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

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, the investigators 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.

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.