Differences in female athlete triad risk factors between Japanese and American female runners: A comparative study

Differences in female athlete triad risk factors between runners from Japan and the United States have not been explored.

To compare the prevalence of Triad risk factors and Triad components between female Japanese and American distance runners.

Observational, cross-sectional.

Two universities; one in the United States and one in Japan.

A total of 77 female runners: 36 Japanese middle- and long-distance runners, and 41 American distance runners.

Not applicable.

Triad components were energy deficiency, menstrual disturbances, and poor bone health. Triad risk factors were, respectively for each component: body mass index, serum total triiodothyronine, and history of diagnosed eating disorders; delayed menarche, history of menstrual irregularity, and current oligoamenorrhea; and bone mineral density and history of stress fractures. Prevalence was compared with chi-square and Fisher's exact tests. Group differences were assessed with t-tests and Mann-Whitney U tests. Data are mean difference (95% confidence interval [CI]).

Japanese runners had lower body weight (-4.15 [95% CI, -7.03.to -1.27] kg, p = .005) and percentage of body fat (-5.2 [95% CI, -6.9 to -3.5] %, p < .001) than American runners, with no differences in body mass index, serum total triiodothyronine, age of menarche, or menstrual cycle length (p > .05). Japanese runners had significantly lower bone mineral density at the lumbar spine (-0.195 [95% CI, -0.246 to -0.143] g/cm², p < .001), total hip (-0.115 [95% CI, -0.165 to -0.064] g/cm², p < .001), and femoral neck (-0.214 [95% CI, -0.260 to -0.167] g/cm², p < .001), but higher total hip Z-scores than the American runners (0.5 [95% CI, 0.1 to 1.0], p = .022). The prevalence of energy deficiency (56% vs. 32%, p = .035), history of stress fractures (50% vs. 17%, p = .003), and of runners experiencing all three Triad components (42% vs. 16%, p = .014) was higher in Japanese than American runners. No other differences in prevalence were observed.

Japanese female runners may be at a higher Triad risk than American peers, given their higher prevalence of energy deficiency risk factors, history of stress fractures, and of athletes experiencing all Triad components.