Dose-response relationship between physical loading and mechanical competence of bone

Effect of six weeks of resistance training on bone preservation in older adults: a randomized control trial

BACKGROUND

It has been established that chronic resistance exercise contributes to positive changes to bone in older adults.

AIMS

This study evaluated the effect of 6 weeks of resistance exercise with either elastic bands or dumbbells vs. a control period on bone morphology of older adults.

METHODS

Fifty-seven adults (mean ± SD; age = 66.5 ± 7.09 yrs; height = 165.2 ± 10.6 cm; body mass = 74.5 ± 14.6 kg) were randomized into three groups (dumbbell, elastic, or control). Participants underwent a total body dual-energy X-ray absorptiometry (DXA) scan for total body and segmental bone mineral content (BMC) and bone mineral density (BMD) before and following 6-week intervention. Age-matched Z-scores for BMD and BMC were recorded. Data were analyzed using two-way repeated measures ANOVAs and 0.05 significance level.

RESULTS

BMCarm improved for the dumbbell group (p = 0.016) after the training, with no change in BMD for any group (p > 0.05). Additionally, significant (time x treatment group) interaction (p = 0.024) of age-matched Z-scores indicated an improvement in only the dumbbell group after 6 weeks (p = 0.015), with no change in the elastic group despite them having greater Z-scores than the control group.

DISCUSSION

This study is the first to demonstrate acute normative adaptations as dumbbell-based programs may promote positive maintenance of bone metrics over 6 weeks, despite the lack of significant change in absolute BMC or BMD.

CONCLUSION

Adults did not lose relative bone mass with acute exercise using dumbbells as the external load applied and this may lead to positive changes following chronic training. There was no bone-related impact from elastic bands, suggesting a weighted load or force produced relative to gravity is beneficial.

Short-Term Increased Physical Activity During Early Life Affects High-Fat Diet-Induced Bone Loss in Young Adult Mice

Mechanical stresses associated with physical activity (PA) have beneficial effects on increasing BMD and improving bone quality. However, a high-fat diet (HFD) and obesity tend to have negative effects on bone, by increasing bone marrow adiposity leading to increased excretion of proinflammatory cytokines, which activate RANKL-induced bone resorption. In the current study, whether short-term increased PA via access to voluntary wheel running during early life has persistent and protective effects on HFD-induced bone resorption was investigated. Sixty 4-week-old male C57BL6/J mice were divided into two groups postweaning: without or with PA (access to voluntary running wheel 7-8 km/day) for 4 weeks. After 4 weeks with or without PA, mice were further subdivided into control diet or HFD groups for 8 weeks, and then all animals were switched back to control diet for an additional 4 weeks. Mice from the HFD groups were significantly heavier and obese; however, after 4 weeks of additional control diet their body weights returned to levels of mice on continuous control diet. Using μ-CT and confirmed by pQCT of tibias and spines ex vivo, it was determined that bone volume and trabecular BMD were significantly increased with PA in control diet animals compared with sedentary animals without access to wheels, and such anabolic effects of PA on bone were sustained after ceasing PA in adult mice. Eight weeks of a HFD deteriorated bone development in mice. Unexpectedly, early-life PA did not prevent persistent effects of HFD on deteriorating bone quality; in fact, it exacerbated a HFD-induced inflammation, osteoclastogenesis, and trabecular bone loss in adult mice. In accordance with these data, signal transduction studies revealed that a HFD-induced Ezh2, DNA methyltransferase 3a, and nuclear factor of activated T-cells 1 expression were amplified in nonadherent hematopoietic cells. In conclusion, short-term increased PA in early life is capable of increasing bone mass; however, it alters the HFD-induced bone marrow hematopoietic cell-differentiation program to exacerbate increased bone resorption if PA is halted. © 2021 Arkansas Children's Nutrition Center. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Voluntary wheel running mitigates the stress-induced bone loss in ovariectomized rats

In estrogen-deficient rodents with osteopenia, repetitive exposure to mild-to-moderate stress, which mimics the chronic aversive stimuli (CAS) of the modern urban lifestyle in postmenopausal women, has been hypothesized to cause the bone microstructure to further deteriorate. Recently, we have provided evidence in rats that voluntary impact exercise, e.g., wheel running, is as effective as pharmacological treatments for stress-induced anxiety and depression. The present study, therefore, aims to investigate whether a 4-week CAS exposure aggravates trabecular bone loss in ovariectomized (Ovx) rats, and whether CAS-induced bone loss can be rescued by voluntary wheel running. CAS was found to elevate the serum levels of corticosterone, a stress hormone from the adrenal gland. Dual energy X-ray absorptiometry revealed a decrease in bone mineral content (BMC) in the tibiae of CAS-exposed Ovx rats as compared to the CAS-free Ovx rats (control), while having no detectable effect on bone mineral density (BMD). Bone histomorphometric analysis of the proximal tibial metaphysis showed that CAS decreased trabecular bone volume and increased trabecular separation, which were completely restored to the baseline values of Ovx rats by voluntary wheel running. This CAS-induced trabecular bone loss in Ovx rats was probably due to an enhancement of osteoclast-mediated bone resorption, as indicated by increases in osteoclast surface and active erosion surface. Moreover, wheel running as well as non-impact exercise (endurance swimming) effectively increased the tibial BMD and BMC of CAS-exposed Ovx rats. It can be concluded that exercise is an effective intervention in mitigating CAS-induced bone loss in estrogen-deficient rats.

Micro-computed tomography and histologic evaluation of the interface of hydrogel expander and underlying bone: influence of pressure distributors on bone resorption

PURPOSE

Tissue expanders lead to changes in the underlying bone and can cause bone resorption. We investigated whether the insertion of mechanical devices that distribute the load on the bone can influence these effects.

MATERIALS AND METHODS

A total of 28 Lewis rats were assigned to 1 of 4 groups. Hydrogel expanders were placed subcutaneously either directly on the calvaria, on titanium mesh, or on a titanium plate. The fourth group of rats served as the controls. The bone quality and thickness were assessed beneath, and at the periphery of, the expanders using micro-computed tomography and histologic examination.

RESULTS

Micro-computed tomography images were obtained before and 21 days after insertion. The images revealed a significant decrease in hydroxyapatite density beneath the expanders in the group with only expanders. This decrease was reduced with the use of titanium mesh and completely prevented with the use of titanium plates. Histologic examination revealed a significant decrease in bone density and marked lacunae beneath the hydrogel expanders in the group with only expanders. In contrast, the titanium mesh decreased the size of the lacunae, and the titanium plates completely prevented both the formation of lacunae and the decrease in bone thickness.

CONCLUSION

The bone resorption caused by hydrogel expanders can be diminished using titanium mesh and completely prevented by the insertion of a titanium plate.

Osteoporosis and Strength Training

Osteoporosis is a major public health problem. Mechanical strain, imparted by muscle action and ground reaction forces, regulates bone size, shape, mineral mass, and density and subsequently bone strength. Thus, physical activity is critical for bone development, bone health, and fracture risk reduction. Animal studies, in which strain can be manipulated and measured directly, consistently show bone responds to high-strain magnitudes and rates, and only a few repetitions are needed to elicit a response. Extrapolation to humans suggests resistance exercise may be effective for osteoporosis prevention. Indeed, strength-trained athletes have significantly higher bone mass and density than athletes and nonathletes who do not engage in similar training. Prospective studies also support the benefits of resistance exercise demonstrating slowed bone loss and often an increase of 1% to 3% in regional bone mineral density, especially in women. Although more work is needed to define the optimal dose and the effects of nonmechanical factors (eg, nutritional, endocrine, body composition) on the response, the effects of resistance exercise on muscle mass and strength, balance, and agility, in addition to direct skeletal benefits, underscore its importance for osteoporosis, falls, and fracture prevention.

The establishment of a mechanobiology model of bone and functional adaptation in response to mechanical loading

BACKGROUND

Mechanical stimuli affected bone adaptation, however, the mechanism on a dose-response relationship between mechanical stimuli and bone response is unclear. Therefore, we established a mechanobiology model to evaluated the adaptive response of bone to strain deformation at high-frequencies (5-15 Hz) of externally applied strain.

METHODS

The ulnae of adult female rats were subjected to dynamic axial loading in vivo using Instron materials-testing machine. The applied loading at frequencies of 5 Hz, 10 Hz, and 15 Hz for 10 min with a haversine, low-magnitude waveform for a 2 weeks period, the peak strains is 2000 muepsilon and 3000 muepsilon. Strain was recorded using strain gauge conditioner and compared to physiological values obtained after testing.

FINDINGS

At frequencies of 10 Hz, 15 Hz groups, loading promoted obviously secreted of osteocalcin and collagen; a relative benefit in Bone Mineral Density (BMD) was found compare to the control (P < 0.05) followed the decline of material mechanical properties (modulus of elasticity, ultimate stress) (P < 0.01).

INTERPRETATION

These data show that a mechanobiology model of the axial ulna loading technique had been established successfully in rat. A short daily period of low-magnitude, high-frequency mechanical stimuli results in an osteogenic response related to peak strain magnitude, which do not result in significant differences in mechanical properties between the groups.

Effect of weighted exercises on bone mineral density in post menopausal women. A systematic review

PURPOSE

Osteoporosis is both preventable and treatable with exercise playing an important role in osteogenesis. The purpose of this systematic review was to determine which specific exercise programs utilizing weights were effective in maintaining or increasing bone mineral density (BMD) in postmenopausal women.

METHODS

A computerized search of the MEDLINE, CINAHL, EMBASE, PEDro, and Science Citation databases was conducted for the period 1990 through February 2005. The search was performed using English language-only keyword searches using MESH terms osteoporosis, postmenopausal, exercise, weight training, and bone mineral density. A total of 20 articles was critically evaluated for the quality of an intervention study using the criteria developed by MacDermid. An expert on the topic was asked to review the list of articles for omissions.

RESULTS

The review revealed evidence to support the effectiveness of weight training exercises to increase BMD in postmenopausal women. The increases in BMD were site-specific and required high loading with a training intensity of 70% to 90% of 1 RM for 8 to 12 repetitions of 2 to 3 sets performed over one year duration.

CONCLUSION

Weighted exercises can help in maintaining BMD in postmenopausal women and increasing BMD of the spine and hip in women with osteopenia and osteoporosis. The exercise program must be incorporated into a lifestyle change and be lifelong due to the chronic nature of bone loss in older women.

Effects of genes, sex, age, and activity on BMC, bone size, and areal and volumetric BMD

Quantitative genetic analyses of bone data for 710 inter-related individuals 8-85 yr of age found high heritability estimates for BMC, bone area, and areal and volumetric BMD that varied across bone sites. Activity levels, especially time in moderate plus vigorous activity, had notable effects on bone. In some cases, these effects were age and sex specific.

INTRODUCTION

Genetic and environmental factors play a complex role in determining BMC, bone size, and BMD. This study assessed the heritability of bone measures; characterized the effects of age, sex, and physical activity on bone; and tested for age- and sex-specific bone effects of activity.

MATERIALS AND METHODS

Measures of bone size and areal and volumetric density (aBMD and vBMD, respectively) were obtained by DXA and pQCT on 710 related individuals (466 women) 8-85 yr of age. Measures of activity included percent time in moderate + vigorous activity (%ModVig), stair flights climbed per day, and miles walked per day. Quantitative genetic analyses were conducted to model the effects of activity and covariates on bone outcomes.

RESULTS

Accounting for effects of age, sex, and activity levels, genes explained 40-62% of the residual variation in BMC and BMD and 27-75% in bone size (all p<0.001). Decline in femoral neck (FN), hip, and spine aBMD with advancing age was greater among women than men (age-by-sex interaction; all p <or= 0.05). %ModVig had the most notable effect on bone; high activity was associated with higher aBMD at all sites, but the magnitude of this effect varied. Activity among men was associated with higher FN BMC and cross-sectional area (CSA) at the 4% radius, but this was not observed among women (sex-by-activity interaction, both p <or= 0.05). Younger women had greater cortical vBMD (Cort-vBMD) than younger men, with minimal difference between low and high activity levels. Influence of activity was greater in older women: older women with low activity had lower Cort-vBMD than older men, but older women with high activity had higher Cort-vBMD than older men (age-by-sex-by-activity interaction, p=0.04).

CONCLUSIONS

High heritability estimates for DXA and pQCT measures varied across bone sites. Percent time spent in moderate to vigorous activity had the most notable effect on bone, and in some cases, this effect was age or sex specific.

Ghrelin directly regulates bone formation

To clarify the role of ghrelin in bone metabolism, we examined the effect of ghrelin in vitro and in vivo. Ghrelin and its receptor, GHS-R1a, were identified in osteoblasts, and ghrelin promoted both proliferation and differentiation. Furthermore, ghrelin increased BMD in rats. Our results show that ghrelin directly affects bone formation.

INTRODUCTION

Ghrelin is a gut peptide involved in growth hormone (GH) secretion and energy homeostasis. Recently, it has been reported that the adipocyte-derived hormone leptin, which also regulates energy homeostasis and opposes ghrelin's actions in energy homeostasis, plays a significant role in bone metabolism. This evidence implies that ghrelin may modulate bone metabolism; however, it has not been clarified. To study the role of ghrelin in skeletal integrity, we examined its effects on bone metabolism both in vitro and in vivo.

MATERIALS AND METHODS

We measured the expression of ghrelin and growth hormone secretagogue receptor 1a (GHS-R1a) in rat osteoblasts using RT-PCR and immunohistochemistry (IHC). The effect of ghrelin on primary osteoblast-like cell proliferation was examined by recording changes in cell number and the level of DNA synthesis. Osteoblast differentiation markers (Runx2, collagen alpha1 type I [COLI], alkaline phosphatase [ALP], osteocalcin [OCN]) were analyzed using quantitative RT-PCR. We also examined calcium accumulation and ALP activity in osteoblast-like cells induced by ghrelin. Finally, to address the in vivo effects of ghrelin on bone metabolism, we examined the BMD of Sprague-Dawley (SD) rats and genetically GH-deficient, spontaneous dwarf rats (SDR).

RESULTS

Ghrelin and GHS-R1a were identified in osteoblast-like cells. Ghrelin significantly increased osteoblast-like cell numbers and DNA synthesis in a dose-dependent manner. The proliferative effects of ghrelin were suppressed by [D-Lys(3)]-GHRP-6, an antagonist of GHS-R1a, in a dose-dependent manner. Furthermore, ghrelin increased the expression of osteoblast differentiation markers, ALP activity, and calcium accumulation in the matrix. Finally, ghrelin definitely increased BMD of both SD rats and SDRs.

CONCLUSIONS

These observations show that ghrelin directly stimulates bone formation.

Weight lifted in strength training predicts bone change in postmenopausal women

PURPOSE

The aim of this study was to examine the relationship between weight lifted in 1 yr of progressive strength training and change in bone mineral density (BMD) in a group of calcium-replete, postmenopausal women.

METHODS

As part of a large clinical trial, 140 calcium-supplemented women, 44-66 yr old, were randomized to a 1-yr progressive strength-training program. Half of the women were using hormone replacement therapy. Three times weekly, subjects completed two sets of six to eight repetitions in eight core exercises at 70-80% of one repetition maximum. BMD was measured at baseline and 1 yr.

RESULTS

In multiple linear regression, the increase in femur trochanter (FT) BMD was positively related to total weight lifted (0.001 g.cm (-2)) for a SD of weight lifted, P< 0.01) after adjusting for age, baseline factors, HRT status, weight change, cohort, and fitness center. The weighted squats showed the strongest (0.002 g.cm(-2)) for a SD of weight lifted, P< 0.001), whereas the back extension exhibited the weakest (0.0005 g.cm(-2)) for a SD of weight lifted, P< 0.26) association with change in FT BMD. The amount of weight lifted in the weighted march exercise was significantly related to total body BMD (0.0006 g.cm(-2)) for a SD of weight lifted, P< 0.01). The associations between weight lifted and BMD for the femur neck or lumbar spine were not significant.

CONCLUSION

Evidence of a linear relationship between BMD change and total and exercise-specific weight lifted in a 1-yr strength-training program reinforces the positive association between this type of exercise and BMD in postmenopausal women.

The sheep as a model for osteoporosis in humans

There is great interest in large animal models for studying different aspects of osteoporosis. Several laboratories around the world have used ovariectomized sheep as a model because of their ease of housing and handling, low expense compared to other large animals, availability and acceptance in society as a research animal. They have been used to study the response to new therapies for post-menopausal osteoporosis, low-magnitude mechanical stimulation, orthopedic implants in osteoporotic bone and bioactive ceramics to strengthen vertebral bodies. To produce severely osteopenic bone comparable to that seen in humans, a combination of estrogen deficiency following ovariectomy plus a calcium-wasting diet is currently being investigated.

Dose-response of physical activity and low back pain, osteoarthritis, and osteoporosis

PURPOSE

The purpose of this study was to examine the evidence for causal relationships between physical activity (PA) and low back pain (LBP), osteoarthritis (OA), and osteoporosis (OP), and for dose-response relations involved.

METHODS

Computer database searches and personal retrieval systems were used to locate relevant literature.

RESULTS

PA can be effective in preventing LBP (Category A) but prolonged, heavy loading can lead to LBP (Category C). Specific exercises have not been found effective in treatment of acute LBP (Category A), but PA can be effective in chronic LBP (Category B), especially for diminishing the effects of deconditioning. No evidence indicates that PA directly prevents OA. Large amounts of intensive PA involving high impacts or torsional loadings or causing injuries increases risk of OA (Category C). Light or moderate PA does not increase the risk of OA (Category C). PA can be effective in the treatment and rehabilitation of OA (Category B). High-intensity loading is osteogenic and possibly useful in prevention of OP (Category A) at the loaded site, but low to moderate loading is not osteogenic (Category D). Static efforts and slow movements are ineffective or less effective than fast application of force (Category B). The types of PA to attain the effects mentioned above are known except in the case of prevention of LBP, but dose-response relationships are poorly known; at best, semiquantitatively on the basis of just a few studies.

CONCLUSION

Given the shown primary and/or secondary preventative effectiveness of PA regarding LBP, OA, and OP, research to elucidate the inadequately known dose-response relations should be given high priority.

Low bone mineral density in the femoral neck of medieval women: a result of multiparity?

An archaeological investigation of a medieval cemetery gave us the opportunity to investigate 49 Danish skeletons dating from 1000 to 1250 A.D. and to compare them with 298 contemporary Danes (aged 19-79 years) and assess the millennial trend in bone mineral density (BMD) in populations considered genetically closely related. BMD and bone mineral apparent density (BMAD) of the femoral neck were measured by dual-energy X-ray absorptiometry (DEXA) and transformed into z scores. BMD(zscore) was significantly lower in medieval women (-0.54 +/- 0.25, p = 0.04), whereas BMD(zscore) in medieval men was significantly higher (0.55 +/- 0.22, p = 0.02). In medieval women, BMD(zscore) tended to increase with age (r = 0.42, p = 0.07), whereas no change was seen in men (r = 0.19, not significant [n.s.]). Also, BMAD(zscore) was significantly elevated in medieval men (1.00 +/- 0.28, p < 0.01), but in medieval women no difference was found (-0.28 +/- 0.21, n.s.). However, the correlation between BMAD(zscore) and age was significant in the medieval women where it increased with advancing age (r = 0.49, p = 0.03). In conclusion, medieval women had lower BMD when compared with contemporary women, but this relationship was reversed in women who survived to older ages. In contrast, medieval men had significantly higher BMD as compared with contemporary men at all ages. The observed lower BMD in medieval women can be explained by the well-known selective mortality among the younger women. A high birth rate and prolonged periods of lactation are the main reasons for the observed increased mortality, and therefore can also very likely explain the associated low BMD. The increase in the incidence of osteoporosis in modern elderly women could possibly, or partially, be explained by the survival of women who would have died prematurely had they lived in earlier centuries.

The prepubertal years: a uniquely opportune stage of growth when the skeleton is most responsive to exercise?

The growing years may be the most opportune time in life for exercise to result in large increases in bone density, enough to reduce the risk of fracture late in life. However, it is not known if there is an 'optimal' time during growth when the skeleton is most responsive to exercise. Comparing the osteotrophic response to exercise between pre- and peripubertal children is complex because: (i) the development of the skeleton within each stage of puberty is characterised by differing temporal patterns of growth in bone size and mass; (ii) the hormonal regulation of the skeleton is unique to each stage of puberty; and (iii) it is difficult to equate the relative mechanical load placed on the prepubertal compared with the pubertal skeleton. There are sound biological bases for the hypotheses being proposed for both the pre- and peripubertal years being the time when the skeleton is most responsive to exercise; that is, exercise may enhance bone formation in a synergistic fashion in the presence of growth hormone (prepubertal years) or sex steroids (peripubertal years). The paucity of data and the complex methodology make it difficult to draw conclusions as to the most opportune time during growth when exercise may lead to the greatest osteotrophic response. The limited data available support the notion that the prepubertal years may be the most opportune time, due to increases in bone density and periosteal expansion of cortical bone.

Mechanical stress induces COX-2 mRNA expression in bone cells from elderly women

Mechanical loading-induced fluid flow in the lacuno-canalicular network is a possible signal for bone cell adaptive responses. In an earlier study we found that pulsating fluid flow (PFF, 0.7+/-0.02 Pa, 5 Hz, 0.4 Pa/s) stimulates the production of prostaglandins by neonatal mouse calvarial cells. In addition, mRNA expression of the inducible form of cyclooxygenase (COX-2), but not the constitutive form (COX-1), the major enzymes in prostaglandin production, was increased by PFF. The present study was performed to determine whether human primary bone cells from the iliac crest, respond to mechanical stress in a similar way as neonatal mouse calvarial cells. We subjected bone cells originating from the iliac crest of nine elderly women, between 56 and 80 yr of age, for 1 h to PFF and measured prostaglandin production and COX-1 and COX-2 mRNA expression. One hour PFF treatment stimulated the release of PGE2 by 3.5 fold and PGI2 by 2.2 fold. PFF also increased the expression of COX-2 mRNA by 2.9 fold, but did not change COX-1 mRNA. No correlation was found between donor age and PFF effect, neither on prostaglandin production nor on COX-2 mRNA expression. This study shows that bone cells from the iliac crest of elderly women react to PFF treatment in a similar way as neonatal mouse calvarial cells, namely with increased production of prostaglandins and upregulation of COX-2 mRNA expression. These results suggest that human bone cells from the iliac crest and neonatal mouse calvarial cells share a similar mechanotransduction pathway.

Oxygen regulation of airway branching in Drosophila is mediated by branchless FGF

The Drosophila tracheal (respiratory) system is a tubular epithelial network that delivers oxygen to internal tissues. Sprouting of the major tracheal branches is stereotyped and controlled by hard-wired developmental cues. Here we show that ramification of the fine terminal branches is variable and regulated by oxygen, and that this process is controlled by a local signal or signals produced by oxygen-starved cells. We provide evidence that the critical signal is Branchless (Bnl) FGF, the same growth factor that patterns the major branches during embryogenesis. During larval life, oxygen deprivation stimulates expression of Bnl, and the secreted growth factor functions as a chemoattractant that guides new terminal branches to the expressing cells. Thus, a single growth factor is reiteratively used to pattern each level of airway branching, and the change in branch patterning results from a switch from developmental to physiological control of its expression.

Running and ovulation positively change cancellous bone in premenopausal women

PURPOSE

Exercise is understood to exert positive effects on bone. However cancellous bone has not been shown to increase with exercise. Previous results of our 1-yr observational prospective study in ovulatory women related 20% of the change in cancellous spinal bone mineral density (BMD), measured by quantitative computed tomography (QCT), to luteal phase length (the time from ovulation to menstruation, LL).

METHODS

The 66 women who documented exercise daily included normally active women (N = 23) and those who ran consistently or were increasing running in preparation for a marathon (N = 43). Exercise did not affect BMD change in the women as a whole. We re-evaluated those data to determine whether exercise-related effects on spinal cancellous BMD change in regularly cycling premenopausal women were related to ovulatory characteristics. The potential relationship of exercise to BMD change was reanalyzed by stratifying women into tertiles according to average LL documented by quantitative basal temperature analysis.

RESULTS

Repeated-measures ANOVA indicated independent positive effects of both luteal length (P = 0.001) and activity (P = 0.041). The 11 runners with LL > 10.9 d had a nonsignificant 0.5% increase in lumbar BMD while the 15 who averaged short LL (<9.9 d) experienced a significant 3.6% loss. In the runners as a group, however, kilometers run per week was negatively related to BMD change throughout (r = -0.347, P = 0.024).

CONCLUSIONS

These data are the first to indicate that, in women with regular cycles, luteal length and exercise independently and positively affect change in spinal cancellous BMD.

The epidemiology and pathogenesis of osteoporosis

Osteoporosis is an increasing health care concern as populations age throughout the developed and developing world. The social and economic costs of osteoporosis are due to its clinical outcome of fracture which increases exponentially with age. This review will highlight some of the key epidemiological aspects of osteoporosis incorporating areas of more recent interest. These include the definition; the magnitude of the problem encompassing differing incidence and prevalence patterns of both low bone mass and fracture in different cultural groups; the social consequences of fracture, including economic costs, morbidity and mortality; the evaluation of fracture risk, including the role of bone density, bone quality and the risk of falling; as well as an overview of some of the factors involved in determining low bone mass. Bone mineral density (BMD) is the most easily measured and accurate predictor of fracture risk. For any individual, BMD is the combination of their peak bone density and subsequent bone loss, both of which are influenced by genetic, hormonal and environmental factors. An understanding of key issues relating to this important disease may lead to earlier detection of the individual at high risk for fracture and rational approach to prevention and management.