Dual X-ray absorptiometry total body bone mineral content and bone mineral density in 18- to 22-year-old caucasian men

Physical activity during life course and bone mass: a systematic review of methods and findings from cohort studies with young adults

Background

The purpose of this paper was to review the literature of the cohort studies which evaluated the association between physical activity during the life course and bone mineral content or density in young adults.

Methods

Prospective cohort studies with bone mineral density or content measured in the whole body, lumbar spine and femoral neck by dual energy x-ray absorptiometry as outcome and physical activity as exposure were searched. Two independent reviewers selected studies retrieved from electronic databases (Medline, Lilacs, Web of Science and Scielo) and reviewed references of all selected full text articles. Downs & Black criterion was used in the quality assessment of these studies.

Results

Nineteen manuscripts met inclusion criteria. Lumbar spine was the skeletal site most studied (n = 15). Different questionnaires were used for physical activity evaluation. Peak strain score was also used to evaluate physical activity in 5 manuscripts. Lack of statistical power calculation was the main problem found in the quality assessment. Positive associations between physical activity and bone mass were found more in males than in females; in weight bearing anatomical sites (lumbar spine and femoral neck) than in total body and when physical activity measurements were done from adolescence to adulthood – than when evaluated in only one period. Physical activity during growth period was associated with greater bone mass in males. It was not possible to conduct pooled analyses due to the heterogeneity of the studies, considering mainly the different instruments used for physical activity measurements.

Conclusions

Physical activity seems to be important for bone mass in all periods of life, but especially the growth period should be taking into account due to its important direct effect on bone mass and its influence in physical activity practice in later life. Low participation in peak strain activities may also explain the lower number of associations found in females.

Age-related distribution of bone and skeletal parameters in 1,322 Japanese young women

We explored factors that could serve as indices for therapeutic intervention aimed at prevention of osteoporosis. In this cross-sectional study, we investigated the timing of peak bone mass (PBM) in 1,322 Japanese women aged 12-30 years old. We measured height, body weight, bone mineral density (BMD), bone mineral content (BMC), and bone area at the lumbar spine and total hip, as well as the blood markers calcium, phosphorus, and the bone metabolic markers bone alkaline phosphatase (BAP) and type I collagen cross-linked N-telopeptide (NTX). All measurements were standardized with the mean at age 18 defined as 100% to identify age-related differences. In the total hip, BMD peaked at age 18, while, in the lumbar spine, BMD peaked at age 29, of which 99.8% was attained at age 18, suggesting that peak BMD was attained at age 18 at both the total hip and lumbar spine. No age difference was observed in serum calcium, while there was a 15.1% decrease between ages 12 and 18 in serum phosphorus. There were 273.8% and 208.5% decreases in serum BAP and NTX, respectively, between ages 12 and 18, while these levels remained constant thereafter, suggesting that bone and calcium metabolism are constant between ages 19 and 30. Factors that had stronger correlations with BMD, BMC, and bone area from 12 years to 18 years were height and body weight. PBM was reached at age 18. Control of body weight by using total hip BMD as an index for intervention should be reasonable.

BMD decreases over the course of a year in competitive male cyclists

Male cyclists have been found to have low BMD in cross-sectional studies. Changes in BMD values over 1 yr of training and competition were studied in 14 male cyclists. BMD decreased significantly at the total hip, neck, trochanter, and shaft regions but not the lumbar spine. This first prospective study of cyclists showed a decrease in BMD over the course of 1 yr.

INTRODUCTION

Cross-sectional studies have shown that some endurance athletes, and cyclists in particular, have low BMD. Whether vigorous cycle training is causally related with low BMD remains unknown.

MATERIALS AND METHODS

Changes in BMD values over 1 yr of training and competition were studied in 14 male road cyclists, 27-44 yr of age. Subjects were randomized to receive 1500 (500 mg with meals) or 250 mg of supplemental calcium citrate daily. BMD measurements were obtained at pre-, mid-, post-, and off-season time points over 1 yr. Dermal calcium loss during exercise was estimated using a patch collection technique to examine calcium loss as a potential mediator of changes in BMD.

RESULTS

Using paired t-tests, BMD was found to decrease significantly from pre- to off-season at the total hip, neck, shaft, and trochanter regions (relative changes of -1.5 +/- 2.1%, -0.7 +/- 2.1%, -0.9 +/- 2.1%, and -1.0 +/- 1.2%, respectively, all p < 0.05). The 1.0 +/- 1.2% decrease in BMD at the lumbar spine failed to reach statistical significance (p = 0.079). There were no differences in changes in BMD between the calcium supplementation groups. The 2-h dermal calcium loss was estimated at 136.5 +/- 60.5 mg. Higher dermal calcium losses were associated with lower baseline BMD values at the total hip, neck, and shaft (all p < 0.05), but were not significantly associated with changes in BMD.

CONCLUSIONS

This study suggests that high intensity cycle training may adversely affect BMD. Excessive dermal calcium loss during exercise may be a contributing factor, but mechanisms remain to be elucidated.

Population-based reference values for bone mineral density in young men

Population-based reference values for peak bone mass density in Danish men. BMD of total hip (1.078 +/- 0,14 g/cm2) differed significantly from values from National Health and Nutrition Examination Survey III and of total lumbar spine ((1.073 +/- 0.125 g/cm2) differed significantly from Hologic values.

INTRODUCTION

Geographic, ethnic, and socio-economic factors are known to affect bone mineral density (BMD) and peak bone mass significantly. Reference values for male peak bone mass are scarce, and the diagnosis of male osteoporosis often relies on values provided by producers of dual-energy X-ray absorptiometry (DXA) equipment.

METHODS

The aim of the present study was 1) to establish population-based reference values for BMD in young men and 2) to study subgroups based on variables with suspected impact on bone metabolism. We included 783 young Caucasian men aged 20 to 30 years in the Odense Androgen Study (OAS).

RESULTS

Peak BMD was attained within the third decade. Obesity (BMI > 30 kg/m2) was associated with higher BMD. Abuse of anabolic steroids as well as chronic illness was associated with lower BMD. Our population-based reference values for BMD of the total hip (1.078 +/- 0.14 g/cm2) differed significantly from published values from National Health and Nutrition Examination Survey III for non-Hispanic white men, while BMD of total lumbar spine (1.073 +/- 0.125 g/cm2) differed significantly from Hologic reference values.

CONCLUSIONS

Locally derived reference values are important to avoid false positive or false negative findings during work-up in patients evaluated for osteoporosis.

Bone metabolism in elite male rowers: adaptation to volume-extended training

We examined the effect of 6-month volume-extended training on bone metabolism in elite male rowers. Twelve elite male rowers (20.8+/-3.0 years; 192.9+/-4.7 cm; 91.9+/-5.3 kg; body fat 10.1+/-2.3%; VO2max 6.2+/-0.5 l min(-1)) participated in this study. Bone biochemical markers, hormones, bone mineral content (BMC), and bone mineral density (BMD) were assessed before and after training. Average weekly training volume was significantly higher (P<0.05) during the 6 months of heavy training compared to relative rest (11.6+/-0.4 h week(-1) vs. 16.8+/-0.6 h week(-1)), while intensity remained the same. At the end of training, only arm BMD was significantly increased by 5.7%. Osteocalcin (16.6%), insulin-like growth factor-1 (IGF-1) (20.2%) and the bioavailability IGF-1 index (17.9%) were significantly increased. Before heavy training, relationships were observed between the whole body BMD and growth hormone (r=0.64; P< or =0.02), lumbar spine BMD and 1.25(OH)2 vitamin D (r=0.69; P< or =0.04), arm BMD and testosterone (r=0.59; P< or =0.05), and arm BMD and adiponectin (r=0.59; P< or =0.05). No relationship was found between BMC or BMD and blood biochemical measures 6 months later (r=0.56; P> or =0.05). In addition, osteocalcin was related to IGF-1 (r>0.58; P<0.048) and bioavailability IGF-1 index (r>0.59; P< or =0.055) before and after training. In summary, heavy training had a moderately favorable effect on BMD. Bone tissue at specific skeleton sites is sensitive to changes in training volume even in athletes with already high BMD values. Changes in BMD and bone formation may be caused by changes in specific hormones such as IGF-1 and adiponectin in male athletes.

Stress fracture injury in young military men and women

Approximately 5% of all military recruits incur stress fracture injuries during intense physical training, predominately in the lower extremity. We compared young men and women with stress fracture injury (subjects) to a matched group of uninjured volunteers (controls) during a summer training program at the United States Naval Academy to identify possible risk factors for stress fracture injury. The subject group was composed of 13 female and 18 male plebes with training-induced stress fracture injury verified by plain radiographs and/or nuclear bone scan. The control group was composed of 13 female and 18 male plebes who remained without injury during plebe summer training but who were matched with the 31 injured plebes for the Initial Strength Test (1-mi run time, means: women, 7.9 min; men, 6.4 min) and body mass index (means: women, 23.4; men, 23.8). We found that the subjects lost significant body weight (mean, 2.63 +/- 0.54 kg) between Day 1 and the date of their diagnosis of a stress fracture (mean, Day 35) and that they continued to lose weight until the date of their DEXA scan (mean, Day 49). Among female plebes, there was no evidence of the female athlete triad (eating disorders, menstrual dysfunction, or low bone density). Thigh girth was significantly smaller in female subjects than in female controls and trended to be lower in male subjects than in male controls. Total body bone mineral content was significantly lower in the male subjects than in male controls. Bone mineral density of the distal tibia and femoral neck were not significantly different between the groups. DEXA-derived structural geometric properties were not different between subjects and controls. Because, on average, tibias were significantly longer in male subjects than in male controls, the mean bone strength index in male subjects was significantly lower than that of male controls. We conclude that significant, acute weight loss combined with regular daily physical training among young military recruits may be a significant contributing risk factor for stress fracture injuries in young military men and women.

Bone mineral density and total body bone mineral content in 18- to 22-year-old women

One hundred sixty-four (164) healthy, young Caucasian women enrolled as midshipmen at the United States Naval Academy with no known disease or bone injury were followed for 3.6 years. Change in bone mineral density (BMD) of the hip, lumbar spine and distal tibia, and total body bone mineral content (TBMC) was measured by dual energy X-ray absorptiometry (DXA). Bone mineral density and TBMC of these women were measured within 2 months (60 +/- 4 days) of entering the Academy and annually. Over the study period, hip BMD increased 2.26% (P < 0.001), lumbar spine BMD increased 3.27% (P < 0.001) and distal tibia BMD increased 5.2% (P < 0.001). Total body bone mineral content showed a 5.25% (P < 0.001) increase during the study period. In this group of young women, gain in BMD and TBMC continued until age 22. These results suggest that bone mass may accrue in certain groups of women beyond age 22. The significance of this increase in bone mass during early adulthood on risk for osteoporotic fractures in later life and its impact on exercise-related bone injuries are unknown and warrant further examination.