Multi-scaling allometry in human development, mammalian morphology, and tree growth.

Various animal and plant species exhibit allometric relationships among their respective traits, wherein one trait undergoes expansion as a power-law function of another due to constraints acting on growth processes. For instance, the acknowledged consensus posits that tree height scales with the two-thirds power of stem diameter. In the context of human development, it is posited that body weight scales with the second power of height. This prevalent allometric relationship derives its nomenclature from fitting two variables linearly within a logarithmic framework, thus giving rise to the term "power-law relationship." Here, we challenge the conventional assumption that a singular power-law equation adequately encapsulates the allometric relationship between any two traits. We strategically leverage quantile regression analysis to demonstrate that the scaling exponent characterizing this power-law relationship is contingent upon the centile within these traits' distributions. This observation fundamentally underscores the proposition that individuals occupying disparate segments of the distribution may employ distinct growth strategies, as indicated by distinct power-law exponents. We introduce the innovative concept of "multi-scale allometry" to encapsulate this newfound insight. Through a comprehensive reevaluation of (i) the height-weight relationship within a cohort comprising 7, 863, 520 Japanese children aged 5-17 years for which the age, sex, height, and weight were recorded as part of a national study, (ii) the stem-diameter-height and crown-radius-height relationships within an expansive sample of 498, 838 georeferenced and taxonomically standardized records of individual trees spanning diverse geographical locations, and (iii) the brain-size-body-size relationship within an extensive dataset encompassing 1, 552 mammalian species, we resolutely substantiate the viability of multi-scale allometric analysis. This empirical substantiation advocates a paradigm shift from uni-scaling to multi-scaling allometric modeling, thereby affording greater prominence to the inherent growth processes that underlie the morphological diversity evident throughout the living world.

Attitude and experience of obstetricians and gynecologists toward eating disorders assessment and management in Japan: A nationwide survey.

AIM: To investigate the attitudes and experiences of obstetricians and gynecologists in treating women with eating disorders (EDs) in Japan. METHODS: Members of the Japan Society of Obstetrics and Gynecology were invited to participate in a web-based survey from March 1 to 31, 2022. We asked about the attitudes of obstetricians and gynecologists toward women with weight loss-related amenorrhea and their experiences in treating EDs. We also assessed the characteristics of physicians who see many ED patients. RESULTS: A total of 662 ob/gyns. responded to the survey. While treating weight loss-related amenorrhea, 25.8% reported screening patients for EDs. 88.5% of respondents reported having treated ED patients. The main medical concerns described when treating pregnant women with ED were fetal growth restriction and preterm delivery. The most common type of ED encountered by participants in both perinatal and infertility care settings was anorexia nervosa. Characteristics of physicians who treated 10 or more EDs per year were being board certified in women's health care and not providing delivery services (OR = 4.809, 1.896). The most common comment regarding optimizing the management of patients with EDs in obstetrics and gynecology practice was the need to implement guidelines for ED management. CONCLUSIONS: Many obstetricians and gynecologists in Japan treat patients with ED. Standardized guidelines for the management of EDs for obstetricians and gynecologists are needed.

Allometric multi-scaling of weight-for-height relation in children and adolescents: Revisiting the theoretical basis of body mass index of thinness and obesity assessment.

The body mass index (BMI), defined as weight in kilograms divided by height in meters squared, has been widely used to assess thinness and obesity in all age groups, including children and adolescents. However, the validity and utility of BMI as a reliable measure of nutritional health have been questioned. This study discusses the mathematical conditions that support the validity of BMI based on population statistics. Here, we propose a condition defined as allometric uni-scaling to ensure the validity of BMI as an objective height-adjusted measure. Any given centile curve, including the median curve, in a weight-for-height distribution should be approximated using power-law functions with the same scaling exponent. In contrast, when the scaling exponent varies depending on the position of the centile curve, it is called allometric multi-scaling. By introducing a method for testing these scaling properties using quantile regression, we analyzed a large-scale Japanese database that included 7,863,520 children aged 5-17 years. We demonstrated the remarkable multi-scaling properties at ages 5-13 years for males and 5-11 years for females, and the convergence to uni-scaling with a scaling exponent close to 2 as they approached 17 years of age for both sexes. We confirmed that conventional BMI is appropriate as an objective height-adjusted mass measure at least 17 years of age, close to adulthood, for both males and females. However, the validity of BMI could not be confirmed in younger age groups. Our findings indicate that the growth of children's weight-for-height relation is much more complex than previously assumed. Therefore, a single BMI-type formula cannot be used to assess thinness and obesity in children and adolescents.

Sleep characteristics in underweight young females across their menstrual cycles: A sleep-monitoring survey study with preliminary results.

This study investigated the association between underweight and sleep in young females across their menstrual cycles. A lifestyle-monitoring survey was conducted among 38 female university students aged 18-24 years in Japan from January to December 2023. Sleep data from 28 participants were analysed. Participants were categorized into underweight (n = 10) and control (n = 18) groups based on a baseline body mass index cut-off of 18.5 kg m-2. Sleep parameters were assessed using a daily sleep questionnaire, sleep sensor mats, and urinary melatonin metabolites across their menstrual cycles. The results indicated no significant differences in sleep patterns between the underweight and control groups or menstrual cycle phases, as assessed using both the daily sleep questionnaire and the sleep sensor mats. However, underweight participants experienced more difficulty maintaining sleep during the follicular phase. Body mass index significantly correlated with sleep efficiency (rs = 0.52) and wake after sleep onset (rs = -0.56). While urinary melatonin metabolite levels did not differ significantly between the groups or menstrual cycle phases, decreased levels during the luteal phase were more prevalent in the underweight group (7 of 10 participants) than in the control group (3 of 13 participants). This study suggests an association between underweight and sleep quality, especially nocturnal awakening, in young females. These findings underscore the importance of considering sleep quality in the management of underweight young females to improve their overall health outcomes.

Age- and height-dependent bias of underweight and overweight assessment standards for children and adolescents.

Background: Precision in evaluating underweight and overweight status among children and adolescents is paramount for averting health and developmental issues. Existing standards for these assessments have faced scrutiny regarding their validity. This study investigates the age and height dependencies within the international standards set by the International Obesity Task Force (IOTF), relying on body mass index (BMI), and contrasts them with Japanese standards utilizing the percentage of overweight (POW). Method: We scrutinized a comprehensive database comprising 7,863,520 children aged 5-17 years, sourced from the School Health Statistics Research initiative conducted by Japan's Ministry of Education, Culture, Sports, Science, and Technology. Employing the quantile regression method, we dissected the structure of weight-for-height distributions across different ages and sexes, quantifying the potentially biased assessments of underweight and overweight status by conventional criteria. Results: Applying IOFT criteria for underweight assessment revealed pronounced height dependence in males aged 11-13 and females aged 10-11. Notably, a discernible bias emerged, wherein children in the lower 25th percentile were classified as underweight five times more frequently than those in the upper 25th percentile. Similarly, the overweight assessment displayed robust height dependence in males aged 8-11 and females aged 7-10, with children in the lower 25th percentile for height deemed obese four or five times more frequently than their counterparts in the upper 25th percentile. Furthermore, using the Japanese POW criteria for assessment revealed significant age dependence in addition to considerably underestimating the percentage of underweight and overweight cases under the age of seven. However, the height dependence for the POW criterion was smaller than the BMI criterion, and the difference between height classes was less than 3-fold. Conclusion: Our findings underscore the intricacies of age-dependent changes in body composition during the growth process in children, emphasizing the absence of gold standards for assessing underweight and overweight. Careful judgment is crucial in cases of short or tall stature at the same age, surpassing sole reliance on conventional criteria results.

Differences of Bone Mineral Density by Characteristics of Sports in Amenorrheic Athletes.

Hypothalamic amenorrhea leads to a hypoestrogenic state, causing decreased bone mineral density (BMD), while strong impact loading on bone has been shown to increase BMD. The purpose of this study is to compare BMD in female athletes based on menstrual status and their sports/events by impact loading characteristics. BMD at the lumbar spine was measured by dual-energy X-ray absorptiometry and hormone level. The subjects were classified into four groups and BMD and hormone levels were compared among the four groups, which were divided into amenorrheic athletes (AAs) and eumenorrheic athletes (EAs). This study recruited 410 female athletes (164 in the AAs and 246 in the EAs), 55 athletes in non-impact sports, 123 in low-impact sports, 141 in multidirectional sports, and 91 in high-impact sports. In the AAs group, BMD Z-score was lowest in low-impact sports (Z-score: -1.53 [-1.76, -1.30]), and was highest in high-impact sports (Z-score: 0.02 [-0.34, 0.38]). In multidirectional and high-impact sports, BMD Z-score in the AAs group did not show results lower than the average for non-athletes. When screening female athletes for low BMD, it is important to evaluate the risk of low BMD based on the impact loading characteristics of their sports/events, in addition to the menstrual state.

Age and menstrual cycle may be important in establishing pregnancy in female athletes after retirement from competition.

BACKGROUND: Although it has been shown that amenorrhea associated with low energy availability or relative energy deficiency in sport affects body physiology in female athletes, the association between menstrual dysfunction during active sports careers and reproductive function after retirement is not clear. OBJECTIVE: To investigate the association between menstrual dysfunction during their active sports career and post-retirement infertility in female athletes. METHODS: A voluntary web-based survey was aimed at former female athletes who had become pregnant and gave birth to their first child after retirement. Nine multiple-choice questions were included, on maternal age, competition levels and menstrual cycles during active sports careers, time from retirement to pregnancy, the time of resumption of spontaneous menstruation after retirement, conception method, and mode of delivery, etc. Regarding cases of primary and secondary amenorrhea among the abnormal menstrual cycle group, only those whose spontaneous menstruation had not recovered from retirement to the time of pregnancy were included in the study. The association between the presence of abnormal menstrual cycles from active sports careers to post-retirement pregnancy and the implementation of infertility treatment was evaluated. RESULTS: The study population included 613 female athletes who became pregnant and gave birth to their first child after retiring from competitive sports. Of the 613 former athletes, the infertility treatment rate was 11.9%. The rate of infertility treatment was significantly higher in athletes with abnormal than normal menstrual cycles (17.1% vs. 10.2%, p = 0.0225). Multivariable logistic regression analysis showed that maternal age (adjusted odds ratio [OR] 1.194; 95% confidence interval [CI] 1.129, 1.262) and abnormal menstrual cycles (OR and 1.903; adjusted OR 1.105, 3.278) were the relevant factors for infertility treatment. CONCLUSION: It was suggested that menstrual dysfunction that persist from active sports careers to post-retirement may be a factor in infertility when trying to conceive after retirement.

Medical issues for female athletes returning to competition after childbirth.

BACKGROUND: In recent years, the number of athletes who aim to return to competition after childbirth has increased. However, few international reports have investigated complications during pregnancy, and changes in physical function after childbirth in many athletes. OBJECTIVE: To conduct a retrospective investigation of medical problems during pregnancy, and postpartum, in female athletes who aim to return to competition after childbirth, and to identify the barriers and facilitators for their return. METHODS: A voluntary web-based survey was aimed at former female athletes who became pregnant with their first child and gave birth during their active sports career. The survey items included respondent background, their exercise activities during and after childbirth, perinatal complications, mode of delivery, symptoms and physical function after childbirth. The participants were divided into a vaginal delivery group and a cesarean section group. RESULTS: Three hundred and twenty-eight (29.1 ± 5.1 years old) former athletes were included in the analysis, and about half reported undertaking exercise during pregnancy. The most common perinatal complication was anemia (27.4%). The appearance of any symptoms after childbirth, including low back pain (44.2%) and urinary incontinence (39.9%), was reported by 80.5%. The rate of urinary incontinence may be higher in the vaginal delivery than in the cesarean section group (p = 0.05). The most common physical decline after childbirth was in muscular strength, followed by speed and endurance. CONCLUSION: Addressing pregnancy-associated anemia and managing low back pain is critical for athletes aiming to return to competition after childbirth. Additionally, interventions to reduce the risk for and treat urinary incontinence are important. In addition, in order to return to competition after childbirth, it is important to strengthen muscles, especially the lower limbs and trunk, as well as to create a training program that takes into account the sport/events.

Differences in screening and treating relative energy deficiency in sport between the United States of America and Japan.

BACKGROUND: The diagnosis and treatment of relative energy deficiency in sport (RED-S) are challenging owing to variations in symptoms and the absence of specific guidelines. This study aimed to investigate differences in the diagnosis and follow-up of RED-S, its consequences, and related factors among sports medicine physicians with different backgrounds in Japan and the USA and examine the differences between the two countries. METHODS: An anonymous survey regarding the diagnosis and treatment processes of RED-S was distributed to sports medicine physicians via email. Respondents included 58 sports medicine physicians from the USA and 241 from Japan. RESULTS: The findings showed that 77.6% of the US physicians screened athletes for RED-S, whereas 17.5% of their Japanese counterparts did so. Moreover, 98.3% and 36.7% of the US and Japanese physicians, respectively, answered that they screened athletes for eating disorders upon suspicion of low energy availability. Logistic regression analysis revealed that the number of US sports medicine physicians who screened athletes for the female athlete triad (Triad) and RED-S (odds ratio [OR] = 12.78, P<0.001) and adhered to specific criteria for athlete suspension and return-to-play (OR=33.67, P<0.01) was higher than that of their Japanese counterparts. CONCLUSIONS: The prevalence of RED-S-related screening and treatment differed between US and Japanese sports medicine physicians. Educating sports medicine physicians about the diagnosis and treatment of athletes with possible signs of RED-S is important in treating female athletes and further investigations are required to identify why the physicians screened/not screened the athletes.

Development of University of Tokyo's eating disorders inventory in female athletes.

AIMS: This study aimed to develop a scale to screen for eating disorders in female athletes. METHODS: Preliminary survey: A total of 275 female athletes (mean age: 19.4 ± 1.0 years) and 7 female athletes diagnosed with eating disorders (mean age: 20.1 ± 2.5 years) were administered screening items prepared based on an existing scale, followed by exploratory factor analysis. Main survey: Six items, relating to three factors, were extracted, and 201 female athletes (mean age: 22.3 ± 4.8 years) and 6 female athletes diagnosed with current or a history of eating disorders (mean age: 18.8 ± 2.9 years) were queried. The diagnostic validity of the scale was then evaluated. RESULTS: Preliminary survey: Questions (α = 0.71) were extracted from six items, relating to three factors, and collectively termed the University of Tokyo's eating disorders inventory in female athletes (TEDIFA). To determine the scale cut-off score, ROC analysis was performed with the total score, and the cut-off and gray zone scores were set at 13 and 11, respectively. Main survey: At the cut-off score of 13, AUC, sensitivity, and specificity were 0.83 (p < 0.05), 75%, and 90%, respectively. CONCLUSIONS: The scale that was developed, TEDIFA, consisted of six items. The cut-off scores were set at 11 for the gray zone (sensitivity: 75%; specificity: 56%; accurate diagnosis rate: 60%), and 13 for positivity (sensitivity: 75%; specificity: 90%; accurate diagnosis rate: 87%), demonstrating the reliability and validity of the scale.

Progressive Changes in Lumbopelvic Alignment during the Three Month-Postpartum Recovery Period.

Pregnancy-related lumbopelvic pain is a common musculoskeletal problem, and postural changes are believed to be involved in these disorders. However, the lumbopelvic alignment changes in postpartum women remain unclear. This study aimed to determine whether there are changes in lumbopelvic alignment following vaginal or cesarean delivery and when these alignment changes occur after delivery. Thirty postpartum females (PP group) and 20 nulliparous female controls (CTL group) underwent anteroposterior, lateral pelvic, and lower-back X-ray in a static upright position. Digital radiographic images were analyzed and three radiographic variables, the pelvic incidence, pubic symphysis width, and sacral slope, were measured. The pubic symphysis width of the PP group was significantly larger immediately and one month after childbirth (PP group: 6.0 ± 1.1 mm (immediately), 5.0 ± 1.2 mm (one month); CTL group: 3.4 ± 0.4 mm; F = 31.79, p < 0.001). The sacrum slope in the PP group was significantly larger than in the CTL group 1 month after childbirth (PP group: 39.9 ± 6.6°; CTL group: 32.8 ± 5.1°; F = 2.59, p = 0.05). A two-way analysis of variance indicated no statistically significant main effects or interaction effects between the delivery modes on the pubic symphysis width or the sacrum slope. This study suggested that the course of lumbopelvic alignment progressed towards recovery for at least one month, and that these changes were independent of the delivery method.

Recovery of Abdominal Muscle Thickness and Contractile Function in Women after Childbirth.

Abdominal muscles may be both morphologically and functionally affected by pregnancy. Dysfunction of the muscles can lead to persistent postpartum low back pain. The recovery process of the abdominal muscles following childbirth is not well understood. This study aimed to demonstrate the changes in the thickness and contractile function of abdominal muscles during the first six months postpartum. Nine perinatal and 15 nulliparous females participated. The thicknesses and contraction/relaxation thickness ratios of the rectus abdominis (RA), external abdominal oblique (EO), internal abdominal oblique (IO), and transverse abdominis (TrA) were measured using ultrasound images from 36-39 weeks' gestation until six months postpartum. The RA, IO, and TrA muscles were thinner in perinatal females than controls at 36-39 weeks of gestation (4.8 vs. 9.47 mm (RA), 5.45 vs. 7.73 mm (IO), 2.56 vs. 3.38 mm (TrA), respectively). The thinner IO muscle persisted for six months after delivery. The decreased TrA thickness ratio persisted until four months post-delivery. Abdominal muscle thickness and contractile function decreased in the postpartum period. Therefore, abdominal muscle exercises might help prevent postpartum symptoms; however, because deterioration of muscle function is significant in the first four months, careful attention should be paid to exercise intensity. The study limitation was a relatively small sample size, thus future studies should involve more participants.

Advancement in female sports medicine and preventive medicine.

Sport plays a major role in maintaining and improving physical function and health of women from adolescence to sexual maturity, through to menopause and old age, and it also plays a key role in social productivity and medicine from the perspective of preventive medicine. However, in routine clinical practice, there are many gynecological problems that affect the condition and performance of female athletes due to a lack of appropriate medical intervention, such as neglect of amenorrhea and menstruation-related symptoms. In addition, the number of athletes aiming to return to competition post-partum has been increasing in recent years, but there is little medical data on the well-being of female athletes during pregnancy and the post-partum period. I previously conducted clinical research on three separate topics, with the aim of clarifying the current issues unique to female athletes, mainly in terms of conditioning and injury prevention. The goal was that clinical research was to examine the situation of athletes with and without disabilities and provide feedback from the survey results to athletes and coaches. This paper divides the clinical studies conducted to date into three topics that will be explored herein: (i) research on the female athlete triad (Triad); (ii) research on oral contraceptives/low-dose estrogen-progestin; and (iii) research on pregnancy and post-partum period.

Effect of administration of monophasic oral contraceptive on the body composition and aerobic and anaerobic capacities of female athletes.

AIM: To examine the effects of administration of monophasic oral contraceptive (OC) on the body composition and aerobic and anaerobic capacities of female athletes. METHODS: Ten female athletes (23.0 ± 4.1 years old) participated in this study. All the subjects were examined during the menstrual cycle (early follicular [EF], middle luteal [ML]) and OC cycle (inactive OC, and active OC phases). After the menstrual cycle measurements, all the subjects began taking OC. The athletes tested using a body composition, circumferences, the lactate curve test, the maximal oxygen consumption test, and the Wingate test during all phases. RESULTS: Waist circumference was lower during the OC cycle than menstrual cycle (P < 0.05), and the other circumferences of parts were not different during the menstrual or OC cycles. However, there were no differences in body composition before and after taking OC. The phase of the menstrual or OC cycle did not affect maximal oxygen consumption, heart rate max or power output at a blood lactate concentration of 2 and 4 mmol/L between the menstrual and OC cycle phases. Although, the peak blood lactate level after the Wingate test was higher during the OC cycle (inactive OC phase, 13.0 ± 2.4 mmol/L; active OC phase, 12.4 ± 3.0 mmol/L) than during the menstrual cycle (EF phase, 11.9 ± 2.1 mmol/L; ML phase, 11.4 ± 2.1 mmol/L; P < 0.05), the peak and average power in the Wingate test did not change during the menstrual and OC cycle phases. CONCLUSION: Administration of monophasic OC did not affect the body composition or aerobic and anaerobic capacities of female athletes.

Guideline for Gynecological Practice in Japan: Japan Society of Obstetrics and Gynecology and Japan Association of Obstetricians and Gynecologists 2020 edition.

Nine years after the first edition of The Guideline for Gynecological Practice, which was jointly edited by The Japan Society of Obstetrics and Gynecology and The Japan Association of Obstetricians and Gynecologists, the 4th Revised Edition was published in 2020. The 2020 Guidelines includes 4 additional clinical questions (CQ), which brings the total to 99 CQ (12 on infectious disease, 29 on oncology and benign tumors, 29 on endocrinology and infertility and 29 on healthcare for women). Currently, a consensus has been reached on the Guidelines, and therefore, the objective of this report is to present the general policies regarding diagnostic and treatment methods used in standard gynecological outpatient care that are considered appropriate. At the end of each answer, the corresponding Recommendation Level (A, B, C) is indicated.

Relationship between tartrate-resistant acid phosphatase 5b and stress fractures in female athletes.

BACKGROUND: Approximately 10% of female athletes have a history of stress fractures, which most commonly occur between the ages of 16 and 17 years old. PURPOSE: We investigated whether tartrate-resistant acid phosphatase 5b (TRACP-5b), which is a bone resorption marker, can serve as a valid predictor of stress fractures in female athletes in their teens and 20s. METHODS: Three hundred and sixteen elite female athletes were recruited between 2013 and 2015. Serum TRACP-5b and various hormones were examined in blood samples. The serum TRACP-5b level was compared between athletes with and without stress fractures within 3 months after the initial collection of their blood samples. RESULTS: The 316 athletes were divided into two age groups: 13-19 years old and 20-29 years old. Thirty-six athletes (11.4%) experienced new stress fractures within 3 months after the initial collection of their blood samples. The median serum TRACP-5b level was significantly higher in teenage athletes with new stress fractures than in teenage athletes without new stress fractures. In univariate logistic regression analysis, the Z-score of serum TRACP-5b was a significant predictive factor of stress fractures in teenage athletes only (odds ratio: 1.87; 95% CI: 1.31-2.66; P < 0.0012). CONCLUSION: For teenage female athletes, TRACP-5b is a predictor of the risk of stress fractures, and measuring TRACP-5b levels may be useful to prevent stress fractures.

Effect of transdermal estradiol therapy on bone mineral density of amenorrheic female athletes.

BACKGROUND: The effects of transdermal estradiol treatment (HT) in amenorrheic athletes (AA) with low body weight (BW) and low bone mineral density (BMD) are unknown. PURPOSE: To investigate whether HT increases BMD in AA with low BW and to compare the results with levels in AA who have recovered spontaneous menstruation (SM). METHODS: Female athletes (n = 151) were recruited at the Japan Institute of Sports Sciences and the University of Tokyo. All participants were divided into four groups: an AA group (untreated group) (n = 36), a HT group (n = 55), a SM group (n = 21), and an eumenorrheic athletes (EA) group (n = 39). Height, body weight, blood tests, and dual-energy X-ray absorptiometry were measured at baseline and after 12 months. The HT group was treated daily for 12 months with transdermal estrogen therapy. In addition, participants received oral progestin for 7 days once every 3 months. RESULTS: After 12 months, BMD in the AA group was significantly lower than at baseline; however, BMD in the other three groups was significantly higher than at baseline. The ratio of the change in BMD values before and after 12 months was -1.6 ± 3.2% for the AA group, 5.3 ± 8.7% for the HT group, 11.1 ± 8.9% for the SM group, and 2.3 ± 5.7% for the EA group. The rate of change in BMD values in the SM group was greater than that in the HT group. CONCLUSION: HT increased BMD in AA with low BW, and the increase in those with SM was greater than that in those treated with HT.

Low Bone Mineral Density in Elite Female Athletes With a History of Secondary Amenorrhea in Their Teens.

OBJECTIVE: To determine whether secondary amenorrhea during teenage years influences bone mineral density (BMD) in female athletes in their 20s. DESIGN: Original research. SETTING: Japan Institute of Sports Sciences. PARTICIPANTS: Two hundred ten elite female athletes older than 20 years were included in the study. MAIN OUTCOME MEASURES: Information on the participants' past (ie, during their teenage years) and current menstrual cycle, training time, history of stress fractures, and blood tests for hormones received was obtained. Bone mineral density of the lumbar spine was evaluated by dual-energy x-ray absorptiometry; low BMD was defined as a Z-score ≤-1. We investigated the correlation factors for low BMD in athletes in their 20s by univariable and multivariable logistic regression analysis. RESULTS: A total of 39 (18.6%) female athletes had low BMD. Secondary amenorrhea in their teens [odds ratio (OR), 7.11, 95% confidence interval (CI), 2.38-21.24; P < 0.001] and present body mass index (BMI) (OR, 0.56, 95% CI, 0.42-0.73; P < 0.001) were independent correlation factors for low BMD in the multivariable logistic regression analysis. The average Z-score for those with secondary amenorrhea in their teens and 20s, secondary amenorrhea in their 20s only, and regular menstruation was -1.56 ± 1.00, -0.45 ± 1.21, and 0.82 ± 1.11 g/cm, respectively. CONCLUSIONS: Secondary amenorrhea for at least 1 year during teenage years in female athletes and BMI at present was strongly associated with low BMD in their 20s.

Risk factors of stress fractures due to the female athlete triad: Differences in teens and twenties.

BACKGROUND: The female athlete triad (Triad), defined by the American College of Sports Medicine as low energy availability (LEA) with or without disordered eating, menstrual dysfunction, and low bone mineral density (BMD), is associated with stress fractures and athletes aged 16-17 years are most susceptible. PURPOSE: To examine whether the Triad increases the risk of stress fractures, athletes were assigned to a "teenage" group and a "20s" group. METHODS: This prospective study enrolled 390 elite female athletes and was conducted from 2012 to 2016 at Japan Institute of Sports Sciences. Blood concentrations of various hormones were examined, and BMD was measured at the lumbar spine and throughout the whole body using dual-energy X-ray absorptiometry. LEA was defined as body weight ≤85% of the ideal body weight for teenage athletes, or BMI ≤17.5 for athletes in their 20s. Low BMD was defined as a BMD Z-score of <-1.0 in the lumbar spine and the whole body. RESULTS: Among 390 athletes enrolled, 36 developed new stress fractures within 3 months of registration. The risk for stress fractures due to the Triad in teenage athletes was higher than for athletes in their 20s. In teenage female athletes, secondary amenorrhea, low BMD for the whole body, and a low ratio of actual body weight to ideal body weight increased the risk for stress fractures by 12.9 times, 4.5 times, and 1.1 times, respectively. CONCLUSION: To prevent stress fractures in female athletes with the Triad, age of athletes should be taken into consideration.