DII calculation
A complete description of DII has been provided by Shivappa et al.25 The index is based on 1943 articles published since 1950 to 2010 and measures the effects of 45 dietary parameters on six inflammatory biomarkers. (IL-1β, IL-6, TNF-α, CRP, IL-4, and IL-10). In fact, each one of these dietary factors received a negative score (-1) if its impact was anti-inflammatory (significantly increased IL-4 or IL-10, or reduced IL-1β, IL-6, TNF-α, CRP), a positive score (+1) if its impact was pro-inflammatory and 0 if no significant changes was observed in biomarkers. To calculate the DII score, each study participant’s dietary data was first linked to the global database that provided a robust estimate of a mean intake and a standard deviation for each of the 45 food parameters. In this study, of the 45 possible food items in the DΠ list, dietary intakes of 30 food parameters including energy, protein, carbohydrates, fiber, total fat, saturated, monounsaturated and, polyunsaturated fatty acids, omega 3 and omega 6 fatty acids, trans fats, cholesterol, vitamins A, beta carotene, E, D, C, B1, B2, B3, B6, B12, folate, zinc, selenium, magnesium, Iron (Fe), garlic, onion, and caffeine, were applied to compute the DII. To obtain the z-score, the mean global for each food parameter was subtracted from the actual intake of each food parameters and then divided by its standard deviation. To minimize the effect of “right skewing,” Z scores were converted to the centered proportion score as multiplied by 2 and subtracting 1. To acquire the food parameter-specific DII score, the final value was multiplied by its respective overall food parameter score. Subsequently, the DII score was computed by summing all food parameter-specific DII scores. The higher DII score, the more pro-inflammatory diet, while a more negative value indicated a more anti-inflammatory diet. The theoretical maximum range of DII scores was from about -8.87 to about +7.9821,25.
Assessment of sleep quality
To assess sleep quality, we applied the 18 self -reported items in Pittsburgh’s sleep quality index (PSQI) 26. The PSQI questionnaire was generated by Buysse et al. for assessment of sleep quality and detection of sleep disturbances and involved 7 subscales, including subjective sleep quality, sleep latency, sleep duration, sleep efficiency, sleep disturbances, use of sleep medication and daytime dysfunction. Scales of each subscale is ranged from 0 to 3. Moreover, the total score of these 7 parts ranges from 0 to 21. The global PSQI score over 5 is considered as poor quality of sleep. Participants were asked to respond their bed time and wake time to the nearest hour and the times were then used to compute duration of sleep39. Validity and reliability of this questionnaire have been investigated in Iran (α = 0.83 and correlation coefficient = 0.88)40.