Abstract
Background
Regular menstruation is an important indicator of well-being in adolescent females. We aimed to assess risk factors associated with menstrual cycle irregularities in a population-based cohort of high school students.
Methods
In the fall of 2022, we recruited a cohort of 1161 first-year female students from 21 socio-economically diverse high schools in the capital region of Finland. Participants completed an online survey addressing menstruation, academic performance and sports participation and validated questionnaires (the Sick-Control-One stone-Fat-Food (SCOFF) eating disorder screening tool and School Burnout Inventory).
Results
Of 935 (81%) participants (mean age 16) not using hormonal preparations, 336 (37%) reported irregular menstruation. Elevated School Burnout Inventory scores (per point OR 1.03, 95% CI 1.01 to 1.05), lower body mass index (OR 1.86, 95% CI 1.12 to 3.08) and high SCOFF scores (OR 2.09, 95% CI 1.40 to 3.10) were associated with irregular menstruation. Overall physical activity levels showed no significant association with menstruation. In subgroup analysis, low body mass index and disordered eating symptoms were associated with irregular menstruation among casual exercisers whereas school burnout was associated with irregular menstruation among competitive athletes.
Conclusion
School-related stress, eating and exercise habits should be evaluated among high school students presenting with menstrual irregularities, as these factors may be relevant in identifying adolescents at risk of more severe reproductive dysfunctions, including amenorrhoea.
Keywords: Physical activity, Eating disorders, Adolescent, Menstruation
WHAT IS ALREADY KNOWN ON THIS TOPIC
Regular menstruation is an important indicator of well-being in adolescent females. Although menstrual irregularities are common during adolescence, they may represent early signs of underlying stress, nutritional deficiencies or excessive exercise, offering an opportunity for timely intervention.
WHAT THIS STUDY ADDS
This large, population-based cohort study provides evidence on menstrual irregularities in adolescents. It is the first study to examine the role of school burnout and uniquely distinguishes the effects of casual versus competitive sports participation on the menstrual cycle.
HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY
Routine evaluation of menstrual cycle may facilitate early identification of school burnout, excessive exercise or disordered eating. Systematic assessment of menstrual irregularities in school health services could guide timely interventions and inform public health policy aimed at preventing progression to more severe reproductive dysfunctions, including amenorrhoea.
Background
Menarche is a crucial indicator of reproductive health among female adolescents. The reported mean age of menarche among European girls varies from 12.8 to 13.4.1,3 By the age of 15 years, 98% of girls will have undergone menarche.4 5 The first postmenarcheal years are often characterised by irregular anovulatory cycles due to hypothalamic–pituitary–ovarian (HPO) axis immaturity.6 By the third year postmenarche, a mature ovulatory cycle emerges, typically lasting 25–35 days.7 Still, menstrual cycle irregularities are common among adolescents.8 Contributing factors to menstrual irregularities in adolescents include chronic diseases and functional hypothalamic amenorrhoea (FHA) due to lifestyle factors.9 The most common factors include psychological stressors, intense exercise and weight loss.9 10 If FHA is prolonged, it may have negative and permanent consequences on reproductive health, thus highlighting the importance of early recognition and interventions.
Today’s adolescents encounter an increasing number of stressors, and the rise in adolescent morbidity is predominantly attributed to mental health problems.11 Socio-economic and lifestyle factors such as low economic status, distress, depressed mood, smoking and insufficient sleep have all been linked to menstrual irregularities in adolescents.12,16 Menstrual irregularities are also frequent consequences of excessive physical activity and low energy availability, frequent dieting and weight fluctuation, especially when combined.17,19 However, the threshold at which physical activity becomes detrimental remains unknown. Inconsistencies in findings between athletes and non-athletes may stem from insufficient assessment of physical activity among the latter.20
While functional menstrual irregularities among adolescents are common, population-based studies that identify lifestyle-related risk factors from the everyday lives of adolescents and their impact on menstrual function allowing for early intervention are scarce. More specifically, despite the high prevalence of school burnout among young females, to our knowledge, the relationship between school burnout, physical activity and menstrual disorders remains unknown.
We aimed to evaluate the everyday life stressors of adolescents and their connections to self-reported age at menarche and menstrual cycle irregularities among female high school students. We hypothesised that adolescents with a goal-directed approach, academically and in sports, are more likely to have later menarche and more menstrual disturbances.
Material and methods
Study population
The School, Sport and Social Media study is a population-based, prospective cohort study conducted in three cities (Helsinki, Espoo and Vantaa) in the capital region of Finland with a combined background population of 1.2 million. The detailed protocol has been described previously.21
This study presents findings from the first wave of data collection involving 1161 first-year high school students assigned female at birth. The students came from 21 socio-economically diverse high schools that chose to participate in the fall of 2022. After providing informed consent, participants completed a survey using Research Electronic Data Capture (REDCap)—a secure online tool for surveys and databases. Surveys were available in both national official languages, Finnish and Swedish. Participants received a movie ticket (value €9.30) after completing the survey. The study participants were representative of the background population, as the sensitivity analysis presented elsewhere confirmed.21
Patient and public involvement
The study was designed in collaboration with the nine young members of the Youth Research Advisory Board of the Helsinki University Hospital, Helsinki, Finland. The youth participants reviewed the original survey forms and provided feedback on the terminology used. The forms were subsequently revised based on their suggestions. They also evaluated the time required to complete the survey and deemed the length of survey reasonable.
Measures
This study used data on menstrual history, academic achievement, school burnout, physical activity and symptoms of disordered eating.
Menstrual history
Questions about pubertal development and the menstrual cycle were as follows: Have you experienced menstruation (Yes/No)? At what age did your periods begin? Is your menstrual cycle regular (Yes/No)? What is the length of your menstrual cycle? What is the duration of menstrual flow? Are you using hormonal preparations (eg, oral contraceptives)? The gynaecological age was computed as the difference between the age when the survey was completed and the age at menarche.
Academic achievement
As a measure of academic achievement, participants provided their grade point average (GPA) at the end of the preceding semester (possible range, 4−10).
School Burnout Inventory
The School Burnout Inventory (SBI) consists of nine items with three subscales: exhaustion, cynicism toward the meaning of studying and sense of inadequacy as a student.22 All items are rated on a 6-point Likert scale ranging from 1 (completely disagree) to 6 (completely agree), yielding a potential range from 9 to 54. Higher composite scores indicate more likely school burnout symptomatology.
Physical activity and sports history
Participants provided information about their exercise routines and level of competitiveness: Do you participate in sports or engage in independent physical activity (Yes, independently/Yes, in a sports club/No)? How many times per week (x/week)? How many hours per week (hours/week)? How goal-oriented are you in your participation in sports (casual level/competitive level/aiming for a professional career)? Based on the responses, participants were categorised into three groups: (1) competitive athletes, actively competing or pursuing a professional sports career; (2) casual exercisers, involved in independent exercise or as part of a sports association without competitive activities; and (3) physically inactive, reported no regular physical activity. Due to the small number of participants, adolescents aiming for professional athlete careers were combined with competitive athletes. Sport types were categorised as ‘lean’ or ‘non-lean’ based on participants’ responses to an open-ended question about their sport. ‘Lean’ sports included aesthetic, weight-dependent and endurance sports, whereas ‘non-lean’ sports comprised ballgames, technical and power sports.
Body mass index
Body mass index (BMI) was calculated using self-reported weight and height data: weight (kg)/height (m)2. For girls up to 18, age-adjusted and sex-adjusted international standardised BMI (ISO-BMI) values were calculated to allow for comparability with adult BMI categories.23 An ISO-BMI below 18.5 kg/m2 was classified as underweight, between 18.5 kg/m2 and 25 kg/m2 as normal weight, and above 25 kg/m2 as overweight.
Disordered eating
The Sick-Control-One stone-Fat-Food (SCOFF) is a validated survey used to screen for eating disorder symptoms.24 It consists of five items dichotomously scored (yes = 1, no = 0; sum range 0−5). Scores ≥2 indicate a greater likelihood of eating disorders.25 26 Disordered eating encompasses behaviours like restrictive dieting, even if the criteria for a clinical eating disorder are not met.
Statistical analysis
Descriptive statistics included frequencies and percentages. The χ² and Fisher’s exact tests were used when appropriate for categorical data. All continuous variables were tested for normality using histograms before statistical analyses; means with SD were used in case of normal distribution and medians with IQRs in non-normal distribution. Participants using hormonal contraceptives were excluded from analyses comparing regular versus irregular menstrual cycles. The differences between irregular and regular menstruation groups were investigated using two-sample t-tests for normally distributed data or the Mann-Whitney U test for skewed data. Multivariable binary logistic regression was used to examine the associations of GPA, SBI scores, SCOFF categories (<2 vs ≥2 scores), ISO-BMI categories (<18.5 kg/m2, 18.5−25 kg/m2 and >25 kg/m2), sports participation status (casual exercisers vs competitive athletes) and physical activity (hours/week) with irregular menstruation (irregular vs regular menstruation). Separate multivariable binary logistic regression analyses were conducted to compare casual exercisers and competitive athletes and examine the associations of GPA, SBI scores, SCOFF categories (score <2 vs ≥2), BMI (kg/m2) and physical activity (hours/week) with the regularity of menstruation (irregular vs regular menstruation). Analyses were adjusted for the age at menarche. Two-way analysis of variance was employed between ISO-BMI categories and casual versus competitive sport participant status in relation to age at menarche. IBM SPSS Statistics V.29 (IBM, Armonk, New York, USA) was used for analyses. The significance level was set at <0.05.
Results
Table 1 presents participant demographics and characteristics.
Table 1. Participant demographics, characteristics and menstrual history by cycle regularity (without hormonal preparations).
| All participants | Irregular* | Regular* menstrual cycle | ||
|---|---|---|---|---|
| n=1161 | n=336 | n=582 | P value | |
| Age, mean (SD) | 15.8 (0.5) | 15.8 (0.5) | 15.8 (0.5) | 0.12 |
| Height, mean cm (SD) | 166.6 (6.0) | 166.9 (6.2) | 166.7 (5.9) | 0.70 |
| Weight, median kg (IQR) | 58 (53–64) | 57 (52–63) | 58 (53–65) | 0.03 |
| BMI, median kg/m2 (IQR) | 20.8 (19.3–22.9) | 20.6 (18.7–22.4) | 20.8 (19.5–23.1) | 0.01 |
| ISO-BMI categories, n (%) | ||||
| ISO-BMI <18.5 kg/m2 | 149 (14.1) | 64 (20.1) | 64 (11.4) | <0.01 |
| ISO-BMI 18.5–25 kg/m2 | 788 (74.4) | 224 (70.2) | 426 (76.2) | ref. |
| ISO-BMI >25 kg/m2 | 122 (11.5) | 31 (9.7) | 69 (12.3) | 0.57 |
| Menarche, n (%) | 1085 (97.8) | |||
| Menarche, mean age (SD) | 12.5 (1.3) | 13.0 (1.3) | 12.5 (1.2) | <0.01 |
| Gynaecological age, mean age (SD) | 3.3 (1.3) | 2.8 (1.4) | 3.4 (1.2) | <0.01 |
| Use of hormonal preparations, n (%) | 170 (15.4) | |||
| Regular menstruation without hormonal preparations, n (%) | 582 (63.4) | |||
| Menstrual cycle, median days (IQR) | 28 (25.5–30.0) | |||
| Duration, mean days (SD) | 5.4 (1.1) | |||
P values indicate differences between participants with regular versus irregular menstrual cycles; calculated using χ² or Fisher’s exact tests for categorical variables and two-sample t-tests or Mann-Whitney U tests for continuous variables depending on data distribution. Significant p values are in bold.
Missing data: age n=23, height n=64, weight n=76, ISO-BMI n=102, menarche n=52, menarche age n=67, gynaecological age n=84, use of hormonal preparations n=56, regular menstruation without hormonal preparations n=17.
Groups include only participants with no hormonal medication.
IQR, Interquartile range; ISO-BMI, international standardised body mass index; SD, standard deviation.
Menstrual history
Of the 1161 participants, 98% (n=1085) were postmenarcheal (table 1). The mean (SD) age at menarche was 12.5 (1.3) years and the gynaecological age at the time of the survey was 3.3 (1.3) years. Fifteen percent (n=170) of participants reported currently using hormonal preparations influencing spontaneous menstrual cycle. Among the 935 participants (81%) with no hormonal preparation use, 582 (63%) reported regular cycles with an average length of 27.8 (4.9) days and a duration of 5.4 (1.1) days.
Academic achievement
Participants with irregular menstruation had a higher median (IQR) middle school GPA than those with regular cycles (9.2±1.2 vs 8.9±1.1, respectively; p=0.03) (table 2). The mean SBI scores (SD) were also higher among adolescents with irregular menstruation (31.2 (9.5) vs 29.0 (9.1), respectively; p<0.01) (table 2).
Table 2. Participant’s academic, sport and dietary history by menstrual cycle regularity (without hormonal preparations).
| All participants | Irregular* | Regular* menstrual cycle | ||
|---|---|---|---|---|
| n=1161 | n=336 | n=582 | P value | |
| Middle school GPA, median (IQR) | 9.0 (8.4–9.5) | 9.2 (8.4–9.6) | 8.9 (8.4–9.6) | 0.03 |
| SBI, mean (SD) | 29.7 (9.5) | 31.2 (9.5) | 29.0 (9.1) | <0.01 |
| Sports | ||||
| Physically inactive, n (%) | 178 (15.8) | 60 (18.3) | 87 (15.2) | 0.26 |
| Physically active, n (%) | 945 (84.2) | 268 (81.7) | 486 (84.8) | 0.26 |
| Casual exercisers,† n (%) | 643 (70.7) | 186 (70.7) | 325 (70.5) | 1.00 |
| Competitive athletes,‡ n (%) | 266 (29.3) | 77 (29.3) | 136 (29.5) | 1.00 |
| Physical activity, median times/week (IQR) | 3.5 (2.0–5.0) | 3.5 (2.5–5.0) | 3.5 (2.0–5.0) | 0.7 |
| Casual exercisers† | 3 (2–4) | 3 (2–4) | 3 (2–4) | |
| Competitive athletes‡ | 5 (4–6) | 5 (4–6) | 5 (4–6) | |
| Physical activity, median hours/week (IQR) | 5.5 (3.0–9.0) | 5.3 (3.0–9.0) | 6.0 (3.0–9.0) | 1.0 |
| Casual exercisers† | 5 (3–7) | 4.5 (3–6) | 5 (3–7) | |
| Competitive athletes‡ | 10 (7–15) | 11 (7.5–17) | 10 (7–15) | |
| Lean sport, n (%) | 283 (41.7) | 90 (47.9) | 143 (43.5) | 0.36 |
| Non-lean sport, n (%) | 396 (58.3) | 98 (52.1) | 186 (56.5) | |
| SCOFF, high scores ≥2 points, n (%) | 326 (31.0) | 125 (39.6) | 148 (26.5) | <0.01 |
| ISO-BMI <18.5 kg/m2 | 34 (10.9) | 22 (18.2) | 9 (6.3) | |
| ISO-BMI 18.5–25 kg/m2 | 221 (70.6) | 80 (66.1) | 104 (73.2) | |
| ISO-BMI >25 kg/m2 | 58 (17.8) | 19 (15.7) | 29 (20.4) | |
| Intentional weight loss | ||||
| at the moment, n (%) | 206 (19.1) | 77 (23.5) | 93 (16.3) | 0.01 |
| ISO-BMI <18.5 kg/m2 | 17 (8.3) | 8 (10.7) | 6 (6.7) | |
| ISO-BMI 18.5–25 kg/m2 | 135 (65.5) | 51 (68.0) | 60 (66.7) | |
| ISO-BMI >25 kg/m2 | 48 (23.3) | 16 (21.3) | 24 (26.7) | |
| in the past, n (%) | 624 (57.6) | 200 (60.8) | 313 (54.6) | 0.08 |
| ISO-BMI <18.5 kg/m2 | 50 (8.4) | 22 (11.5) | 22 (7.3) | |
| ISO-BMI 18.5–25 kg/m2 | 449 (75.2) | 143 (74.9) | 220 (73.3) | |
| ISO-BMI >25 kg/m2 | 98 (16.4) | 26 (13.6) | 58 (19.3) | |
P values indicate differences between participants with regular versus irregular menstrual cycles; calculated using χ² or Fisher’s exact tests for categorical variables and two-sample t-tests or Mann-Whitney U tests for continuous variables depending on data distribution. Significant p values are in bold.
Missing data: middle school GPA n=9, SBI n=32, casual exercisers/competitive athletes n=38, lean/non-lean n=512, SCOFF n=109, intentional weight loss at the moment n=81 and in the past n=78.
Groups include only participants with no hormonal medication.
Casual exercisers; participants exercising independently and participants involved in recreational organised sports.
Competitive athletes; participant involved in organised sports and either actively competing or pursuing a professional athletic career.
GPA, grade point average; IQR, interquartile range; ISO-BMI, international standardised body mass index; SBI, School Burnout Inventory; SCOFF, Sick-Control-One stone-Fat-Food; SD, standard deviation.
Physical activity and sports history
The participants engaging in casual exercise reported physical activity on average three times per week for a total of 5 hours per week. Competitive athletes trained on average five times per week, totalling 10 hours. The amount of physical activity or the level of exercise showed no association with irregular menstruation (table 2).
Body mass index and disordered eating
Most participants (74%, n=788) had normal weight, while 14% (n=149) were classified as underweight (table 1). Normal-weight competitive athletes reported later menarche than casual exercisers (figure 1). Over half (58%, n=624) of participants had attempted weight loss at some point. Of the 206 adolescents actively attempting to lose weight, 17 (8.3%) were already underweight (table 2). Nearly a third (31%, n=326) of participants scored ≥2 points in the SCOFF questionnaire, suggestive of an eating disorder, with 34 (10.9%) of them already underweight (table 2). Participants with ≥2 points in the SCOFF questionnaire more often had irregular menstruation (p<0.01). Current intentional weight loss was also associated with irregular menstruation (p=0.01) (table 2).
Figure 1. Mean age at menarche according to ISO-BMI category and exercise status (casual vs competitive). Result of a two-way ANOVA depicting the interaction between ISO-BMI categories concerning menarche age in competitive athletes versus casual exercisers. Adjusted means and SE of menarche age for ISO-BMI categories <18.5 kg/m,2 18.5–25 kg/m2, >25 kg/m2 with casual exercisers/competitive athletes are 12.9 (0.1)/13.3 (0.2), 12.5 (0.1)/12.8 (0.1), 12.0 (0.1)/12.0 (0.3) years, respectively. Pairwise comparisons with Bonferroni adjustment revealed significant differences between all groups (p<0.04). No statistically significant combined effect was observed (casual/competitive × ISO-BMI categories, p=0.62). ANOVA, analysis of variance; ISO-BMI, internationally standardised body mass index.
Associations of academic performance, physical activity and disordered eating with self-reported irregular menstruation
In multivariable logistic regression, a higher middle school GPA (OR 1.39, 95% CI 1.06 to 1.82), an increase in SBI scores (per point OR 1.03, 95% CI 1.01 to 1.05, per 10-point OR 1.30), SCOFF scores ≥2 (OR 2.09, 95% CI 1.40 to 3.10) and an ISO-BMI below 18.5 kg/m2 compared with normal weight (OR 1.86, 95% CI 1.12 to 3.08) were associated with higher odds for irregular menstruation (table 3). In subgroup analysis, the associations between GPA, SCOFF scores and lower BMI with irregular menstruation remained significant among casual exercisers but not competitive athletes. Among competitive athletes, higher SBI scores were associated with increased odds of irregular menstruation. For each point increase in SBI scores, the OR was 1.05. For a 10-point increase in SBI scores (equal to one SD), the OR was 1.60 (table 4). Variance inflation factors (VIFs) were calculated for the predictors included in the model, yielding values of 1.00. In addition, the Pearson correlation between GPA and SBI scores was –0.057 (p=0.056), indicating no evidence of multicollinearity. In sensitivity analyses restricted to participants with a gynaecological age >2 years, associations were largely unchanged; however, the association with GPA was attenuated and no longer statistically significant. The restricted sample comprised 973 participants (90.3% of 1,077) and 553 participants (88.3% of 626) in the multivariable model.
Table 3. Multivariable binary logistic regression analysis of factors associated with self-reported irregular menstruation (n=626).
| Independent variable | Adjusted OR (95% CI) | P value |
|---|---|---|
| GPA, grades 6.8–10 | 1.39* (1.06 to 1.82) | 0.02 |
| SBI, points 9–54 | 1.03* (1.01 to 1.05) | 0.01 |
| SCOFF (high scores ≥2 vs scores <2) | 2.09 (1.40 to 3.10) | <0.01 |
| ISO-BMI, kg/m2 | 0.04 | |
| ISO-BMI 18.5–25 kg/m2 | ref. | |
| ISO-BMI <18.5 kg/m2 | 1.86 (1.12 to 3.08) | 0.02 |
| ISO-BMI >25 kg/m2 | 0.85 (0.47 to 1.53) | 0.59 |
| Physical activity, hours/week | 0.99* (0.95 to 1.02) | 0.45 |
| Casual† versus competitive‡ sport participation | 0.95 (0.61 to 1.46) | 0.80 |
Adjusted for the age at menarche.
Significant p values are in bold.
OR per unit increase in continuous variables.
Casual exercisers; participants exercising independently and participants involved in recreational organised sports.
Competitive athletes; participant involved in organised sports and either actively competing or pursuing a professional athletic career.
CI, confidence interval; GPA, grade point average; ISO-BMI, international standardised body mass index; OR, odds ratio; SBI, School Burnout Inventory; SCOFF, Sick-Control-One stone-Fat-Food.
Table 4. Multivariable binary logistic regression analyses of factors associated with self-reported irregular menstruation in casual (n=443) and competitive (n=191) sport participation groups.
| Independent variable | Casual exercisers* | Competitive athletes† | ||
|---|---|---|---|---|
| Adjusted OR (95% CI) | P value | Adjusted OR (95% CI) | P value | |
| GPA, grades 6.8–10 | 1.42‡ (1.41 to 1.93) | 0.03 | 1.33‡ (0.76 to 2.34) | 0.32 |
| SBI, points 9–54 | 1.02‡ (0.99 to 1.04) | 0.22 | 1.05‡ (1.01 to 1.09) | 0.02 |
| SCOFF (high scores ≥2 vs scores <2) | 2.55 (1.60 to 4.07) | <0.01 | 1.27 (0.59 to 2.72) | 0.55 |
| BMI, kg/m2 | 0.93‡ (0.86 to 1.00) | 0.05 | 0.99‡ (0.85 to 1.14) | 0.86 |
| Physical activity, hours/week | 0.99‡ (0.93 to 1.028) | 0.38 | 0.99‡ (0.93 to 1.04) | 0.60 |
Adjusted for the age at menarche.
Significant p values are in bold.
Casual exercisers; participants exercising independently and participants involved in recreational organised sports.
Competitive athletes; participant involved in organised sports and either actively competing or pursuing a professional athletic career.
OR for unit to increase in continuous variables.
BMI, body mass index; GPA, grade point average; SBI, School Burnout Inventory; SCOFF, Sick-Control-One stone-Fat-Food.
Discussion
The aim of this study was to evaluate everyday lifestyle stressors among female high school students, using self-reported menstrual cycle irregularities as a screening tool to identify individuals who may benefit from further assessment. In this study, a higher score on the eating disorder screening tool (SCOFF scores >2) and low international standardized body mass index (ISO-BMI) emerged as risk factors for self-reported irregular menstruation. As the first study to explore this, school burnout was associated with an increased risk for irregular menstruation among competitive athletes.
School burnout
In our study, adolescents with higher School Burnout Inventory (SBI) scores more often reported irregular menstruation than their peers with more modest SBI scores. Despite the high prevalence of school stress among young females, its relationship with menstrual disorders has been studied infrequently. In Estonia, high school students who were never pleased to attend school were more likely to report irregular menstruation.12 Moreover, among adolescents who consistently earned good grades, the prevalence of irregular menstruation was high (60%). The most frequently documented risk factors for school burnout are female gender and high school academic track.27 28 In 2023, 23% of female high school students in Finland reported feelings of school exhaustion29 and thus irregular menstruation may be more prevalent than previously understood.
School and sports-related burnout
Although causality cannot be fully established in a cross-sectional design, our subgroup analysis revealed a significant association between higher school burnout scores and irregular menstruation among competitive athletes but not among casual exercisers. The pressure of pursuing an athletic career alongside secondary education may place adolescent student-athletes at risk for school and sports-related burnout.30 31 Sorkkila et al found an association between school and sports burnout, suggesting that exhaustion from academic demands can spill over into the athletic domain.31 The authors attributed this to increasing academic demands in high school, leaving student-athletes with insufficient time to recover.
Comparison of casual and competitive exercisers
Our population-based study found no significant association between irregular menstruation and the quantity or competitiveness of physical activity. The impact of athletic activity and energy expenditure on menstrual health has been widely researched.32 However, less attention has been given to individuals engaging in moderate physical activity or those who train independently without coaching. Thus, the threshold at which physical activity becomes detrimental remains unclear. Although menstrual cycle dysfunction is common among female athletes, studies comparing its prevalence have also produced mixed results.1220 32,34 In line with our results, Wojtys et al found no correlation between moderate physical activity and oestrogen and progesterone levels in adolescent girls.33 Ravi et al found no difference in menstrual dysfunction between athletes and non-athletes, although they reported higher rates of menstrual irregularities among younger athletes.20 In their study, low energy availability, eating disorders and menstrual dysfunction were also more prevalent among athletes participating in lean sports. In our study, however, no differences in menstrual irregularities were observed between lean and non-lean athletes, which may be partly explained by the relatively high amount of missing data.
In our subgroup analysis among adolescents who train casually, disordered eating and low ISO-BMI were associated with irregular menstruation. A Spanish study using the SCOFF questionnaire found higher rates of disordered eating among non-athletes compared with athletes (26% vs 18%, respectively).35 Regular monitoring by coaches may be a protective factor for disordered eating. While some athletes may face a higher risk of an eating disorder due to body composition pressures, physical activity may also promote healthier attitudes towards food. In our study, however, competitive athletes and casual exercisers with low ISO-BMI displayed a trend toward later menarche, consistent with previous studies.36 37 This suggests that intense sports training, especially among girls approaching menarche, may delay the onset of normal menstruation.
Disordered eating
In our study, 31% of all participants scored above the screening threshold of the SCOFF questionnaire, indicating a potential risk for disordered eating. Disordered eating is prevalent among adolescent girls, particularly in middle-income and high-income countries38 and elite female athletes.39 Early identification of disordered eating behaviours and timely interventions are critical to prevent an actual eating disorder.38 Irregular menstruation may be a warning sign.
Strengths and limitations
Our study’s strengths include the population-based cohort and high participation rate. We asked the same questions regarding physical activity of competitive athletes and their peers. This approach enhanced the comparability of responses and provided a more comprehensive perspective. To our knowledge, this is the first study to explore the associations of school burnout and physical activity with irregular menstruation. Because participants with higher SBI scores were more likely to be excluded due to missing data, this may suggest healthy responder bias. Consequently, the observed association between school burnout and menstrual irregularity may underestimate the true effect size in the population. Our data is based on 16-year-old high school students with an average gynaecological age of 3.3 (SD 1.3), which should be considered when interpreting the results, as gynaecological age reflects time since menarche and menstrual cycles are often irregular during the first 1–2 years postmenarche due to physiological immaturity of the HPO axis. Additionally, while ISO-BMI was used as a standardised anthropometric measure, it may not accurately reflect body composition or energy availability, particularly in athletes. Sleep duration and quality were not assessed in this study and may represent potential confounders of the observed associations between school burnout and menstrual irregularity. A primary limitation of our study stems from its reliance on self-reported data, introducing potential reporting bias. Menstrual irregularity was assessed using a subjective binary question, which may introduce potential recall bias and subjective interpretation. Although the irregular menstruation group is likely a heterogenous mix of both undiagnosed diseases or syndromes and lifestyle-related conditions, menstrual irregularity is one indicator warranting comprehensive assessment. To avoid this potential recall bias we suggest that in further studies a more informative question would be how many times per year you have menstruation. Self-reports also hinder actual assessment of exercise intensity. The cross-sectional design infers assessment of causality.
Clinical implications
While irregular menstruation is common for two to three years postmenarche, addressing the lifestyle factors that influence the menstrual cycle in adolescents at an early stage is crucial. Evaluation of school-related stress, exercise (including adolescents training without a coach) and eating habits may help support management of menstrual cycle dysfunction, including prolonged amenorrhoea and potentially permanent negative consequences to reproductive health.
Conclusion
Among high school students presenting with menstrual irregularities, assessment of school-related stress as well as eating and exercise behaviours is warranted, as these factors may help identify adolescents at increased risk for more severe reproductive disturbances, including amenorrhoea.
Acknowledgements
We thank the members of the Youth Research Advisory Board, all study participants and the participating schools. We acknowledge the help of medical student Ines Sederholm in the recruitment process. Our gratitude goes to Professor Katariina Salmela-Aro for allowing us to use the School Burnout Inventory and to biostatistician Tero Vahlberg for his valuable contributions, which significantly enhanced the quality of the statistical analysis.
Footnotes
Funding: This work was supported by the Helsinki University Hospital, Department of Gynecology and Obstetrics; the Foundation for Pediatric Research; the Gyllenberg Foundation; the Olvi Foundation; the Wihuri Foundation; and the Finnish Society of Pediatric and Adolescent Gynecology. Open access funded by Helsinki University Library.
Data availability free text: De-identified individual participant data will not be shared, as data sharing was not included in the informed consent provided by participants.
Patient consent for publication: Consent obtained directly from patient(s).
Ethics approval: The HUS Regional Committee on Medical Research Ethics (HUS/117/2022) approved this study. Participants gave informed consent to participate in the study before taking part.
Provenance and peer review: Not commissioned; externally peer reviewed.
Patient and public involvement: Patients and/or the public were involved in the design, or conduct, or reporting, or dissemination plans of this research. Refer to the Methods section for further details.
Data availability statement
No data are available.
References
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