2-1. Study design
In this cross-sectional study, 181 single women aged 18-25 years, were recruited from 5 different universities in Birjand, South Khorasan, Iran in January 2020. We excluded women with any acute or chronic disease. The Ethics Committee of Birjand University of Medical Sciences approved the study. All participants provided written informed consent,
2-2. Dietary assessment
A valid and reliable 65 item semi-quantitative food frequency questionnaire was used to assess the food intake of subjects over the previous year (20, 21). Experienced dietitians, asked participants to describe their consumption frequency for each food item during the previous year on a daily, weekly, monthly, rarely or never basis. Food analysis was done using Diet Plan 6 software (forest field Software Ltd., Horsham West Sussex, UK). The DASH dietary pattern scoring was determined according to the method of Fung et al (17). The DASH score, focusing on 8 components: high intake of vegetables, fruits, legumes and nuts, whole grains and low intake of sodium, low-fat dairy products, red and processed meats, and sweetened beverages. For the composition of DASH score, values of 1 or 5 were assigned to each nutritional component using the quintiles as cut-off values. For vegetables, fruits, legumes and nuts, whole grains and low-fat dairy products the lowest quintile was scored 1 point and the highest quintile was scored 5 points. For red and processed meats, salt and sweetened beverages the scoring was inverted. Finally, the score of each group was integrated and with a value of 8 (minimal adherence) to 40 (maximal adherence).
2-3. Demographic and anthropometric analysis
General demographic and anthropometric data such as age, height, weight, waist circumference, hip circumference, systolic blood pressure (SBP) and, diastolic blood pressure (DBP) were collected in all contributors by employing standardized protocols (22). Body mass index (BMI) was computed as weight in kilograms divided with height in meters squared (5). Blood samples were collected of all participants since nightly fasting. A complete blood count (CBC) was operated as segment of the evaluation of hematological parameters using the SysmexK-800.
2-4: Neuropsychological analysis
2-4-1. Cognitive Ability Assessment (CAA):
The Cognitive Abilities Questionnaire (CAQ) is a valid and reliable tool which estimate 7 distinctive abilities including: memory, inhibitory control and selective attention, decision making, planning, sustained attention, social cognition and cognitive flexibility (23). This instrument is comprised of 30 items, each rated on 1- 5 to yield a total score ranging from 30 to 150. Higher scores reflected better cognitive performance (24).
2-4-2. Depression Anxiety Stress Scales (DASS):
Depression Anxiety and Stress Scale (DASS-21) is a valid and reliable tool to measure status of negative well-beings (25). This questionnaire consists of 21 items with 3 subscales (each consist of 7 questions) in which each items is rated on a 4-point Likert scale 0-3 measuring severity of depression, anxiety and stress. Because DAS-21 is the brief version of DAS-42; the total score of each sub-class must be doubled. Higher score correlated with severe negative emotional. The validity and reliability of the DASS-21 has been previously validated in an Iranian population (26).
2-4-3. Quality of Life (QoL)
The Short Form health survey (SF-12) derivative from the SF-36 is a widely reliable tool for measuring of physical and mental components of QoL. Validity and, reliability from this tool has been established in Iranian population (27). The SF-12 consists of 12 questions covering 8 health domains with higher scores indicating a better health dependent QoL (28).
2-4-4. Insomnia Severity Index (ISI)
This tool is a 7 item itself-detail instrument measuring the nature, intensity and, effect from insomnia. The areas assessed are: severity of sleep initiation, sleep maintenance, and timely morning awakening complications, degree of sleep satisfaction and interfering of sleep difficulties with daytime activities. A 5-level Likert score is applied to level ever part (0 = no problem; 4 = many problem) efficiency all scales ranging of 0 to 28. The Persian version of this tool with good reliability and validity for Iranian population was established in current study (29, 30).
2-4-5. Epworth Sleepiness Scale (ESS)
The Epworth Sleepiness Scale (ESS) is an 8-item reliable questionnaire for assessing the individual's daytime sleepiness propensity. Each item rated on 4-point Likert scale (0 to 3) which measures the intensity of sleepiness in daily life conditions. Total scores range from 0 to 24 and higher scores correlated to intensive sleepiness (31, 32).
2-4-6. Short sleep duration and difficult sleep initiating
Sleep signs were evaluated based on 2 asks reporting to sleep during the past month: (1) “Do you have difficulty falling asleep at night?” (2) “How many times have you woken up early and, have trouble getting back to sleep?” Short sleep duration was determined if a subject slept for fewer than 5 h/day, once or more a week (33, 34). Difficult sleep initiating was determined as had problems falling asleep in half an hour one time or rather a week (35-38).
2-5. Statistical analysis
All statistical analyses were conducted by using SPSS, version 16 software packages. Data were evaluated for normality by applying the Kolmogorov-Smirnov test. One-way ANOVA test was used for comparison of continues variables with normal distribution across tertiles of DASH-style diet score. Depression, anxiety, stress, insomnia and sleepiness scores were divided into two categories (No/Minimal state and some degree of disorder) regarding to scores. Acquiring a score below median cut of QoL score was considered as low QoL. The correlation between component of the DASH diet score and neuro-psychological test scores was evaluated using Pearson correlation analysis. Multinomial logistic regression was used to evaluate the association between adherence to DASH diet and neuropsychological difficulties and we adjusted all variables for age, BMI and energy intake. P-value <0.05 was set as significant level.