This study aimed to investigate the association between adherence to the Dietary Approaches to sleep quality and Stop Hypertension diet (DASH), sleep duration, as well as markers of oxidative stress and inflammation in Iranian adults. This cross-sectional study, conducted in 2021, included 535 participants. Dietary intake was evaluated using a validated 168-item food frequency questionnaire, and participants’ adherence to the DASH diet was estimated via a DASH score. Sleep quality and duration were assessed using the Pittsburgh Sleep Quality Index (PSQI). Fasting blood samples were collected to measure serum biomarkers of inflammation and oxidative stress. Individuals with higher levels of DASH diet adherence (relative to those with lower adherence) showed lower risks of experiencing poor sleep quality and short sleep duration [fully-adjusted model for for short sleeping: ORT3 vs. T1 = 0.66; 95%CI: 0.45–0.96; poor sleep quality: ORT3 vs. T1 = 0.64; 95%CI: 0.44–0.94]. Such associations appeared stronger among female participants [fully-adjusted model for for short sleeping: ORT3 vs. T1 = 0.12; 95%CI: 0.03–0.55; poor sleep quality: ORT3 vs. T1 = 0.14; 95%CI: 0.04–0.56]. Additionally, moderate adherence was associated with reduced likelihood of delayed sleep onset [fully-adjusted model: ORT2 vs. T1 = 0.39; 95%CI: 0.15–0.98], while higher adherence correlated with lower odds of sleep disturbances [fully-adjusted model: ORT3 vs. T1 = 0.26; 95%CI: 0.08–0.84]. After full adjustment, DASH diet adherence displayed no significant relationship with markers of oxidative or inflammation stress (p ≥ 0.05).Among middle-aged Iranian adults, greater adherence to the DASH diet was related to enhanced sleep quality and longer sleep duration, particularly in women. The examined biomarkers did not mediate these associations
