Determinants of bone mass and bone size in a large cohort of physically active young adult men

Using machine learning techniques to predict the risk of osteoporosis based on nationwide chronic disease data

Osteoporosis is a major public health concern that significantly increases the risk of fractures. The aim of this study was to develop a Machine Learning based predictive model to screen individuals at high risk of osteoporosis based on chronic disease data, thus facilitating early detection and personalized management. A total of 10,000 complete patient records of primary healthcare data in the German Disease Analyzer database (IMS HEALTH) were included, of which 1293 diagnosed with osteoporosis and 8707 without the condition. The demographic characteristics and chronic disease data, including age, gender, lipid disorder, cancer, COPD, hypertension, heart failure, CHD, diabetes, chronic kidney disease, and stroke were collected from electronic health records. Ten different machine learning algorithms were employed to construct the predictive mode. The performance of the model was further validated and the relative importance of features in the model was analyzed. Out of the ten machine learning algorithms, the Stacker model based on Logistic Regression, AdaBoost Classifier, and Gradient Boosting Classifier demonstrated superior performance. The Stacker model demonstrated excellent performance through ten-fold cross-validation on the training set and ROC curve analysis on the test set. The confusion matrix, lift curve and calibration curves indicated that the Stacker model had optimal clinical utility. Further analysis on feature importance highlighted age, gender, lipid metabolism disorders, cancer, and COPD as the top five influential variables. In this study, a predictive model for osteoporosis based on chronic disease data was developed using machine learning. The model shows great potential in early detection and risk stratification of osteoporosis, ultimately facilitating personalized prevention and management strategies.

Association between normal-weight obesity and bone mineral density in older Korean adults: A population-based cross-sectional study

The effects of normal-weight obesity, which is defined as having a high level of body fat despite a normal body mass index, on the health of bones in older adults are poorly understood. This cross-sectional study examined the relationship between normal-weight obesity and bone mineral density in Korean adults aged 50 years or more (2815 men and 2744 women) from the 2008-2011 Korea National Health and Nutrition Examination Surveys. Between the ages of 50 and 69 years, individuals with normal-weight obesity had a higher risk of low bone mineral density (odds ratio = 1.596, 95 % confidence interval = 1.189-2.141, p = 0.002) compared with individuals with normal-weight non-obesity. However, no significant association between normal-weight obesity and bone mineral density was observed among people between the ages of 70 and 89 years. The study findings support the clinical significance of normal-weight obesity as a proxy biomarker to identify in primary care settings people who are at increased risk of developing osteoporosis at an early stage of aging.

Polymorphisms in Genes Encoding VDR, CALCR and Antioxidant Enzymes as Predictors of Bone Tissue Condition in Young, Healthy Men

The aim of the study was to assess significant predictors of bone mineral content (BMC) and bone mineral density (BMD) in a group of young, healthy men at the time of reaching peak bone mass. Regression analyses showed that age, BMI and practicing combat sports and team sports at a competitive level (trained vs. untrained group; TR vs. CON, respectively) were positive predictors of BMD/BMC values at various skeletal sites. In addition, genetic polymorphisms were among the predictors. In the whole population studied, at almost all measured skeletal sites, the SOD2 AG genotype proved to be a negative predictor of BMC, while the VDR FokI GG genotype was a negative predictor of BMD. In contrast, the CALCR AG genotype was a positive predictor of arm BMD. ANOVA analyses showed that, regarding SOD2 polymorphism, the TR group was responsible for the significant intergenotypic differences in BMC that were observed in the whole study population (i.e., lower BMC values of leg, trunk and whole body were observed in AG TR compared to AA TR). On the other hand, higher BMC at L1-L4 was observed in the SOD2 GG genotype of the TR group compared to in the same genotype of the CON group. For the FokI polymorphism, BMD at L1-L4 was higher in AG TR than in AG CON. In turn, the CALCR AA genotype in the TR group had higher arm BMD compared to the same genotype in the CON group. In conclusion, SOD2, VDR FokI and CALCR polymorphisms seem to affect the association of BMC/BMD values with training status. In general, at least within the VDR FokI and CALCR polymorphisms, less favorable genotypes in terms of BMD (i.e., FokI AG and CALCR AA) appear to be associated with a greater BMD response to sports training. This suggests that, in healthy men during the period of bone mass formation, sports training (combat and team sports) may attenuate the negative impact of genetic factors on bone tissue condition, possibly reducing the risk of osteoporosis in later age.

Does the osteon morphology depend on the body mass? A scaling study on macroscopic and histomorphometric differences between cow (Bos taurus) and sheep (Ovis aries)

The structure and geometry of bone depend on many biological and environmental factors. These factors affect the bone tissue's microstructure differently, and their interaction has not yet been fully elucidated. Our research investigated the effect of body mass on the macro- and microstructure of the compact bone. Therefore we analyzed the humerus and femur bones from females of 11 cows and 11 sheep at the age of 4–10 years. Both species have very similar dietary and locomotion patterns, but their body size and weight are very different. Within macroscopical analyzes of bones were observed ascending order of robustness index and bone diaphysis index. In both animals, plexiform and irregular Haversian bone tissues were identified in humerus and femur. Conversely, the dense Haversian tissue present only in cow above all in the femur. The most considerable interspecific osteonal difference between sheep and cow was in the osteon density, whose average value is 37% higher in the cow. The osteons of sheep humerus are almost circular, and osteons of cow femur are more elliptical. Within both species, the femoral osteons are elliptical than those of humerus. Despite the cow weighing more than 10 times the sheep, the measurements of osteons and Haversian canals, are very similar (the values of the ratio cow/sheep for these types are comprised from 1.04 to 1.86). Our findings indicate that the body mass does not affect the size of bone microstructure, probably more sensitive to other factors as a lifestyle and locomotor ability.

Serum 25-hydroxyvitamin D fluctuations in military personnel during 6-month summer operational deployments in Afghanistan

Soldier operational performance is determined by their fitness, nutritional status, quality of rest/recovery, and remaining injury/illness free. Understanding large fluctuations in nutritional status during operations is critical to safeguarding health and well-being. There are limited data world-wide describing the effect of extreme climate change on nutrient profiles. This study investigated the effect of hot-dry deployments on vitamin D status (assessed from 25-hydroxyvitamin D (25(OH)D) concentration) of young, male, military volunteers. Two data sets are presented (pilot study, n 37; main study, n 98), examining serum 25(OH)D concentrations before and during 6-month summer operational deployments to Afghanistan (March to October/November). Body mass, percentage of body fat, dietary intake and serum 25(OH)D concentrations were measured. In addition, parathyroid hormone (PTH), adjusted Ca and albumin concentrations were measured in the main study to better understand 25(OH)D fluctuations. Body mass and fat mass (FM) losses were greater for early (pre- to mid-) deployment compared with late (mid- to post-) deployment (P<0·05). Dietary intake was well-maintained despite high rates of energy expenditure. A pronounced increase in 25(OH)D was observed between pre- (March) and mid-deployment (June) (pilot study: 51 (sd 20) v. 212 (sd 85) nmol/l, P<0·05; main study: 55 (sd 22) v. 167 (sd 71) nmol/l, P<0·05) and remained elevated post-deployment (October/November). In contrast, PTH was highest pre-deployment, decreasing thereafter (main study: 4·45 (sd 2·20) v. 3·79 (sd 1·50) pmol/l, P<0·05). The typical seasonal cycling of vitamin D appeared exaggerated in this active male population undertaking an arduous summer deployment. Further research is warranted, where such large seasonal vitamin D fluctuations may be detrimental to bone health in the longer-term.

THE USE OF ULTRASONOGRAPHY TO EVALUATE MUSCLE THICKNESS AND SUBCUTANEOUS FAT IN CHILDREN AND ADOLESCENTS WITH CYSTIC FIBROSIS

Objective:

To compare muscle thickness and subcutaneous fat in cystic fibrosis (CF) patients and healthy controls using ultrasonography (US), and to correlate US findings with nutritional, clinical and functional variables.

Methods:

Patients aged 6 to 18 years old with a diagnosis of CF and healthy controls were included. Participants underwent anthropometric measurements, an ultrasonographic evaluation of muscle thickness and subcutaneous fat in the triceps, quadriceps, and gastrocnemius regions, and skinfold thickness measurements. Body fat percentage was estimated using skinfold measurement. Subjects with CF also underwent a pulmonary function assessment using spirometry.

Results:

We studied 39 CF patients and 45 controls. Alower body mass index was observed in CF patients (p=0.011). Body composition and muscle thickness were similar between the groups. Only calf (p=0.023) circumference and femur diameter (p<0.001) were lower in CF patients. Although there were no significant between-group differences in the comparison of US measurements of subcutaneous fat, CF patients exhibited decreased skinfold thickness in the triceps (p=0.031) and quadriceps (p=0.019). Moreover, there were weak and moderate correlations of US quadricep thickness with forced vital capacity (FVC) and lean mass, respectively. Moderate correlations of the triceps, quadriceps and gastrocnemius between US subcutaneous fat and skinfold measurements were found.

Conclusions:

Patients with CF presented a reduction in subcutaneous fat content. Muscle thickness correlated with FVC and nutritional parameters. In addition, US findings correlated positively with skinfold measurements.

Anatomic Variation in Morphometry of Human Coracoid Process among Asian Population

Ethnic origin plays an important role in bone morphometry. Studies examining the influence of coracoid process have focused primarily on adults and have not included people from diverse Asian ethnic backgrounds. Our goal was to explore ethnic differences in morphometry of coracoid among Asian population. We performed morphometric measurements of coracoid process on cadaveric shoulders and shoulder CT scans from 118 specimens. The cadaveric sample included Indian (46%), Chinese (27%), and Myanmarese (27%) subjects, while the CT scans sample included Chinese (67%) and Malay (33%) subjects. The morphometric measurements were performed using digital caliper and software developed at Golden Horses Health Sanctuary (GHHS). In the Indian cadaveric shoulders, the coracoid process is better developed than the other groups with the exception of the tip width of coracoid process. There are significant differences in almost all measurements (P < 0.05) between the ethnic groups. On the other hand, the morphometry of coracoid process from CT scans data is bigger in Chinese than Malay subjects when stratified by sex (P < 0.05). Moreover, in all morphometric measurements, the females had smaller measurements than males (P < 0.05). Understanding such differences is important in anatomy, forensic and biological identity, and orthopaedic and shoulder surgeries.

Subjective evaluation of the frequency of coffee intake and relationship to osteoporosis in Chinese men

BACKGROUND

The main purpose of this study was to evaluate the associations between frequency of coffee intake and osteoporosis (OP) in a general Chinese male sample.

METHODS

We conducted a large-scale, community-based, cross-sectional study to investigate the associations by using a self-report questionnaire to estimate the frequency of coffee intake. A total of 992 men were available for data analysis in this study. Multiple regression models controlling for confounding factors to include frequency of coffee intake variable were performed to investigate the relationships for OP.

RESULTS

Positive correlations between frequency of coffee intake and T-score were reported (β = 0.211, P = 0.024). Multiple regression analysis indicated that the frequency of coffee intake was significantly associated with OP (P < 0.05 for model 1 and model 2). The men with moderate frequency of coffee intake had a lower prevalence of OP.

CONCLUSIONS

The findings indicated that consumption of coffee was independently and significantly associated with OP. The prevalence of OP was less frequent in Chinese men with moderate coffee intake.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02451397.

Wrist circumference as a novel negative risk factor for cardiovascular disease among adult men: a median follow-up of 9 years

PURPOSE

Wrist circumference is an easy to measure anthropometric index of body frame and bone size. The aim of this study was to examine the association of wrist circumference with incidence of cardiovascular disease (CVD) among adult men.

METHODS

For this study 2531 male participants aged ≥30 years, without any history of CVD were selected and followed from 1999 to 2011. Cox proportional hazard models and logistic regression were used to examine the relation of wrist circumference with incident CVD.

RESULTS

A total of 339 cases of CVD were reported throughout a median follow-up of 9.4 years. In the multi-variable Cox model, 1 unit increase of wrist circumference was inversely associated with incident CVD with a HR (95 % CI) of 0.84 (0.72-0.98, P value = 0.02). The receiver operating characteristics curve in a logistic regression model for wrist circumference in prediction of CVD showed a cutoff of 17.75 cm, beyond which was associated with a lower risk for CVD.

CONCLUSION

In a population with a high prevalence of CVD risk factors, it was shown that a higher wrist circumference was associated with lower risk for incident CVD. Further studies are needed to explore the underlying mechanisms of this inverse relation.

A Prospective Cluster-Randomized Trial of Telehealth Coaching to Promote Bone Health and Nutrition in Deployed Soldiers

Findings from previous studies suggest that inadequate consumption of calcium and vitamin D and a decrease in exercise while deployed can be detrimental to bone health. This study enrolled 234 soldiers randomized to receive one-time nutrition and exercise education pre-deployment (n = 149), or telehealth coaching (n = 85), throughout the deployment cycle. Results suggest that online educational efforts may enhance sports activity, bone turnover, and vitamin D status. Improving vitamin D status and remaining active while deployed appears to sustain healthy bone density in young soldiers. Early and aggressive educational outreach to young adults may prevent chronic musculoskeletal conditions and disabling osteoporosis later in life.

Stress fractures of the foot and ankle in athletes

Context:

Stress fractures of the foot and ankle are a common problem encountered by athletes of all levels and ages. These injuries can be difficult to diagnose and may be initially evaluated by all levels of medical personnel. Clinical suspicion should be raised with certain history and physical examination findings.

Evidence Acquisition:

Scientific and review articles were searched through PubMed (1930-2012) with search terms including stress fractures and 1 of the following: foot ankle, medial malleolus, lateral malleolus, calcaneus, talus, metatarsal, cuboid, cuneiform, sesamoid, or athlete.

Study Design:

Clinical review.

Level of Evidence:

Level 5.

Results:

Stress fractures of the foot and ankle can be divided into low and high risk based upon their propensity to heal without complication. A wide variety of nonoperative strategies are employed based on the duration of symptoms, type of fracture, and patient factors, such as activity type, desire to return to sport, and compliance. Operative management has proven superior in several high-risk types of stress fractures. Evidence on pharmacotherapy and physiologic therapy such as bone stimulators is evolving.

Conclusion:

A high index of suspicion for stress fractures is appropriate in many high-risk groups of athletes with lower extremity pain. Proper and timely work-up and treatment is successful in returning these athletes to sport in many cases. Low-risk stress fracture generally requires only activity modification while high-risk stress fracture necessitates more aggressive intervention. The specific treatment of these injuries varies with the location of the stress fracture and the goals of the patient.

Stress fractures of the pelvis and legs in athletes: a review

CONTEXT

Stress fractures are common injuries in athletes, often difficult to diagnose. A stress fracture is a fatigue-induced fracture of bone caused by repeated applications of stress over time.

EVIDENCE ACQUISITION

PubMed articles published from 1974 to January 2012.

RESULTS

Intrinsic and extrinsic factors may predict the risk of stress fractures in athletes, including bone health, training, nutrition, and biomechanical factors. Based on their location, stress fractures may be categorized as low- or high-risk, depending on the likelihood of the injury developing into a complete fracture. Treatment for these injuries varies substantially and must account for the risk level of the fractured bone, the stage of fracture development, and the needs of the patient. High-risk fractures include the anterior tibia, lateral femoral neck, patella, medial malleolus, and femoral head. Low-risk fractures include the posteromedial tibia, fibula, medial femoral shaft, and pelvis. Magnetic resonance is the imaging test of choice for diagnosis.

CONCLUSIONS

These injuries can lead to substantial lost time from participation. Treatment will vary by fracture location, but most stress fractures will heal with rest and modified weightbearing. Some may require more aggressive intervention, such as prolonged nonweightbearing movement or surgery. Contributing factors should also be addressed prior to return to sports.

Gender aspects of osteoporosis and bone strength

Although postmenopausal and elderly women are more frequently affected by osteoporosis, men are not protected from the disease. Age-related osteoporosis involves several gender-specific clinical aspects such as disease onset time and different dynamics of bone loss. Men benefit from larger bones and a time-delay of age-related changes in bone density and quality. Moreover, secondary osteoporosis is more common in males than in females. High-resolution peripheral quantitative computed tomography (HR-pQCT) and high-resolution magnetic resonance imaging (HR-MRI) represent novel research tools for a noninvasive quantification of bone microstructure which is of interest for musculoskeletal gender studies. For optimal design of such studies, researchers should be aware of technical pitfalls and site-specificity of bone microstructure.

Nutritional factors that influence change in bone density and stress fracture risk among young female cross-country runners

OBJECTIVE

To identify nutrients, foods, and dietary patterns associated with stress fracture risk and changes in bone density among young female distance runners.

DESIGN AND SETTING

Two-year, prospective cohort study. Observational data were collected in the course of a multicenter randomized trial of the effect of oral contraceptives on bone health.

PARTICIPANTS

One hundred and twenty-five female competitive distance runners ages 18-26 years.

ASSESSMENT OF RISK FACTORS

Dietary variables were assessed with a food frequency questionnaire.

MAIN OUTCOME MEASUREMENTS

Bone mineral density and content (BMD/BMC) of the spine, hip, and total body were measured annually by dual x-ray absorptiometry (DEXA). Stress fractures were recorded on monthly calendars, and had to be confirmed by radiograph, bone scan, or magnetic resonance imaging.

RESULTS

Seventeen participants had at least one stress fracture during follow-up. Higher intakes of calcium, skim milk, and dairy products were associated with lower rates of stress fracture. Each additional cup of skim milk consumed per day was associated with a 62% reduction in stress fracture incidence (P < .05); and a dietary pattern of high dairy and low fat intake was associated with a 68% reduction (P < .05). Higher intakes of skim milk, dairy foods, calcium, animal protein, and potassium were associated with significant (P < .05) gains in whole-body BMD and BMC. Higher intakes of calcium, vitamin D, skim milk, dairy foods, potassium, and a dietary pattern of high dairy and low fat were associated with significant gains in hip BMD.

CONCLUSIONS

In young female runners, low-fat dairy products and the major nutrients in milk (calcium, vitamin D, and protein) were associated with greater bone gains and a lower stress fracture rate. Potassium intake was also associated with greater gains in hip and whole-body BMD.

Correlates of trabecular and cortical volumetric bone mineral density of the radius and tibia in older men: the Osteoporotic Fractures in Men Study

Quantitative computed tomography (QCT) can estimate volumetric bone mineral density (vBMD) and distinguish trabecular from cortical bone. Few comprehensive studies have examined correlates of vBMD in older men. This study evaluated the impact of demographic, anthropometric, lifestyle, and medical factors on vBMD in 1172 men aged 69 to 97 years and enrolled in the Osteoporotic Fractures in Men Study (MrOS). Peripheral quantitative computed tomography (pQCT) was used to measure vBMD of the radius and tibia. The multivariable linear regression models explained up to 10% of the variance in trabecular vBMD and up to 9% of the variance in cortical vBMD. Age was not correlated with radial trabecular vBMD. Correlates associated with both cortical and trabecular vBMD were age (-), caffeine intake (-), total calcium intake (+), nontrauma fracture (-), and hypertension (+). Higher body weight was related to greater trabecular vBMD and lower cortical vBMD. Height (-), education (+), diabetes with thiazolidinedione (TZD) use (+), rheumatoid arthritis (+), using arms to stand from a chair (-), and antiandrogen use (-) were associated only with trabecular vBMD. Factors associated only with cortical vBMD included clinic site (-), androgen use (+), grip strength (+), past smoker (-), and time to complete five chair stands (-). Certain correlates of trabecular and cortical vBMD differed among older men. An ascertainment of potential risk factors associated with trabecular and cortical vBMD may lead to better understanding and preventive efforts for osteoporosis in men.

Coffee consumption and CYP1A2 genotype in relation to bone mineral density of the proximal femur in elderly men and women: a cohort study

Background

Drinking coffee has been linked to reduced calcium conservation, but it is less clear whether it leads to sustained bone mineral loss and if individual predisposition for caffeine metabolism might be important in this context. Therefore, the relation between consumption of coffee and bone mineral density (BMD) at the proximal femur in men and women was studied, taking into account, for the first time, genotypes for cytochrome P450 1A2 (CYP1A2) associated with metabolism of caffeine.

Methods

Dietary intakes of 359 men and 358 women (aged 72 years), participants of the Prospective Investigation of the Vasculature in Uppsala Seniors (PIVUS), were assessed by a 7-day food diary. Two years later, BMD for total proximal femur, femoral neck and trochanteric regions of the proximal femur were measured by Dual-energy X-ray absorptiometry (DXA). Genotypes of CYP1A2 were determined. Adjusted means of BMD for each category of coffee consumption were calculated.

Results

Men consuming 4 cups of coffee or more per day had 4% lower BMD at the proximal femur (p = 0.04) compared with low or non-consumers of coffee. This difference was not observed in women. In high consumers of coffee, those with rapid metabolism of caffeine (C/C genotype) had lower BMD at the femoral neck (p = 0.01) and at the trochanter (p = 0.03) than slow metabolizers (T/T and C/T genotypes). Calcium intake did not modify the relation between coffee and BMD.

Conclusion

High consumption of coffee seems to contribute to a reduction in BMD of the proximal femur in elderly men, but not in women. BMD was lower in high consumers of coffee with rapid metabolism of caffeine, suggesting that rapid metabolizers of caffeine may constitute a risk group for bone loss induced by coffee.

Proximal tibia volumetric bone mineral density is correlated to the magnitude of local acceleration in male long-distance runners

The beneficial effect of physical exercise on bone mineral density (BMD) is at least partly explained by the forces exerted directly on the bones. Male runners present generally higher BMD than sedentary individuals. We postulated that the proximal tibia BMD is related to the running distance, as well as to the magnitude of the shocks (while running) in male runners. A prospective study (three yearly measurements) included 81 healthy male subjects: 16 sedentary lean subjects, and 3 groups of runners (5-30 km/wk, n = 19; 30-50 km/wk, n = 29; 50-100 km/wk, n = 17). Several measurements were performed at the proximal tibia level: volumetric BMD (vBMD) and cortical index (CI), i.e., an index of cortical bone thickness and peak accelerations (an index of shocks during heel strike) while running (measured by a three-dimensional accelerometer). A general linear model assessed the prediction of vBMD or CI by 1) simple effects (running distance, peak accelerations, time); and 2) interactions (for instance, if vBMD prediction by peak acceleration depends on running distance). CI and vBMD 1) increase with running distance to reach a plateau over 30 km/wk; and 2) are positively associated with peak accelerations over 30 km/wk. Running may be associated with high peak accelerations to have beneficial effects on BMD. More important strains are needed to be associated with the same increase in BMD during running sessions of short duration than those of long duration. CI and vBMD are associated with the magnitude of the shocks during heel strike in runners.

Correlates of trabecular and cortical volumetric BMD in men of African ancestry

QCT provides a measure of volumetric BMD (vBMD) and distinguishes trabecular from cortical bone. Few studies have determined the factors related to vBMD in men, especially among men of African heritage. This study evaluated the relationship of anthropometric, medical, and behavioral factors and vBMD in a population-based cohort of men of African ancestry (n = 1901) >or=40 yr of age who had undergone screening for prostate cancer for the first time. Trabecular and cortical vBMD were measured at the radius and tibia by pQCT. Multiple linear regression analysis identified age, height, body weight, cigarette smoking, history of diabetes, fracture, and prostate cancer as the independent correlates of vBMD. However, associations with several variables differed between cortical and trabecular vBMD and between the radius and tibia. Longitudinal studies are needed to gain a better understanding of the mechanisms underlying these differential associations that may show new insight into the etiology of trabecular and cortical bone loss in men.

Bone mass assessment in naval crew members by quantitative ultrasound technique

OBJECTIVE

Of necessity, naval crews live in confined spaces when on board warships, which may lead to decreased bone mass and to subsequent bone fractures. Therefore, we investigated the bone mass of crew members and the relationship between bone mass and lifestyle factors.

METHODS

We selected 1510 crew members of the Japan Maritime Self-Defense Force. All were men between 18 and 58 years of age. We measured their bone mass by applying quantitative ultrasound (QUS) to the calcaneus. In addition, we reviewed daily milk consumption, levels of physical exercise, type of on-board job, fracture history, nutritional supplementation habits, and body mass index (BMI).

RESULTS

Bone mass values were lower than the published mean values for Japanese men across the twenties to forties age groups.

CONCLUSIONS

The factors found to be related to bone mass in this study were age, type of on-board job, exercise level, and milk consumption. Lifestyle factors are usually within our control. Our data suggest that moderate levels of regular exercise and milk consumption may maintain bone mass.

Stress fracture and military medical readiness: bridging basic and applied research

PURPOSE

Military recruits and distance runners share a special risk of stress fracture injury. Recent efforts by US and Israeli military-sponsored researchers have uncovered important mechanisms and practical low-cost interventions. This article summarizes key findings relevant to prevention of stress fracture, including simple strategies to identify and to mitigate risk.

METHODS

Published research supported through the Bone Health and Military Medical Readiness research program and related military bone research was analyzed for contributions to preventing stress fracture in military recruits and optimizing bone health.

RESULTS

Thousands of military recruits helped test hypotheses about predictors of risk, safer exercise regimens, and rest, nutrition, gait training, and technology interventions to reduce stress fracture risk. Concurrent cellular, animal, and human laboratory studies were used to systematically investigate mechanisms of mechanical forces acting on bone and interactions through muscle, hormonal and genetic influences, and metabolism. The iterative and sometimes simultaneous process of basic discovery and field testing produced new knowledge that will provide safer science-based physical training.

DISCUSSION

Human training studies evaluating effects on bone require special commitment from investigators and funders due to volunteer compliance and attrition challenges. The findings from multiple studies indicate that measures of bone elasticity, fragility, and geometry are as important as bone mineral density in predicting fracture risk, with applications for new measurement technologies. Risk may be reduced by high intakes of calcium, vitamin D, and possibly protein (e.g., milk products). Prostaglandin E2, insulin-like growth factor 1, and estrogens are important mediators of osteogenesis, indicating reasons to limit the use of certain drugs (e.g., ibuprofen), to avoid excessive food restriction, and to treat hypogonadism. Abnormal gait may be a correctable risk factor. Brief daily vibration may stimulate bone mineral accretion similar to weight-bearing exercise. Genetic factors contribute importantly to bone quality, affecting fracture susceptibility and providing new insights into fracture healing and tissue reengineering.

Relationship between growth hormone in vivo bioactivity, the insulin-like growth factor-I system and bone mineral density in young, physically fit men and women

CONTEXT

Bone mineral density (BMD) is influenced by growth factors, such as growth hormone (GH) and insulin-like growth factor-I (IGF-I). The in vivo bioassay for GH (bioGH) provides a more physiologically relevant measurement than an in vitro immunoassay, since bioGH is quantified on a biological outcome.

OBJECTIVE

To determine if bioGH and components of the IGF-I system were associated with BMD in age-matched men (M; n=41, 19.1+/-0.2 year, 70+/-3 kg, 163+/-25 cm) and women (W; n=39, 18.6+/-0.3 year, 66+/-3 kg, 141+/-15 cm).

DESIGN

Blood was analyzed for growth-related hormones [bioGH, immunoreactive growth hormone (iGH), IGF-I and associated binding proteins], and BMD was measured by pDXA, pQCT, and central DXA (spine, hip). For the bioGH assay, hypophysectomizied female Sprague-Dawley rats were injected with a s.c. bolus of either a GH standard or unknown (each subject's plasma) in four daily injections. The tibia was then examined for epiphyseal growth plate width from which bioGH concentrations were extrapolated.

RESULTS

M had greater (P<0.05) calcaneal BMD when measured by pDXA (M: 1.27+/-0.02; W: 1.14+/-0.02 g/cm2), while pQCT-assessed BMD at the tibia was not different (M: 777+/-16; W: 799+/-16 g/cm2). bioGH was similar between M (5388+/-800 microg/L) and W (4282+/-643 microg/L) and was not correlated with BMD. The only BMD-related biomarkers in women were acid-labile subunit (ALS; r=0.40) and IGFBP-3 (r=0.42) with DXA-measured spine and femoral neck BMD, and ALS (r=0.47) with pQCT-assessed tibial BMD and cortical thickness, respectively.

CONCLUSION

Although bioGH was not associated with BMD, IGF-I and associated binding proteins (IGFBP-3 and ALS) emerged as correlates in W only.

Assessment of the bone density of nomadic Fulani Herdsmen in northern Nigeria using calcaneal ultrasonography

CONTEXT

Osteoporosis is characterized by decreased bone density and increased bone fragility. Genetics, diet, and physical activity are established determinants of bone density. The seminomadic Fulani of northern Nigeria trek long distances on foot daily to graze and water their animals, and have access to calcium-rich dairy products.

OBJECTIVE

We sought to determine whether the high level of physical activity and presumed calcium-rich diet of the Fulani would promote a higher bone density, compared with their relatively inactive counterparts in the general population.

DESIGN

Cross-sectional study.

SETTING

Three Fulani settlements (Toro, Tilden Fulani, and Magaman Gumau) within 5 to 15 kilometers of Jos Metropolis on the Jos Plateau in northern Nigeria.

PATIENTS

We assessed the calcaneal characteristics of a consecutive sample of 51 active seminomadic Fulani men using the Lunar Achilles+ ultrasonometer.

MAIN OUTCOME MEASURES

Calcaneal broadband ultrasound attenuation (BUA), speed of sound (SOS), stiffness index (SI), and SI T-scores.

RESULTS

The mean age of the herdsmen was 26 +/- 9 years (range, 16 to 49), and the mean BMI was 19.9 +/- 2.3 kg/m(2). The mean BUA was 124 +/- 13 dB/MHz (95% CI, 120 to 128), the mean SOS was 1572 +/- 33 m/s (95% CI, 1563 to 1581), the mean SI was 102 +/- 17 (95% CI, 97 to 107], and the mean SI T-score was -0.74 +/- 0.97 (95% CI, -0.47 to 1.01]. The mean SI was 1 T-score unit below that of an age-matched cohort in the general population.

CONCLUSION

Fulani herdsmen have a theoretically increased risk for bone fracture in a background of low BMI and potentially high calcium intake.

Assessment of the bone quality of black male athletes using calcaneal ultrasound: a cross-sectional study

BACKGROUND

Lifestyle, genetics and environmental factors are established determinants of bone density. We aimed to describe the bone characteristics of competitive top-ranked Nigerian male athletes using calcaneal ultrasound and to assess whether intensive training promotes higher bone density in an environment with reportedly low calcium intake; to compare the bone characteristics of footballers with runners and other sportsmen; and to assess the correlation of stiffness index (SI) with activity level, since energy expenditure correlates with length of training and by extension, magnitude of skeletal loading.

METHODS

We recruited 102 male athletes: these included football (n = 68), running (n = 15), handball (n = 7), taekwando (n = 6), cycling (n = 2), judo (1), badminton (1) and high jump (1). Anthropometric data were first recorded on a structured form and energy expenditure was indirectly estimated with a validated questionnaire. Bone density was assessed using the Lunar Achilles+ calcaneal ultrasonometer.

RESULTS

The mean age of athletes was 25 +/- 6 years. The means of BMI and energy expenditure were 21.9 +/- 2.0 kg/m2 and 35.0 +/- 13.7 kcal/kg/day, respectively. Footballers were younger (p < 0.001) and heavier (p < 0.001) than runners. Football was a significant determinant of BUA independent of age, BMI and energy expenditure (p = 0.001). Football was also a significant determinant of SOS independent of age, height, weight and BMI (p < 0.001). The mean SI was 127 +/- 16 and the median T-score was 0.82 (-1.88, 3.35). The mean SI of footballers (130 +/- 15), runners (130 +/- 12) and other sportsmen (115 +/- 18) differed significantly (p = 0.001). Multivariate analyses revealed that football (p < 0.001) and running (p < 0.001) were significant determinants of SI independent of age and BMI. Footballers when compared with other sportsmen had a higher mean SI independent of age and BMI (p < 0.001). Age was not correlated with SI. The median T-score of footballers, 0.94 (-1.0, 3.35) was higher than that of other sportsmen.

CONCLUSION

Repetitive skeletal loading at the heel has the potential to improve bone density in black male athletes. The magnitude of increase may be higher in medium impact sports such as soccer and running compared with low or non-impact sports such as judo or taekwando, and is independent of age and BMI. However, future longitudinal data will be required to support our observations.

High impact exercise is more beneficial than dietary calcium for building bone strength in the growing rat skeleton

The benefits of impact exercise and dietary calcium on bone development are controversial. We used inbred rats under highly controlled conditions to test the independent and combined effects of impact exercise and physiological levels of calcium intakes on the growing skeleton. Forty growing F-344 female rats were fed diets containing either 100% (Ca+; 0.5% Ca) or 40% (Ca(-); 0.2% Ca) of their calcium requirements. Half of each dietary group was subjected to either 10 impacts per day from 45 cm freefall drops (Impact+), or no impact (Impact(-)). All rats received a free choice of physical activity period daily. After 8 weeks, the mechanical strength, volumetric density, geometry, and microarchitecture of their ulnae were measured. Body weight and bone length did not differ among groups. On both diets, freefall impact resulted in greater bone strength, cross-sectional moments of inertia, and endosteal and periosteal circumferences in the shaft. Only Ca+ resulted in greater shaft volumetric bone mineral density (vBMD) but that did not affect shaft breaking strength. In the bone ends, both Impact+ and Ca+ positively affected density and structure of both cortical and trabecular bone but the effects of Impact+ were more pervasive. In the proximal end, Impact+ resulted in greater bone volume fraction (BV/TV) in the trabecular bone due to greater trabecular thickness, and cortical thickness was greater due to a smaller endosteal circumference. Impact+ exerted a compensatory effect on vBMD and BV/TV in Ca(-) rats at the proximal site. In Impact(-) rats only, Ca+ resulted in greater total and cortical vBMD and BV/TV in the proximal ulna. Impact+ and Ca+ exerted additive effects on cortical bone area (BA) in the proximal ulna and on total BA, periosteal circumference, and trabecular vBMD in the distal ulna. In conclusion, impact exercise was more beneficial than adequate dietary calcium to growing bones, although sufficient dietary calcium was beneficial in rats not subjected to impact exercise.

Risk factors for stress fracture among young female cross-country runners

PURPOSE

To identify risk factors for stress fracture among young female distance runners.

METHODS

Participants were 127 competitive female distance runners, aged 18-26, who provided at least some follow-up data in a randomized trial among 150 runners of the effects of oral contraceptives on bone health. After completing a baseline questionnaire and undergoing bone densitometry, they were followed an average of 1.85 yr.

RESULTS

Eighteen participants had at least one stress fracture during follow-up. Baseline characteristics associated (P<0.10) in multivariate analysis with stress fracture occurrence were one or more previous stress fractures (rate ratio [RR] [95% confidence interval]=6.42 (1.80-22.87), lower whole-body bone mineral content (RR=2.70 [1.26-5.88] per 1-SD [293.2 g] decrease), younger chronologic age (RR=1.42 [1.05-1.92] per 1-yr decrease), lower dietary calcium intake (RR=1.11 [0.98-1.25] per 100-mg decrease), and younger age at menarche (RR=1.92 [1.15-3.23] per 1-yr decrease). Although not statistically significant, a history of irregular menstrual periods was also associated with increased risk (RR=3.41 [0.69-16.91]). Training-related factors did not affect risk.

CONCLUSION

The results of this and other studies indicate that risk factors for stress fracture among young female runners include previous stress fractures, lower bone mass, and, although not statistically significant in this study, menstrual irregularity. More study is needed of the associations between stress fracture and age, calcium intake, and age at menarche. Given the importance of stress fractures to runners, identifying preventive measures is of high priority.

Racial and ethnic differences in bone turnover markers in men

CONTEXT

Whereas racial and ethnic differences in fracture risk and bone mineral density (BMD) in men have been well described, the influence of race and ethnicity on biochemical markers of bone turnover is less clear.

METHODS

To examine the relationship between bone turnover, BMD, and race and ethnicity in men, we measured BMD, serum intact osteocalcin (OC), and serum C-terminal telopeptides of type 1 collagen (CTx) in 1029 men (aged 30-79 yr) enrolled in the Boston Area Community Health/Bone Survey, a population-based random sample of Black, Hispanic, and White. Men with diseases or on medications known to affect bone metabolism were excluded from the analysis. Mean serum levels of OC and CTx were adjusted for age, month and time of blood sample, and 25-hydroxyvitamin D.

RESULTS

Compared with Black men, adjusted mean OC levels were 17.6 and 20.5% higher in Hispanic (P = 0.02) and White men (P < 0.01), respectively. There was no significant difference between White and Hispanic men. Adjusted mean CTx levels were 14.3% higher in White men, compared with Black men (P = 0.04), but no other differences were significant. OC declined by 0.4%/yr from age 30 to 65 yr and increased thereafter by 2.1%/yr. The age trend in CTx appeared to follow a pattern consistent with a quadratic function of age. Model-estimated annual percent changes within age decade were as follows: 30-39 yr, -2.5%; 40-49 yr, -1.4%; 50-59 yr, -0.3%; 60-69 yr, +0.9%; 70-79 yr, +1.7%. There was no variation in the shape of the age trend in OC or CTx by race or ethnic group. Correlations between bone turnover markers and BMD (adjusted for age, height, weight, serum 25-hydroxyvitamin D, and PTH and month and time of blood sample) were generally weak.

CONCLUSIONS

Bone turnover markers are lower in Black men, compared with White and Hispanic men. Age trends in bone turnover markers are not influenced by race or ethnicity. Future studies in this cohort and others are needed to explore further these reported differences in bone metabolism among Black, Hispanic, and White men.