Study: Gardening improves health outcomes for breast cancer patients

IN-DEPTH REVIEW OF RESEARCH

Study background:

Most breast cancer survivors in the United States do not meet The American Cancer Society recommendations of eating at least 5 daily servings of fruits and vegetables and getting 150 minutes of moderate or 75 minutes of vigorous physical activity per week. Gardening may be one approach towards both goals.

The therapeutic nature of gardening is associated with improved physical and psychosocial well-being. It can increase physical activity and improve body weight issues, and it has been shown to increase vegetable consumption across several populations.

Researchers of this study wanted to know:

Whether a mentored home-based gardening intervention changes health-related outcomes among breast cancer survivors.

Study design:

This 2-arm trial randomly assigned breast cancer survivors to a 1-year mentored gardening intervention or to a wait-list control group. Breast cancer survivors in the Birmingham, Alabama area were recruited by a mailed invitation between August 2013 and May 2014. Potential participants were identified using the Alabama Statewide Cancer Registry and local hospital registries. Self-referrals were also recruited through support groups and media.

Inclusion criteria were:

• Completion of cancer treatment
• Currently eating less than 5 daily servings of vegetables and fruits
• Exercising less than 150 minutes per week
• One or more physical function limitations
• Ability to speak and write English
• Residing within 15-miles of a Master Gardener
• Living in a residence with 6 or more hours of sunlight a day, running water, and space for 1 raised garden bed or 4 grow boxes
• Willingness to be randomized to either study arm

Exclusion criteria were:

• Other health conditions that would impair a participant’s ability to complete study assessments or participate in unsupervised activity
• Current use of Warfarin
• Having had a successful vegetable garden in the past 2 years

Each breast cancer survivor was paired with an Alabama Cooperative Master Gardener Extension System-certified Master Gardener. (A survey of the Master Gardeners suggested that approximately 70% were extremely interested in volunteering for this project.)  Master Gardeners met bimonthly with participants to mentor planning, planting, and maintaining 3 seasons (spring, summer, and fall) of home-based gardening over the course of a year.

All participants were provided with approximately $500 worth of supplies, including raised beds or grow boxes, soil, seeds, plans, fertilizer, natural pest repellant, a hose and watering can, a gardening workbook, and a gardening journal to record observations and notes.  Participants were also encouraged to participate in a private Facebook group to facilitate interaction with others study participants and Master Gardeners.

The primary outcome was feasibility which was measured by accrual, retention, and satisfaction.  Targeted accrual was set at 100, based on Master Gardener capacity in the greater Birmingham area.  Data on satisfaction was collected via phone interview after completion of the study.  Sustainability was assessed at 2 years by phone interview.

Secondary, health-related outcomes, including vegetable consumption, physical activity, performance and function, health-related quality of life, BMI and waist circumference, and biomarkers were collected at participants’ homes at the beginning and end of the study.  Physical performance measurements included: 30-Second Chair Stand that measured lower body strength; Arm Curl (upper body strength); Sit-and-Reach (lower body flexibility); Back Scratch (upper body flexibility); 8-Foot Get-Up & Go (agility/dynamic balance); 2-Minute Step Test (endurance); and Hand Grip Strength.

Vegetable consumption was assessed using the National Cancer Institute Diet History Questionnaire, while physical activity was self-reported using the Godin Leisure-Time Exercise Questionnaire and collected via an accelerometer (a device that measures acceleration). Health-related quality of life was measured using the Medical Outcomes Study 36-item Short-Form Health Survey (SF-36).  Body measurements included height, weight, and waist circumference. Participants’ toenail clippings were analyzed for levels of cortisol, which measures levels of chronic stress. Their blood samples were assessed for biomarkers, including measurements of telomerase activity, which measures healthful aging, and interleukin 6 levels, which indicates levels of inflammation.

Study findings:  

The trial enrolled 82 breast cancer survivors (60% from the cancer registry and 40% from self referral).  Participants were White (60) or African American (22). The majority were well educated, employed, married and living with other family members. Most lived in urban rather than rural areas. Most participants had been diagnosed with localized breast cancer; mean time from diagnosis was 5 years. Most individuals were overweight or obese and living with multiple functional limitations. Four participants did not complete the study (2 wanted to garden immediately and refused to be wait-listed). 

The trial surpassed all benchmarks:

• 82% accrual
• 95% retention
• 100% satisfaction

Statistically significant differences between the intervention group and the control group were observed in the following:

• Self-reported physical activity
  • +14 vs -17 minutes per week
• Demonstrated improvement in 2 of 7 physical performance scores:
  • 2-Minute Step Test (21.9 vs +10 steps)
  • Arm Curl (2.7 vs +0.1 repetitions)

While not statistically significant, there was a trend toward increased physical activity +14.2 vs -17.1 minutes per week.

Statistically significant differences in the intervention group at baseline compared to the end of the study included:

• Vegetable consumption (1.5 servings per day vs 2.4 servings per day)
• Waist circumference (92.2 centimeters vs 95.3 centimeters)
• 2-Minute step test (64 steps vs 89 steps)
• 30-sec Chair Stand (12.6 rises vs 14.2 rises)
• Sit & Reach (0.2 inches vs 1.4 inches)
• Back Scratch (-3.6 inches vs -2.1 inches)
• Arm Curls (16 curls vs 18.7 curls)
• Hand Grip Strength (23.1 kilograms vs 24.4 kilograms)

Approximately 86% of participants were still gardening after 2 years.

Limitations:

Having only 82 total participants limited this study. Geographic area was also a limitation. Vegetable gardening can be done successfully during 3 of the 4 seasons in Birmingham. It can be considerably more challenging to successfully garden that much of the year in other areas of the country.

The design of the intervention was both a strength and a weakness. While the enthusiastic participation by the Alabama Cooperative Extension System Master Gardeners was a plus, the intervention required more time from the Master Gardeners than community-based classes or gardens. To ensure standardization across the study, participants were provided needed gardening supplies free of charge. This would likely limit expansion of this program. 

Conclusions:

The findings of this study suggest that mentored home-based vegetable gardening is an integrative approach that may improve vegetable consumption, physical activity and function, body weight status, and health-related quality of life outcomes for breast cancer survivors.  However, larger and geographically broader studies are needed to confirm the benefits of gardening across breast cancer survivors.

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