This pilot study evaluates the role terpenes play in the stress-reducing effects of a forest bathing intervention. Participants will participate in two interventions in random order: 1) terpene exposure and 2) no terpene exposure.
The investigators will use an individual-level crossover design in which each session is conducted independently and on different days. Participants will be outfitted with a powered air purifying respirator (PAPR) to selectively modulate exposure to a natural suite of forest-derived volatile organic compounds (VOCs) while present in forest environments. Each participant will undergo two forest bathing sessions, one in which VOCs are not filtered (treatment condition), and one in which they are filtered (control condition). Sessions will be separated by a washout period of at least 8 days for each participant, and order will be counterbalanced. The investigators will estimate the average effect of treatment over 40 distinct treatment days against 40 distinct control/filtered days. The power and sample size calculations (N = 40) were determined using previous nature exposure studies of similar cross-over design. The study is adequately powered assuming the conventional targets of α = 0.05 and β = 0.80 with a 10% anticipated dropout rate, and including temperature, wind, and light variability during treatment days. The specific aim of this project is to 1) assess whether VOC inhalation regulates increases in the high frequency (HF) (ms2) component of heart rate variability (HRV) as the primary outcome (with decreases in blood pressure, heart rate, self-reported stress, and levels of inflammatory cytokines in serum included as secondary outcomes); and 1a) assess the degree of association of absorbed dose of six forest-derived VOCs (i.e., α-pinene, β-pinene, β-myrcene, Δ-3-carene, limonene, β- carophyllene) in serum with these outcomes.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
PREVENTION
Masking
DOUBLE
Enrollment
43
Participants will be seated in a forest environment for an hour-long exposure to the forest
Pack Forest
Eatonville, Washington, United States
Changes in the HF (ms^2) Component of HRV
Assess whether VOC inhalation regulates psychophysiological outcomes of the terpenes-on vs. terpenes-off sessions. Ln High Frequency Heart Rate Variability at T2 (20 minutes into duration of exposure for each session)
Time frame: At time point 2 (20 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).
Baseline HF (ms^2) Component of HRV
Assess whether VOC inhalation regulates psychophysiological outcomes of the terpenes-on vs. terpenes-off sessions. Ln High Frequency Heart Rate Variability at baseline.
Time frame: At baseline (pre-exposure)
Blood Pressure (Diastolic in mmHg)
Assessed using mobile physiology equipment Diastolic blood pressure at T4 (60 minutes of exposure)
Time frame: At time point 4 (60 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).
Beats Per Minute (BPM)
Assessed using mobile physiology equipment BPM at time point 4 (60 minutes of exposure)
Time frame: At time point 4 (60 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).
Skin Conductance (μS)
Assessed using mobile physiology equipment Skin conductance levels at time point 2 (20 minutes into exposure)
Time frame: At time point 2 (20 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).
Self-reported Positive Affect
Assessed using the shortened Positive and Negative Affect Schedule (PANAS) Positive affect at time point 2 (20 minutes of exposure) Higher scale scores are indicative of better outcome Range 5-50
This platform is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional.
Time frame: At time point 2 (20 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).
Self-reported Stress
Assessed using a single-item self report non-validated scale Self-reported stress at time point 2 (20 minutes of exposure) Higher scale score indicative of worse outcome Range 1-5
Time frame: At time point 2 (20 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).
Self-reported Negative Affect
Assessed using the shortened Positive and Negative Affect Schedule (PANAS) Negative affect at time point 2 (20 minutes of exposure) Higher score on scale indicative of worse outcome Range 5-50
Time frame: At time point 2 (20 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).
Levels of CRP
Assessed using blood serum collected via standard clinical methods. CRP levels at time point 4 (60 minutes of exposure).
Time frame: At time point 4 (60 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).
Levels of Cortisol in Serum (ng/mL)
Assessed using blood serum collected via standard clinical methods Cortisol levels at time point 4 (60 minutes of exposure).
Time frame: At time point 4 (60 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).
Blood Pressure (Systolic in mmHg)
Assessed using mobile physiology equipment Systolic blood pressure at T4 (60 minutes of exposure)
Time frame: At time point 4 (60 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).
Level of TNF-alpha
Assessed using blood serum collected via standard clinical methods TNF-alpha levels at time point 4 (60 minutes of exposure).
Time frame: At time point 4 (60 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).
Levels of Il-6
Assessed using blood serum collected via standard clinical methods IL-6 levels at time point 4 (60 minutes of exposure).
Time frame: At time point 4 (60 minutes into duration of exposure for Session 1 and Session 2 (which occurred at least 8 days after Session 1)).
Baseline Blood Pressure (Diastolic in mmHg)
Assessed using mobile physiology equipment Diastolic blood pressure at baseline.
Time frame: At baseline (pre-exposure).
Beats Per Minute (BPM)
Assessed using mobile physiology equipment BPM at baseline.
Time frame: At baseline (pre-exposure).
Skin Conductance (μS)
Assessed using mobile physiology equipment Skin conductance levels at baseline.
Time frame: At baseline (pre-exposure).
Self-reported Positive Affect
Assessed using the shortened Positive and Negative Affect Schedule (PANAS) Positive affect at baseline Higher scale scores are indicative of better outcome Range 5-50
Time frame: At baseline (pre-exposure).
Self-reported Stress
Assessed using a single-item self report non-validated scale Self-reported stress at baseline Higher scale score indicative of worse outcome Range 1-5
Time frame: At baseline (pre-exposure).
Self-reported Negative Affect
Assessed using the shortened Positive and Negative Affect Schedule (PANAS) Negative affect at baseline Higher score on scale indicative of worse outcome Range 5-50
Time frame: At baseline (pre-exposure).
Levels of CRP
Assessed using blood serum collected via standard clinical methods. CRP levels at baseline
Time frame: At baseline (pre-exposure).
Levels of Cortisol in Serum (ng/mL)
Assessed using blood serum collected via standard clinical methods Cortisol levels at baseline
Time frame: At baseline (pre-exposure).
Blood Pressure (Systolic in mmHg)
Assessed using mobile physiology equipment Systolic blood pressure at baseline
Time frame: At baseline (pre-exposure).
Level of TNF-alpha
Assessed using blood serum collected via standard clinical methods TNF-alpha levels at baseline
Time frame: At baseline (pre-exposure).
Levels of Il-6
Assessed using blood serum collected via standard clinical methods IL-6 levels at baseline
Time frame: At baseline (pre-exposure).