Design

This study utilized a single-group pretest and repeated posttest experimental design. The dependent variables were measured three times at intervals of 46weeks, depending upon each participants menstrual cycle (Fig.1).

Research process and timeline of data collection

Volunteers were recruited by a research assistant after flyers were posted throughout a college dormitory located in W city, Korea. Women were included if they (1) reported a score of 5 or higher on a menstrual pain scale of 10 points, (2) had not been diagnosed with any gynecologic diseases, (3) lived in a dormitory, and (4) voluntarily agreed to participate in the intervention involving collection of urine samples. Each woman with an intention to participate was informed by the research assistant to select one of three slots that would be within a week after their period, keeping in mind individual differences in the menstrual cycle. The participants were composed of nursing students in their sophomore and junior years, for whom participation in this trial was feasible and accessible, particularly for dropping off the fresh urine samples.

The study sample size was determined considering a one-tailed, Wilcoxon signed rank test, a type I error of 0.05, a statistical power of 0.80, and an effect size of 0.50. Using G*Power 3.1.9.2, this study required a total of 28 participants. Initially, 32 students were enrolled, anticipating a 10% attrition rate, and two students discontinued participation during the intervention period due to temporary withdrawal from school. Thus, there were 30 participants.

The intervention involved dietary modifications targeting reduction of fast/processed food consumption. It was composed of three parts: (1) small-group education (2) follow-up monitoring, and (3) peer support via social network communication (Table 1).

To ensure feasibility of the intervention, three groups were established and the participants selected one of the intervention slots depending upon their menstrual cycle; thus, each group was composed of 8, 9, and 13 participants, respectively. All participants received all three parts of the intervention.

The small-group education consisted of a 90-min session, which included information about EDCs and their impacts on womens reproductive health problems, self-appraisal of exposure to EDCs, recommendations for restricting EDC intake, and a self-contract. The education was provided to each group in a seminar room available for audiovisual media services by a nurse interventionist who had a masters degree and was blind to the study purpose. She was trained by the research team to deliver the educational content to each of the small groups. As human behavior is habitual and guided by automatic cognitive processes, knowledge and information were assumed to lead the women to act to protect themselves from exposure to EDCs.

Follow-up monitoring was conducted by a research assistant during the next 4weeks covering the average interval of a menstrual cycle. Four-week follow-ups were assumed to be necessary to change the individuals longstanding dietary habits [27, 28]. The participants in each group were monitored how well they adhered to the dietary modification intervention. Participants sent a weekly checklist to the assigned group assistant every Sunday. Then the research assistant replied with encouragement and praise after confirmation that participants had filled out the checklist. The checklist developed for this study was provided as Additional file 1.

Peer support via social network communication was composed of sharing their experiences and providing each other with emotional support within each small group. Peer support was planned based on a previous finding that peer recommendations positively influenced pro-environmental health behaviors in young women [28].

The outcomes measured included menstrual pain and urinary BPA levels.

Menstrual pain was measured by a 10-point pain scale to indicate the maximum pain level experienced during their menstrual cycles. At baseline and after three consecutive menstrual cycles, women marked their perceived degree of pain on a visual analogue scale (1=no pain to 10=the worst possible pain) and returned it to the research team with the urine specimens. The menstrual pain recording sheet developed for this study was provided as Additional file 2.

Urinary BPA levels were measured because it has been used as a reliable method to monitor human intake of BPA [25, 29, 30]. The measurements were made four times, at baseline before the intervention and for three menstrual cycles after the intervention. To collect the urine samples, BPA-free specimen tubes labeled with the participants identification number and the order of the cycle were distributed to the participants at baseline data collection. Women were advised to obtain at least 2mL of the first morning midstream urine, collected at their earliest convenience within one week after their period ended, and then to submit it to the research assistant that morning. Since all the participants resided in a campus dormitory, they dropped the samples at the office, which was about a 5-min walk from their dormitory, and it was then immediately frozen. As urinary BPA levels were not expected to show any significant difference according to the time lapsed from collection to analysis [31], the urine specimens were frozen until 30 samples were collected, after which the samples were sent to the Institute for Life & Environmental Technology for analysis. Urinary BPA levels were analyzed using high-performance liquid chromatography-mass spectrometry (a 6410b/Agilent; Agilent, Santa Clara, CA, USA) with corrected creatinine (Cr) values. The research team was blinded to the results until the specimens from the third cycle were analyzed to avoid possible interference with the participants.

When the participants were invited to the educational component of the intervention, they were asked to provide a urine sample and to assess their menstrual pain as baseline data before starting the education session. After the session ended, they were provided three urine collection tubes and a sheet for recording menstrual pain for three consecutive menstrual cycles to take home. The sheet for recording menstrual pain and the urine collection tubes were delivered to the research office within a week after each of the three menstrual cycles during the study. Participants were also asked to fill out a checklist assessing their adherence to the dietary modification intervention every Sunday during the 4weeks after the intervention. The participants e-mailed the checklist or sent it through a social networking service to the research assistant for each of the three groups. Study data were collected between December 2017 and May 2018.

SAS version 9.4 and R version 3.6.3 were utilized with a significance level of less than 0.05. As descriptive statistics, median (minimum to maximum score) values were calculated. First, to examine the effects of the intervention on menstrual pain and urinary BPA levels at the first, second, and third menstrual cycles, the Friedman test was conducted. Second, to identify whether there were any significant differences in menstrual pain and urinary BPA levels from pre-intervention to the first, second, and third menstrual cycles according to adherence levels, the Wilcoxon signed-rank test was conducted. The Bonferroni correction was also applied to control for the increased risk of type I error due to multiple comparisons.

The degree of adherence was measured by the dietary modification checklist. It contained five items (cup noodles, instant food, delivery food with a disposable container, microwaving food in a plastic container, and using a paper cup for hot beverages and tea). Responses for each item were coded as 1 if a participant indicated that she had not engaged in the corresponding behavior at all, 2 for a frequency of 12 times/week, 3 for a frequency of 34 times/week, 4 for a frequency of 56 times/week, and 5 for a frequency of every day. When comparing scores between the baseline and the fourth week after the intervention, if intake or usage was reduced, it was coded as 1, whereas a score of 0 was assigned for items with the same or higher scores. The scores for changes in the five items were then summed to yield a score ranging from 0 to 5 points. Based on the median score, participants with a score of 3, 4, and 5 were classified as the high-adherence group and those with a score of 0, 1, and 2 were classified as the low-adherence group.

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Effects of a dietary modification intervention on menstrual pain and urinary BPA levels: a single group clinical trial - BMC Blogs Network