 ± 0.13	0.68 ± 0.16	2.997	0.075
	SD 3 cm	Early follicular phase	N group (n = 8)	0.46 ± 0.19	0.43 ± 0.20	0.53 ± 0.19	0.619	0.553	0.81 ± 0.21	0.62 ± 0.23	0.68 ± 0.23	5.156	0.021^*
		Early follicular phase	P group (n = 10)	0.37 ± 0.13	0.33 ± 0.15	0.50 ± 0.20	1.667	0.217	0.84 ± 0.20	0.66 ± 0.20	0.64 ± 0.20	3.803	0.042^*
		Late luteal phase	N group (n = 8)	0.25 ± 0.08	0.18 ± 0.12	0.27 ± 0.13	0.533	0.598	0.58 ± 0.16	0.28 ± 0.18	0.39 ± 0.18	3.636	0.064
		Late luteal phase	P group (n = 10)	0.39 ± 0.14	0.28 ± 0.17	0.68 ± 0.26	6.089	0.010^*	0.80 ± 0.23	0.58 ± 0.23	0.81 ± 0.30	3.483	0.053

p < 0.05, ^**p < 0.01, Dunnett's test.

SD, sensor distance.

For the four essential oils, the changes in total hemoglobin at the 1-cm depth on the left side significantly increased during the language task compared with those of the resting state across the favorite essential oils. This was not observed with the disliked essential oils. The changes in total hemoglobin at the 3-cm depth area during the sniffing exercise with the disliked pine sylvestre, lemongrass, and lavender vera were significantly decreased compared with those during the resting state (Table 5).

Table 5.

Changes in Total Hemoglobin in Prefrontal Cortex Associated with Kinds of Essential Oil

		Essential oil	Before sniffing exercise	During sniffing exercise	During language task	Within-group comparison
		Essential oil	Mean ± SE	Mean ± SE	Mean ± SE	F	p
Left	SD 1 cm	Pin sylvestre (n = 16)	0.61 ± 0.10	0.62 ± 0.11	0.67 ± 0.11	1.789	0.185
		Geranium bourbon (n = 8)	0.55 ± 0.08	0.63 ± 0.10	0.84 ± 0.14^**	9.427	0.003
		Lemongrass (n = 26)	0.54 ± 0.08	0.59 ± 0.08	0.65 ± 0.09^**	5.699	0.006
		Lavender vera (n = 22)	0.48 ± 0.08	0.55 ± 0.09	0.62 ± 0.09^**	6.591	0.003
	SD 3 cm	Pin sylvestre (n = 16)	0.52 ± 0.11	0.33 ± 0.10^**	0.43 ± 0.11	5.681	0.008
		Geranium bourbon (n = 8)	0.68 ± 0.14	0.57 ± 0.15	0.83 ± 0.27	1.613	0.234
		Lemongrass (n = 26)	0.50 ± 0.09	0.41 ± 0.10	0.53 ± 0.12	2.870	0.066
		Lavender vera (n = 22)	0.44 ± 0.09	0.30 ± 0.10	0.47 ± 0.10	3.872	0.029
Right	SD 1 cm	Pin sylvestre (n = 16)	0.48 ± 0.08	0.46 ± 0.07	0.53 ± 0.08	0.970	0.391
		Geranium bourbon (n = 8)	0.72 ± 0.06	0.79 ± 0.09	0.95 ± 0.15^*	3.834	0.047
		Lemongrass (n = 26)	0.51 ± 0.10	0.46 ± 0.09	0.53 ± 0.10	1.196	0.311
		Lavender vera (n = 22)	0.28 ± 0.07	0.30 ± 0.08	0.39 ± 0.09^*	4.791	0.013
	SD 3 cm	Pin sylvestre (n = 16)	0.62 ± 0.13	0.45 ± 0.12^*	0.54 ± 0.13	2.854	0.073
		Geranium bourbon (n = 8)	0.86 ± 0.13	0.79 ± 0.18	1.07 ± 0.30	1.924	0.183
		Lemongrass (n = 26)	0.63 ± 0.13	0.44 ± 0.13^**	0.59 ± 0.15	5.165	0.009
		Lavender vera (n = 22)	0.35 ± 0.08	0.25 ± 0.10	0.39 ± 0.10	3.424	0.042

p < 0.05, ^**p < 0.01, versus before sniffing exercise, Dunnett's test.

Assessment of symptoms

The MDQ total scores during the late luteal phase were significantly higher than those during the early follicular phase in both groups (N group p = 0.012; P group p = 0.005). Although the total MDQ scores during the early follicular phase were similar across both groups, the scores during the late luteal phase were significantly higher in the P group (p = 0.021). In the P group, the MDQ scores for all domains, excluding mood elevation, were significantly higher during the late luteal phase than during the early follicular phase (p < 0.01). In the N group, the MDQ scores of the four domains were significantly higher during the late luteal phase than during the early follicular phase (p < 0.05). During the late luteal phase, MDQ scores of the three domains in the P group were significantly higher (p < 0.05). During the early follicular phase, MDQ scores of all domains were similar in both groups (Table 6).

Table 6.

Comparison of Menstrual Distress Questionnaire During the Menstrual Cycle of Each Group

Variables	Early follicular phase			Late luteal phase			Early follicular phase vs. late luteal phase ( p )
Variables	N group ( n = 8)	P group ( n = 10)	p	N group ( n = 8)	P group ( n = 10)	p	N group	P group
Total score	22.50 ± 5.94	17.70 ± 3.27	0.515	47.50 ± 8.04	70.70 ± 4.98	0.021^*	0.012⁺	0.005⁺⁺
Moisture storage	2.00 ± 0.46	2.00 ± 0.65	0.762	8.00 ± 0.73	8.90 ± 0.85	0.460	0.012⁺	0.005⁺⁺
Concentration force	3.25 ± 1.50	2.10 ± 0.69	0.891	6.88 ± 1.62	11.60 ± 1.00	0.034^*	0.012⁺	0.005⁺⁺
Negative feelings	3.25 ± 1.26	1.90 ± 1.07	0.460	10.50 ± 2.59	16.70 ± 1.05	0.034^*	0.018⁺	0.005⁺⁺
Behavioral changes	2.38 ± 0.75	1.90 ± 0.75	0.762	8.14 ± 1.77	10.50 ± 0.92	0.315	0.012⁺	0.005⁺⁺
Pain	4.13 ± 1.55	2.20 ± 0.33	0.573	7.75 ± 1.10	12.50 ± 1.06	0.006^**	0.068	0.005⁺⁺
Control	1.88 ± 0.95	0.70 ± 0.33	0.515	3.00 ± 1.39	4.40 ± 0.96	0.274	0.066	0.007⁺⁺
Mood elevation	5.13 ± 1.20	6.70 ± 0.90	0.315	2.63 ± 0.63	2.50 ± 0.60	0.762	0.045⁺	0.008⁺⁺
Autonomic dysregulation	0.50 ± 0.27	0.20 ± 0.13	0.515	2.00 ± 0.53	3.60 ± 1.13	0.408	0.057	0.011⁺

p < 0.05, ^**p < 0.01, Mann–Whitney U test.

p < 0.05, ⁺⁺p < 0.01, Wilcoxon signed-rank sum test.

Discussion

Essential oil preferences

We found that lemongrass was preferred by the P group but disliked by the N group. Conversely, pine sylvestre was disliked by the P group. These observations suggest a relationship between preference and symptom severity experienced during the menstrual cycle.

PMS, which causes various symptoms during the luteal phase, is caused by a sex hormone imbalance. The sex hormones of the participants in the P group may have been imbalanced compared with those in the N group. Experiments in mice have reported that progesterone and estradiol modulate the odor responsiveness of olfactory receptor neurons.¹³ Estrogen levels also make women more sensitive to exaltolide odors during the follicular phase than during the luteal phase.¹⁴ In this study, essential oil preference varied with luteal phase symptoms, possibly related to estrogen and progesterone secretions.

Symptoms during the late luteal phase and autonomic nervous activity

In this study, the MDQ score during the late luteal phase was considerably higher in the P group. Matsumoto et al. reported that patients with PMS exhibited high MDQ scores during the luteal phase, equivalent to the control group during the follicular phase.¹⁵ The total MDQ score of our study participants was only elevated during the luteal phase, with the P group's score echoing that of the PMS group in Matsumoto's study.

Compared with those in the N group, significant differences were observed in the MDQ domain scores (concentration, negative emotions, and pain) during the luteal phase in the P group. Matsumoto et al. observed high MDQ domain scores, specifically for concentration and negative emotions, and low HF values during the luteal phase of the PMS group.¹⁵ The HF nu values of the P group were significantly lower during the late luteal and early follicular phases. Furthermore, the LF/HF ratios were higher in the P group. A previous study demonstrated that individuals more aware of physical and mental symptoms during the luteal phase exhibit higher sympathetic and lower parasympathetic nervous system activities.¹⁶ Our results resonate with these findings, suggesting that an ANS characterized by decreased parasympathetic function and increased sympathetic activity influences subjective symptoms. Regulating the ANS during the luteal phase might help mitigate these symptoms.

Several studies have suggested that ANS activity changes during the menstrual cycle.^17–19 However, due to the sitting position adopted during our experiment, neither group's ANS activity changed significantly during menstruation. For both groups, HF nu values decreased significantly during the sniffing exercise, and the LF/HF values increased significantly compared with those during the resting phase, regardless of the menstrual cycle phase.

Kai et al. reported an increase in LF/HF values during slow breathing in a supine position in young men,²⁰ and similar results were obtained in our participants, who were women. They proposed that this increase is attributable to increased airway resistance.²⁰ Nakamura et al. suggested that peripheral airway obstruction is likely to occur in a supine position as the head is lower than in the standing position.²¹ Our study was performed with the participants in a sitting position. Saito reported that sympathetic activity rises during exercise and modulates circulatory dynamics.²² Our study's sniffing exercise may have elevated sympathetic nervous system activity since slow breathing exercises could be associated with the activation of respiratory muscles.

Essential oil preferences and ANS responses

During the sniffing exercise, participants used essential oils per their preferences. Shiotani proposed that HF nu values are high, while LF/HF ratios are low for favored scents; conversely, HF nu values are low and LF/HF ratios are high for unpleasant scents.³ In this study, no substantial differences were observed in the ANS responses correlating with participants' essential oil preferences. This discrepancy may be due to methodological differences, as our study used a sitting position with slow breathing, while Shiotani et al. used a supine position with normal breathing. These methodological differences may have influenced ANS responses.

In the P group, compared with those in the resting state, salivary amylase levels were significantly elevated after the sniffing exercise and language tasks with disliked essential oils during the follicular phase. Kai et al. suggested that salivary α-amylase is a more sensitive indicator of psychological stress than HRV.²³ The increase in salivary amylase levels during the use of disliked essential oils implies the discomfort invoked by odor-induced stress. Although HRV failed to capture this biological response, salivary amylase might have effectively responded. However, this was observed in the P group during the follicular phase, necessitating future validation.

Impact on prefrontal cerebral blood flow

In this study, geranium bourbon, lemongrass, and lavender vera increased cerebral blood flow at a depth of 1 cm, while pine sylvestre and lemongrass decreased cerebral blood flow at a depth of 3 cm. Studies show that essential oils, such as lemon, rosemary, lavender, orange, and peppermint, decrease amyloid-β levels and enhance memory performance in mice and rats.^24,25 This suggests that essential oils may have an effect on brain functioning.

Total hemoglobin levels at the 1-cm depth increased significantly during the sniffing exercise and language task with preferred essential oils, compared with the resting state levels. Conversely, levels at the 3-cm depth markedly decreased with disliked essential oil compared with the resting state levels. Ueda et al. reported that lemon oil was highly palatable, and 2 min of inhalation enhanced memory performance and activated the orbitofrontal cortex.²⁶ Studies have found that preferred music increases skin conductance,²⁷ whereas unpleasant emotions decrease deep skin temperature.²⁸ These findings suggest that essential oil preferences, manifesting as “pleasant or unpleasant” feelings, can affect biological functions. Herein, total hemoglobin level increases with preferred essential oils and decreases with disliked ones, implying that pleasant feelings induced by preferred odors enhance cerebral blood flow, whereas unpleasant feelings induced by disliked odors reduce it.

However, the number of selections of geranium bourbon, lemongrass, and lavender vera as the favorite essential oil accounted for ∼80%, and the number of selections of pine sylvestre and lemongrass as the disliked essential oil accounted for ∼70%. Therefore, it cannot be ruled out that the pharmacological effects of the essential oils are involved. As cerebral blood flow contributes to brain metabolic function, the influence of essential oils on cognitive function warrants further exploration.

Limitations

This study has some limitations. First, we used only four essential oils. Second, the participants' age range was restricted. Finally, the protocol involved inhaling preferred essential oils before less preferred ones, which are still debated upon. Future research needs to address these issues.

Conclusions

Essential oil preferences in young women seem to be influenced by symptoms during the late luteal phase. The increase in sympathetic activity and decrease in parasympathetic activity were caused by conscious breathing exercises rather than essential oil preference. Favorable oils appeared to enhance cerebral blood flow, whereas disliked oils reduced it. These findings suggest that essential oil preference may affect cerebral blood flow, paving the way for future studies on essential oils' cognitive effects.

Footnotes

Acknowledgments

The authors thank all the participants included in this study. We would like to thank Editage () for English language editing.

Authors' Contributions

N.K.: conceptualization, data curation, formal analysis, writing—original draft. T.Y.: conceptualization, data curation, writing—review and editing.

Data Sharing Statement

The datasets generated and/or analyzed during the current study are not publicly available due to privacy restrictions, as the databases contain information that could compromise the privacy of research participants. However, the deidentified datasets are available from the corresponding author upon reasonable request.

Author Disclosure Statement

No competing financial interests exist.

Funding Information

This work was supported by the JSPS KAKENHI grant no. JP 22K10945.

Abbreviations Used

References

Shinohara

, Doi

, Kumagai

, et al. Effects of essential oil exposure on salivary estrogen concentration in perimenopausal women. Neuro Endocrinol Lett, 2017; 37(8):567–572.

Matsumoto

, Kimura

, Hayashi

. Does Japanese Citrus Yuzu (Citrus junos Sie. ex Tanaka) fragrance have lavender-like therapeutic effects that alleviate premenstrual emotional symptoms? A single-blind randomized crossover study. J Altern Complement Med, 2017; 23(6):461–470; doi: 10.1089/acm.2016.0328

Shiotani

, Sakakihara

. Effects of inhalation of aroma essential oil on the autonomic nervous. -Investigation of the relationship between preference and the effect of aroma essential oils-. J Jpn Soc Aromather, 2022; 21(1):049–05.

Matsumoto

, Asakura

, Hayashi

. Does lavender aromatherapy alleviate premenstrual emotional symptoms? A randomized crossover trial. Biopsychosoc Med, 2013; 7:12; doi: 10.1186/1751-0759-7-12

Kunihiro

, Myoda

, Tajima

, et al. Volatile components of the essential oil of artemisia montana and their sedative effects. J Oleo Sci, 2017; 66(8):843–849; doi: 10.5650/jos.ess16006

Igarashi

, Ikei

, Song

, et al. Effects of olfactory stimulation with rose and orange oil on prefrontal cortex activity. Complement Ther Med, 2014; 22(6):1027–1031; doi: 10.1016/j.ctim.2014.09.003

Vierra

, Boonla

, Prasertsri

. Effects of sleep deprivation and 4-7-8 breathing control on heart rate variability, blood pressure, blood glucose, and endothelial function in healthy young adults. Physiol Rep, 2022; 10(13):e15389; doi: 10.14814/phy2.15389

Fumoto

, Sato-Suzuki

, Seki

, et al. Appearance of high-frequency alpha band with disappearance of low-frequency alpha band in EEG is produced during voluntary abdominal breathing in an eyes-closed condition. Neurosci Res, 2004; 50(3):307–317; doi: 10.1016/j.neures.2004.08.005

Hayano

, Sakakibara

, Yamada

, et al. Accuracy of assessment of cardiac vagal tone by heart rate variability in normal subjects. Am J Cardiol, 1991; 67(2):199–204; doi: 10.1016/0002-9149(91)90445-Q

10.

Pomeranz

, Macaulay

RJB

, Caudill

, et al. Assessment of autonomic function in humans by heart rate spectral analysis. Am J Physiol, 1985; 248(1 Pt. 2):H151–H153; doi: 10.1152/ajpheart.1985.248.1.H151

11.

Pagani

, Lombardi

, Guzzetti

, et al. Power spectral analysis of heart rate and arterial pressure variabilities as a marker of sympatho-vagal interaction in man and conscious dog. Circ Res, 1986; 59(2):178–193; doi: 10.1161/01.res.59.2.178

12.

Akiyama

, Kayashima

Gekkei Zuihanshoujyou nihonngoban (MDQ: Menstrual Distress Questionnaire). In: Shinrisokuteishakudoshu III. ( Hori

, Matsui

eds.): Saiensu Co. Pte. Ltd.: Tokyo; 2001; pp. 272–277.

13.

Ninthujah

, Maximillian

, Paul

, et al. Modulatory effects of sex steroids progesterone and estradiol on odorant evoked responses in olfactory receptor neurons. PLoS One, 2016; 11(8):e0159640; doi: 10.1371/journal.pone.0159640

14.

Pedro

, Regis

, Andres

, et al. Why the olfactory acuity to exaltolide test is different in women?. Acta Otolaryngol, 2021; 141(11):994–999; doi: 10.1080/00016489.2021.1992011

15.

Matsumoto

, Ushiroyama

, Kimura

, et al. Altered autonomic nervous system activity as a potential etiological factor of premenstrual syndrome and premenstrual dysphoric disorder. Biopsychosoc Med, 2007; 1:24; doi: 10.1186/1751-0759-1-24

16.

Matsumoto

, Ushiroyama

, Morimura

, et al. Autonomic nervous system activity in the late luteal phase of eumenorrheic women with premenstrual symptomatology. J Psychosom Obstet Gynecol, 2006; 27(3):131–139; doi: 10.1080/01674820500490218

17.

Yao

, Lei

, Lulu

, et al. Menstrual attitude and social cognitive stress influence autonomic nervous system in women with premenstrual syndrome. Stress, 2022; 25(1):87–89; doi: 10.1080/10253890.2021.2024163

18.

Tada

, Yoshizaki

, Tomata

, et al. The impact of menstrual cycle phase on cardiac autonomic nervous system activity: An observational study considering lifestyle (Diet, physical activity, and sleep) among female college students. J Nutr Sci Vitaminol, 2017; 63(4):249–255; doi: 10.3177/jnsv.63.249

19.

Brar

, Singh

, Kumar

. Effect of different phases of menstrual cycle on heart rate variability (HRV). J Clin Diagn Res, 2015; 9(10):CC01–CC04; doi: 10.7860/JCDR/2015/13795.6592

20.

Kai

, Nagino

, Aoki

, et al. Cardiac autonomic nervous system activity during slow breathing in supine position. Rehabi Res Pract, 2021; 2021:661957; doi: 10.1155/2021/6619571

21.

Nakamura

, Itoh

, Yamasaki

, et al. A preliminary study on the posture dependency of pulmonary functions. Jpn J Aerospace Environ Med, 2008; 45(4):160. Available from: https://www.sasappa.co.jp/online/abstract/jsasem/1/045/html/1110450446.html [Last accessed: February 14, 2024].

22.

Saito

Sympathetic adjustments to exercise: Insights from microneurographic recordings. J Inst Psychol Phys Sci, 2017; 9(1):49–57. https://agu.repo.nii.ac.jp/records/1404 [Last accessed: February 14, 2024].

23.

Kai

, Koga

. Autonomic nerve responses in a psychological stress task and subsequent slow breathing. J Phys Ther Sci, 2012; 24:257–259; doi: 10.1589/jpts.24.257

24.

Okuda

, Fujita

, Takada-Takatori

, et al. Aromatherapy improves cognitive dysfunction in senescence-accelerated mouse prone 8 by reducing the level of amyloid beta and tau phosphorylation. PLoS One, 2020; 15(10):e024037; doi: 10.1371/journal.pone.0240378

25.

, Feng

, Ma

, et al. Effects of peppermint essential oil on learning and memory ability in APP/PS1 transgenic mice. Molecules, 2022; 27(7):2051; doi: 10.3390/molecules27072051

26.

Ueda

, Horita

, Suzuki

. Effects of inhaling essential oils of Citrus limonum L., Santalum album, and Cinnamomun camphora on human brain activity. Brain Behav, 2023; 13(2):e2889; doi: 10.1002/brb3.2889

27.

Luaute

, Dubois

, Heine

, et al. Electrodermal reactivity to emotional stimuli in healthy subjects and patients with disorders of consciousness. Ann Phys Rehabi Med, 2018; 61(6):401–406; doi: 10.1016/j.rehab.2018.04.007

28.

Shimada

Relationships between the affects of comfort and discomfort and deep skin temperature and the skin conductance level. Jpn J Nurs Art Sci, 2004; 3(2):5–12; doi: 10.18892/jsnas.3.2_5

Associations Between Autonomic Nervous System Activity,Cerebral Blood Flow,and Essential Oil Preferences Across the Menstrual Cycle

Abstract

Introduction:

Methods:

Results:

Conclusion:

Introduction

Materials and Methods

Study sample

Experimental setting and duration

Procedure

Essential oil preference evaluation

HRV analysis

Salivary amylase level analysis

NIRS analysis

Menstrual cycle symptoms

Statistical analyses

Ethical considerations

Results

Essential oil preferences

Salivary amylase levels

Heart rate variability

Prefrontal cerebral blood flow (changes in total hemoglobin levels)

Assessment of symptoms

Discussion

Essential oil preferences

Symptoms during the late luteal phase and autonomic nervous activity

Essential oil preferences and ANS responses

Impact on prefrontal cerebral blood flow

Limitations

Conclusions

Footnotes

Acknowledgments

Authors' Contributions

Data Sharing Statement

Author Disclosure Statement

Funding Information

Abbreviations Used

References