CAPS on the move: Crafting an approach to recruitment for a randomized controlled trial of community gardening

A process evaluation of a randomized-controlled trial of community gardening to improve health behaviors and reduce stress and anxiety

As part of the Community Activation for Prevention (CAPS) randomized controlled trial (RCT) of community gardening, we conducted a process evaluation to assess the implementation of a community gardening intervention over nine months, as measured by reach, fidelity (delivery, receipt, enactment), and acceptability. Evaluation instruments included repeated semi-structured interviews with study participants, direct observation of community garden sites, and an exit survey of participants. Primary outcomes were diet, physical activity, and anthropometry; secondary outcomes were stress and anxiety. The CAPS trial included 291 participants (19% non-white; 34% Hispanic/Latino; 35% without a college degree; 58% with income < $50,000 per year). Intervention delivery and receipt were high for environmental supports. Garden social events were offered by 73% of gardens, although only 48% of intervention participants reported attending these events. Of the 145 participants assigned to the gardening intervention, 97 (67%) reported gardening the entire season and reported visiting the community garden a median of 90 min per week (range: 0-840). Of the participants who completed the exit survey (48%), 89% were highly satisfied with the overall garden experience. The CAPS trial was favorably received and implemented with high fidelity, supporting the validity of the trial outcomes. These findings suggest that community gardens are a viable health promotion strategy that can be successfully implemented among new gardeners from diverse backgrounds. Strategies that engage new gardeners in the social aspects of the garden environment and connect gardeners with garden "mentors" or "buddies" to ensure new gardeners achieve success in their first years of gardening are recommended.Trial registration: NCT03089177. Registered 24 March 2017, https://clinicaltrials.gov/study/NCT03089177 .

Effects of a community gardening intervention on diet, physical activity, and anthropometry outcomes in the USA (CAPS): an observer-blind, randomised controlled trial

BACKGROUND

Unhealthy diet, physical inactivity, and social disconnection are important modifiable risk factors for non-communicable and other chronic diseases, which might be alleviated through nature-based community interventions. We tested whether a community gardening intervention could reduce these common health risks in an adult population that is diverse in terms of age, ethnicity, and socioeconomic status.

METHODS

In this observer-blind, randomised, controlled trial, we recruited individuals who were on Denver Urban Garden waiting lists for community gardens in Denver and Aurora (CO, USA), aged 18 years or older, and had not gardened in the past 2 years. Participants were randomly assigned (1:1), using a randomised block design in block sizes of two, four, or six, to receive a community garden plot (intervention group) or remain on a waiting list and not garden (control group). Researchers were masked to group allocation. Primary outcomes were diet, physical activity, and anthropometry; secondary outcomes were perceived stress and anxiety. During spring (April to early June, before randomisation; timepoint 1 [T1]), autumn (late August to October; timepoint 2 [T2]), and winter (January to March, after the intervention; timepoint 3 [T3]), participants completed three diet recalls, 7-day accelerometry, surveys, and anthropometry. Analyses were done using the intention-to-treat principle (ie, including all participants randomly assigned to groups, and assessed as randomised). We used mixed models to test time-by-intervention hypotheses at an α level of 0·04, with T2 and T3 intervention effects at an α level of 0·005 (99·5% CI). Due to potential effects of the COVID-19 pandemic on outcomes, we excluded all participant data collected after Feb 1, 2020. This study is registered with ClinicalTrials.gov, NCT03089177, and data collection is now complete.

FINDINGS

Between Jan 1, 2017, and June 15, 2019, 493 adults were screened and 291 completed baseline measures and were randomly assigned to the intervention (n=145) or control (n=146) groups. Mean age was 41·5 years (SD 13·5), 238 (82%) of 291 participants were female, 52 (18%) were male, 99 (34%) identified as Hispanic, and 191 (66%) identified as non-Hispanic. 237 (81%) completed measurements before the beginning of the COVID-19 pandemic. One (<1%) participant in the intervention group had an adverse allergic event in the garden. Significant time-by-intervention effects were observed for fibre intake (p=0·034), with mean between-group difference (intervention minus control) at T2 of 1·41 g per day (99·5% CI -2·09 to 4·92), and for moderate-to-vigorous physical activity (p=0·012), with mean between-group difference of 5·80 min per day (99·5% CI -4·44 to 16·05). We found no significant time-by-intervention interactions for combined fruit and vegetable intake, Healthy Eating Index (measured using Healthy Eating Index-2010), sedentary time, BMI, and waist circumference (all p>0·04). Difference score models showed greater reductions between T1 and T2 in perceived stress and anxiety among participants in the intervention group than among those in the control group.

INTERPRETATION

Community gardening can provide a nature-based solution, accessible to a diverse population including new gardeners, to improve wellbeing and important behavioural risk factors for non-communicable and chronic diseases.

FUNDING

American Cancer Society, University of Colorado Cancer Centre, University of Colorado Boulder, National Institutes of Health, US Department of Agriculture National Institute of Food and Agriculture, Michigan AgBioResearch Hatch projects.