Association between dietary phytochemical index, inflammation and oxidative stress with sleep duration and sleep quality in Iranian adults

We aimed to explore the link between dietary phytochemical index (DPI) and sleep quality/duration, along with oxidative stress and inflammatory biomarkers in Iranian adults. The present cross-sectional investigation was carried out on 535 adults (54% male) with a mean age of 42.6 years. Sleep quality and duration were assessed using the Pittsburgh Sleep Quality Index, and dietary intake was evaluated using a 168-item food frequency questionnaire. DPI was calculated as a percentage of energy intake derived from phytochemical-rich foods. An overnight fasting blood sample was collected from each participant to evaluate serum malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GPX), and high-sensitivity C-reactive protein (hs-CRP) levels. Participants in the third tertile of DPI had 43% lower odds of having short sleep duration (OR = 0.57, 95%CI: 0.32–0.99) and 53% lower odds of having poor sleep quality (OR = 0.47, 95%CI: 0.26–0.86). Regarding specific domains of poor sleep quality, an inverse association was observed between sleep latency (OR = 0.39, 95%CI: 0.17–0.89) and sleep disturbances (OR = 0.40, 95%CI: 0.16–1.02). Higher scores of DPI were associated with marginally lower odds of having short sleep duration in overweight/obese individuals (OR = 0.55, 95%CI: 0.27–1.09) and males (OR = 0.42, 95%CI: 0.18–1.01). A significant inverse relationship was observed between DPI and having poor sleep quality in normal-weight subjects (OR = 0.20, 95%CI: 0.06–0.74) and females (OR = 0.40, 95%CI: 0.17–0.94). A marginally inverse association was observed between each tertile increment in DPI and hs-CRP levels (B (non-standardized β) =-0.31 mg/L, 95%CI: -0.64, 0.01; P = 0.06). Individuals with good quality of sleep also had lower serum levels of MDA than those with poor quality of sleep (162.0 vs. 185.5 nmol/mL; P = 0.01). However, no significant association was observed regarding SOD, GPX, and hs-CRP levels and sleep quality. Iranian adults with higher DPI scores had lower odds of having short sleep duration and poor sleep quality. MDA and hs-CRP might be intermediate factors for this association.