Objective:To evaluate the association between three behavioural economics ‘nudges’ and store sales of promoted healthier foods.Design:Multiple interrupted time series.Setting:Two predominantly rural counties in central North Carolina, USA.Participants:Aggregated store transaction data from two grocery stores (one intervention, one control) and two convenience stores (one intervention, one control) were analysed using ANOVA to examine the association between three ‘nudges’ and store sales of promoted items. The nudges included: a ‘cognitive fatigue’ experiment, in which floor arrows guided customers to the produce sections; a ‘scarcity’ experiment, in which one sign in one area of the produce section portrayed a ‘limited amount’ message; and a ‘product placement’ experiment, where granola bars were moved into the candy bar aisle.Results:In convenience stores, there were no significant differences between sales of the promoted items during the intervention period for any of the nudges when implemented individually. However, compared with baseline sales, implementation of all three nudges simultaneously was associated with an increase in sales during the intervention period based on proportional computations (P = 0·001), whereas no significant changes in sales were observed in the control convenience store. Among the grocery stores, there were no significant differences in sales during the intervention period for any of the nudges or the combined intervention compared with baseline sales.Conclusions:Implementing three nudges concurrently in a convenience store setting may increase sales of promoted items. However, before stores consider implementing these nudges to increase sales of nutritious foods, additional research is warranted.

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Natural experiments are often used for answering research questions in which randomization is implausible. Effective recruitment strategies are well documented for observational cohort studies and clinical trials, unlike recruitment methods for time-sensitive natural experiments. In this time-sensitive study of the impact of a minimum wage policy, we aimed to recruit 900 low-wage workers in Minneapolis, Minnesota, and Raleigh, North Carolina. We present our recruitment strategies, challenges, and successes for participant screening and enrollment of a difficult-to-reach population.

Objective: In 2018, Minneapolis began phased implementation of an ordinance to increase the local minimum wage to $15/hour. We sought to determine whether the first phase of implementation was associated with changes in frequency of consumption of fruits and vegetables, whole grain-rich foods, and foods high in added sugars among low-wage workers. Design: Natural experiment. Setting: The Wages Study is a prospective cohort study of 974 low-wage workers followed throughout the phased implementation of the ordinance (2018-2022). We used difference-in-difference analysis to compare outcomes among workers in Minneapolis, Minnesota, to those in a comparison city (Raleigh, North Carolina). We assessed wages using participants’ pay stubs and dietary intake using the National Cancer Institute Dietary Screener Questionnaire. Participants: Analyses use the first two waves of Wages data (2018 [baseline], 2019) and includes 267 and 336 low-wage workers in Minneapolis and Raleigh (respectively). Results: After the first phase of implementation, wages increased in both cities, but the increase was $0.82 greater in Minneapolis (p=0.02). However, the first phase of the policy’s implementation was not associated with changes in daily frequency of consumption of fruits and vegetables (IRR=1.03, 95% CI: 0.86-1.24, p=0.73), whole grain-rich foods (IRR=1.23, 95% CI: 0.89-1.70, p=0.20), or foods high in added sugars (IRR=1.13, 95% CI: 0.86-1.47, p=0.38) among workers in Minneapolis compared to Raleigh. Conclusions: The first phase of implementation of the Minneapolis minimum wage policy was associated with increased wages, but not with changes in dietary intake. Future research should examine whether full implementation is associated dietary changes.

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