2.1. Study design
A quasi-experimental (pretest- posttest with a control group) study was conducted on patients with hypertension attended to the Health Houses that regularly provided by the routine cares.
The current study was conducted in Gorgan city of Iran between June 2018 and February 2019. The study protocol was approved by the Ethics Committee of Golestan University of Medical Sciences. Patients suitable for inclusion were as follows; a definitive diagnosis by a physician, having a health record in the Health House, lack of chronic and severe complications, no other lasting diseases, aged between 30 to 65 years, no history of surgery or hospitalization in the last three months, willingness to participate in the study, lack of specific mental illnesses and no dementia, and those excluded if they did not meet the following criteria; pregnancy during the study, need a special diet, involved with diseases and absent more than two sessions in the educational interventions. Prior to the study, the informed written consent was obtained by all patients.
To collect data, a standard 12- part questionnaire was used including, 1) demographic characteristics (job, education and marital status and …), 2) nutritional knowledge (10 items, correct answers scored 2 and false, and I don’t know scored 0, ranged 0 to 20) , 3) perceived benefits (nine items), 4) perceived barriers (10 items), 5) perceived self-efficacy (10 items), 6) affects related to behavior (eight items), 7) interpersonal influences (nine items), 8) situational influences (seven items), 9) commitment to action (nine items), 10) nutritional behavior, 11) nutritional follow-up (five items). Part 3 and 4 were 4-point Likert scale and scored completely agree 4, agree 3, disagree 2, and completely disagree 1. Furthermore, parts of 6, 7, 8, 9 and 11 were 5-point Likert Scale and scored always 5, often 4, sometimes 3, rarely 2, never 1. In final, self-efficacy was tested using a 10-point continuum such that patients with lower and higher self-efficacy select number of near 1 and 10, accordingly. This self-administered questionnaire was used and validated by Kamran et al (23). According to a pilot study, reliability of the questionnaire was as follows in detail; nutritional knowledge (0.81), perceived benefits (0.77), perceived barriers (0.84), perceived self-efficacy (0.75), affects related to behavior (0.82), interpersonal influences (0.91), situational influences (0.88), commitment to action (0.73).
The primary outcomes were nutritional behavior that measured by the HPM-based standard questionnaire and 3-day diet record. While, the secondary ones were anthropometric indexes that tested using waist circumference, body weight, height, and BMI variables as well as hypertension.
2.2.2. Variable definition
Hypertension was defined as systolic blood pressure (SBP) ≥ 140 mmHg, or diastolic blood pressure (DBP) ≥ 90 mmHg (10). According to the WHO criterion, BMI categorized into 25 ≥ BMI< 30 for overweight and ≥ 30 for obesity (24).
The present study was run in four stages, including, 1) educational planning, 2) sampling, 3) intervention and 4) evaluation.
2.3.1. Educational planning
A cross-sectional study was conducted to determine the effect of Pender Health Promotion Model constructs in predicting nutritional behaviors in patients with hypertension. By exploring the data, path analysis identified the most important factors affecting nutritional behavior. In final, education content was provided according to the cross-sectional study and Dietary Approach to Stop Hypertension (DASH).
Four Health Houses were recruited. Before intervention, data were collected by distributing questionnaires about model constructs, 3-day diet record and their anthropometric indices.
2.3.3. Educational intervention
Education was just conducted in the intervention arm, including six sessions during three weeks (two sessions per week, 30 to 45 minutes for each session, and 17 patients were participated in each session). A brief overview of hypertension, symptoms, and side effects of non-controlling illness was presented by a public health student at the Health House for 10 minutes. At the end of the training sessions, nutrition education pamphlets were distributed to all study participants. Participant in the control group was only received the routine education for patients who usually provided by the health care personnel working in the Health Houses.
All participants had two and six months’ assessments by personnel who were not involved in supporting the interventions.
To measure BP, the patients were not recently indulged in any activity similar exercise or eating that may likely affect the BP, also the patients were quietly rested in a comfortable chair for 3 to 5 minutes with the upper arm at heart levels were tested. Three measurements were done in succession, separated by at least one minute (25).
Waist circumference was measured in the mid-axillary line at the midpoint between the costal margin and the iliac crest. Body weight was assessed to the closest 100 g. Height was estimated with a stadio-meter to the nearest one mm, and then BMI was calculated as weight (kg)/height(m2)(26).
Nutritional behavior was measured using 3-day diet record (two normal days and one day off) and were also coded and verified by registered dietitians. In brief, it was estimated based on the energies consumed by macro and micro-nutrients.
All measurements were performed at pre-intervention (baseline), two and six month follow-ups.
2.5. Sample size
The sample size was estimated based on the repeated measurements as follows; correction factor (R= 0.44) in accordance with 0.6 of pre-test observation number (v=1) and pre-test observation number (w=2), significance level of 0.05, statistical power 80 % and the standardized effect size of 0.2, 124 patients were estimated that with consideration of attrition risk, 136 patients (68 patients in the control arm and 68 patients in the intervention arm) were recruited.
Cluster sampling method was used such that from 80 Health Houses in the Golestan Province, 10 percent of them selected based on the systematic random sampling. Four Health Houses for the control arm and four ones for the intervention arm were enrolled. In total, 17 patients were provided with education in each Health House (68 in the control and 68 in the intervention arm).
A single-blind study was implemented such that participants were blinded after assignment to the intervention.
2.8. Data analyses
T-test was used for comparing the means of two independent groups. One-way ANOVA was performed to examine means before and after intervention. For two dependent groups paired t-test was used. Repeated Measures ANOVA was examined in independent groups to find differences between groups over time. To predict the patient's nutritional behavior based on the HPM model, Linear Regression model was also used. Data analyzed by the SPSS software for windows (version 18), moreover, nutritionist (N4) software (version 4) was used to test nutritional variables. A P-value of <0.05 was considered significant.
Kamal Mirkarimi: Preparing the manuscript, Abdurrahman Charkazi: data analyses, Alireza Heidari: preparing the manuscript, Rahman Berdi Ozouni- Davaji: implementation the education and supporting the interventions
2.9.1. Ethics approval and consent to participate
All methods were implemented in accordance with relevant guidelines and regulations. Also, all experimental protocols were approved by the Golestan University of Medical Sciences. In final, informed consent was obtained from all subjects.
2.10. Availability of data and materials
Data of the study will be provided by the corresponding author of the study through the website of the journal or by a valid email.