Effects of Walking in Greenspace and the Built Environment in Adults With Prediabetes: A Randomized Crossover Trial

The goal of this randomized crossover trial is to compare the differences in psychological and physiological effects of walking in two different outdoor environments (urban/suburban commercial environments vs. urban/suburban nature areas/preserves) in adults with prediabetes. The main questions it aims to answer are:

• Do psychological measures of stress, anxiety, and affect improve more in one type of outdoor environment over the other?
• Do physiological measures of stress improve more in one type of outdoor environment over the other?

As this is a crossover trial, participants will serve as their own controls. Researchers will compare both the psychological and physiological effects walking in the two types of outdoor environments.

Participants will:

• Walk 150-minutes per week for six weeks in each of the two outdoor conditions.
• Visit the clinic four times, including before and after each six-week walking period.
• Collect saliva samples immediately proceeding or following the four clinic visits.
• Return to their pre-study level of physical activity for a 5-week washout period between each of the two walking interventions.

Study Overview

• Status: Recruiting
• Conditions: PreDiabetes; Stress and Anxiety; Heart Rate Variability (HRV); Stress Biomarkers
• Intervention / Treatment: Behavioral: Nature-based Walking; Behavioral: Built-environment/Commercial Walking

Detailed Description

Approximately 92 million U.S. adults (~38% of population) have prediabetes (PreD). Because people with PreD are at high risk CMD, they are a target population for diabetes prevention programs. The focus is people with PreD because of their high risk for developing CMD and large numbers, providing an opportunity to investigate behavioral and environmental approaches as preventive measures in a well-defined population. Urbanization affords challenges and opportunities to public health that include exposure to obesogenic environments, air pollution, and psychosocial stressors. In healthy adults suggest exposure to nature has health benefits relative to exposure to built environments. Hypothesized mechanisms for health benefits of Greenspace exposure include increased physical activity (PA), attention restoration, stress reduction, and reduced exposure to pollution. Many of the health benefits are associated with reduced psychological and physiological stress leading to better autonomic functioning as assessed by heart rate variability (HRV) and other biomarkers. Multiple studies suggest that PA and exposure to natural environments may act together to improve health. Yet, aside from our preliminary studies, we are not aware of any studies that examined how physical activity may interact with exposure to urban Greenspace ('Green') compared with built urban environments ('Gray'), to reduce stress and improve health. The purpose of this proposed study is to conduct a randomized crossover trial comparing differences in the psychosocial and physiological effects of walking in urban Green and Gray spaces in adults with PreD.

• Study Type: Interventional
• Enrollment (Estimated): 216
• Phase: Not Applicable

Contacts and Locations

• Study Contact: Name: Sarah Rydell, MPH; Phone Number: 612-437-6126; Email: rydel004@umn.edu

Study Locations

• United States
  • Illinois
    • Lake Forest, Illinois, United States, 60045
      • Recruiting
      • Lake Forest Hospital
      • Contact: Molly Schau; Email: mschau@nm.org
    • Winfield, Illinois, United States, 60190
      • Recruiting
      • Central DuPage Hospital
      • Contact: Molly Schau; Email: mschau@nm.org
  • Minnesota
    • Minneapolis, Minnesota, United States, 55415
      • Recruiting
      • Epidemiological Clinical Research Center
      • Contact: Chris Hoefer; Phone Number: 612-626-9199

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• 25-64 years old.
• Classified as overweight or obese with BMI 20.0-39.9 kg/m2 per self-report and a BMI of 20.0- 41.9 kg/m2 upon actual measure.
• Documentation* of a PreD diagnosis within one year of enrollment by physician or primary care provider based on lab tests showing a fasted blood glucose of 100-125 mg/dL, a 2-hour oral glucose tolerance test of 140-199 mg/dL, or an HbA1c level of 5.7%-6.49%271; OR a study screening lab value of HbA1C within the aforementioned range.
• Currently engaged in ≤100 min/week of moderate to vigorous exercise -confirmed via a 7-day activity recall.
• No exercise contraindications as assessed by the Physical Activity Readiness Questionnaire (PAR-Q) -this Questionnaire involves seven "yes" or "no" questions regarding an individual's health status. Answering "yes" to any one of these questions may require a prospective participant to acquire a written doctor's note stating they can safely participate in the trial's exercise intervention. The participant would not be enrolled until this doctor's note is received.
• Stable weight over the last 3 months (less than 10% change).
• Not currently pregnant, planning to become pregnant, or currently breastfeeding.
• Willing to maintain current dietary and exercise habits, aside from any changes to be made per the study exercise protocol.
• Must own a smartphone and be willing and able to download the Garmin Connect app
• Ability to speak and understand English.
• Any level of income
• Any race/ethnicity

Exclusion Criteria:

• Individuals <25 or >64: younger individuals may have not yet reached physiological maturity and in whom PreD prevalence is low; older individuals are more likely to have contraindications to PA and other comorbidities.
• BMI <20 or ≥42.
• Individuals with an HbA1c level <5.7% or >6.4%.
• Currently engaged in >100 min/wk of PA.
• Individuals with contraindications to exercise participation as indicated by the PAR-Q.
• A self-reported physical/mental disability that would prevent them from being able to adhere to the intervention.
• Past or current diagnosis of Diabetes (Type 1, 1.5 or 2) or use of diabetic medications (e.g. medications to control blood sugar)
• Any history of a cardiovascular disease event (e.g. heart attack, ablation, pacemaker, stroke)
• Current treatment for cancer or heart disease (lipid and hypertensive medications acceptable but will be tracked closely).
• Any change within the last 3 months, or anticipated changes, of any medications that would affect study outcomes (e.g. medications for lipids, blood pressure, anxiety, depression)
• The use of any medication that significantly interferes with the autonomic nervous system
• Current tobacco or nicotine users, or those who have quit within the last six months
• Excessive alcohol (on average>1 drinks/day for women and >2 drinks/day for men) or excessive recreational drug use (reported usage of once a week or more).
• Unstable weight over the last three months (>10% change).
• Those with major surgery planned or recent history of bariatric surgery (within last 2 years) or a history of other medical interventions that would interfere with study outcomes
• Currently within one-year postpartum, currently pregnant, or planning to become pregnant during the study period.
• Currently breastfeeding.
• Unwilling to comply with study randomization procedures.
• Unwilling to maintain current dietary and exercise habits, aside from any changes to be made per the study exercise protocol.
• Current participation in another interventional clinical trial.
• Previous randomization in this study.

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Basic Science
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Single

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Nature-based Walking then Built-environment/Commercial Walking; People with prediabetes randomized to six weeks of nature-based walking followed by a five week washout, and then six weeks of built-environment/commercial-based walking	Behavioral: Nature-based Walking; All participants will be asked to walk three to five times per week for 30-50 minutes per walk, totaling 150 min/week, at moderate intensity over a 6-week period in a designated nature-based, or 'green', urban environment.; Behavioral: Built-environment/Commercial Walking; All participants will be asked to walk three to five times per week for 30-50 minutes per walk, totaling 150 min/week, at moderate intensity over a 6-week period in a designated built-environment/commercial, or 'Gray', urban environment.
Experimental: Built-environment/Commercial Walking then Nature-based Walking; People with prediabetes randomized to six weeks of built-environment/commercial-based walking followed by a five week washout, and then six weeks of nature-based walking	Behavioral: Nature-based Walking; All participants will be asked to walk three to five times per week for 30-50 minutes per walk, totaling 150 min/week, at moderate intensity over a 6-week period in a designated nature-based, or 'green', urban environment.; Behavioral: Built-environment/Commercial Walking; All participants will be asked to walk three to five times per week for 30-50 minutes per walk, totaling 150 min/week, at moderate intensity over a 6-week period in a designated built-environment/commercial, or 'Gray', urban environment.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Measure of Anxiety	An Ecological Momentary Assessment of anxiety (rating level on a 0-10 point Likert scale) will be assessed pre/post each assessment walk.	Before and after each of the four assessment walks, which occur in weeks 4, 7, 15, and 18 (weeks 3 and 6 of each 6-week walking intervention).
Perceived stress assessment	Perceived stress will be measured using an Ecological Momentary Assessment of stress (rating level on a 0-10 point Likert scale) will be assessed pre/post each assessment walk.	Before and after each of the four assessment walks, which occur in weeks 4, 7, 15, and 18 (weeks 3 and 6 of each 6-week walking intervention).
Mood assessment	Mood will be evaluated using an Ecological Momentary Assessment of mood (i.e.. sadness, happiness, relaxation, mental energy, and physical energy) will be assessed pre/post each assessment walk (rating level on a 0-10 point Likert scale).	Before and after each of the four assessment walks, which occur in weeks 4, 7, 15, and 18 (weeks 3 and 6 of each 6-week walking intervention).
Restorativeness	Assessing the restorativeness of the walked environment (using the perceived restorativeness scale) after each of the four assessment walks.	Assessment given after each of the four assessment walks, which occur in weeks 4, 7, 15, and 18 (weeks 3 and 6 of each 6-week walking intervention).

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Walking Heart Rate variability	Heart rate variability (HRV) will be measured before, during (within steady-state walking), and after each of the four assessment walks. We will use the Zephyr BioHarness and associated BioModule to complete these measurements. The a priori metric for analysis is the HRV during the walk between minutes 10 and 30.	Before, during, and after each of the four assessment walks, which occur in weeks 4, 7, 15, and 18 (weeks 3 and 6 of each 6-week walking intervention).
Salivary cortisol levels	Saliva will be collected using the passive drool collection method at the following daily times: (1) immediately upon waking; (2) 30-45 minutes after waking; and (3) 14 hours after waking. Sampling times allow for calculation of the cortisol awakening response and diurnal decline in cortisol, metrics well correlated with health outcomes. Salivary cortisol will be assayed using validated ELISA assays	Within 7 days of each of the four clinic visits which occur before and after each of the 6-week walking interventions (i.e. study weeks 1, 7, 12 and 18).
Ambient Particulate Matter	Ambient Particulate Matter will be assessed using the AirBeam3, a palm-sized air quality instrument that measures PM1, PM2.5, PM10, temperature, and relative humidity. It will be worn during each of the four assessment walks, measuring air-quality in real time as the participant is out on their walk.	During each of the four assessment walks, which occur in weeks 4, 7, 15, and 18 (weeks 3 and 6 of each 6-week walking intervention).
CMD risk	CMD risk score will be computed as the average of the z-scores comprised of systolic blood pressure, and fasting blood glucose, insulin, triglycerides, and HDL-cholesterol (reverse scored).	At each of the four clinic visits which occur before and after each of the 6-week walking interventions (i.e. study weeks 1, 7, 12 and 18).

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Resting Heart Rate Variability	Resting Heart rate variability (HRV) will be measured at the Baseline and Follow-up visits for each of the two study conditions (Weeks 1, 7, 12, and 18). We will use the Zephyr BioHarness and associated BioModule to complete these measurements.	At each of the four clinic visits which occur before and after each of the 6-week walking interventions (i.e. study weeks 1, 7, 12 and 18).
Anxiety	Anxiety will be assessed at each of the four clinical visits (occurring before and after each of the 6-week walking interventions) using the PROMIS Anxiety 8a.	At each of the four clinic visits which occur before and after each of the 6-week walking interventions (i.e. study weeks 1, 7, 12 and 18).
CMD-Risk Mediation	The extent to which physiological, psychological, and air pollution measures mediate the differential impact of Green versus Grey walking on CMD-risk using regression-based mediation models.	Throughout the study, up to 18 weeks.
Stress	Stress will be assessed at each of the four clinical visits (occurring before and after each of the 6-week walking interventions) using the Perceived Stress Scale.	At each of the four clinic visits which occur before and after each of the 6-week walking interventions (i.e. study weeks 1, 7, 12 and 18).
Affect	Affect will be assessed at each of the four clinical visits (occurring before and after each of the 6-week walking interventions) using the PROMIS Affect 15a.	At each of the four clinic visits which occur before and after each of the 6-week walking interventions (i.e. study weeks 1, 7, 12 and 18).

Collaborators and Investigators

• Sponsor: University of Minnesota
• Collaborators: Northwestern University
• Investigators: Principal Investigator: Mark Pereira, PhD, University of Minnesota

Publications and helpful links

Helpful Links

• Study website for more information and contacts.

Study record dates

Study Major Dates

• Study Start (Actual): June 6, 2024
• Primary Completion (Estimated): November 30, 2027
• Study Completion (Estimated): November 30, 2027

Study Registration Dates

• First Submitted: March 20, 2024
• First Submitted That Met QC Criteria: April 12, 2024
• First Posted (Actual): April 15, 2024

Study Record Updates

• Last Update Posted (Actual): September 22, 2025
• Last Update Submitted That Met QC Criteria: September 17, 2025
• Last Verified: September 1, 2025

More Information

Terms related to this study

• Keywords: stress; urban; prediabetes; walking intervention; built environment; outdoor environment
• Additional Relevant MeSH Terms: Endocrine System Diseases; Mental Disorders; Metabolic Diseases; Glucose Metabolism Disorders; Diabetes Mellitus; Nutritional and Metabolic Diseases; Anxiety Disorders; Prediabetic State; Environment and Public Health; Environment; Environment Design; Built Environment
• Other Study ID Numbers: SPH-2023-32410

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No