The prevalence and associated risk factors of primary dysmenorrhea among women in Beijing: a cross-sectional study.

A total of 516 women participated in this study, of whom 446 women reported experiencing dysmenorrhea in the past year. The prevalence of dysmenorrhea was 86.4% in this investigation. However, 26 women were diagnosed with gynecological diseases or secondary dysmenorrhea, and 12 women living abroad for a long time, 4 under 18 years old, 24 over 45 years old, leaving data of 450 women for analysis, with a mean age of 27.52 ± 5.07 years, a mean height of 163.05 ± 5.23 cm, a mean weight of 56.51 ± 8.14 kg and a BMI of 21.23 ± 2.75 m 2 /kg. According to the BMI classification of the World Health Organization (WHO), 12.9% were underweight, 72.7% were normal weight, 14.4% were overweight 12 (Detailed data are shown in Fig.  1 ). Fig. 1 Socio-demographic characteristics of the respondents. Socio-demographic characteristics of the respondents. The mean age at menarche was 12.82 ± 1.572 years, ranging from 11 to 15 years. Of these, 356 (79.1%) had a menstrual cycle of 21–35 days. The average duration of menstruation was 5.56 ± 1.452 days. Of these, 313 (69.6%) had periods within the normal range (3–7 days). Among the women with dysmenorrhea, 25.1% immediate family members of subjects also had a history of dysmenorrhea (Detailed data are shown in Table  1 ). Table 1 Menstrual characteristics of the respondents. Characteristics Category Frequency ( n = 450) Percent (%) Age at menarche Younger than 13 years 209 46.4 13 years or older 241 53.6 Menstrual cycle <21 days 8 1.8 21–35 days 356 79.1 ≥ 35 days 86 19.1 Duration of flow <3 days 6 1.3 3–7 days 313 69.6 ≥ 7 days 131 29.1 Amount of menstrual blood light 36 8.0 moderate 384 85.3 heavy 30 6.7 Family history of dysmenorrhea Yes 113 25.1 No 337 74.9 History of pregnancy Never been pregnant 369 82.0 Pregnant but did not give birth (< 28 weeks) 8 1.8 Had a baby (≥ 28 weeks) 73 16.2 Menstrual characteristics of the respondents. Very few women had ever smoked (including quitting ≥ 3 months) or were currently smoking (including quitting 3 times per week, basically did not eat spicy foods, did not eat breakfast, had a very irregular diet, basically did not eat sweets, basically did not eat cold and raw food, slept < 5 h, and considered themselves to be terrible. 49.1% of subjects exercised 1–3 times per week, with a majority of them choosing running, walking, riding a bicycle and other forms of exercise. About one-third of the subjects basically did not drink coffee, were sedentary for < 8 h a day, and went to sleep between 11p.m.-0 a.m. every day (more than half of them delayed sleep due to recreation, and one-third of them due to study and work). More than half of the subjects considered themselves “I accept myself even though I know I’m not perfect” (Detailed data are shown in Table  2 ). Table 2 Lifestyle habits and emotional factors of the respondents. Characteristics Category Frequency ( n = 450) Percent (%) Smoking status Ever smoked has quit smoking ≥ 3 months 6 1.3 Never smoked 432 96.0 Smoking now includes quitting smoking 3/w 10 2.2 ≤ 3/w 152 33.8 Never drink 288 64.0 Caffeine intake Hardly 152 33.8 Often 153 34.0 Sometimes 145 32.2 Sweet food Hardly 77 17.1 Often 131 29.1 Sometimes 242 53.8 Cold and raw food Hardly 110 24.4 Often 119 26.4 Sometimes 221 49.2 Spicy food Hardly 40 8.9 Often 161 35.8 Sometimes 249 55.3 Dietary Regular 291 64.7 Irregular 141 31.3 Extremely irregular 18 4.0 Breakfast Hardly 71 15.8 Often 267 59.3 Sometimes 112 24.9 Sedentary time < 8 h 160 35.6 ≥ 8 h 290 64.4 Sleep time < 5 h 6 1.3 5–6 h 78 17.3 6–7 h 170 37.8 7–8 h 160 35.6 ≥ 8 h 36 8.0 Bedtime Before 10 pm 11 2.4 10 pm-11 pm 122 27.1 11 pm-0 am 168 37.3 0 am-1 am 114 25.4 After 1 am 35 7.8 Frequency of physical exercise Never 166 36.9 Occasionally (< 3/w) 221 49.1 Often (≥ 3/w) 63 14 Self-awareness When I have a good day, I have nothing to complain about, but occasionally I get a little frustrated 128 28.4 I accept myself even though I know I’m not perfect 264 58.7 It doesn’t matter what I look like, I don’t care 8 1.8 I think I’m perfect, I like the way I look 44 9.8 I think I’m ugly, I don’t dare to look at myself straight in the eye 6 1.3 Lifestyle habits and emotional factors of the respondents. We examined the relationship between the basic characteristics of the subjects and the prevalence of primary dysmenorrhea. It was found that there was a statistically significant correlation between age at menarche, BMI and the incidence of primary dysmenorrhea ( p < 0.05). However, no statistically significant differences were found in the prevalence of primary dysmenorrhea in terms of age, menstrual cycle and duration of flow (Table  3 ). In addition, the lower abdomen hot compress, drinking hot water and other ways (82.91%) are the most preferable management options used by women during dysmenorrhea. If the time and place were suitable, people will also choose to stay in bed (71.94%). Table 3 The relationship between basic characteristics of the subject population and dysmenorrhea. Characteristics Overall ( N = 450) Dysmenorrhea OR (95% CI) P Yes ( N = 392) No ( N = 58) Age Younger than 30 years 353(78.4) 323(82.4) 30(51.7) 2.435(0.981–5.982) 0.063 30 years or older 97(21.6) 69(17.6) 28(48.3) 3.150(1.192–8.323) 0.052 BMI <18.5 58(12.9) 47(14.8) 11(0) 1.502(0.384–5.883) 0.038 18.5–24 323(72.2) 283(70.7) 40(82.8) 0.719(0.234–2.206) 0.013 ≥ 24 69(14.9) 62(14.5) 7(17.2) 0.592(0.014–1.983 -0.023 Age at menarche Younger than 13 years 209(46.4) 182(46.4) 27(46.6) 5.600(2,097 − 13,953) 0.037 13years or older 241(53.6) 210(53.6) 31 (53.4) 10.293(4.298–19.348) 0.029 Menstrual cycle <21 days 8(1.8) 6(1.5) 2(3.4) 5.295(1.384–9.583) 0.184 21–35 days 356(79.1) 315(80.4) 41(70.7) 9.284(4.139–10.494) 0.492 ≥ 35 days 86(19.1) 71(18.1) 15(25.9) 5.293(1.128–9.281) 0.294 Duration of flow <3 days 6(1.3) 5(1.3) 1(1.7) 0.892(0.118–6.238) 0.412 3–7 days 313(69.6) 260(66.3) 53(91.4) 3.195(0.394–9.484) 0.942 ≥ 7 days 131(29.1) 127(32.4) 4(6.9) 10.921(4.294–15.295) 0.392 The relationship between basic characteristics of the subject population and dysmenorrhea. We then studied the relationship between the different lifestyle variables and the prevalence of primary dysmenorrhea. The study found that there was a statistically significant correlation between primary dysmenorrhea and smoking(p ˂0.001), eating sweet foods frequently( p = 0.042), sedentary time( p = 0.037), self-awareness( p = 0.043). Surprisingly, there were no significant difference between the prevalence of primary dysmenorrhea and lifestyle habits such as alcohol intake, eating spicy food, raw and cold foods, and eating patterns (Table  4 ). Table 4 The prevalence of primary dysmenorrhea impacted by different lifestyle variables and emotional factors. Lifestyle habit Overall ( N = 450) Dysmenorrhea OR (95% CI) P Yes ( n = 392) No ( n = 58) Smoking status Ever smoked has quit smoking ≥ 3 months 6(1.3) 6(1.5) 0(0) - - Never smoked 432(96) 374(95.4) 58(100) 1.215(0.102–14.535) <0.001 Smoking now includes quitting smoking3/w 10(2.2) 8(2.0) 2(3.4) 4.219(1.339–9.284) 0.092 ≤ 3 /w 152(33.8) 144(36.8) 8(13.8) 5.294(2.390–9.249 0.202 Never drink 288(64) 240(61.2) 48(82.8) 8.104(2.391–10.129) 0.070 Caffeine intake Hardly 152(33.8) 127(32.4) 25(43.1) 1.024(0.901–5.204) 0.193 Often 153(34) 141(36.0) 12(20.7) 1.491(0.913–4.193) 0.492 Sometimes 145(32.2) 124(31.6) 21(36.2) 5.204(2.194–9.193) 0.924 Sweet food Hardly 77(17.1) 67(17.1) 10(17.2) 7.140(2.029–25.127) 0.002 Often 131(29.1) 122(31.1) 9(15.5) 1.121(0.491–2.559 0.785 Sometimes 242(53.8) 203(51.8) 39(67.3) 1.394(0.791–2.490) 0.019 Cold and raw food Hardly 110(24.4) 98(25) 12(20.7) 5.200(2.494–9.250) 0.066 Often 119(26.4) 109(27.8) 10(17.2) 5.242(1.395–10.539) 0.092 Sometimes 221(49.1) 185(47.2) 36(62.1) 2.592(0.194–8.382) 0.224 Spicy food Hardly 40(8.9) 32(8.2) 8(13.8) 5.295(1.482–9.185) 0.144 Often 161(35.8) 150(38.3) 11(19) 2.520(1.491–5.295) 0.196 Sometimes 249(55.3) 210(53.5) 39(67.2) 1.304(0.193–5.194) 0.252 Dietary Regular 291(64.7) 252(64.3) 39(67.2) 1.693(0.901–6.295) 0.244 Irregular 141(31.3) 126(32.1) 15(25.9) 0.290(0.001–1.492) 0.863 Extremely irregular 18(4) 14(3.6) 4(6.9) 2.950(1.530–9.295) 0.825 Breakfast Hardly 71(15.8) 61(15.6) 10(17.2) 6.295(2.495–9.184) 0.245 Often 267(59.3) 235(59.9) 32(55.2) 2.492(0.909–5.294) 0.673 Sometimes 112(24.9) 96(24.5) 16(27.6) 5.928(1.059–9.203) 0.720 Sedentary time < 8 h 160(35.6) 134(34.2) 26(44.8) 1.425(0.650–3.123) 0.041 ≥ 8 h 290(64.4) 258(65.8) 32(55.2) 3.529(1.348–9.394 0.080 Sleep time < 5 h 6(1.3) 6(1.5) 0(0) - - 5–6 h 78(17.3) 70(17.9) 8(13.8) 6.293(2.349–8.328) 0.094 6–7 h 170(37.8) 140(35.7) 30(51.8) 3.299(1.230–8.391) 0.714 7–8 h 160(35.6) 142(36.2) 18(31.0) 3.209(1.934–4.292) 0.345 ≥ 8 h 36(8) 34(8.7) 2(3.4) 2.349(0.902–3.298) 0.672 Bedtime Before 10 pm 11(2.4) 9(2.3) 2(3.4) 3.209(0.909–4.203) 0.914 10 pm-11 pm 122(27.1) 94(24) 28(48.3) 1.204(0.520–4.209) 0.134 11 pm-0 am 168(37.3) 152(38.8) 16(27.6) 4.029(2.304–5.928) 0.671 0 am-1 am 114(25.3) 106(27) 8(13.8) 2.304(1.090–4.209) 0.734 After 1 am 35(7.8) 31(7.9) 4(6.9) 5.298(3.209-0.504) 0.673 Frequency of physical exercise Never 166(36.9) 141(36) 25(43.1) 3.298(1.398–5.202) 0.373 Occasionally (< 3/w) 221(49.1) 196(50) 25(43.1) 4.298(2.537–5.172)) 0.838 Often(≥ 3/w) 63(14) 55(14) 8(13.8) 1.298(0.203–4.298) 0.469 Self-awareness I think I’m perfect, I like the way I look 44(9.8) 37(9.5) 7(12.1) 2.398(1.223–3.174) 0.145 It doesn’t matter what I look like, I don’t care 8(1.8) 6(1.5) 2(3.4) 2.495(1.149–5.395) 0.935 I accept myself even though I know I’m not perfect 264(58.7) 229(58.4) 35(60.4) 3.294(1.234–4.246) 0.006 When I have a good day, I have nothing to complain about, but occasionally I get a little frustrated 128(28.4) 116(29.6) 12(20.7) 3.478(1.347–4.287) 0.000 I think I’m ugly, I don’t dare to look at myself straight in the eye 6(1.3) 4 (1.0) 2(3.4) 2.378(1.476–4.172) 0.001 The prevalence of primary dysmenorrhea impacted by different lifestyle variables and emotional factors. Of the 450 participants, 392 women suffered from dysmenorrhea. Among 392 subjects with PD, 44.9% described their menstrual pain as mild, 44.4% described their pain as moderate, and 10.7% described their pain as severe on the basis of the VAS score. The mean severity of pain was 4.41 ± 2.27 on the VAS. Nearly 80% of the subjects had knowledge about menstruation before the onset of menstruation and were able to cope up with it when it occurred, with the most important sources of knowledge being female relatives in the family, and some from friends and classmates, books on the Internet, and so on. About 50% of the subjects felt pain on the first day of menstruation or less, and 45% felt pain two years after the onset of menstruation. Approximately 50% of subjects perceived pain on the first day of menstruation. Chi-square test showed that there was a significant difference between BMI, alcohol consumption, sleeping time and the severity of dysmenorrhea ( p < 0.05). Chi-square test further revealed a statistically significant correlation between BMI ( P = 0.032), alcohol consumption ( P = 0.046), sleep time ( P = 0.006) and the severity of dysmenorrhea (Table  5 ). Table 5 The prevalence of primary dysmenorrhea impacted by different lifestyle variables and emotional factors. Characteristics Category Overall ( N = 392) VAS for pain P * Mild ( n = 176) Moderate ( n = 174) Severe ( n = 42) Understanding of menstruation Basic understanding 92(23.5) 31(17.6) 51(29.3) 10(20.8) 0.151 A little 215(54.8) 102(58.0) 89(51.1) 24(57.2) Not at all 85(21.7) 43(24.4) 34(19.6) 8(19.0) Condition of menarche Handle it well 121(30.9) 55(31.3) 50(28.7) 16(38.1) 0.213 No fuss 185(47.2) 79(44.9) 85(48.9) 21(50.0) At a loss 86(21.9) 42(23.8) 39(22.4) 5(11.9) Pain time D2-3 65(16.58) 45(25.57) 17(9.77) 3(7.14) 0.061 D1 188(47.96) 72(40.91) 89(51.15) 27(64.29) 1-3days before 139(35.46) 59(33.52) 68(39.08) 12(28.57) Pain onset time Can not specify the time of menarche 112(28.57) 62(35.23) 36(20.69) 14(33.33) 0.256 Within 2 years 103(26.28) 41(23.30) 46(26.44) 16(38.10) 2 years later 177(45.15) 73(41.47) 92(52.87) 12(28.57) History of dysmenorrhea 0–5 years 193(49.23) 109(61.93) 70(40.23) 14(33.33) 0.205 6–10 years 104(26.53) 38(21.59) 53(30.46) 13(30.95) > 10 years 95(24.24) 29(16.48) 51(29.31) 15(35.72) BMI <18.5 58(14.80) 20(11.36) 32(18.39) 6(14.29) 0.032 ** 18.5–24 277(70.66) 129(73.30) 122(70.12) 26(61.90) ≥ 24 57(14.54) 27(15.34) 20(11.49) 10(23.81) Age at menarche Young than 13 years 182(46.43) 82(46.59) 84(48.28) 16(38.10) 0.305 13years or older 210(53.57) 94(53.41) 90(51.72) 26(61.90) History of pregnancy Never been pregnant 311(79.34) 127(72.16) 148(85.06) 36(85.71) 0.177 Pregnant but did not give birth (< 28 weeks) 8(2.04) 6(3.41) 2(1.15) 0 Had a baby (≥ 28 weeks) 73(18.62) 43(2.43) 24(13.79) 6(14.29) Smoking status Ever smoked has quit smoking ≥ 3 months 6(1.53) 2(1.14) 2(1.15) 2(4.76) 0.481 Never smoked 374(95.41) 166(94.32) 168(96.55) 40(95.24) Smoking now includes quitting smoking 3/w 8(2.04) 3(1.70) 3(1.73) 2(4.76) 0.046 ** ≤ 3 /w 144(36.74) 66(37.50) 58(33.33) 20(47.62) Never drink 240(61.22) 107(60.80) 113(64.94) 20(47.62) Caffeine intake Hardly 127(32.40) 68(38.64) 50(28.74) 9(21.43) 0.341 Often 124(31.63) 52(29.54) 61(35.06) 11(26.19) Sometimes 141(35.97) 56(31.82) 63(36.20) 22(52.38) Sweet food Hardly 67(17.09) 35(19.89) 28(16.09) 4(9.52) 0.701 Often 206(52.55) 89(50.57) 92(52.87) 25(59.53) Sometimes 119(30.36) 52(29.54) 54(31.04) 13(30.95) Cold and raw food Hardly 98(25) 44(25.00) 47(27.01) 7(16.67) 0.388 Often 185(47.19) 81(46.02) 82(47.13) 22(52.38) Sometimes 109(27.81) 51(28.98) 45(25.86) 13(30.95) Spicy food Hardly 32(8.16) 14(7.95) 14(8.05) 4(9.52) 0.152 Often 210(53.57) 94(53.41) 99(56.90) 17(40.48) Sometimes 150(38.27) 68(38.64) 61(35.05) 21(50.0) Dietary Regular 252(64.29) 106(60.23) 121(69.54) 25(59.52) 0.158 Irregular 126(32.14) 60(34.09) 49(28.16) 17(40.48) Extremely irregular 14(3.57) 10(5.68) 4(2.3) 0 Breakfast Hardly 61(15.56) 32(18.18) 23(13.22) 6(14.29) 0.788 Often 96(24.49) 45(25.57) 41(23.56) 10(23.81) Sometimes 235(59.95) 99(56.25) 110(63.22) 26(61.90) Sedentary time <8 h 134(34.18) 66(37.50) 55(31.61) 13(30.95) 0.616 ≥ 8 h 258(65.82) 110(62.50) 119(68.39) 29(69.05) Sleep time <5 h 6(1.53) 2(1.13) 2(1.15) 2(4.76) 0.006 ** 5–6 h 70(17.86) 29(16.48) 26(14.94) 15(35.72) 6–7 h 140(35.71) 72(40.91) 60(34.48) 8(19.05) 7–8 h 142(36.22) 62(35.23) 66(37.93) 14(33.33) ≥ 8 h 34(8.68) 11(6.25) 20(11.50) 3(7.14) *p < 0.05; Chi-square Test. **Bonferroni Test. The prevalence of primary dysmenorrhea impacted by different lifestyle variables and emotional factors. *p < 0.05; Chi-square Test. **Bonferroni Test.

This was a cross-sectional study that was conducted in Beijing, China, from March to June 2023. The following formula was used to calculate the sample size for the cross-sectional study: \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$N = \frac{{Z_{{1 - \alpha /2}}^{2} p\left( {1 - p} \right)}}{{d^{2} }}$$\end{document} where Z 1−α/2 represents standard deviation = 1.96 when α = 0.05, P is the prevalence of primary dysmenorrhea among Chinese women (which was 60.5% according to a previous study 6 ) and d is admissible error (which was 5% here). According to the formula, the theoretical sample size was 408 subjects, which included an extra 10% to allow for subjects’ no response during the study. The study sample included females between the ages of 18 and 45, living in Beijing and in good health. The exclusion criteria were: females outside the age of 18–45 years, women having any chronic or gynecological illnesses, and participants failing to provide consent to take part in the study. The instrument of the study used a structured self-report questionnaire distributed online. We distributed questionnaires to patients with primary dysmenorrhea attending our outpatient clinic, healthcare workers and their families, internship students and so on. All of them met the above inclusion criteria and did not meet the exclusion criteria. The participants have given their consent to participate in the study when filling out the questionnaire. We guarantee that their privacy will be protected and that they will not be charged any additional fees for completing the questionnaire. Furthermore, they had the right to withdraw from the questionnaire at any time without any repercussions. All participants were informed of the purpose of the survey, which was based on the Declaration of Helsinki. The study was registered with the Clinical Trial Registry (registration number: NCT05799924 ). Data were collected using a self-administered questionnaire designed in Chinese. This questionnaire was carefully designed by the research team based on previous studies. It has 3 parts, the first part contained socio-demographic information about the participants. The second part was about menstrual patterns and information. The third part was related to the lifestyle behaviors and emotional characteristics. The questionnaires were distributed to each participant and collected on the same day to ensure confidentiality and prevent information contamination. Finally, the researcher checked the completion of the questionnaires and the quality of completion individually. Socio-demographic information, including age, education level, height and weight was first collected. Education levels were indicated on the basis of the following choices: middle school and below education, high school, college, bachelor’s degree, master’s degree, doctoral degree and above. Anthropometric data including age, height and weight were accurately recorded by the participants themselves. Body mass index (BMI) was calculated as weight in kilograms divided by the square of height in meters; according to their BMI, participants were divided into 3 groups: underweight (<18.5), normal (18.5–24.0), and overweight or obese (≥ 24.0). Menstrual information was also collected, including information related to menarche, cycle regularity, menstrual cycle, and history of dysmenorrhea. Knowledge of menarche includes age of menarche, sources of knowledge and status of menarche. Primary dysmenorrhea was identified on the basis of the following questions, “Have you experienced one or more periods of menstrual cramps or abdominal pain during your menstrual cycle in the past year?” and, “Do you have any of the following diseases or symptoms?” Listed diseases in this regard included pelvic inflammatory disease, endometriosis, adenomyosis, leiomyoma, secondary dysmenorrhea and other conditions. Students who reported having any of these listed conditions were excluded from this study. Participants who experienced pain symptoms had to answer additional questions, which included the intensity of the pain, the moment at which pain is perceived, duration of dysmenorrhea, the pain symptoms they experienced, and the way to relieve pain. The intensity of self-reported menstrual pain was evaluated using the horizontal visual analogue scale (VAS) from 0 to 10 and was interpreted as in previous studies: mild (1–3), moderate (4–6) and severe (7–10) 4 . Pain symptoms included lower abdominal pain, dizziness, headache, nausea, vomiting, fatigue, diarrhea, insomnia and irritability, which were assessed using the Cox menstrual symptom scale, which has a high degree of validity and reliability in the Chinese female population (Cronbach α = 0.833) 11 . Lifestyle habits included smoking, alcohol consumption, physical activity, sedentary time, sleep duration, bedtime, and dietary habits. Smoking status was classified as current smoker(including having quit < 3 months), never smoker and ever smoker (including having quit ≥ 3 months). Daily sitting time was self-reported by participants and subsequently categorized into 2 groups: < 8 h and ≥ 8 h. The participants were divided into 5 groups according to their sleep duration (5, 6, 7, 8 h). In this study, participants who skipped breakfast one or more times in the past week were considered as breakfast skippers. Eating habits were broken down into smaller categories such as eating breakfast on time, spicy foods, cold and raw foods, sweets, and foods rich in caffeine. This questionnaire also involves the problem of self-perception, related responses included “I think I’m perfect, I like the way I look”,“It doesn’t matter what I look like, I don’t care”, “I accept myself even though I know I’m not perfect”, “When I have a good day, I have nothing to complain about, but occasionally I get a little frustrated”, “I think I’m ugly, I don’t dare to look at myself straight in the eye”. The collected questioners first manually checked for completeness, and then the data were imported into an Excel spreadsheet of the Microsoft Office package and exported to SPSS version 26 for data analysis. The descriptive statistics, such as frequencies and percentages were used for qualitative variables. The means and standard deviations were used for quantitative variables. Chi-square test of independence was used to analyze the relationship between different lifestyles and dysmenorrhea and the effect on different degrees of dysmenorrhea. The results were displayed in categories. P values less than 0.05 were considered significant. Bonferroni correction was used to adjust the significance level to control for multiple comparisons. Multiple logistic regression analysis was used to analyze the risk factors affecting dysmenorrhea. These variables included smoking, sleep duration, alcohol consumption, coffee, sugar, fruits, sedentary behavior, physical activity, cycle regularity, and cycle duration. Finally, text, tables and graphs were used to present the results.

PD is a vital public health problem reducing the quality of life significantly by affecting different aspects of life in the childbearing age population. This study found that women with dysmenorrhea were characterized with a family history of dysmenorrhea, early age of menarche, frequent smoking, eating sweet foods frequently, sedentary lifestyle, abnormal BMI and low self-esteem. We suggest that it is necessary to focus on the related factors of dysmenorrhea and to take a proactive and effective approach to preventing it. Based on the limitations of this study discussed earlier, further studiesh are needed to assess the factors affecting PD through a more objective and detailed approach.

Our study reported that the prevalence of dysmenorrhea among young and middle-aged women in Beijing was as high as 86.4%. However, the prevalence was higher than 80.0% in Hong Kong 13 and lower than 89.1% in Iran 14 . The reasons for these differences in estimates might be explained by the ethnic and socio-cultural factors. In addition, this difference might result from the lack of a standardized definition of PD and an objective assessment method used to determine this condition. Many studies have diagnosed dysmenorrhea solely on the basis of subjects’ perceived level of pain, which is difficult to quantify and might be caused by non- menstrual events. The present study found that the common symptoms associated with PD were lower abdominal pain (85.9%), fatigue (60.9%), and irritability (50.8%), which is similar to the results of a study among Spanish female university students. This study showed edema (92.7%), irritability (81.9%), and fatigue (79.3%) were common symptoms 15 . Menarche is a sign of sexual maturity in women. The median age at menarche has remained quite stable at 12–13 years in developed countries 16 . Ansong et al. has documented that women who develop menarche later are likely to experience irregular menstruation 13 . Our study confirms that women who develop menarche earlier are less likely to experience dysmenorrhea. It can be speculated that early puberty, especially early menarche, marks an earlier start to reproductive life and reduces the sensitivity of the uterus to prostaglandins. On the other hand, delayed puberty procrastinate reproductive life and increases the sensitivity of uterus to prostaglandins, which in turn causes severe dysmenorrhea 17 , 18 , 20 . But many studies have reported that early menarche is associated with increased dysmenorrhea 19 , 20 . However, this difference should be further explored since another study showed that the timing of puberty (especially age at menarche) cannot determine the presence or absence of dysmenorrhea, as the timing of puberty and menstrual characteristics act independently 17 . Previous studies have identified a lower incidence of dysmenorrhea in vegetarian women due to reduced estrogenic activity resulting from the absence of meat intake 4 , 21 , 22 .Meanwhile, in women with a high consumption of meat, a greater duration of the menstrual cycle was detected. Previous studies have shown that high intake of meat from the diet prolongs the duration of the cycle by modifying the release of gonadotropin hormones and follicular maturation 23 . However, the present study did not find a significant correlation between meat intake and the incidence of dysmenorrhea. Consistent with previous findings from different studies in different countries, there was no significant association between alcohol consumption and dysmenorrhea 4 , 24 , 25 . However, the period of abstinence from alcohol is shorted in women due to changes in specific hormonal stimulation systems 26 . In addition, studies in rats have shown that chronic alcohol consumption is associated with endometrial changes and reproductive disorders 27 . These studies confirm previous reports of other researchers, that alcohol consumption had no significant effect on the development of dysmenorrhea 28 . This study confirms that women with a history of dysmenorrhea in their immediate family are more likely to experience dysmenorrhea. This is similar to the findings of the Polat. But the latter study provided further evidence that the daughters of women who suffered from dysmenorrhea were also affected by dysmenorrhea 29 . It has been speculated that this may not just be a matter of genetic susceptibility 30 – 32 , but also related to behaviors that daughters learn from their mothers 33 . Parazzini et al. 34 found that the relative risk of dysmenorrhea was increased by smoking and decreased among alcohol drinkers. Consistent with this result, a meta-analysis of observational study conducted by Qin et al. 35 found a significant association between smoking(both current and former smoking)and dysmenorrhea. Some researchers have suggested that nicotine, which is frequently detected in women with dysmenorrhea, is a vasoconstrictor that reduces blood flow to the endometrium 15 . Meanwhile, nicotine may negatively affect the estrogen levels in women, which can lead to dysmenorrhea 36 , 37 . Although Khalid et al. found that dysmenorrhea was significantly associated with body mass index and age, our study did not find that these two factors affected the severity of dysmenorrhea 38 , 39 . However, both our study and the study by Çinar et al. 40 found that the higher BMI, the less severe pain. It is speculated that the reason for this may be poorer blood circulation and slower metabolism of local analgesic substances such as prostaglandins than normal. Our study identified that sweet consumption was an important determinant of dysmenorrhea. Similarly, a systematic review of observational studies indicated that excessive sugar intake causes pain during the menstrual cycle 41 . A study in Debre Markos town also showed that dysmenorrhea was three times more prevalent in students who consumed excessive sugar than in normal students 39 . This might be due to the fact that high sugar levels compromise the absorption and metabolism of important vitamins and minerals, leading to muscle spasms that can manifest as dysmenorrhea 42 . In addition, sugary diets may contain precursors of prostaglandins, which can cause dysmenorrhea in women 39 . The study also demonstrated that sitting or standing for long periods of time was associated with dysmenorrhea. The pelvic vein is rich in blood vessels but weak in structure, or the anastomotic branches of the venous plexus with congenital defects are anastomotic with each other, which is easily affected by pelvic pressure 43 . Standing or sitting for long periods of time can lead to increased pressure on the pelvic venous plexus. In addition, estrogen and progesterone change greatly during menstruation 44 , and the pelvic vein is easy to varicose, regurgitation and congestion, which is easy to lead to pelvic vein congestion, manifested as non-periodic pelvic pain and aggravated menstrual period. The present study showed that the prevalence of dysmenorrhea was associated with higher levels of depression and anxiety. However, previous studies examining the association between dysmenorrhea and mental disorders showed inconsistent findings. A study by László et al. 39 . showed no significant correlations between dysmenorrhea and higher incidence of mental disorders, whereas Namvar et al. 40 . showed that women without dysmenorrhea exhibited higher levels of anxiety symptoms than those with dysmenorrhea, and those with dysmenorrhea had higher scores of depression than those without dysmenorrhea. Cyclical pain causes central sensitization, which increases the perception of pain and psychological changes in the long term 45 . Some studies have proved that the occurrence of dysmenorrhea is related to pregnancy. Dysmenorrhea usually occurs in women aged 20–25 years and is usually relieved after the first pregnancy 46 , 47 . Consumption of thyme tea and consumption of vegetables and fruits have been shown to alleviate dysmenorrhea, while coffee consumption was positively associated with primary dysmenorrhea 48 . However, the results of the present study were contrary to these findings, which may be due to differences in the subjects themselves. PD is a common and neglected gynecological disorder. Despite its adverse effects on their daily activities, academic performance, and psychological well-being, most women do not seek formal medical advice, and they perceive as a normal physiological cycle. In addition to non-steroidal anti-inflammatory drugs and hormonal contraceptives, treatments such as transcutaneous electrical acupoints stimulation and traditional Chinese medicine can be used 49 . There is a lack of understanding of dysmenorrhea and its optimal management among clinicians today. Therefore, educational programs and interventions that address PD, its modifiable risk factors, and self-management support should be incorporated to prevent unnecessary pain. Meanwhile, the study also included some limitations. Firstly, our study was a cross-sectional study and we were unable to assess causality. Secondly, most of the information, including pubertal timing, menstrual characteristics and gynecological diseases, was assessed by questionnaires, which could lead to recall bias. Thirdly, our findings may be affected by confounding factors because important variables such as socioeconomic status, physical activity, daily energy, and food intake were not measured in this study for various reasons such as very low response rate or we were unable to quantify some index (physical activity). Therefore, our interpretation of the study results may be limited. Fourthly, the results found in this study cannot be generalized to all Chinese women. A population-based national study is required to substantiate these findings and generalize the results to all Chinese women. We suggest t hat it is necessary to focus on the related factors of dysmenorrhea. Nevertheless, we have confirmed a high incidence of dysmenorrhea among Chinese women, and there is some correlation with lifestyle. We should pay attention to the related factors of dysmenorrhea.

Regular menstruation is the embodiment of healthy and mature female reproductive endocrine system. A healthy, mature woman’s menstrual cycle is regular and lasts from 21 to 35 days. Once per cycle, women experience menstruation, which lasts from 3 to 7 days. The usual amount of menstrual blood is between 20 and 60 mL 1 , 2 . Menstrual pain or cramping, also known as dysmenorrhea, is a commonly recurrent health problem for young and middle-aged women. It usually presents as chronic pelvic or lower abdominal pain. Sometimes, it is accompanied by several other symptoms, such as depression, dizziness, irritability, diarrhea, or nausea. In most cases, this problem has nothing to do with any organic cause, in which case it is known as primary dysmenorrhea 3 , 4 . Primary dysmenorrhea is a gynecological condition that affects about 45-95% of women of childbearing age 5 . The prevalence of dysmenorrhea is also difficult to be measured in different countries around the world, but it can generally reach up to 90% 6 . Despite the high prevalence of dysmenorrhea, young women usually fail to consult a health professional or seek medical help. They are also incapable of applying alternative effective treatments to relieve menstrual pain. As a result, this condition causes a huge public health because of its high prevalence, the broad population it affects, the costs of medications, and decreased productivity. Many studies in the current literature have shown that a range of risk factors may be associated with primary dysmenorrhea, including biological, psychological, social, and lifestyle factors. Biological factors might include early age at menarche, heavy menstrual flow, and family history of dysmenorrhea 7 , 8 ; psychological factors include stress, anxiety, and depression 9 ; social factors include low level of social support 10 ; and lifestyle factors include smoking and irregular diet. However, until now, few scholars in China have comprehensively investigated and studied the effects of the above factors on dysmenorrhea. So further, a study was conducted at Peking university people’s hospital to investigate the prevalence of dysmenorrhea and the severity of primary dysmenorrhea in women. It also explored the effect of lifestyles on the prevalence and severity of dysmenorrhea among this group of women. The results of this study may be useful in providing recommendations to women’s health organizations, thus contributing to the improvement of dysmenorrhea in women.