Association Between DASH Diet Quality and 24 h Ambulatory Blood Pressure in Treatment-Naive Adults Referred for Diagnostic Monitoring: A Cross-Sectional Study

Background/Objectives: Dietary adherence to the Dietary Approaches to Stop Hypertension (DASH) pattern is associated with lower blood pressure; however, most prior studies have relied on office-based measurements and non-specific dietary assessment tools. This study examined the association between DASH diet quality, assessed by the validated DASH-Q questionnaire, and 24-h ambulatory blood pressure in treatment-naive adults referred for diagnostic ambulatory blood pressure monitoring (ABPM). Materials and Methods: This cross-sectional study enrolled 227 consecutive treatment-naive adults referred for diagnostic 24-h ABPM at a cardiology outpatient clinic. DASH diet quality was assessed using the validated Turkish version of the DASH-Q questionnaire and categorized as low (<36), moderate (36–49), or high (≥50). Hypertension was defined by ABPM-based thresholds. Multivariable linear regression was performed to identify independent predictors of 24-h mean systolic and diastolic blood pressure, and binary logistic regression was used to evaluate independent predictors of ABPM-defined hypertension, with both models adjusted for age, sex, BMI, smoking, physical activity, and self-reported discretionary salt-adding behavior. Results: DASH-Q total score was the sole statistically significant independent predictor of both 24-h mean systolic blood pressure (B = −1.068, 95% CI: −1.270 to −0.866; β = −0.589; p < 0.001) and diastolic blood pressure (B = −0.560, 95% CI: −0.706 to −0.414; β = −0.470; p < 0.001) in the adjusted models. Each one-unit higher DASH-Q score was also associated with 14.6% lower odds of ABPM-defined hypertension (OR = 0.854, 95% CI: 0.820–0.890; p < 0.001). Higher DASH-Q scores were further associated with a more favorable metabolic profile, including lower LDL cholesterol, triglycerides, glucose, and C-reactive protein levels. Conclusions: DASH diet quality was independently and inversely associated with 24-h ambulatory blood pressure and the odds of ABPM-defined hypertension in this treatment-naive population. Given the cross-sectional design and the possibility of reverse causality, these results should be interpreted as hypothesis-generating and require confirmation in prospective studies.