Do Terpenes Play a Role in the Stress-reducing Effects of a Forest Bathing Intervention?

NCT ID: NCT05316597

Last Updated: 2024-09-19

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 43 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2022-07-12
• Study Completion Date: 2023-09-21

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.

Conditions

Monoterpene Exposure During a Forest Bathing Intervention

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: CROSSOVER
• Primary Study Purpose: PREVENTION
• Blinding Strategy: DOUBLE

Study Groups

Terpenes On

Forest bathing intervention with no filtration of terpenes from inhaled air using PAPR with particle-only filter ("terpenes on")

Group Type: EXPERIMENTAL

Forest bathing

Intervention Type: BEHAVIORAL

Participants will be seated in a forest environment for an hour-long exposure to the forest

Terpenes Off

Forest bathing intervention with filtration of terpenes from inhaled air using PAPR with activated charcoal filter ("terpenes off")

Group Type: ACTIVE_COMPARATOR

Forest bathing

Intervention Type: BEHAVIORAL

Participants will be seated in a forest environment for an hour-long exposure to the forest

Interventions

Forest bathing

Participants will be seated in a forest environment for an hour-long exposure to the forest

Intervention Type: BEHAVIORAL

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).

• Minimum Eligible Age: 18 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: Yes

Sponsors

National Center for Complementary and Integrative Health (NCCIH)

NIH

Sponsor Role: collaborator

University of Washington

OTHER

Sponsor Role: lead

Responsible Party

Gregory Bratman

Assistant Professor: Environmental and Forest Sciences

Responsibility Role: PRINCIPAL_INVESTIGATOR

Principal Investigators

Gregory Bratman, PhD

Role: PRINCIPAL_INVESTIGATOR

University of Washington

Locations

Pack Forest

Eatonville, Washington, United States

Countries

United States

Provided Documents

Document Type: Study Protocol

View Document

Document Type: Statistical Analysis Plan

View Document

Document Type: Informed Consent Form

View Document

Other Identifiers

R21AT011242

Identifier Type: NIH

Identifier Source: secondary_id

View Link

STUDY00013134

Identifier Type: -

Identifier Source: org_study_id