Abstract:
The effects of two different concentrations of orange aroma on peripheral and cardiac
autonomic nervous system activity were investigated under a short-term cognitive
stressor in a highly reproducible manner using an olfactometer. In a within-subjects
experiment, 19 male university students performed a 30-min calculation task under three
aroma conditions: 1% orange, 20% orange, and scentless air (control). Each aroma was
intermittently delivered using a proprietary olfactometer in a counter-balanced order.
Along with a visual analogue scale (VAS) comprising seven items (nervousness, effort,
concentration, tiredness, irritation, boredom, and fed up), the nose tip temperature and
the cardiac activity on electrocardiograms were recorded throughout each experiment.
Regardless of the aroma condition, significant decreases in nose tip temperature (p <
0.001) and the high-frequency (HF) component of heart rate variability (p < 0.01), and a
significant increase in heart rate (HR) (p < 0.001) were observed during the task. These
results indicated a typical acute stress response. However, the increase/decrease in HR
and HF were significantly lower with 1% orange compared to 20% orange and the control
condition (p < 0.01), indicating an inhibition of sympathetic nervous system elevation and
parasympathetic nervous system suppression by 1% orange. However, none of the VAS
scores showed a significant difference between the two doses (p > 0.05). There were also
no significant differences between the two doses either in terms of preference or
perceived strength (p > 0.05). The findings suggest that mild orange essential oil
inhalation inhibits the cardiac stress response, but with no significant effect on the
subjective stress.
