Influence of Heredity and Environment on Peak Bone Density: A Review of Studies in Croatia
One of the main determinants of who will develop osteoporosis is the amount of bone accumulated at peak bone density. There is poor agreement, however, on when peak bone density occurs. Ethnic differences were observed in age at peak bone density and their correlates. Since the diagnosis of osteoporosis and osteopaenia is based on the comparison between patients' bone mineral density (BMD) and optimal peak bone density in healthy young people (T-score), it is of great importance that each country should provide its own reference peak bone density data.
This review article presents our published results on peak bone density in Croatia and compares them with findings in other populations. Our research included 18 to 25-year-old students from Zagreb University and their parents. The results showed that peak bone mass in young Croatian women was achieved before the age of twenty, but BMD continued to increase after the mid-twenties in the long-bone cortical skeleton. BMD was comparable to the values reported by the National Health and Nutrition Examination Survey (NHANES) and other studies that included the same age groups, except for the cortical part of the radius, where it was significantly lower. Men achieved peak bone density in the spine later than women, which cannot be explained by different diet or physical activity. As expected, heredity was more important for peak bone density than the environmental factors known to be important for bone health. However, the influence of heredity was not as strong as observed in most other populations. It was also weaker in the cortical than in the trabecular parts of the skeleton. Future research should include young adolescent population to define the exact age of achieving peak bone density in different skeletal sites.
Differences in Peak Bone Density Between Male and Female Students
As an important determinant of osteoporotic fracture risk, peak bone density tends to be higher in men than in women. The aim of this study was to see whether young men and women differed in the time and skeletal region of peak bone density. We also investigated the influence of diet and physical activity on bone mass. The study group included 51 male and 75 female students aged 19 to 25 years. Bone mineral density was measured for the spine, total femur, and the distal third of the radius using dual energy x-ray absorptiometry. Dietary data were obtained using a specially designed semiquantitative food frequency questionnaire. Bone mineral density (BMD; g cm-2) was higher in boys than in girls at all measured sites, while bone mineral apparent density (BMAD; g cm-3) was higher in girls. Age negatively correlated with bone mineral density in all measured sites except in the boys' spine. Sodium, protein, and fibres were nutrients that significantly correlated with bone mineral density. The study suggests that boys achieve peak bone density later than girls, and that this delay is the most prominent in the spine. In our study group, this difference could not be explained by different nutrition or the level of physical activity.