Abstract
BackgroundFor community interventions to be effective in real-world conditions, participants need to have sufficient exposure to the intervention. It is unclear how the dose and intensity of the intervention differ among study participants in low-income areas. We aimed to understand patterns of exposure to different components of a multi-level multi-component obesity prevention program to inform our future impact analyses.MethodsB’more Healthy Communities for Kids (BHCK) was a community-randomized controlled trial implemented in 28 low-income zones in Baltimore in two rounds (waves). Exposure to three different intervention components (corner store/carryout restaurants, social media/text messaging, and youth-led nutrition education) was assessed via post-intervention interviews with 385 low-income urban youths and their caregivers. Exposure scores were generated based on self-reported viewing of BHCK materials (posters, handouts, educational displays, and social media posts) and participating in activities, including taste tests during the intervention. For each intervention component, points were assigned for exposure to study materials and activities, then scaled (0–1 range), yielding an overall BHCK exposure score [youths: mean 1.1 (range 0–7.6 points); caregivers: 1.1 (0–6.7), possible highest score: 13]. Ordered logit regression analyses were used to investigate correlates of youths’ and caregivers’ exposure level (quartile of exposure).ResultsMean intervention exposure scores were significantly higher for intervention than comparison youths (mean 1.6 vs 0.5, p < 0.001) and caregivers (mean 1.6 vs 0.6, p < 0.001). However, exposure scores were low in both groups and 10% of the comparison group was moderately exposed to the intervention. For each 1-year increase in age, there was a 33% lower odds of being highly exposed to the intervention (odds ratio 0.77, 95% confidence interval 0.69; 0.88) in the unadjusted and adjusted model controlling for youths’ sex and household income.ConclusionTreatment effects may be attenuated in community-based trials, as participants may be differentially exposed to intervention components and the comparison group may also be exposed. Exposure should be measured to provide context to impact evaluations in multi-level trials. Future analyses linking exposure scores to the outcome should control for potential confounders in the treatment-on-the-treated approach, while recognizing that confounding and selection bias may exist affecting causal inference.Trial RegistrationClinicalTrials.gov, NCT02181010. Retrospectively registered on 2 July 2014.
Highlights
For community interventions to be effective in real-world conditions, participants need to have sufficient exposure to the intervention
This study aimed to identify the patterns and determinants of the different levels of exposure to the B’more Healthy Community for Kids (BHCK) intervention, a community-based randomized childhood obesity prevention trial intervening at multiple levels of the food system in low-income urban areas of Baltimore City in two rounds [18]
Our findings are important to implementation science, as they may inform pilot or feasibility trials of future large environmental community interventions prior to the implementation of the main program to better understand how the population perceives the activities and the dose and intensity needed in the setting
Summary
For community interventions to be effective in real-world conditions, participants need to have sufficient exposure to the intervention. It is unclear how the dose and intensity of the intervention differ among study participants in low-income areas. It is suggested that multi-level multi-component (MLMC) interventions are more effective than single-component interventions, due to synergistic effects between multiple intervention components [4, 5] To achieve these effects, MLMC interventions need to reach the population of interest in sufficient intensity, i.e., achieve adequate exposure. The evaluation of a program’s implementation needs to be systematically measured and evaluated, as it informs research into practice gaps [6], allowing replication in real-world settings and large-scale public health dissemination [7]. Exposure (dose received) is rarely measured, but it allows researchers to understand how well a program has reached its intended audience from the participants’ perception of their personal exposure and the extent to which they actively engaged with the research activities and materials [12]
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