Menstruation, also known as menses or menstrual period, is a physiological condition experienced by a woman of reproductive age. During menstrual cycle, women may experience various symptoms repetitively and cyclically that may affect their daily lives.

The International Society for Premenstrual Disorders has categorized premenstrual disorders (PMDs), including various symptoms a woman experiences before her menstruation, into two groups: core PMD (typical, pure, or reference disorders associated with spontaneous ovulatory menstrual cycles) and variant PMD (more complex features, including premenstrual exacerbation, PMD with anovulation, PMD with absent menstruation, and progestogen-induced PMD). Premenstrual syndrome (PMS) and premenstrual dysphoric disorder (PMDD) are distinguished as core PMD [1].

PMS is a type of PMD that is characterized by various physical and emotional symptoms that occur repetitively during the luteal phase before menstruation and resolve in a few days into the period. This is considered the basic definition of PMS [2]. More detailed criteria are used by different classifications. For example, the 10th revision International Classification of Diseases only requires one symptom to establish the diagnosis of PMS, while the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) and the American Congress of Obstetricians and Gynecologists (ACOG) focus more on the control of symptoms and treatments to identify PMS/PMDD in more clinically significant way [2].

Not only sensitivity and specificity for the identification of women with PMS symptoms but also estimation of PMS prevalence are influenced by various definitions of PMS [3]. Certainly, a meta-analysis study on PMS prevalence has stated that pooled PMS prevalence globally, obtained from articles reviewed in that study is 47.8%, with large differences between countries (ranging from 12.0% to 98.0%) [4]. Conversely, PMS prevalence shown in studies using the Premenstrual Symptoms Screening Tools (PSST) or Daily Record of Severity of Problems (DRSP), tools used to assess the symptoms based on the definitions of PMS by the DSM-IV or ACOG to identify women with clinically significant PMS/PMDD, ranged from 20.7% to 30.4% [5, 6].

Currently, the definition of PMS by the ACOG is clinically accepted for its diagnosis. According to ACOG's definition, symptoms appeared during the luteal phase before menstruation and should disappear within 4 days after the start of the period without showing recurrence until at least the 13th day of the menstruation cycle. Moreover, retrospectively, at least one emotionally distressing symptom and one physically distressing symptom should be observed for 5 days before menstruation for three cycles in a row, while based on the prospective daily recording, the above-mentioned symptoms should be observed for 5 days before menstruation for two cycles in a row [2, 7]. In other words, this definition requires not only retrospective recalls of the symptoms but also prospective recording of symptoms for the diagnosis of PMS. An accurate diagnosis of the condition using defined classification and customized care based on patient's symptom profile are required for the control and treatment of PMS symptoms. This means specific timing and severity of PMS symptoms should be identified [7, 8]. In this regard, the use of DRSP is recommended as this tool is developed to obtain an accurate prospective recording of the severity and timing of symptoms [7, 8, 9, 10].

However, daily recording of symptoms for two cycles may be inconvenient and difficult to be used in a clinical setting. Borenstein et al. [6] have compared the retrospective observation of DRSP on the first day of the period and the prospective observation of DRSP for two cycles and found that the retrospective observation on the first day of the period can screen women with PMS symptoms. This results in a complementary method, where the retrospective DRSP is used for the initial identification of women with PMS while the additional DRSP observation for two cycles is performed on these women identified as having PMS to ensure accuracy [6]. Conversely, in a comparative study between the retrospective PSST and prospective DRSP of two cycles, the retrospective use of PSST underreported PMS but overreported PMDD with high sensitivity (79.0%) but low specificity (33.3%). This led to the study's suggestion to reevaluate the positive PMS/PMDD cases by PSST using DRSP [10]. Therefore, initially identifying women with PMS using the retrospective DRSP or PSST and additionally using DRSP for women with PMS for two cycles might be required for convenience and accuracy.

In this regard, the retrospective DRSP recording on the first day of menstruation and the prospective DRSP recording for two menstrual cycles should be applied sequentially to investigate clinically significant PMS prevalence. This approach provides basic data on the positive predictive value of the retrospective DRSP. However, there have been no studies reporting PMS prevalence and the positive predictive value of the retrospective DRSP in Korean women by applying both retrospective and prospective recordings of DRSP, which are recommended for the diagnosis of clinically significant PMS. Additionally, the basic data on the menstrual cycle characteristics (regularity, frequency, duration, and volume) and menarche age in Korean women of reproductive age should be continuously updated with more objective measures.

Therefore, the present study aimed to assess the characteristics of menstruation (volume of menstrual blood flow, menstrual cycle frequency, regularity in cycle-to-cycle variation, and duration of blood flow) and menarche age, to investigate PMS symptoms using the retrospective DRSP on the first day of the menstruation, and to estimate clinically significant PMS prevalence and positive predictive value of the retrospective DRSP in Korean young adult women.

The results of this study showed that the mean menarche age of the participants was 12.4 years. Of the total participants, 68.9% (104 women) reported that their periods were generally regular. The number of periods for those with regular intervals experienced in a year was 11.97 in average, ranging from 9.5 to 15. Their average menstrual cycle was 29.38 days, ranging from 20 to 36 days. In average, the period duration was 5.72 days long, ranging from 4 to 8 days.

In a recent study that analyzed the Fourth Korea National Health and Nutrition Examination Survey (2007~2009), women born between 1985~1989 and 1990~1994 (at the time of the survey, they had similar ages to the participants of this study) experienced their first stages of menstruation when they were 12.88 and 12.60 years old in average, respectively [13]. The mean menarche age of 538 women in another survey with an average age of 16.1 years was 12.6 years [14]. Compared to these studies, the mean menarche age of the participants in the present study was approximately 0.2 years younger. Regarding period characteristics, less number of women in this study had regular periods compared to 74.4% (1,940 in number) of 2,613 unmarried Danish women aged between 18 and 40 years. In that Danish study, women with a cycle shorter than 25 days accounted for 7.8% of women with regular periods, while 6.9% of women with regular periods reported a cycle longer than 33 days. Regarding the duration of a period, 35.8% of participants answered long periods lasting 5 days or longer [15]. A study with 4,892 Italian youth aged between 13 and 21 years showed a mean and median age of the first stage of 12.4. Of these participants, about 9% reported irregular periods, 3.0% had short menstrual cycles of 21 days or less, 3.4% had longer cycles of 35 days or more, 3.2% had period lasting ≤4 days, while 19% had period lasting ≥7 days [16]. Conversely, in a study conducted in women in North India, after 131 participants who did not answer the survey were excluded, 74.1% of the participants reported regular periods, with period lasting 3.96 days in average [17]. Compared to these studies reported so far, Korean women experienced their first menstruation at similar ages to other women worldwide. However, significantly higher number of Korean women reported irregular periods. Direct comparison with the Italian study was not possible since that study did not analyze the duration of a period and menstrual cycle separately for regular and irregular periods. However, it seems that a relatively lower percentage of Korean women falls under the “normal” range of menstrual cycle or duration of a period. On the contrary, the Fifth National Health and Nutrition Examination Survey (2010~2012) on Korean women aged between 19 and 40 years reported that 14.3% of 3,194 women had irregular periods [18]. Among those aged between 19 and 29 years, 18.4% had irregular periods [19]. According to Lee et al.'s study [14], 32.3% of participants answered that they had irregular periods.

However, most of the previous studies in Korea used multiple-choice questions to measure menstrual cycles and duration of a period. Moreover, even if the studies reported the menstrual characteristics of Korean women with large samples, they were based on secondary data analysis [18, 20, 21]. Therefore, these studies did not clearly present the menstrual characteristics of Korean women. Additionally, a study analyzing the menstrual cycles and duration of periods based on regularity of a period has not been conducted yet. This study presents some advantages in this regard by showing more accurate characteristics of periods experienced by Korean women. However, this study has the following limitation: it has a small sample size. Further improvements can be made by conducting studies with larger sample sizes to provide more accurate data to comprehensively understand the menstrual cycle characteristics of women with regular and irregular periods.

In particular, this study used PBAC scoring to more objectively evaluate the blood volume during a period. Results showed that 37.4% of young adult women who participated in the study gave a PBAC score higher than 100, indicating the presence of menorrhagia. Regarding the volume of blood flow, most Korean studies [14] subjectively measured the blood volume as “little,” “normal,” and “much.” Even when the volume was measured in an objective manner, the above mentioned studies had the following limitation: they used sanitary pads to measure blood volume. The study conducted in 376 female university students used the same PBAC scoring as this study, showing that 21.8% (n=82) of participants gave a PBAC score higher than 100, which indicated blood loss >80 mL during a period [22]. Compared to that study, it seems that menorrhagia is more common in Korean women. Additionally, the study cited above conducted pelvic examination on 82 women who were diagnosed with menorrhagia. Among the 76 women who received pelvic examination, 11 (14.5%) were found to have bleeding disorders including platelet function disorder and von Willebrand disease [22]. However, this study could not further examine women found to have menorrhagia. Therefore, the presence of menorrhagia should be screened using PBAC scoring, and the cause should be investigated in future studies.

In the present study, PMS prevalence was 42.4% based on the retrospective DRSP on the first day of a period. PMS prevalence was 22.5% when the positive predictive value (52.9%) obtained from the two prospective DRSP was applied to the second stage of the study.

In the study conducted in 897 Iranian youth aged between 12 and 18 years, PMS prevalence was 47.3%, among which 37.3% required drug to relieve their symptoms [23]. However, the tool used to screen PMS in that study was developed by the researcher. It required only one physical symptom and one emotional symptom to establish the diagnosis of PMS. A study conducted in 258 Ethiopian women aged between 18 and 25 years using the DSM-IV definition for PMS has reported a prevalence of 37.0% [24]. However, a study conducted in Chinese women having regular cycles (25 to 35 days) showed a PMS/PMDD prevalence of 21.1% with PMS under the ACOG definition and 2.1% with PMS under the prospective DRSP (the one used in the present study) [25]. A Korean study conducted in 934 women with an average age of 15.9 years who were retrospectively diagnosed with PMS using PSST and analyzed participant responses by four groups (PMDD, subthreshold PMDD, moderate/severe PMS, and no/mild PMS) has found that the percentage of women with PMS/PMDD women (i.e., women who gave responses other than no/mild PMS) was 20.0% [26]. Thus, PMS prevalence of 22.4% found in this study by identifying women with PMS using the retrospective DRSP on the first day of the period and having prospective DRSP on those women with PMS can be interpreted as a reliable result. However, the sample size was relatively small. Hence, studies with larger sample sizes are required in the future. Additionally, the positive predictive value of 52.9% found in this study was similar to a value of 53.8% found in international studies [6]. However, additional local studies should be conducted to add validity to the positive/negative predictive values in Korea.

Difficulties experienced by PMS/PMDD symptoms can negatively affect women in reaching academic and social achievements, resulting in decreased quality of life [24, 26]. Additionally, these symptoms have significant association with the occurrence of physical disorders such as high blood pressure and irritable bowel syndrome [27, 28]. PMS/PMDD symptoms are also known to be associated with dangerous impulse of committing suicide since these symptoms are related to impulsive emotions and anger [29]. Therefore, clear categorization of clinically significant PMS/PMDD and careful plan for treatment are required. In this regard, this study aimed to accurately measure and diagnose the period characteristics and PMS of young adult Korean women. However, this study has the following limitation: it has a small sample size. This needs to be improved by future studies.

Consequently, this study provide basic data on the PMS prevalence of women who require clinical management and the positive predictive value of the retrospective DRSP in Korean young adult women. Additionally, it provides basic data on the four parameters (regularity, frequency, duration, and volume of menstrual blood flow) of menstrual cycle characteristics surveyed by more accurate and objective measures in Korean young adult women.

In the first stage of this study, a retrospective cross-sectional design was used to determine the menstrual cycle characteristics and to determine Korean young adult women with PMS. In the second stage of this study, daily prospective DRSP recording was established for two menstruation cycles to identify clinically significant PMS prevalence. In conclusion, this study shows clinically significant PMS prevalence among Korean young adult women and positive predictive value of the retrospective DRSP. It provides reliable and valid data to basically understand the characteristics and the nature of a menstrual period experienced by Korean young adult women. A more extensive study with a larger sample size is required in the future to overcome the limitations of the current study.