People use aromatherapy to relieve the symptoms of physical and psychological stress. However, previous studies have not precisely clarified a scientific basis for the beneficial effects of aromatherapy. Therefore, the overall purpose of this study was to elucidate the beneficial effect of aromatherapy in relieving work-related stress. Twenty-nine elementary school teachers from Taiwan participated in this study. The experimental procedures comprised 2 phases. First, we verified the effect of aromatherapy by conducting 2 blind tests. We used natural bergamot essential oil extracted from plants and synthesized a chemical essential oil as the placebo to do the aromatherapy. Second, we analyzed the performance of the aromatherapy treatment on the teachers who had various workloads. We measured the teachers’ heart rate variability to evaluate their autonomic nervous system activity. The results show that only the natural bergamot essential oil had an effect and that the aromatherapy treatment relieved work-related stress of teachers with various workloads. However, the aromatherapy treatment had a weak effect on young teachers who had a heavy workload. Moreover, the aromatherapy treatment exhibited no effect on teachers who belong to the abnormal body mass index subgroup having a heavy workload.
In modern society, job-related stress is a substantial problem because 40%–50% of all relative work misses are related to stress [
Various methods for coping with stress have been studied [
The autonomic nervous system includes sympathetic and parasympathetic systems. When people feel physical or psychological stress, the sympathetic system becomes more active. When this stressor disappears, the parasympathetic system reduces the heart rate and the breathing rate. The response of the autonomic nervous system can be monitored using the heart rate variability (HRV), which is derived from heartbeat interval time series [
Chang and Shen examined the effect of aromatherapy on elementary school teachers [
The overall objective of our study was to clarify the beneficial effects of aromatherapy in alleviating work stress. The experiment comprised two phases. The purpose of the first phase was to verify the effect of aromatherapy by using two blind tests. We used natural essential oil extracted from plants and synthetic essential oil made with chemical materials to do the aromatherapy. The second phase involved analyzing the performance of aromatherapy for participants with varying workloads. To compare our results with those obtained by Chang and Shen, we also recruited elementary school teachers in Taiwan, and natural bergamot essential oil was used during treatment.
We recruited 29 elementary schoolteachers who did not have asthma, hypertension, or a heart condition. Because an aromatherapy spray may induce asthma, participants with a history of asthma were excluded. Moreover, numerous studies have shown that heart conditions such as arrhythmia, myocardial ischemia, and a history of heart failure affect the HRV [
For this study, we used 100% pure bergamot essential oil made in Italy, diluted to 2%. The placebo was a synthetic essential oil (Shunyi Chemical Co., Ltd., Taiwan) with a similar scent to the bergamot essential oil. An ultrasonic ionizer aromatherapy diffuser was used for aroma evaporation (type YHL668/I, ultrasound frequency 2.5 MHz, Nature Creart Co., Ltd, Taiwan). For the heart rate measurements and HRV analysis, we employed a handheld HRV meter (LR8Z11, made by Yunyin Co., Ltd., Taiwan). It measures one lead electrocardiogram (ECG), the sampling rate is 500 Hz, and the resolution is 12 bits. The blood pressure was measured using an electronic blood pressure monitor (type HEM-7210, made by OMRON Co., Ltd., Japan).
The HRV is derived from the heartbeat interval time series whose resampling is 4 Hz by using the further discrete Fourier transform. Low-frequency power (LF: 0.04–0.15 Hz), high-frequency power (HF: 0.15–0.4 Hz), and the logarithmic ratio low- to high-frequency power (LF/HF) were calculated. We also used the normalized LF (LF%) and HF (HF%) to indicate the response of autonomic nervous activity. LF is affected by the vagal nervous and the sympathetic nervous, and HF is affected by the parasympathetic nervous [
This experiment was approved by the Asia University Medical Research Ethics Committee. This was a two-phase experiment. The purpose of the first phase was to verify the effect of aromatherapy by conducting a blind test. The second experiment involved analyzing the effect of aromatherapy on teachers with varying workloads.
In this experiment, each participant underwent the aroma treatment twice. Although the scent of the natural and synthetic essential oils is similar, certain people who carefully compare them at the same time can distinguish between them. Therefore, we set an interval of one week between the two experiments. To avoid the effect of different workloads, the aroma treatment for each participant was conducted on the same weekday at the same time. In both experiments, the participant did not know which essential oil was used. The experiment procedure is described below.
Each participant was required to complete a consent form and a BAI survey and provide personal information including gender, age, years of employment, height, weight, and relationship status. Participants were required to abstain from smoking, alcohol, and coffee 6 hours before aroma treatment. At the resting time, the participants were then asked to sit in a chair and rest for approximately 3 minutes.
Their blood pressure was measured. We then measured the ECG lasting 3 minutes as a pretest. The participants kept their eyes open and remained still.
The aroma treatment lasted approximately 15 minutes. The respiration rate and volume during this time were asked the same as the resting time.
Blood pressure was again measured after completion of the aroma treatment. We then measured the ECG lasting 3 minutes as a posttest.
In this experiment, we recruited the same participants. Each participant underwent aroma treatment twice: once during a heavy-workload state, and once more during a light-workload state. A heavy workload was defined as teaching more than four classes in one day, whereas a light workload was defined as teaching less than two classes in one day. All aroma treatment was conducted after the end of a day’s classes. To allow independence for the two treatments, the second treatment was delayed one week from the first treatment. Natural bergamot essential oil was used. The experiment procedure is the same as in Section
We employed the SPSS 12.0 software package to conduct the one-way ANOVA analysis. Significance for the
Detailed participant information is shown in Table
Participant information (
Items | People number |
---|---|
Gender | Male: 3 |
Female: 26 | |
BAI | Minor: 20 |
Light: 9 | |
Age (years) | Elder (>40): 18 |
Young (≤40): 11 | |
BMI (Kg/m2) | >24 : 9 |
≤24 and ≥21 : 20 |
The results obtained after natural bergamot essential oil treatment are shown in Table
The HRV one-way ANOVA results before and after natural bergamot essential oil treatment for all participants.
Indicators | Before ( |
After ( |
|
|
---|---|---|---|---|
LF (ms2) | 9.80 ± 1.19 | 9.05 ± 1.31 | 15.21 | 0.00** |
HF (ms2) | 8.91 ± 1.45 | 8.96 ± 1.36 | 0.04 | 0.840 |
LF/HF (nu) | 0.88 ± 1.00 | 0.10 ± 1.10 | 24.34 | 0.00** |
LF% (nu) | 68.6 ± 19.4 | 52.2 ± 22.2 | 26.76 | 0.00** |
HF% (nu) | 32.3 ± 19.5 | 48.7 ± 22.1 | 26.92 | 0.00** |
RRI (ms) | 766.3 ± 90.2 | 781.5 ± 98.4 | 1.12 | 0.290 |
*
The HRV one-way ANOVA results before and after synthetic essential oil treatment for all participants.
Indicators | Before ( |
After ( |
|
|
---|---|---|---|---|
LF (ms2) | 9.5 ± 1.1 | 9.3 ± 1.2 | 0.43 | 0.511 |
HF (ms2) | 8.8 ± 1.2 | 9.0 ± 1.2 | 0.99 | 0.322 |
LF/HF (nu) | 0.64 ± 1.01 | 0.34 ± 1.13 | 3.27 | 0.075 |
LF% (nu) | 63.25 ± 20.11 | 57.09 ± 22.94 | 3.54 | 0.061 |
HF% (nu) | 37.45 ± 20.10 | 43.64 ± 23.05 | 3.54 | 0.061 |
RRI (ms) | 740.1 ± 85.9 | 760.2 ± 85.7 | 2.48 | 0.124 |
*
Tables
The HRV one-way ANOVA results before and after natural bergamot essential oil treatment for all participants with a light workload.
Indicators | Before ( |
After ( |
|
|
---|---|---|---|---|
LF (ms2) | 9.74 ± 1.18 | 8.97 ± 1.30 | 16.96 | 0.000** |
HF (ms2) | 8.98 ± 1.49 | 8.92 ± 1.39 | 0.07 | 0.790 |
LF/HF (nu) | 0.76 ± 0.97 | 0.04 ± 1.14 | 20.13 | 0.000** |
LF% (nu) | 65.85 ± 20.35 | 50.68 ± 22.57 | 21.69 | 0.000** |
HF% (nu) | 34.45 ± 19.88 | 50.27 ± 22.43 | 24.21 | 0.000** |
RRI (ms) | 773 ± 96.4 | 778 ± 102 | 0.09 | 0.763 |
*
The HRV one-way ANOVA results before and after natural bergamot essential oil treatment for all participants with a heavy workload.
Indicators | Before ( |
After ( |
|
|
---|---|---|---|---|
LF (ms2) | 9.68 ± 1.15 | 9.12 ± 1.13 | 10.41 | 0.001** |
HF (ms2) | 8.98 ± 1.59 | 9.26 ± 1.27 | 1.68 | 0.196 |
LF/HF (nu) | 0.70 ± 1.15 | −0.14 ± 1.16 | 23.04 | 0.000** |
LF% (nu) | 63.6 ± 22.3 | 47.3 ± 24.0 | 21.47 | 0.000** |
HF% (nu) | 37.2 ± 22.4 | 53.4 ± 23.9 | 21.42 | 0.000** |
RRI (ms) | 771 ± 114 | 7821 ± 109 | 0.36 | 0.548 |
*
The HRV one-way ANOVA results of the age subgroups with a light workload before and after natural bergamot essential oil treatment for all participants.
Indicators | Elder ( |
Young ( |
||||||
---|---|---|---|---|---|---|---|---|
Before | After |
|
|
Before | After |
|
|
|
LF (ms2) | 9.74 ± 1.15 | 9.06 ± 1.41 | 7.50 | 0.007** | 9.75 ± 1.25 | 8.81 ± 1.10 | 10.42 | 0.002** |
HF (ms2) | 8.70 ± 1.42 | 8.70 ± 1.38 | 0.00 | 0.995 | 9.45 ± 1.52 | 9.29 ± 1.36 | 0.19 | 0.660 |
LF/HF (nu) | 1.04 ± 0.82 | 0.36 ± 1.13 | 12.71 | 0.001** | 0.30 ± 1.02 | −0.48 ± 0.94 | 10.41 | 0.002** |
LF% (nu) | 71.2 ± 17.5 | 57.1 ± 21.8 | 13.59 | 0.000** | 57.2 ± 21.9 | 40.2 ± 19.9 | 10.92 | 0.002** |
HF% (nu) | 28.7 ± 16.5 | 43.1 ± 21.8 | 16.61 | 0.000** | 43.8 ± 21.6 | 60.7 ± 19.6 | 11.04 | 0.001** |
RRI (ms) | 763 ± 74.7 | 771 ± 76.5 | 0.36 | 0.552 | 792 ± 123 | 790 ± 136 | 0.01 | 0.946 |
*
The HRV one-way ANOVA results of the age subgroups with a heavy workload before and after natural bergamot essential oil treatment for all participants.
Indicators | Elder ( |
Young ( |
||||||
---|---|---|---|---|---|---|---|---|
Before | After |
|
|
Before | After |
|
|
|
LF (ms2) | 9.55 ± 1.23 | 9.08 ± 1.16 | 4.258 | 0.042* | 9.89 ± 0.98 | 9.19 ± 1.10 | 7.32 | 0.009** |
HF (ms2) | 8.55 ± 1.67 | 9.11 ± 1.30 | 3.71 | 0.057 | 9.67 ± 1.17 | 9.51 ± 1.20 | 0.31 | 0.583 |
LF/HF (nu) | 1.00 ± 1.18 | −0.03 ± 1.07 | 22.53 | 0.000** | 0. 21 ± 0.91 | −0.32 ± 1.30 | 3.71 | 0.058 |
LF% (nu) | 69.0 ± 22.2 | 49.6 ± 22.9 | 20.02 | 0.000** | 54.8 ± 19.8 | 43.6 ± 25.7 | 3.91 | 0.052 |
HF% (nu) | 31.7 ± 22.4 | 51.2 ± 22.9 | 20.15 | 0.000** | 46.1 ± 19.7 | 57.0 ± 25.4 | 3.78 | 0.056 |
RRI (ms) | 759 ± 86.2 | 769 ± 76.4 | 0.46 | 0.498 | 792 ± 148 | 801 ± 147 | 0.07 | 0.797 |
*
The HRV one-way ANOVA results of the BMI subgroups with a light workload before and after natural bergamot essential oil treatment for all participants.
Indicators | BMI > 40 ( |
21 ≤ BMI ≤ 24 ( |
||||||
---|---|---|---|---|---|---|---|---|
Before | After |
|
|
Before | After |
|
|
|
LF (ms2) | 9.7 ± 1.6 | 8.8 ± 1.6 | 4.59 | 0.037* | 9.8 ± 0.9 | 9.1 ± 1.2 | 13.46 | 0.000** |
HF (ms2) | 8.71 ± 2.09 | 8.63 ± 2.05 | 0.02 | 0.895 | 9.11 ± 1.13 | 9.1 ± 1.0 | 0.07 | 0.790 |
LF/HF (nu) | 0.97 ± 0.77 | 0.12 ± 0.97 | 12.89 | 0.001** | 0.66 ± 1.04 | 0.01 ± 1.21 | 10.16 | 0.002** |
LF% (nu) | 71.1 ± 15.4 | 52.3 ± 20.1 | 14.95 | 0.000** | 63.5 ± 21.94 | 50.0 ± 23.7 | 10.53 | 0.002** |
HF% (nu) | 29.9 ± 15.5 | 48.7 ± 20.4 | 14.47 | 0.000** | 36.5 ± 21.36 | 51.0 ± 23.4 | 12.53 | 0.001** |
RRI (ms) | 767 ± 139 | 773 ± 163 | 0.02 | 0.888 | 777 ± 70.1 | 781 ± 60.2 | 0.11 | 0.740 |
*
The HRV one-way ANOVA results of the BMI subgroups with a heavy workload before and after natural bergamot essential oil treatment for all participants.
Indicators | BMI > 40 ( |
21 ≤ BMI ≤ 24 ( |
||||||
---|---|---|---|---|---|---|---|---|
Before | After |
|
|
Before | After |
|
|
|
LF (ms2) | 9.40 ± 1.30 | 9.33 ± 1.13 | 0.05 | 0.817 | 9.80 ± 1.06 | 9.02 ± 1.13 | 14.93 | 0.000** |
HF (ms2) | 8.88 ± 1.93 | 8.96 ± 1.48 | 0.08 | 0.774 | 9.04 ± 1.43 | 9.40 ± 1.16 | 2.18 | 0.143 |
LF/HF (nu) | 0.58 ± 0.93 | 0.37 ± 0.91 | 0.71 | 0.402 | 0.76 ± 1.24 | −0.37 ± 1.20 | 25.60 | 0.000** |
LF% (nu) | 62.4 ± 19.1 | 58. 6 ± 20.1 | 0.50 | 0.481 | 64.2 ± 23.7 | 42.3 ± 24.1 | 25.20 | 0.000** |
HF% (nu) | 38.7 ± 19.6 | 42.4 ± 20.3 | 0.45 | 0.507 | 36.4 ± 23.7 | 58.4 ± 23.8 | 25.54 | 0.000** |
RRI (ms) | 768 ± 153 | 802 ± 152 | 0.64 | 0.426 | 773 ± 93.0 | 772 ± 82.9 | 0.00 | 0.989 |
*
The HRV one-way ANOVA results of the anxiety-degree subgroups with a light workload before and after natural bergamot essential oil treatment for all participants.
Indicators | Minor ( |
Light ( |
||||||
---|---|---|---|---|---|---|---|---|
Before | After |
|
|
Before | After |
|
|
|
LF (ms2) | 9.72 ± 1.24 | 9.12 ± 1.36 | 6.27 | 0.014* | 9.80 ± 1.08 | 8.62 ± 1.10 | 15.85 | 0.000** |
HF (ms2) | 8.95 ± 1.54 | 8.89 ± 1.43 | 0.04 | 0.834 | 9.06 ± 1.40 | 9.00 ± 1.33 | 0.03 | 0.870 |
LF/HF (nu) | 0.77 ± 1.03 | 0.23 ± 1.24 | 6.69 | 0.011* | 0.74 ± 0.82 | −0.38 ± 0.72 | 28.01 | 0.000** |
LF% (nu) | 65.6 ± 21.7 | 54.4 ± 24.4 | 6.94 | 0.010* | 66.5 ± 17.4 | 42.3 ± 15.0 | 29.99 | 0.000** |
HF% (nu) | 34.3 ± 21.0 | 46.6 ± 24.3 | 8.73 | 0.004** | 34.8 ± 17.4 | 58.5 ± 14.8 | 29.02 | 0.000** |
RRI (ms) | 778 ± 102 | 788 ± 115 | 0.24 | 0.626 | 763 ± 82.5 | 756 ± 64.5 | 0.12 | 0.733 |
*
The HRV one-way ANOVA results of the anxiety-degree subgroups with a heavy workload before and after natural bergamot essential oil treatment for all participants.
Indicators | Minor ( |
Light ( |
||||||
---|---|---|---|---|---|---|---|---|
Before | After |
|
|
Before | After |
|
|
|
LF (ms2) | 9.62 ± 1.27 | 9.14 ± 1.23 | 4.28 | 0.041* | 9.82 ± 0.81 | 9.07 ± 0.88 | 10.46 | 0.002** |
HF (ms2) | 8.83 ± 1.66 | 9.21 ± 1.33 | 1.91 | 0.170 | 9.31 ± 1.40 | 9.38 ± 1.15 | 0.04 | 0.841 |
LF/HF (nu) | 0.79 ± 1.18 | −0.06 ± 1.25 | 14.82 | 0.000** | 0.51 ± 1.08 | −0.31 ± 0.95 | 8.74 | 0.005** |
LF% (nu) | 65.3 ± 22.9 | 49.2 ± 25.3 | 13.32 | 0.000** | 60.0 ± 20.8 | 43.2 ± 20.8 | 8.75 | 0.005** |
HF% (nu) | 35.4 ± 23.0 | 51.6 ± 25.2 | 13.59 | 0.000** | 41.1 ± 21.1 | 57.5 ± 20.7 | 8.30 | 0.006** |
RRI (ms) | 77.3 ± 9.5 | 74.7 ± 11.6 | 0.08 | 0.783 | 68.3 ± 9.6 | 66.9 ± 9.6 | 0.94 | 0.337 |
*
Chang and Shen examined the effect of aromatherapy on elementary schoolteachers in Taiwan [
In this study, the HF indicator did not show a significant difference in the two experiments. Because the respiration frequency at a resting time is within 0.1~0.4 Hz, which locates at the range of HF, the calculated power of HF will include the power of respiratory frequency [
According to Tables
Tables
We conducted this trial to examine the potential of using natural bergamot essential oil in appeasing the work stress of elementary schoolteachers. The response of automatic nervous system has a significant change after the natural essential bergamot oil treatment. We also analyzed the effect of aromatherapy at different workloads. The aromatherapy may alleviate the symptoms of physical and psychological stress. The results also suggest that age and BMI factors affect aromatherapy performance when teachers have a heavy workload.
This work has been supported by the National Science Council of Taiwan (Grants nos. NSC 102-2221-E-324-004- and NSC 102-2221-E-468-003-).