Evolution of lumbar bone mineral content during adolescence and adulthood:A longitudinal study in 395 healthy females 10-24 years of age and 206 premenopausal women

In a longitudinal study of 395 normal 10- to 24-year-old female volunteers, 105 of whom were initially premenarcheal, lumbar bone mineral density (BMD ) and content (BMC) were measured by dual-energy X-ray absorptiometry (DXA) at inclusion and after a 2-year interval. The mean age of menarche was 13. 1 +/- 1.1 years (n = 395). In a multiple regression analysis the BMD and BM C relative gains were highly correlated with the height and weight relative gains and with the time since menarche (r = 0.91 and r = 0.93, respectivel y). The mean relative annual increments in body height, in L2-4 vertebral h eight, in BMD and in BMC peaked respectively at 1.5, 1.0, 0.6 and 0.7 years before menarche. The four perimenarcheal years, beginning with the first p ubertal clinical signs, are essential for bone acquisition, since 46.7% of adult BMC is acquired during this period. Two years after menarche, BMC is 85% of the adult value. Seven years after menarche no further significant v ariation in BMC is observed. In 206 menstruating women 27-47 years old, a D XA, lumbar measurement was also performed after a 4-year interval. There wa s a small but significant increase of 0.3 %/year in BMD and 0.7 %/year in B MC, contrasting with the results in the young population. This could be exp lained by a volumetric expansion with aging, which is supported by a small increase in L2-4 area (0.4 %/year). In conclusion, this longitudinal study on the lumbar site emphasizes the importance of the pre- and perimenarcheal period, when half of lumbar adult BMC is acquired. This suggests that grea ter attention must be paid to this period regarding nutrition and physical activity.