Published papers

Background: The prevalence of low bone mineral density (BMD) among female athletes is higher than that among their male counterparts up to 40%. Low BMD increases the risk of stress fractures. Purpose: To examine factors associated with low BMD in female athletes, and to develop, test, and evaluate a Pre-screening Tool for Early Detection of Low BMD in Female Athletes (PreST-LBMD). Method: The development and validation groups (381 and 233 subjects, respectively) underwent a medical interview and a BMD test at the lumbar spine using dual-energy X-ray absorptiometry (DXA). A Z-score < −1 was classified as low BMD. After extracting factors associated with low BMD from univariate logistic regression and multivariate least absolute shrinkage and selection operator (LASSO) regression analyses, each variable was scored based on the β coefficients from LASSO regression to create the PreST-LBMD. The development model was validated using receiver operating characteristic (ROC) curves. Furthermore, using external validation data, sensitivity, negative predictive value (NPV), and area under the curve (AUC) were calculated to evaluate the performance of PreST-LBMD. Result: Factors associated with low BMD included age at menarche, amenorrhea for more than 1 year during the teenage years, current duration of amenorrhea, body mass index, history of stress fractures, and exercise load. The calculated cutoff value for a high likelihood of low BMD was 3 points, with a sensitivity of 0.83 (0.79–0.88), a negative predictive value of 0.85 (0.81–0.90), and an area under the curve of 0.74 (0.67–0.81). Conclusion:  We successfully developed the PreST-LBMD, which showed promising results identifying female athletes with low BMD. Those scoring ≥3 should be assessed by DXA and evaluated for the likelihood of low BMD by the athlete’s health and performance team.

Objectives: The cardiac morphology of elite athletes is related to sports disciplines and race; however, no studies have examined the effects of sports discipline on East Asian athletes. Therefore, this study aimed to assess left ventricular (LV) remodeling using transthoracic echocardiography in elite Japanese athletes and establish standard values for the indicators of the cardiac morphology of elite athletes in East Asia, considering the influence of body size. Methods: We retrospectively evaluated 1,363 elite Japanese athletes who underwent electrocardiography and transthoracic echocardiography between January 2011 and December 2021. The athletes were assigned to four sports discipline categories (skill, power, mixed, and endurance). We evaluated the differences in LV volume and mass between the groups for each sex. Results: The LV end-diastolic volume (LVEDV) and LV mass indexed to the body surface area (BSA) in the endurance group (LVEDV/BSA: 72.3 ± 11.4 mL/m2 in males and 68.7 ± 11.0 mL/m2 in females, LV mass/BSA: 121.1 ± 19.1 g/m2 in males and 106.5 ± 18.0 g/m2 in females) were significantly larger than those of any other groups. Both values were affected by sex, BSA, and endurance sport type, whereas only LV mass was affected by age. Conclusion: Cardiac remodeling is proportional to the sport type, with a significantly greater effect in athletes playing endurance sports. The remodeling is particularly evident in the left ventricle; however, the corresponding remodeling is also observed in other heart chambers. Cardiac remodeling in elite Japanese athletes is similar to that observed in elite athletes of other races, except for the changes in LV wall thickness.

Aim: There is limited evidence showing a relationship with age in the incidence of sudden cardiac arrest during exercise, which can be lethal at times. Methods: To examine the incidence by age group in sudden cardiac arrest, we prospectively observed cases of sudden cardiac arrest in full marathons certified by the Japan Association of Athletics Federations held between April 2011 and March 2019. Sudden cardiac arrest was defined as collapse during or 1 h after the race requiring chest compressions or the use of an automatic electrical defibrillation. Results: 4.1 million persons ran in 516 marathons. Of the participants, 78.6 % were men. By age group, 37.4 %, 34.7 %, 19.6 %, and 8.3 % belonged to the < 40 s, 40 s, 50 s, and ≥ 60 s groups, respectively. During the study period, 69 sudden cardiac arrests (1.7 per 100,000 participants, 95 % confidence interval [CI]: 1.3–2.1) were observed, of which 66 were men. The incidence per 100,000 runners of sudden cardiac arrest was 0.9 (95 % CI: 0.4, 1.4), 0.9 (95 % CI: 0.4, 1.4), 2.6 (95 % CI: 1.5, 3.8), and 5.5 (95 % CI: 2.9, 8.2) for those in their under 40 s, 40 s, 50 s, and over 60 s, respectively, with higher rates for older age groups. Compared to men, the cases of SCA among women were less common (only three cases), and the incidence did not differ by age group. Conclusions: Men, unlike women, had a higher incidence of sudden cardiac arrest during marathons according to age. Identification of this high-risk population could be important information in encouraging marathoners pre-participation self-screening.

Objectives: Anemia is a common condition in long-distance runners (LDRs). Recently, not only iron deficiency (ID) but also energy deficiency has been considered as a risk factor for anemia in athletes but no evidence has yet been established. The aim of this study was to investigate the prevalence of anemia and ID and the influence of body mass index (BMI) on anemia in high-school LDRs. Methods: The participants were 406 male and 235 female elite Japanese LDRs who competed in the All-Japan High-School Ekiden Championship 2019. They submitted their anthropometric data and results of a blood test within five days after the competition. The prevalence of anemia and ID and the influence of BMI on anemia were assessed retrospectively. Results: Mean hemoglobin concentrations (Hb) were 14.8 ± 0.9 g/dl in males and 13.2 ± 0.9 g/dl in females. The prevalence of anemia (Hb < 14 g/dl in males and < 12 g/dl in females) was significantly higher in males (16.3%) than females (6.4%), but males also showed higher prevalence of non-iron deficiency anemia (NIDA) than females (11.6% and 3.0%, respectively). No significant gender difference was found in the prevalence of iron deficiency anemia (IDA) (4.7% in males and 3.4% in females). ID (serum ferritin level < 25 ng/ml) was significantly more prevalent in females (37.4%) than males (18.5%). A binary logistic regression analysis revealed that low BMI was a contributor to anemia in females (odds ratios: 0.577 (95% CI: 0.369–0.901), p = 0.012). Conclusion: In Japanese high-school LDRs, one in six males was anemic, but most males did not have ID. Conversely, one-third of females were diagnosed with ID. Lower BMI was identified as a risk for anemia in females, suggesting that leanness may also lead to anemia in females.

Background: While scientific evidence supports the efficacy of only limited nutritional supplements (NS) on sports performance, the use of NS is widespread in athletes. Given the serious issues of health damage or unintended Anti-Doping Rule Violations due to ingestion of contaminated NS in sports, accurately understanding NS practices by athletes is crucial. This study therefore elucidated the use of NS by elite Japanese track and field (TF) athletes. Methods: The subjects were 574 Japanese TF athletes, including 275 junior athletes (under 20 years) and 299 senior athletes, who participated in international competitions from 2013 to 2018. Data on NS use were collected through pre-participation medical forms obtained from all entrants before their participation in competitions. NS users were requested to report the product names and primary components of all NS they were taking. Results: The overall prevalence of NS use was 63.9%. The mean number of NS products used per athlete was 1.4. The prevalence was significantly higher in women (69.2%) than in men (59.6%) (p = 0.018) and significantly higher in senior athletes (68.9%) than in junior athletes (58.9%) (p = 0.012). The prevalence of NS use was higher in long-distance runners (75.8%) and lower in jumpers (52.3%) and throwers (49.2%) than other disciplines (p < 0.001). The most prevalent components were amino acids (49.3%), followed by vitamins (48.3%), minerals (22.8%), and protein (17.8%). Conclusions: Approximately two-thirds of elite Japanese TF athletes reported the use of NS, and NS practices varied by gender, age, and discipline.