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Secular changes in relative leg length in post-war Japan.
Md. Ayub Ali1, Teruo Uetake, Fumio Ohtsuki
1Laboratory of Human Morphology, Graduate School of Science, Tokyo Metropolitan University, Tokyo, Japan.
Summary
Japanese children and youth show increased relative leg length over four decades. However, this trend of longer legs is slowing or has stopped, with growth stabilizing at younger ages.
Area of Science:
- Human Biology
- Anthropometry
- Pediatric Growth
Background:
- Secular trends in human physical characteristics are influenced by environmental and genetic factors.
- Leg length relative to stature is a key indicator of human physical development.
Purpose of the Study:
- To investigate longitudinal secular changes in height and estimated leg length (ELL) in Japanese children and youth.
- To analyze trends in long-leggedness and the timing of adolescent growth spurts.
Main Methods:
- Analysis of data from the "Statistical Report of the School Health Survey" in Japan (approx. 4 decades).
- Statistical methods including regression analysis to identify trends and timing of maximum growth increments.
Main Results:
- A significant increase in relative leg length (long-leggedness) was observed in Japanese children and youth.
- The trend of increasing relative leg length has slowed or stopped, particularly after the 1943-1963 birth years.
- Estimated leg length growth stabilized earlier in girls (9 years) than in boys (11 years).
- Maximum increment ages for height and ELL showed slight accelerations, with ELL spurts occurring earlier in girls but to a lesser extent than in boys.
Conclusions:
- Japanese children exhibit increased long-leggedness, but this trend is decelerating.
- The timing of adolescent growth spurts for leg length differs between sexes, with girls maturing earlier.
- Understanding these secular changes is crucial for monitoring population health and growth patterns.