Educational inequality in the Dietary Approach to Stop Hypertension diet in the UK: evaluating the mediating role of income

Apparent differences in the adoption of the Dietary Approach to Stop Hypertension (DASH) diet have been reported between less and more educated individuals. However, the mediating role of income has not been clarified. In this study, we aimed at quantifying the mediating effect of income on the relationship between education and the DASH score in the UK population. We analysed data on 4864 subjects aged 18 years and older collected in three waves of the National Diet and Nutrition Survey (2008-2016). The DASH score was calculated using sex-specific quintiles of DASH items. We carried out a counterfactual-based mediation analysis to decompose the total effect of education on DASH score into average direct effect and average causal mediation effect mediated by income. We found that the overall mediating effect of income on the relationship between education and the DASH score was only partial, with an estimated proportion mediated ranging between 6 and 9 %. The mediating effect was higher among females (11·6 %) and younger people (17·9 %). Further research is needed to investigate which other factors may explain the socio-economic inequality in the adoption of the DASH diet in the UK.