A nonlinear association and threshold effect of healthy eating index-2015 with hypertension in US children and adolescents: a cross-sectional analysis of NHANES 1999–2020

Pediatric hypertension is an increasingly recognized health concern with long-term cardiovascular implications. Diet quality is a modifiable factor that may influence blood pressure in youth. However, research on the association between diet quality and hypertension in Children and Adolescents remains limited. This study aims to assess the potential nonlinear association between diet quality, measured by the Healthy Eating Index 2015 (HEI-2015) score, and the potential threshold effect with hypertension in US Children and Adolescents. We conducted a cross-sectional study using data from the National Health and Nutrition Examination Survey (NHANES) 1999–2020. A total of 17,528 participants aged 8–18 years were included after excluding those with missing diet or blood pressure data and other ineligible cases. Diet quality was assessed by Healthy Eating Index-2015(HEI-2015) scores (range 0-100). Multivariable logistic regression was used to evaluate the association between HEI-2015 and hypertension. We examined potential non-linear relationships using a two-piecewise linear spline approach to identify any threshold effect. Subgroup and sensitivity analyses were performed to assess the robustness of the findings. The analysis included 17,528 children and adolescents aged 8–18 years from NHANES 1999–2020. The prevalence of hypertension was 6.14% (n = 1,076). The participants were classified according to HEI-2015 tertiles (T1:12.36–41.47; T2:41.47–51.28; T3: 51.28–95.65.). Compared with T2 and T3 group, participants in the lowest tertile of the HEI-2015, had higher prevalence of hypertension (6.73% vs. 6.23% and 5.56%). Specifically, below an HEI-2015 score of 65.13, each 10-point increase in HEI-2015 was associated with a 7% lower prevalence of hypertension (adjusted OR = 0.93, 95% CI: 0.87–0.99; p = 0.023). In contrast, above this threshold (HEI-2015 ≥ 65.13), each 10-point increase was associated with a much higher (52%) prevalence of hypertension(OR = 0.48, 95% CI: 0.28–0.83; p = 0.009). This analysis reveals a nonlinear association between HEI-2015 and pediatric hypertension, with an inflection point identified at an HEI-2015 score of ≈ 65. A formal test for threshold nonlinearity was significant (p = 0.012), confirming a change in slope at an HEI-2015 score of ≈ 65. Sensitivity analyses yielded consistent results. In this cross-sectional study, a higher HEI-2015 score was nonlinearly associated with a lower prevalence of hypertension in US children and adolescents, with an observed inflection point near a score of 65. This finding provides a specific, quantifiable hypothesis for future prospective studies investigating dietary thresholds for hypertension prevention in children and adolescents. Evidence supporting specific, quantifiable dietary thresholds for hypertension prevention in children and adolescents remains limited. The study identifies a specific HEI-2015 score threshold (≈65) that maybe associated with a lower prevalence of hypertension in children and adolescents. The study provides a data-derived target (HEI-2015≈65), which establishes a hypothesis for future longitudinal and intervention studies to validate its predictive value and explore its potential utility in preventing hypertension in children and adolescents.