Statistical Association Between Dietary Quality and Risk of Chronic Diseases

Diet quality is believed to be associated with risks of multiple chronic diseases, yet evidence based on different dietary scoring systems needs to be compared and integrated within a unified framework. Using nationally representative NHANES 2017–March 2020 data, we constructed a composite dietary Z-score to assess its associations with cardiovascular disease, type 2 diabetes and obesity. Individual‐level HEI-2015, Mediterranean Diet Score (MDS), and DASH scores were standardized using survey-weighted means and standard deviations under the complex sampling design, then summed to form the composite diet Z-score (Zsum). We fitted design-weighted multivariable logistic regression models in three stages: M1 unadjusted; M2 adjusted: M1 + age, sex, race/ethnicity; M3 extended the M2 specification by adjusting for education, poverty-income ratio, smoking status, alcohol consumption, and physical activity level. The primary exposure was Zsum per +1 SD, supplemented by tertile analyses (Low/Mid/High; Low as reference) and trend tests. Results remained robust after accounting for timing and season. Future longitudinal studies with causal inference are warranted to verify directionality and quantify preventable risk.