Shuailong Li, Y X Li, Xiaowei Yu, Zhixian Liu, Long Li, Jingjing Liu, Haibin Yuan, Qiang Luo
Background Type 2 diabetes mellitus (T2DM) is associated with sleep disturbances, inflammation, and gut dysbiosis, potentially modifiable by diet. This study examined associations between the dietary phytochemical index (DPI), sleep quality, systemic inflammation, and oxidative stress markers in adults with T2DM. Methods In this cross-sectional study, 675 adults with T2DM (aged 35–75 years) were recruited. DPI was calculated from a validated Food Frequency Questionnaire. Objective sleep was assessed via BodyMedia SenseWear armband (duration, efficiency, latency, WASO); subjective sleep via Pittsburgh Sleep Quality Index (PSQI). Inflammatory markers (CRP, IL-6, TNF-α), oxidative stress (MDA, TAC, SOD), and hormones (melatonin, cortisol) were measured. Linear regression and mediation analyses were performed. Results Participants in the highest DPI quartile (Q4) had longer sleep duration (422.69 ± 20.01 vs. 367.47 ± 43.36 min, p < 0.001), shorter sleep latency (11.9 ± 2.47 vs. 19.1 ± 7.8 min, p < 0.001), lower wake-after-sleep-onset (39.44 ± 4.09 vs. 52.3 ± 9.64 min, p < 0.001), higher sleep efficiency (90.21 ± 3.14 vs. 84.83 ± 6.68%, p < 0.001), and lower PSQI scores (4.49 ± 1.1 vs. 6.81 ± 1.5, p < 0.001) compared with Q1. Inflammatory markers were lower in Q4: CRP (1.90 ± 0.40 vs. 3.60 ± 0.90 mg/L), IL-6 (3.28 ± 0.58 vs. 5.07 ± 1.02 pg./mL), and TNF- α (4.71 ± 0.55 vs. 6.59 ± 1.13 pg./mL, all p < 0.001). Higher DPI was also associated with more favorable oxidative stress profiles and hormone concentrations. Conclusion Higher DPI scores is associated with better sleep quality, and lower systemic inflammation in adults with T2DM. These findings highlight the potential role of phytochemical-rich diets in supporting sleep quality and metabolic health among adults with type 2 diabetes; however, prospective randomized controlled trials are required to confirm these associations and to establish causality.