Changes in supermarket sales during and after a staged health promotion campaign

To test the feasibility of the use of supermarket sales data in evaluating a local point of purchase intervention and to assess the impact of the intervention six and 12 months later. Staged point of purchase intervention pilot study followed by a longitudinal observational study. The study was carried out in one supermarket in Mikkeli, Finland. Foods were classified as healthier or reference products based on their labelled content of salt and saturated fat. The sales of packaged foods containing reduced amounts of salt and/or saturated fat were promoted with a stepwise increasing intervention culminating in a “heart week”. In addition all unplanned promotional activities during the intervention were surveyed. Information on the sales of both the promoted products and reference products was collected daily from the supermarket’s computer system. Direct and proportional sales of both single products and whole food groups were analysed during the intervention and at follow‐up. In addition the supermarket environment and the supermarket’s advertising in the local newspaper were checked. Short‐term variations in the sales could be seen related to the promotion activities. During the heart week the sales of actively promoted healthier products increased by 37‐49 per cent. Variations in the sales of reference products could also be seen; the proportional sales of some healthier products declined significantly when the reference products were actively promoted. The supermarket environment was still affected by the intervention at both follow‐ups. The mean percentage salt content of the weekly sales had declined in all food groups and the mean percentage fat content had either declined or remained unchanged. Computerised sales data provide a useful and rapid means of evaluating supermarket based interventions. The intervention had an impact on the supermarket environment which was visible at follow‐up.