Clinical trial NCT05316597: Do Terpenes Play a Role in the Stress-reducing Effects of a Forest Bathing Intervention?
Official title: Do Terpenes Play a Role in the Stress-reducing Effects of a Forest Bathing Intervention?
Study type: INTERVENTIONAL
Overall status: COMPLETED
Phase: NA
Conditions: Monoterpene Exposure During a Forest Bathing Intervention
Lead sponsor: University of Washington
Sponsor class: OTHER
Collaborators: name: National Center for Complementary and Integrative Health (NCCIH)
First posted: 2022-04-07
Enrollment: 43
Sex: ALL
Minimum age (years): 18
Standard ages: ADULT
OLDER_ADULT
Accepts healthy volunteers: yes
Allocation: RANDOMIZED
Intervention model: CROSSOVER
Intervention model description: Participants are assigned to both arms in random order
Primary purpose: PREVENTION

Brief summary: 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.

Detailed description: 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.

Eligibility criteria: Inclusion Criteria:

* 18 years and older
* Non-smoker
* Physically capable of walking for approximately 15-20 min from the study vehicle to the clinic and experimental locations.

Exclusion Criteria:

* Pregnancy
* Current or prior diagnosis of neurologic, hypertensive, psychiatric, respiratory disorder, or anosmia/hyposmia
* Some types of medication.
* Olfactory sensitivity threshold (assessed via UPSIT® test kit (Sensonics International, Haddon Heights, NJ)

At enrollment, participants will complete a baseline survey on demographics, personality traits, and regular nature contact and perceptions. Study staff will also use the clinically-validated UPSIT® test kit (Sensonics International, Haddon Heights, NJ) to evaluate olfactory sensitivity and identify/exclude participants with undiagnosed smell loss.

Study staff will work with participants to schedule their forest bathing sessions and review instructions on how to prepare (e.g., by avoiding alcohol, marijuana, and certain foods, drinks, and household cleaning products with high terpene concentrations 24 hrs before their session).

Primary outcomes:
measure: Changes in the HF (ms^2) Component of HRV
timeFrame: 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)).
measure: Baseline HF (ms^2) Component of HRV
timeFrame: At baseline (pre-exposure)
Secondary outcomes:
measure: Blood Pressure (Diastolic in mmHg)
timeFrame: 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)).
measure: Beats Per Minute (BPM)
timeFrame: 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)).
measure: Skin Conductance (μS)
timeFrame: 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)).
measure: Self-reported Positive Affect
timeFrame: 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)).
measure: Self-reported Stress
timeFrame: 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)).
measure: Self-reported Negative Affect
timeFrame: 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)).
measure: Levels of CRP
timeFrame: 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)).
measure: Levels of Cortisol in Serum (ng/mL)
timeFrame: 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)).
measure: Blood Pressure (Systolic in mmHg)
timeFrame: 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)).
measure: Level of TNF-alpha
timeFrame: 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)).
measure: Levels of Il-6
timeFrame: 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)).
measure: Baseline Blood Pressure (Diastolic in mmHg)
timeFrame: At baseline (pre-exposure).
measure: Beats Per Minute (BPM)
timeFrame: At baseline (pre-exposure).
measure: Skin Conductance (μS)
timeFrame: At baseline (pre-exposure).
measure: Self-reported Positive Affect
timeFrame: At baseline (pre-exposure).
measure: Self-reported Stress
timeFrame: At baseline (pre-exposure).
measure: Self-reported Negative Affect
timeFrame: At baseline (pre-exposure).
measure: Levels of CRP
timeFrame: At baseline (pre-exposure).
measure: Levels of Cortisol in Serum (ng/mL)
timeFrame: At baseline (pre-exposure).
measure: Blood Pressure (Systolic in mmHg)
timeFrame: At baseline (pre-exposure).
measure: Level of TNF-alpha
timeFrame: At baseline (pre-exposure).
measure: Levels of Il-6
timeFrame: At baseline (pre-exposure).
Other outcomes:
measure: Degree of Association of Sum Composite of Absorbed Dose of VOCs in Serum (μg/mL)
timeFrame: Time point 4 (60 min) for absorbed dose associations with same time point for DBP, SBP, Cortisol, Il-6, TNF-alpha, and CRP; and associations with Time point 2 (20 minutes) for HRV, SCL, positive affect, negative affect, self-reported stress, heart rate.
Locations:
city: Eatonville
country: United States
facility: Pack Forest
state: Washington
Study officials:
affiliation: University of Washington
name: Gregory Bratman, PhD
role: PRINCIPAL_INVESTIGATOR
References: