2023 HSR&D/QUERI National Conference

1148 — Is this Patient Following the Recommended Diet? Validity and Reliability of a Brief Dietary Stage of Change Instrument

Lead/Presenter: Andrew Nicholson
All Authors: Nicholson A (VA NY Harbor Healthcare System/NYU Grossman School of Medicine), Pappalardo L (VA NY Harbor Healthcare System) Wang B (VA NY Harbor Healthcare System) Wylie-Rosett J (Albert Einstein College of Medicine/VA NY Harbor Healthcare System) Natarajan S (VA NY Harbor Healthcare System/NYU Grossman School of Medicine)

Hypertension is the most common chronic condition affecting Americans. The Dietary Approaches to Stop Hypertension (DASH) diet can reduce systolic blood pressure (BP) by approximately 8 mmHg, which is equivalent to a potent BP-lowering drug. Providers routinely provide dietary advice to patients but assessing diet is difficult, especially in busy clinical settings. We evaluated the validity and reliability of a 3-item dietary stage of change (DSOC) questionnaire that was used to stage participants in a successful intervention trial to control BP.

The DSOC questionnaire assessed participant readiness to adhere to the DASH diet based on the transtheoretical model stages of change. After describing the DASH diet, participants were asked how many days a week they adhered to this diet. If they were adherent, they were asked when they became adherent, and if not adherent, they were asked when they planned to start adhering. Based on their responses, participants were categorized as: precontemplation, contemplation, preparation, action and maintenance. Later stages (action and maintenance stages) indicate current adherence. The Willett Food Frequency Questionnaire (FFQ) was used to calculate DASH adherence score. Dietary sodium intake, a critical part of the DASH diet, was assessed using urinary sodium/creatinine ratio (UNa/UCr). We compared baseline characteristics by adherence group (adherent vs. non-adherent) including comparisons for sociodemographic characteristics, body mass index (BMI), the overall DASH score, and key clinical measures. We evaluated criterion validity by assessing if DSOC is associated with DASH scores in total (Kruskal-Wallis test) and by domain (Mann-Whitney test). Spearman’s Correlation (Rho) was used to evaluate: a) convergent validity by comparing DSOC to UNa/UCr, b) discriminant validity by comparing DSOC to Psychosocial Support for Exercise Participation, and c) test-retest reliability by comparing baseline data to 3-month follow-up.

At baseline (n = 533), later dietary stages of change were associated with higher DASH adherence scores (Kruskal-Wallis p < 0.0001). Adherent individuals appeared to be older, have slightly lower BMI, and were more likely to be in Action or Maintenance stages of change for exercise as compared to non-adherent individuals (p < 0.05). Participants in adherent stages had higher DASH scores in total (p < 0.0001) and by domain (all p-values < 0.05). Baseline DSOC was associated with UNa/UCr (Rho -0.11, p = 0.019), and not associated with Psychosocial Support for Exercise Participation (Rho 0.05, p = 0.25). Finally, baseline DSOC was correlated with 3-month DSOC (Rho 0.21, p = 0.0087).

The DSOC questionnaire is valid and reliable in assessing adherence to the DASH diet in adults with hypertension. This short 3-item survey can swiftly categorize individuals into stages, and thereby as adherent or non-adherent, even in busy clinical settings.

This 3-item dietary assessment presents a practical alternative to more time-consuming dietary assessments and can be made suitable to integrate into clinical care, not just for adults with hypertension, but also for those with other chronic conditions like diabetes or cardiovascular disease. Furthermore, DSOC questions can be easily administered by phone, which can facilitate the implementation of remote dietary assessment and interventions.