Peak bone mass development in U.S. females with varied physical activity patterns: a longitudinal view using three maturational clocks.

Abstract

Biological timing of peak bone mass is poorly characterized. Using whole body bone mass growth curves from childhood into adulthood, we show peak bone mass is reached 7 years after peak height velocity, 6 years post-menarche, and 19 years after birth. Early post-menarcheal screening would provide a window for intervention. We evaluated bone mass growth curves for individuals representing diverse physical activity patterns from childhood into adulthood. We used three age clocks centered on birth (chronological age, CHRON_age), menarche (gynecological age, GYN_age), and peak height velocity (PHV_age). We evaluated whether this methodology improved estimates of peak bone mass (PBM) to inform the timing of interventions to boost PBM. Whole-body bone mineral content (WBBMC, g) was measured annually by DXA, with semi-annual stature measurements, in young females with heterogeneous musculoskeletal loading patterns. Data included participants with known menarche dates and ≥ 3 serial measures (CHRON_age 8-25 years). Super-imposition by translation and rotation (SITAR) longitudinal growth curves were modeled to extract individual ages at PHV to model PHV_age curves. SITAR models identified ages at peak velocity for WBBMC accrual (PKVBMC) and PBM (WBBMC gain < 3% to < 1%) using all three clocks. Data were modeled for 137 females, median 11 scans per individual (IQR (7,12); range 3-17; total 1343 scans). Mean ages (years) at PHV and menarche were 11.9 (SD 0.9) and 13.2 (SD 1.3), respectively. Mean ages at PKVBMC and PBM were CHRON_age (PKVBMC 13.0, PBM 17-19), GYN_age (PKVBMC 0.0, PBM +4 to +6), and PHV_age (PKVBMC, +1.1; PBM, +5 to +7). On average, females reached PBM by CHRON_age 19 years, 6 years post-menarche, or 7 years post-PHV. Menarche-centered and PHV-centered analyses provide clocks for effective clinical assessment of early, average, and late maturers; we favor menarche-centering to handle divergent timing of menarche relative to PHV, which may be common in physically active females.