Department of Epidemiology, Biostatistics, and Occupational Health.
Surveillance Laboratory, McGill Clinical and Health Informatics.
Int J Epidemiol. 2018 Dec 1;47(6):1877-1886. doi: 10.1093/ije/dyy108.
Price discounting is a marketing tactic used frequently by food industries and retailers, but the extent to which education modifies the effect of discounting on the purchasing of unhealthy foods has received little attention. We investigated whether there was a differential association of price discounting of soda with store-level soda purchasing records between 2008 and 2013 by store-neighbourhood education in Montreal, Canada.
Using data on grocery purchase transactions from a sample of supermarkets, pharmacies, supercentres and convenience stores, we performed an ecological time-series analysis, modelling weekly store-level sales of soda as a function of store-level price discounting, store- and neighbourhood-level confounders and an interaction term between discounting and categorical education in the neighbourhood of each store.
Analysis by store type (n = 18 743, 12 437, 3965 and 49 533 store-weeks for superstores, pharmacies, supercentres and convenience stores, respectively) revealed that the effect measure modification of discounting by neighbourhood education on soda purchasing was lower in stores in the more educated neighbourhoods, most notably in pharmacies: -0.020 [95% confidence interval (CI): -0.028, -0.012] and -0.038 (95% CI: -0.051, -0.025), for middle- and high-education categories, respectively). Weaker effect modification was observed in convenience stores. There was no evidence of effect modification in supercentres or superstores.
Price discounting is an important environmental risk factor for soda purchasing and can widen education inequalities in excess sugar intake across levels of education. Interventions to regulate price discounting warrant further investigation as a public health strategy to improve population nutrition, particularly in lower-education neighbourhoods.
价格折扣是食品行业和零售商经常采用的营销策略，但教育在多大程度上改变了折扣对购买不健康食品的影响，这方面的研究还很少。我们调查了在加拿大蒙特利尔，价格折扣对苏打水的影响是否因商店所在社区的教育程度不同而有所不同。
我们利用超市、药店、大型购物中心和便利店的杂货购买交易数据，采用生态时间序列分析方法，将每周商店层面的苏打水销售量作为商店层面价格折扣、商店和社区层面混杂因素以及商店所在社区教育程度的分类与折扣之间的交互项的函数进行建模。
按商店类型（超级市场、药店、大型购物中心和便利店分别为 18743、12437、3965 和 49533 个商店周）进行分析的结果显示，折扣对苏打水购买的影响在教育程度较高的社区的商店中受到的调节作用较小，在药店中最为明显：中教育程度类别为-0.020（95%置信区间：-0.028，-0.012），高教育程度类别为-0.038（95%置信区间：-0.051，-0.025）。在便利店中观察到较弱的调节作用。在大型购物中心和超级市场中没有证据表明存在调节作用。
价格折扣是苏打水购买的一个重要环境风险因素，它可以扩大不同教育程度人群过度摄入糖分的教育不平等。作为改善人口营养的公共卫生策略，进一步调查监管价格折扣的干预措施是合理的，特别是在教育程度较低的社区。
