Peak bone mineral area density and determinants among females aged 9 to 24 years in Mexico

Introduction: Peak bone mineral area density is the amount of bone tissue present when skeletal maturation is completed. The exact age at which bone accumulation reaches a plateau varies with skeletal region. In Mexico and other Latin American countries, there are very few reports on bone mineral area density at early age. Material and methods: A cross-sectional study of 461 females between 9 and 24 years of age in Cuernavaca, Mexico, distributed proportionately by age group, determined the bone mineral density (BMD) in femur, lumbar spine, and subcranial skeleton, using a Hologic 4500-Series A osteodensitometer. The peak bone mineral area density (PBM) was determined by using the sigmoid growth model defined by Raymond-Pearl (CSRP). Cohort comparisons among different age groups were developed to evaluate BMD in three skeletal regions, with the Dunnett test, comparing the slopes of BMD by each age stratum. Also, the primary determinants of BMD were evaluated through models of multiple linear regression. Results: The timing of PBM is highly site specific with some skeletal regions reaching PBM earlier: beginning with the femur, and later reaching the lumbar spine and subcranial skeleton. Using a multivariate model, age and body weight were important predictors of BMD in the three anatomical regions studied (p<.001). The percentage of fat is associated in an inversely proportionate manner (p<.005), as independent predictors for BMD in the lumbar spine. The age of the onset of menstruation is also a predictor of BMD in the lumbar spine (p<0.05); vigorous activity is an important predictor in the subcranial skeleton (p<0.001). Discussion: For Mexican females in the state of Morelos, the BMD are similar to that reported in a number of ethnic groups. In mestizo females the timing of PBM is highly site specific with some skeletal regions acquiring PBM earlier: specifically, in the femoral region where PBM rapidly reached a plateau. In Mexico, early strategies for preventing osteoporosis should be focused on promoting physical activity and appropriate eating habits (control of obesity, among others) during the puberty stage.