Association among Dietary Inflammatory Index, sleep quality and nutritional status in fixed daytime and rotating shift workers.

Shift work is associated with irregular eating behaviors, increased energy intake, and impaired sleep quality. Poor dietary patterns may elevate systemic inflammation, contributing to long-term metabolic and cardiovascular risks. The aim of this study was to investigate differences in the Dietary Inflammatory Index (DII), sleep quality, dietary intake, and anthropometric and body composition measures between fixed daytime workers and rotating shift workers and to examine the associations among these parameters. This cross-sectional study included 52 male workers employed at a defense industry factory in Ankara, Türkiye, who worked either fixed daytime or rotating shifts. Dietary intake was assessed using 24-h dietary recalls for three non-consecutive days, from which macronutrient and micronutrient intakes were calculated. DII scores were computed to assess the inflammatory potential of the diet. Sleep quality was evaluated using the Pittsburgh Sleep Quality Index (PSQI). Anthropometric measurements, body composition, blood pressure, and biochemical parameters, including fasting plasma glucose, lipid profile (total cholesterol, HDL-C, LDL-C, and triglycerides), C-reactive protein, and homocysteine, were measured using standardised protocols. Rotating shift workers had significantly higher total energy intake and higher daily intakes of fructose, total fat, saturated and monounsaturated fatty acids, cholesterol, and several micronutrients, including vitamin A, folate, iron, calcium, and phosphorus compared with fixed daytime workers (p < 0.05). Mean DII scores did not differ significantly between the groups (Fixed daytime: 0.2 ± 1.86; rotating shift: -0.2 ± 2.25). DII scores were positively correlated with global PSQI score (r = 0.278, p = 0.046), the PSQI sleep duration component score (r = 0.319, p = 0.021), and daytime dysfunction component score (r = 0.287, p = 0.039); however, the association between DII and overall sleep quality was no longer statistically significant after adjustment for potential confounding factors (age, BMI, smoking status, physical activity, and work schedule). These findings suggest that dietary habits, pro-inflammatory dietary patterns, and poor sleep quality may represent co-existing factors associated with metabolic risk, and addressing these factors may contribute to better overall metabolic health.