Abstract P429: Adiposity: Full or Partial Mediator of the Association of Diet With Blood Pressure?

Abstract

Background: Recently published results suggest body mass index (BMI) fully mediates the association of Dietary Approaches to Stop Hypertension (DASH) diet score with hypertension in women from the United Kingdom. The DASH diet has been shown to reduce systolic and diastolic blood pressure (SBP & DBP) while keeping BMI constant in United-States-(US)-based trials. Thus, we quantified the mediation of adiposity in the association of DASH diet with SBP and DBP in a US nationally representative sample. Methods: Using National Health and Nutrition Examination Survey (NHANES) data, years 2011-2018, the association of DASH score (scale: 8 - 40) with SBP and DBP was quantified with and without BMI or waist circumference (WC) in models adjusted for age, sex, education, income, and physical activity. Percent mediation was calculated from all sets of models. Results: The included sample (n=11,662) was aged 20 years or older (median 41 years), was not taking blood pressure medication, and was weighted to be representative of the US population. For SBP, in models without BMI or WC, a one-point higher DASH score was associated with a -0.21 mmHg lower SBP in the adjusted base model (p < 0.001). With the addition of BMI to the adjusted base model, the effect estimate was -0.12 mmHg (p = 0.005) for DASH score. With the addition of WC to the base model, the effect estimate was -0.13 mmHg (p=0.006) for DASH score. Thus, BMI and WC mediated 34% and 41% of the association between DASH and SBP in adjusted models, respectively. For DBP, in models without BMI or WC, a one-point higher DASH score was associated with a -0.15 mmHg lower DBP in the adjusted model (p < 0.001). With the addition of BMI to the base model, the effect estimate was -0.10 mmHg (p = 0.004). With the addition of WC to the base model, the effect estimate was -0.11 mmHg (p = 0.003) for DASH score. Thus, BMI and WC mediated 29% and 52% of the association between DASH and DBP in adjusted models, respectively. Conclusion: Adiposity is a partial mediator of the association of DASH score with SBP and DBP. The mechanisms that explain the greater mediation of WC than BMI in the association of DASH score with SBP and DBP require further elucidation. The effect of the DASH diet on blood pressure may have multiple mechanistic pathways: one that works through adiposity and others that work through non-adiposity-based mechanisms including higher potassium consumption and lower sodium consumption.