Peak bone density in Croatian women: variations at different skeletal sites

Diurnal Salivary Cortisol in Relation to Body Composition and Heart Rate Variability in Young Adults

OBJECTIVE

Chronic stress has been related to impaired body composition (bone, muscle, adipose tissue), and disturbed autonomic nervous system (ANS), the latter regulated by hypothalamic-pituitary-adrenal (HPA) axis. Our objective was to investigate the relationship between salivary cortisol, body composition and heart rate variability (HRV-highly influenced by ANS), in a young student population.

METHODS

Body composition and HRV parameters were measured using two portable devices based on multi-frequency bioelectrical impedance and photoplethysmography. Body composition included measurement of bone, lean/muscle and adipose tissues. HRV included time domain and frequency domain indices. Salivary cortisol, immediately after awakening, 60 min post awakening and late night was collected and analyzed by ELISA.

RESULTS

Participants included n = 43 healthy university students (39 women, 4 men); 21.1 ± 1.3 years, BMI = 21.8 ± 3.4 kg/m². Skeletal muscle was reduced in most of the participants, bone mass was at the lower normal range, while the fat tissue parameters were normal with only 7% participants being overweight. Cortisol and HRV parameters of sympathetic predominance (low frequency-LF and low frequency/high frequency ratio-LF/HF) were significantly associated with higher fat tissue parameters (fat mass-FM% and intramuscular adipose tissue-IMAT%) (p <0.001 and p = 0.035, respectively) and with lower skeletal muscle (p = 0.002) and bone mass (p = 0.025).

CONCLUSIONS

The results point to a role of cortisol and ANS in the control of all three body composition compartments, suggesting that the stress can result in adverse effects on body composition, even in young, apparently healthy individuals.

Fat mass increase in 7-year-old children: more bone area but lower bone mineral density

The main aims of this study were, to evaluate what effect a change in fat mass (FM) and lean body mass (LBM) has on bone parameters over 2 years' time, in 7-year-old school children and to see what effect fitness had on bone parameters in these children. A repeated-measures design study was conducted where children born in 1999 from six elementary schools in Reykjavik, Iceland were measured twice. All children attending second grade in these six schools were invited to participate. Three hundred twenty-one children were invited, 211 underwent dual-energy X-ray absorptiometry (DXA) scans at the age of seven, and 164 (78 %) of the 211 had DXA scans again 2 years later. Increase in both FM and LBM was associated with increased total body bone mineral content (BMC) and bone area (BA). An increase in FM was more strongly positively associated with BA while an increase in LBM was more strongly associated with an increase in BMC. An increase in FM was negatively associated with change in bone mineral density (BMD), but an increase in LBM was positively associated with change in BMD. Fitness was positively associated with bone parameters when weight, height and sex were accounted for. The present results suggest that an increase in fat mass over 2 years is associated with an increase in BA and BMC, but a decrease in BMD in the whole body. An increase in LBM accrual, on the other hand, is positively associated with all bone parameters in the body. Fitness is associated with both BMC and BMD but not BA.

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.

Bone mineral accrual from 8 to 30 years of age: an estimation of peak bone mass

Bone area (BA) and bone mineral content (BMC) were measured from childhood to young adulthood at the total body (TB), lumbar spine (LS), total hip (TH), and femoral neck (FN). BA and BMC values were expressed as a percentage of young-adult values to determine if and when values reached a plateau. Data were aligned on biological ages [years from peak height velocity (PHV)] to control for maturity. TB BA increased significantly from -4 to +4 years from PHV, with TB BMC reaching a plateau, on average, 2 years later at +6 years from PHV (equates to 18 and 20 years of age in girls and boys, respectively). LS BA increased significantly from -4 years from PHV to +3 years from PHV, whereas LS BMC increased until +4 from PHV. FN BA increased between -4 and +1 years from PHV, with FN BMC reaching a plateau, on average, 1 year later at +2 years from PHV. In the circumpubertal years (-2 to +2 years from PHV): 39% of the young-adult BMC was accrued at the TB in both males and females; 43% and 46% was accrued in males and females at the LS and TH, respectively; 33% (males and females) was accrued at the FN. In summary, we provide strong evidence that BA plateaus 1 to 2 years earlier than BMC. Depending on the skeletal site, peak bone mass occurs by the end of the second or early in the third decade of life. The data substantiate the importance of the circumpubertal years for accruing bone mineral.

Influence of heredity and environment on peak bone density: a parent-offspring study

The aim of the study was to determine the relative influence of heredity and environment on peak bone density and also to estimate the risk of having low peak bone density if the bone density of parents is low. The study comprised 83 families (48 daughters and 35 sons and their parents). The children were at an age when bone density is at its peak at most skeletal sites (22.2+/-1.8 girls; 23.1+/-1.2 boys). Bone mineral density (BMD; g/cm(2)) was determined by dual-energy X-ray absorptiometry. Anthropometric measurements were made, and calcium intake and physical activity were assessed. Heredity accounted for 22-42% of the variation in BMD of the children, depending on the skeletal site. Heritability for cortical BMD of mid-radius was considerably lower than that for spinal trabecular BMD. Children whose parents had low BMDs (T-score< or =-1) were 1.1 times more likely to inherit low BMD. Child BMD depended significantly on parent BMD and also on physical activity. In our study, heredity accounted for the total BMD variation more than the environmental factors. This influence was lower in the cortical than in the trabecular parts of the skeleton. Optimal environmental factors, such as physical activity, may influence the risk of inheriting low BMD.

Bone mass of overweight affluent Indian youth and its sex-specific association with body composition

SUMMARY: The study assessed whether overweight is associated with better bone densities in healthy youth. It was observed that overweight individuals had better BMDs at the hip but not at other sites after controlling for the bone area. Lean body mass was an important determinant of BMDs in men, but both lean and fat mass were important for BMDs in women. INTRODUCTION: The study assessed the relationship of overweight and obesity to the bone mass in young men and women consuming adequate calcium. METHODS: Bone and body composition parameters were measured using dual energy X-ray absorptiometry in overweight men (n = 74) and women (n = 77) in the age group of 20-35 years and compared with controls having normal body mass index (BMI). Biochemical parameters of bone metabolism were also assessed. RESULTS: After adjustment for whole body bone area, bone mineral densities (BMDs) at femoral neck and hip were significantly higher in overweight individuals when compared with controls. However, BMD at lumbar spine, forearm, and whole body were not significantly different in the two BMI groups. Overweight women had lower vitamin D and higher parathormone levels than controls. Regression analyses indicated that height was an important determinant of BMD at most of the skeletal sites in both men and women. Lean body mass was an important determinant of BMDs in men, but both lean and fat mass were important for BMDs in women. CONCLUSION: Overweight may be associated with better BMDs at the hip but not at other sites after controlling for the bone area. Body composition parameters may have sex-specific associations with BMD.