Dowthwaite Jodi N, Kliethermes Stephanie A, Scerpella Tamara A
Department of Orthopedics and Rehabilitation, University of Wisconsin-Madison, Madison, Wisconsin, USA.
Department of Orthopedic Surgery, SUNY Upstate Medical University, Syracuse, New York, USA.
Am J Hum Biol. 2025 Aug;37(8):e70118. doi: 10.1002/ajhb.70118.
In growing humans, densitometric scans of whole-body bone mass "less head" are recommended to circumvent the excessive contribution of youths' proportionally larger heads but potentially inflate inter-scan variation and least significant change due to measurement error. We aimed to determine biological benchmarks for achievement of adult head-body proportions in a sample of US females.
Annual whole-body dual energy x-ray absorptiometry (DXA) scans tracked growth, maturation, and bone mass accrual in a prospective longitudinal cohort of girls for up to 19 years (baseline age 7-15 years). We used cubic smoothing spline mixed effects models to generate chronological and gynecological age-based curves for head versus whole-body bone mass proportions (ratios). Females with ≥ 3 annual scans were included (n = 148, age 7-30 years).
Models yielded trajectories extending beyond observed age at peak bone mass for our sample. From age 18 years, "adult" mean of means for head vs. whole-body bone mass proportions was 0.204 (n = 66: 95% confidence interval = 0.198-0.210). Individual proportions stabilized to "adult" mean levels circum-menarche (n = 124: mean = 0.198; 95% confidence interval = 0.194-0.202). The minimum age for 95% confidence intervals overlapping with adult values was 12 years, circum-peak height velocity (n = 120: mean = 0.211; 95% confidence interval = 0.207-0.216).
In US girls with diverse activity exposures, head vs. whole-body bone mass proportions are "adult" from menarche onward; an "adult" age threshold of 12 years, or age at peak height velocity, may be used in the absence of extreme maturational delay to evaluate whole-body bone mass including the head.
对于成长中的人类，建议进行全身“不含头部”骨密度扫描，以避免年轻人比例较大的头部产生的过度影响，但这可能会夸大扫描间的差异以及由于测量误差导致的最小显著变化。我们旨在确定美国女性样本中达到成人头身比例的生物学基准。
在一个前瞻性纵向队列中，对女孩进行长达19年（基线年龄7至15岁）的年度全身双能X线吸收法（DXA）扫描，以跟踪生长、成熟和骨量积累情况。我们使用三次平滑样条混合效应模型来生成基于年龄和妇科年龄的头部与全身骨量比例（比率）曲线。纳入每年至少进行3次扫描的女性（n = 148，年龄7至30岁）。
模型得出的轨迹超出了我们样本中观察到的骨量峰值年龄。从18岁起，头部与全身骨量比例的“成人”均值为0.204（n = 66：95%置信区间 = 0.198 - 0.210）。个体比例在初潮前后稳定到“成人”平均水平（n = 124：均值 = 0.198；95%置信区间 = 0.194 - 0.202）。95%置信区间与成人值重叠的最小年龄为12岁，即身高增长峰值速度时（n = 120：均值 = 0.211；95%置信区间 = 0.207 - 0.216）。
在活动暴露情况多样的美国女孩中，头部与全身骨量比例从初潮开始即为“成人”比例；在没有极度成熟延迟的情况下，12岁或身高增长峰值速度时的“成人”年龄阈值可用于评估包括头部在内的全身骨量。
