Dietary inflammatory and phytochemical indices as predictors of sleep quality, chronotype, and psychological health in adults

The dietary pattern might impact physiological and psychological health. Therefore, the present study aims to examine the associations of dietary phytochemical index (DPI) and dietary inflammatory index (DII) with chronotype, sleep, and psychological health in adults. This cross-sectional study included 628 healthy adults aged 19–64 y (mean age: 25.9 ± 9.7 y). Data on anthropometrics, physical activity, chronotype (Morningness-Eveningness Questionnaire (MEQ)), sleep quality (Pittsburgh Sleep Quality Index (PSQI)), and psychological status (Depression, Anxiety, and Stress Scale-21 (DASS-21)) were collected. Dietary intake was assessed using a validated semi-quantitative Food Frequency Questionnaire. The DPI was calculated using two different methods, one developed by McCarty and the other by Bahadoran et al. while the DII was computed based on the method developed by Shivappa et al. In the adjusted models, the DPI (according to McCarty) was positively associated with MEQ scores and negatively associated with PSQI and DASS-21 subscale scores, and increasing DPI was associated with significantly decreased odds of exhibiting mid- or evening chronotypes and poor sleep quality (p < 0.05). Although DPI (according to Bahadoran et al.) was positively associated with MEQ total score (p < 0.05), no significant associations were observed in the risk estimates for chronotype, sleep quality, and DASS-21 scores after adjustment (p > 0.05). Moreover, in the adjusted models, DII was not significantly associated with chronotype, sleep quality, or any DASS-21 sub-group (p > 0.05). A higher dietary phytochemical index was associated with a higher morningness tendency, better sleep quality, and lower levels of depression, anxiety, and stress. These findings underscore the potential link between an anti-inflammatory, phytochemical-rich dietary pattern, and psychological and physiological well-being.