Associations of physical activity and calcium intake with bone mass and size in healthy women at different ages

Genetically Predicted Milk Intake Increased Femoral Neck Bone Mineral Density in Women But Not in Men

Background

Cow milk contains more calcium, magnesium, potassium, zinc, and phosphorus minerals. For a long time, people have believed that increasing milk intake is beneficial to increasing bone density. Many confounding factors can affect milk consumption, and thus the association described to date may not be causal. We explored the causal relationship between genetically predicted milk consumption and Bone Mineral Density (BMD) of the femoral neck and lumbar spine based on 53,236 individuals from 27 studies of European ancestry using the Mendelian randomization (MR) study. 32,961 individuals of European and East Asian ancestry were used for sensitivity analysis.

Methods

A genetic instrument used for evaluating milk consumption is rs4988235, a locus located at 13,910 base pairs upstream of the LCT gene. A Mendelian randomization (MR) analysis was conducted to study the effect of selected single nucleotide polymorphisms (SNPs) and BMD. The summary-level data for BMD of the femoral neck and lumbar spine were obtained from two GWAS meta-analyses ['Data Release 2012' and 'Data Release 2015' in the GEnetic Factors for OSteoporosis Consortium (GEFOS)].

Results

we found that genetically predicted milk consumption was not associated with FN-BMD(OR 1.007; 95% CI 0.991-1.023; P = 0.385), LS-BMD(OR 1.003; 95% CI 0.983-1.024; P = 0.743) by performing a meta-analysis of several different cohort studies. High levels of genetically predicted milk intake were positively associated with increased FN-BMD in Women. The OR for each additional milk intake increasing allele was 1.032 (95%CI 1.005-1.059; P = 0.014). However, no causal relationship was found between milk consumption and FN-BMD in men (OR 0.996; 95% CI 0.964-1.029; P = 0.839). Genetically predicted milk consumption was not significantly associated with LS-BMD in women (OR 1.017; 95% CI 0.991-1.043; P = 0.198) and men (OR 1.011; 95% CI 0.978-1.045; P = 0.523).

Conclusion

Our study found that women who consume more milk have a higher FN-BMD. When studying the effect of milk consumption on bone density in further studies, we need to pay more attention to women.

Nutritional intake and bone health

Osteoporotic or fragility fractures affect one in two women and one in five men who are older than 50. These events are associated with substantial morbidity, increased mortality, and an impaired quality of life. Recommended general measures for fragility fracture prevention include a balanced diet with an optimal protein and calcium intake and vitamin D sufficiency, together with regular weight-bearing physical exercise. In this narrative Review, we discuss the role of nutrients, foods, and dietary patterns in maintaining bone health. Much of this information comes from observational studies. Bone mineral density, microstructure-estimated bone strength, and trabecular and cortical microstructure are positively associated with total protein intake. Several studies indicate that fracture risk might be lower with a higher dietary protein intake, provided that the calcium supply is sufficient. Dairy products are a valuable source of these two nutrients. Hip fracture risk appears to be lower in consumers of dairy products, particularly fermented dairy products. Consuming less than five servings per day of fruit and vegetables is associated with a higher hip fracture risk. Adherence to a Mediterranean diet or to a prudent diet is associated with a lower fracture risk. These various nutrients and dietary patterns influence gut microbiota composition or function, or both. The conclusions of this Review emphasise the importance of a balanced diet including minerals, protein, and fruit and vegetables for bone health and in the prevention of fragility fractures.

Characterisation of genetic regulatory effects for osteoporosis risk variants in human osteoclasts

Background

Osteoporosis is a complex disease with a strong genetic contribution. A recently published genome-wide association study (GWAS) for estimated bone mineral density (eBMD) identified 1103 independent genome-wide significant association signals. Most of these variants are non-coding, suggesting that regulatory effects may drive many of the associations. To identify genes with a role in osteoporosis, we integrate the eBMD GWAS association results with those from our previous osteoclast expression quantitative trait locus (eQTL) dataset.

Results

We identify sixty-nine significant cis-eQTL effects for eBMD GWAS variants after correction for multiple testing. We detect co-localisation of eBMD GWAS and osteoclast eQTL association signals for 21 of the 69 loci, implicating a number of genes including CCR5, ZBTB38, CPE, GNA12, RIPK3, IQGAP1 and FLCN. Summary-data-based Mendelian Randomisation analysis of the eBMD GWAS and osteoclast eQTL datasets identifies significant associations for 53 genes, with TULP4 presenting as a strong candidate for pleiotropic effects on eBMD and gene expression in osteoclasts. By performing analysis using the GARFIELD software, we demonstrate significant enrichment of osteoporosis risk variants among high-confidence osteoclast eQTL across multiple GWAS P value thresholds. Mice lacking one of the genes of interest, the apoptosis/necroptosis gene RIPK3, show disturbed bone micro-architecture and increased osteoclast number, highlighting a new biological pathway relevant to osteoporosis.

Conclusion

We utilise a unique osteoclast eQTL dataset to identify a number of potential effector genes for osteoporosis risk variants, which will help focus functional studies in this area.

Age at attainment of peak bone mineral density and its associated factors: The National Health and Nutrition Examination Survey 2005-2014

Osteoporosis is a major public health problem worldwide. Lower peak bone mineral density (BMD) in youth may be the single most important factor leading to the development of osteoporosis in the elderly. Using cross-sectional data from the National Health and Nutrition Examination Survey (NHANES) 2005-2014, we included 18,713 individuals with complete and valid data on femoral neck, total hip and lumbar spine BMD. Generalized additive models were used to estimate the age at attainment of peak BMD and 95% confidence intervals (95%Cls); model covariates were sex, race, body mass index (BMI) and we also examine factors potentially affecting age at attainment of peak BMD. This study clearly stated that age at attainment of peak femoral neck, total hip and lumbar spine BMD were 20.5 years, 21.2 years and 23.6 years in males, and 18.7 years, 19.0 years and 20.1 years in females, respectively and age at attainment of peak BMD varied by skeletal sites and sex. The study also found that females achieved peak femoral neck, total hip and lumbar spine BMD earlier than males (all P < 0.001); race and BMI were not associated with the age at attainment of peak BMD (all P > 0.05). These results suggested that improving bone health among individuals before 20 years old may be useful for reducing future risk of osteoporosis and osteoporotic fractures.

Therapeutic effect of localized vibration on alveolar bone of osteoporotic rats

OBJECTIVES

Vibration, in the form of high frequency acceleration (HFA), stimulates alveolar bone formation under physiologic conditions and during healing after dental extractions. It is not known if HFA has an anabolic effect on osteoporotic alveolar bone. Our objective is to determine if HFA has a regenerative effect on osteoporotic alveolar bone.

METHODS AND MATERIALS

Adult female Sprague-Dawley rats were divided into five groups: 1) Ovariectomized Group (OVX), 2) Sham-OVX Group that received surgery without ovariectomy, 3) OVX-HFA Group that was ovariectomized and treated daily with HFA, 4) OVX+Static Force Group that was ovariectomized and received the same force as HFA, but without vibration, and 5) Control Group that did not receive any treatment. All animals were fed a low mineral diet for 3 months. Osteoporosis was confirmed by micro-CT of the fifth lumbar vertebra and femoral head. HFA was applied to the maxillary first molar for 5 minutes/day for 28 and 56 days. Maxillae were collected for micro-CT, histology, fluorescent microscopy, protein and RNA analysis, and three-point bending mechanical testing.

RESULTS

Micro-CT analysis revealed significant alveolar bone osteoporosis in the OVX group. Vibration restored the quality and quantity of alveolar bone to levels similar to the Sham-OVX group. Animals exposed to HFA demonstrated higher osteoblast activity and lower osteoclast activity. Osteogenic transcription factors (RUNX2, Foxo1, Osterix and Wnt signaling factors) were upregulated following vibration, while RANKL/RANK and Sclerostin were downregulated. HFA did not affect serum TRAcP-5b or CTx-1 levels. The osteogenic effect was highest at the point of HFA application and extended along the hemimaxillae this effect did not cross to the contra-lateral side.

CONCLUSIONS

Local application of vibration generated gradients of increased anabolic metabolism and decreased catabolic metabolism in alveolar bone of osteoporotic rats. Our findings suggest that HFA could be a predictable treatment for diminished alveolar bone levels in osteoporosis patients.

High dairy products intake reduces osteoporosis risk in Korean postmenopausal women: A 4 year follow-up study

BACKGROUND/OBJECTIVES

The aim of this study was to identify the effect of dairy products, milk and yogurt on osteoporosis incidence among Korean postmenopausal women using prospective cohort data.

MATERIALS/METHODS

Between 2001 and 2003, 10,038 participants were recruited in rural and urban areas for a baseline examination of a community-based cohort study. Of those, 1,573 postmenopausal women (aged 40–69 years at baseline) were eligible for the present study. Intakes of dairy products, milk, and yogurt were assessed using a validated semi-quantitative food frequency questionnaire. The speed of sound at the radius and tibia were measured using a quantitative ultrasound device and osteoporosis was defined based on the WHO criteria (T-score ≤ −2.5).

RESULTS

During the 4-years follow-up study, the cumulative incidence of osteoporosis was 18.4% (273 cases) in the radius and 33.6% (407 cases) in the tibia. The subjects with higher frequency of dairy product consumption showed a decreased risk of radius osteoporosis after adjusting for potential confounders [hazard ratio (HR) = 0.51, 95% confidence interval (CI): 0.33–0.80 for >1 time/day vs. non consumer; P for trend = 0.0027]. Similarly, high frequency of milk and yogurt consumption had a protective effect on radius osteoporosis risk [milk: HR = 0.60, 95% CI: 0.42–0.87 for > 5–6 times/week vs. non consumer (P for trend = 0.0130), yogurt: HR = 0.51, 95% CI: 0.30–0.85 for > 5–6 times/week vs. non consumer (P for trend = 0.0167)]. However, high dairy products consumption was not related with tibia osteoporosis.

CONCLUSIONS

This study suggests that daily intake of dairy products could potentially reduce radius osteoporosis incidence among Korean postmenopausal women.

Expression Quantitative Trait Locus Study of Bone Mineral Density GWAS Variants in Human Osteoclasts

Osteoporosis is a complex disease with a strong genetic component. Genomewide association studies (GWAS) have been very successful at identifying common genetic variants associated with bone parameters. A recently published study documented the results of the largest GWAS for bone mineral density (BMD) performed to date (n = 142,487), identifying 307 conditionally independent single-nucleotide polymorphisms (SNPs) as associated with estimated BMD (eBMD) at the genomewide significance level. The vast majority of these variants are non-coding SNPs. Expression quantitative trait locus (eQTL) studies using disease-specific cell types have increasingly been integrated with the results from GWAS to identify genes through which the observed GWAS associations are likely mediated. We generated a unique human osteoclast-specific eQTL data set using cells differentiated in vitro from 158 participants. We then used this resource to characterize the 307 recently identified BMD GWAS SNPs for association with nearby genes (±500 kb). After correction for multiple testing, 24 variants were found to be significantly associated with the expression of 32 genes in the osteoclast-like cells. Bioinformatics analysis suggested that these variants and those in strong linkage disequilibrium with them are enriched in regulatory regions. Several of the eQTL associations identified are relevant to genes that present strongly as having a role in bone, particularly IQGAP1, CYP19A1, CTNNB1, and COL6A3. Supporting evidence for many of the associations was obtained from publicly available eQTL data sets. We have also generated strong evidence for the presence of a regulatory region on chromosome 15q21.2 relevant to both the GLDN and CYP19A1 genes. In conclusion, we have generated a unique osteoclast-specific eQTL resource and have used this to identify 32 eQTL associations for recently identified BMD GWAS loci, which should inform functional studies of osteoclast biology. © 2018 American Society for Bone and Mineral Research.

Assessment of Lactose-Free Diet on the Phalangeal Bone Mineral Status in Italian Adolescents Affected by Adult-Type Hypolactasia

Adult-type hypolactasia (ATH) is a clinical syndrome of primary lactase deficiency. A lactose-free diet is advisable to avoid the symptoms linked to the condition, but this potentially creates problems for optimal bone mineralization due to reduced calcium intake. To evaluate the effect of the lactose-free diet on the bone mineral status (BMS), we compared the phalangeal BMS of adolescents with ATH to that of peers on a normal diet. Also, we analyzed the correlations between BMS and dietary behavior, physical exercise, and calcium and vitamin D intake. A total of 102 cases and 102 healthy controls filled out a diet record and underwent phalangeal Quantitative Ultrasound (QUS). No difference in BMS was observed. The time spent on lactose-free diet (4.8 ± 3.1 years) was inversely correlated to the BMS. More than 98% of cases consumed lactose-free milk, but calcium and vitamin D intake were significantly lower. Calcium intake was correlated to physical exercise but not to BMS. Our results suggest that a lactose-free diet does not affect the phalangeal BMS of adolescents with primary lactase deficiency when their diet includes lactose-free cow’s milk. However, there is still a significantly lower calcium intake than in the population reference. The inverse correlation observed between the BMS and the time spent on a lactose-free diet suggests that a long-term follow-up is advisable.

Dietary calcium intake and physical activity levels among people living in Karnataka, India - An observational hospital-based study

Background:

Calcium is the most abundant mineral in our body with varied functions, and its dietary deficiency leads to osteoporosis. Various studies have shown that adequate dietary calcium intake (DCI) and moderately increased physical activity if maintained for long term prevent osteoporosis. The data regarding DCI of people living in Karnataka, south India, are limited. Thus, we aimed to assess DCI, physical activity, and their predictors among people living in Karnataka.

Methodology:

A cross-sectional study was done among 250 inpatients and normal relatives of orthopedics department of a tertiary care teaching hospital. Multistage random sampling was performed. DCI and physical activity were measured using validated questionnaires.

Results:

The mean (standard deviation) DCI was 499.94 (251.5). The prevalence [95 confidence interval (CI)] of poor intakers of DCI [DCI < Recommended Dietary Allowance (RDA)] was 76.6% (70.9, 81.7). However, only 43.52% of all participants with poor DCI were on supplements. Male gender [2.189 (1.125, 4.257)], elderly [1.988 (1.067, 3.705)], and low knowledge score [1.240 (1.093, 1.407)] were significant predictors of low DCI. The proportion (95 CI) of patients who were categorized as having low physical activity (LPA) was 44.0% (37.8, 50.4). The predictors for LPA [adjusted odds ratio (95 CI)] were marital status, being single [1.853 (1.047, 3.282)], and low socioeconomic status class [1.209 (1.002, 1.458)].

Conclusion:

DCI was below the RDA for three-fourths of our patients with nearly half of them being physically inactive, indicating the need for better education regarding DCI and improving physical activity, all of which can prevent osteoporosis.

Comparison of bone density on the dominant and nondominant sides between healthy elderly individuals and stroke patients

[Purpose] This study evaluated differences between healthy elderly individuals and stroke patients by comparing their dominant and nondominant sides. [Subjects and Methods] Thirty-five elderly individuals participated in this study and divided into a stroke group and a control group. The outcome measures were general characteristics and bone mineral density. Bone mineral density was evaluated by using the osteoporosis index. OsteoPro, T score, and Z score were used for the calcaneus region of the dominant side, and OsteoPro was used for that of the nondominant side. Data were analyzed by using the SPSS 12.0 software, paired-samples t-test, and independent-samples t-test. [Results] The T and Z scores showed no significant differences between the dominant and recessive sides in the control group. However, the stroke group showed significant differences in osteoporosis index, T score, and Z score between the paretic and nonparetic sides. Changes in the scores between the recessive and dominant sides showed significant differences between the two groups. [Conclusion] A positive relationship was found between physical activity and bone mineral density in the stroke patients. Therefore, improved physical activity can be beneficial by reducing osteoporosis in stroke patients.

Administration duration influences the effects of low-magnitude, high-frequency vibration on ovariectomized rat bone

Low-magnitude, high-frequency vibration (LMHFV) has been proposed as a non-drug anti-osteoporosis treatment. However, the influence of administration duration on its effect is seldom investigated. In this study, the effect of 16-week LMHFV (0.3 g, 30 Hz, 20 min/day) on the bone mineral densities (BMDs), bone mechanical properties, and cellular responses of osteoporotic and healthy rats was examined by in vivo peripheral quantitative computed tomography (pQCT), fracture tests, cell assays, and mRNA quantification. Forty-eight adult rats were equally assigned to sham surgery (SHM), sham surgery with LMHFV (SHM+V), ovariectomy (OVX), and ovariectomy with LMHFV (OVX+V) groups. At week 8, LMHFV ameliorated ovariectomy-induced deterioration of trabecular bone, with a significantly higher tibia trabecular BMD (+11.2%) being noted in OVX+V rats (vs. OVX). However, this positive effect was not observed at later time points. Furthermore, 16 weeks of LMHFV caused significant reductions in the vertebral mean BMD (-13.0%), trabecular BMD (-15.7%), and maximum load (-21.5%) in OVX+V rats (vs. OVX). Osteoblasts derived from osteoporotic rat bone explants showed elevated BSP and OSX mRNA expression induced by LMHFV on day 1. However, no further positive effect on osteoblastic mRNA expression, alkaline phosphatase activity, or calcium deposition was observed with prolonged culture time. A higher ratio of RANKL/OPG induced by LMHFV suggests that osteoclastogenesis may be activated. Together, these results demonstrate that administration duration played an important role in the effect of LMHFV. Early exposure to LMHFV can positively modulate osteoporotic bone and osteoblasts; however, the beneficial effect seems not to persist over time. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1147-1157, 2016.

Genome-wide association study using family-based cohorts identifies the WLS and CCDC170/ESR1 loci as associated with bone mineral density

Background

Osteoporosis is a common and debilitating bone disease that is characterised by a low bone mineral density (BMD), a highly heritable trait. Genome-wide association studies (GWAS) have proven to be very successful in identifying common genetic variants associated with BMD adjusted for age, gender and weight, however a large portion of the genetic variance for this trait remains unexplained. There is evidence to suggest significant genetic correlation between body size traits and BMD. It has also recently been suggested that unintended bias can be introduced as a result of adjusting a phenotype for a correlated trait. We performed a GWAS meta-analysis in two populations (total n = 6,696) using BMD data adjusted for only age and gender, in an attempt to identify genetic variants associated with BMD including those that may have potential pleiotropic effects on BMD and body size traits.

Results

We observed a single variant, rs2566752, associated with spine BMD at the genome-wide significance level in the meta-analysis (P = 3.36 × 10⁻⁰⁹). Logistic regression analysis also revealed an association between rs2566752 and fracture rate in one of our study cohorts (P = 0.017, n = 5,654). This is an intronic variant located in the wntless Wnt ligand secretion mediator (WLS) gene (1p31.3), a known BMD locus which encodes an integral component of the Wnt ligand secretion pathway. Bioinformatics analyses of variants in moderate LD with rs2566752 produced strong evidence for a regulatory role for the variants rs72670452, rs17130567 and rs1430738. Expression quantitative trait locus (eQTL) analysis suggested that the variants rs12568456 and rs17130567 are associated with expression of the WLS gene in whole blood, cerebellum and temporal cortex brain tissue (P = 0.034–1.19 × 10⁻²³). Gene-wide association testing using the VErsatile Gene-based Association Study 2 (VEGAS2) software revealed associations between the coiled-coil domain containing 170 (CCDC170) gene, located adjacent to the oestrogen receptor 1 (ESR1) gene, and BMD at the spine, femoral neck and total hip sites (P = 1.0 × 10⁻⁰⁶, 2.0 × 10⁻⁰⁶ and 2.0 × 10⁻⁰⁶ respectively).

Conclusions

Genetic variation at the WLS and CCDC170/ESR1 loci were found to be significantly associated with BMD adjusted for only age and gender at the genome-wide level in this meta-analysis.

Dietary calcium intake and physical activity levels among urban South Indian postmenopausal women

INTRODUCTION

Calcium is the most abundant mineral in our body with varied functions and its dietary deficiency leads to osteoporosis, besides playing a significant role in the pathogenesis of other diseases. The data regarding dietary calcium intake (DCI) among postmenopausal women in urban areas of South India is limited.

OBJECTIVES

This study was aimed to assess DCI and physical activity among postmenopausal women. The risk factors for a low intake of dietary calcium were also assessed.

MATERIALS AND METHODS

A cross-sectional study was done among 106 postmenopausal women selected by systematic random sampling from the city of Erode, Tamil Nadu, India. DCI and physical activity were measured using validated questionnaires.

RESULTS

The mean DCI was 632.72 ± 28.23 mg/day. The proportion of women consuming less than 800 mg/day of dietary calcium was 74.5%. Only 10.4% of the women studied (11 out of 106) were on calcium supplements while 55% had low physical activity. A low knowledge score [adjusted odds ratio (OR): 5.17; 95% confidence interval (CI): 1.31-20.42] and a low socioeconomic status (SES) score of the family (adjusted OR: 4.00; 95% CI: 1.32-12.11) were significantly associated with low DCI after adjusting the age, dietary preferences, and educational and occupational statuses.

CONCLUSIONS

DCI was below the Recommended Dietary Allowance (RDA) and the majority of postmenopausal women were physically inactive, indicating the need for better education regarding DCI and the need for calcium supplements and physical activity, all of which can contribute to the prevention of the consequences of osteoporosis.

Evidence for an interaction between exercise and nutrition for improving bone and muscle health

Regular exercise and adequate nutrition, particularly dietary calcium, vitamin D, and protein, are prescribed as strategies to optimize peak bone mass and maintain bone and muscle health throughout life. Although the mechanism of action of exercise and nutrition on bone and muscle health are different-exercise has a site-specific modifying effect, whereas nutrition has a permissive generalized effect-there is evidence that combining calcium (or calcium rich dairy foods) or dietary protein with exercise can have a synergetic effect on bone mass and muscle health, respectively. However, many questions still remain as to whether there is a threshold level for these nutrients to optimize the exercise-induced gains. Further studies are also needed to investigate whether other dietary factors, such as vitamin D, soy isoflavones or omega-3 fatty acids, or a multinutrient supplement, can enhance the effects of exercise on bone and muscle health.

Discontinuation of leisure time impact-loading exercise is related to reduction of a calcaneus quantitative ultrasound parameter in young adult Japanese females: a 3-year follow-up study

A 3-year follow-up study on 334 young Japanese females enrolled in a university at the age of 18 years revealed that discontinuation of leisure time impact-loading exercises performed in junior high and/or high school was associated with increased risk of reduction in calcaneus osteo-sono assessment index (OSI).

INTRODUCTION

Bone strength rapidly increases during puberty and reaches its peak by the end of adolescence. The aim of this study was to determine the lifestyle factors that influence the maintenance of calcaneus OSI in young adult females around the time when peak bone mass is attained.

METHODS

Annual health checkups including OSI measurements, anthropometrics, lifestyle analysis, and blood examination were performed 4 times on 334 Japanese females enrolled in a university at the age of 18 years. According to the slope of OSI change during the 3-year follow-up, the subjects were grouped into two categories: OSI loss (the lowest tertile) and OSI gain/stable (the second and third tertiles).

RESULTS

At the baseline assessment, the OSI loss group had higher OSI and height and an earlier menarche age than the OSI gain/stable group. Performing leisure time impact-loading exercise in junior high and/or high school but discontinuing it at university was associated with increased risk of OSI loss, independent of OSI, height and weight at the age of 18 years, weight change during follow-up, age of menarche, energy-adjusted nutrient intake, and alcohol drinking; the odds ratios were 4.1-4.9 compared with those performing impact-loading exercise at university. In particular, duration, frequency, and subjective intensity of impact-loading exercise during high school were positively associated with OSI loss.

CONCLUSION

Discontinuation of leisure time impact-loading exercises performed during late adolescence is associated with an increased risk of OSI loss in young adult females during the 3-year follow-up period.

Physical activity as determinant of femoral neck strength relative to load in adult women: findings from the hip strength across the menopause transition study

Our objective was to examine associations of physical activity in different life domains with peak femoral neck strength relative to load in adult women. Greater physical activity in each of the domains of sport, active living, home, and work was associated with higher peak femoral neck strength relative to load.

INTRODUCTION

Our objective was to examine the associations of physical activity in different life domains with peak femoral neck strength relative to load in adult women. Composite indices of femoral neck strength integrate body size with femoral neck size and bone mineral density to gauge bone strength relative to load during a fall, and are inversely associated with incident fracture risk.

METHODS

Participants were 1,919 pre- and early perimenopausal women from the Study of Women's Health Across the Nation. Composite indices of femoral neck strength relative to load in three failure modes (compression, bending, and impact) were created from hip dual-energy X-ray absorption scans and body size. Usual physical activity within the past year was assessed with the Kaiser Physical Activity Survey in four domains: sport, home, active living, and work. We used multiple linear regression to examine the associations.

RESULTS

Greater physical activity in each of the four domains was independently associated with higher composite indices, adjusted for age, menopausal transition stage, race/ethnicity, Study of Women's Health Across the Nation study site, smoking status, smoking pack-years, alcohol consumption level, current use of supplementary calcium, current use of supplementary vitamin D, current use of bone-adverse medications, prior use of any sex steroid hormone pills or patch, prior use of depo-provera injections, history of hyperthyroidism, history of previous adult fracture, and employment status: standardized effect sizes ranged from 0.04 (p < 0.05) to 0.20 (p < 0.0001).

CONCLUSIONS

Physical activity in each domain examined was associated with higher peak femoral neck strength relative to load in pre- and early perimenopausal women.

Body size and pubertal development explain ethnic differences in structural geometry at the femur in Asian, Hispanic, and white early adolescent girls living in the U.S

Variation in structural geometry is present in adulthood, but when this variation arises and what influences this variation prior to adulthood remains poorly understood. Ethnicity is commonly the focus of research of skeletal integrity and appears to explain some of the variation in quantification of bone tissue. However, why ethnicity explains variation in skeletal integrity is unclear.

METHODS

Here we examine predictors of bone cross sectional area (CSA) and section modulus (Z), measured using dual-energy X-ray absorptiometry (DXA) and the Advanced Hip Analysis (AHA) program at the narrow neck of the femur in adolescent (9-14 years) girls (n=479) living in the United States who were classified as Asian, Hispanic, or white if the subject was 75% of a given group based on parental reported ethnicity. Protocols for measuring height and weight follow standardized procedures. Total body lean mass (LM) and total body fat mass (FM) were quantified in kilograms using DXA. Total dietary and total dairy calcium intakes from the previous month were estimated by the use of an electronic semi-quantitative food frequency questionnaire (eFFQ). Physical activity was estimated for the previous year by a validated self-administered modifiable activity questionnaire for adolescents with energy expenditure calculated from the metabolic equivalent (MET) values from the Compendium of Physical Activities. Multiple regression models were developed to predict CSA and Z.

RESULTS

Age, time from menarche, total body lean mass (LM), total body fat mass (FM), height, total calcium, and total dairy calcium all shared a significant (p<0.05), positive relationship with CSA. Age, time from menarche, LM, FM, and height shared significant (p<0.05), positive relationships with Z. For both CSA and Z, LM was the most important covariate. Physical activity was not a significant predictor of geometry at the femoral neck (p≥0.339), even after removing LM as a covariate. After adjusting for covariates, ethnicity was not a significant predictor in regression models for CSA and Z.

CONCLUSION

Variability in bone geometry at the narrow neck of the femur is best explained by body size and pubertal maturation. After controlling for these covariates there were no differences in bone geometry between ethnic groups.

Bone health: part 2, physical activity

Mechanical loading is a crucial factor for maintaining skeletal health. Physical activities, exercise, and sports provide a wealth and variety of mechanical loads to bones, through muscle forces, ground reaction forces, and other contact or impact forces. Weightbearing activities can be effective exercises to enhance bone health-particularly, those that involve jumping and impact loads (with greater strain magnitudes, rates, and frequencies). Physical activity appears to be acutely beneficial for enhancing bone health in the early pubertal period and in older age, such as in postmenopausal women. In preparing this article, PubMed, Web of Science, and relevant edited books (English language) were reviewed from 1961 to present.

The amount of periosteal apposition required to maintain bone strength during aging depends on adult bone morphology and tissue-modulus degradation rate

Although the continued periosteal apposition that accompanies age-related bone loss is a biomechanically critical target for prophylactic treatment of bone fragility, the magnitude of periosteal expansion required to maintain strength during aging has not been established. A new model for predicting periosteal apposition rate for men and women was developed to better understand the complex, nonlinear interactions that exist among bone morphology, tissue-modulus, and aging. Periosteal apposition rate varied up to eightfold across bone sizes, and this depended on the relationship between cortical area and total area, which varies with external size and among anatomical sites. Increasing tissue-modulus degradation rate from 0% to -4%/decade resulted in 65% to 145% increases in periosteal apposition rate beyond that expected for bone loss alone. Periosteal apposition rate had to increase as much as 350% over time to maintain stiffness for slender diaphyses, whereas robust bones required less than a 32% increase over time. Small changes in the amount of bone accrued during growth (ie, adult cortical area) affected periosteal apposition rate of slender bones to a much greater extent compared to robust bones. This outcome suggested that impaired bone growth places a heavy burden on the biological activity required to maintain stiffness with aging. Finally, sex-specific differences in periosteal apposition were attributable in part to differences in bone size between the two populations. The results indicated that a substantial proportion of the variation in periosteal expansion required to maintain bone strength during aging can be attributed to the natural variation in adult bone width. Efforts to identify factors contributing to variation in periosteal expansion will benefit from developing a better understanding of how to adjust clinical data to differentiate the biological responses attributable to size-effects from other genetic and environmental factors.

Physical activity reduces bone loss in the distal forearm in post-menopausal women--a 25-year prospective study

Intervention studies have shown that high-intensity training programs with duration of 1-3 years can influence bone mass in post-menopausal women. We wanted to investigate whether moderate physical activity could be associated with reduced post-menopausal bone loss also in the long-term perspective. We evaluated changes in bone mass and bone structure by repeated single-photon absorptiometry measurements of the distal forearm in 91 moderately physically active and 21 inactive women, categorized according to information from questionnaires, from menopause and on average 25 years onwards. Data were calculated with analysis of variance and analysis of covariance tests and presented as means with 95% confidence interval. There were no group differences in bone mass or bone structure at menopause. The mean annual loss in bone mineral content was 1.2% (1.1, 1.3) in the physically active and 1.6% (1.3, 1.8) in the inactive women (after adjustment for menopausal age P = 0.02) and the mean decline in a strength index based on bone mass and bone structure was 0.7% (0.6, 0.8) in the physically active and 1.2% (0.8, 1.5) in the inactive women (P = 0.004). There were no group differences in the changes in bone structure. Physical activity is also in a long-term perspective associated with reduced post-menopausal bone loss.

Changes in Hip Bone Mineral Density and Objectively Measured Physical Activity in Middle-Aged Women: A 6-Year Prospective Study

Purpose.

This study was conducted to determine if physical activity volume (PAv) and intensity (PAi) at baseline influence the likelihood of gaining hip bone mineral density (BMD) over 6 years.

Design and Sample.

In a prospective study, the sample was limited to 244 female nonsmokers, ages 35 to 45 years, and was approximately 90% white.

Setting and Measures.

PAv and PAi were measured in daily living conditions using accelerometers at baseline. BMD, measured by dual energy x-ray absorptiometry, and several confounding factors were measured in the lab.

Analysis.

On the basis of BMD change scores, participants were divided into three categories: BMD loss, minimal change, and BMD gain. Risk ratios were used to show the likelihood of BMD gains over time across different levels of PAv and PAi at baseline.

Results.

Women with higher PAv were more likely to show improvements in hip BMD from baseline to follow-up than their counterparts, as indicated by the Mantel-Haenszel chi-square (χ2mh = 6.1, p = .01). Women with high PAv were 2.50 times (95% CI, 1.19–5.24) more likely to experience hip BMD gains than women with low PAv, and women with moderate PAv were 2.20 times (95% CI, 1.08–4.45) more likely. PAi was not predictive of gains in hip BMD. Adjusting for potential confounders had little influence on the results.

Conclusions.

Middle-aged women with moderate or high levels of PAv are more likely to experience BMD gains at the hip over time compared with those who have low levels of PAv. However, PAi does not appear to influence the likelihood of gaining BMD at the hip over 6 years.

Rheumatoid arthritis is associated with less optimal hip structural geometry

The overall goal of this study was to assess the longitudinal changes in bone strength in women reporting rheumatoid arthritis (RA; n=78) compared with nonarthritic control participants (n=4779) of the Women's Health Initiative bone mineral density (WHI-BMD) subcohort. Hip structural analysis program was applied to archived dual-energy X-ray absorptiometry scans (baseline, years 3, 6, and 9) to estimate bone mineral density (BMD) and hip structural geometry parameters in 3 femoral regions: narrow neck (NN), intertrochanteric (IT), and shaft (S). The association between RA and hip structural geometry was tested using linear regression and random coefficient models. Compared with the nonarthritic control, the RA group had a lower BMD (p=0.061) and significantly lower outer diameter (p=0.017), cross-sectional area (p=0.004), and section modulus (p=0.035) at the NN region in the longitudinal models. No significant associations were seen at the IT regions or S regions, and the association was not modified by age, ethnicity, glucocorticoid use, or time. Within the WHI-BMD, women with RA group had reduced BMD and structural geometry at baseline, and this reduction was seen at a fixed rate throughout the 9 yr of study.

Targeted exercise against osteoporosis: A systematic review and meta-analysis for optimising bone strength throughout life

BACKGROUND

Exercise is widely recommended to reduce osteoporosis, falls and related fragility fractures, but its effect on whole bone strength has remained inconclusive. The primary purpose of this systematic review and meta-analysis was to evaluate the effects of long-term supervised exercise (> or =6 months) on estimates of lower-extremity bone strength from childhood to older age.

METHODS

We searched four databases (PubMed, Sport Discus, Physical Education Index, and Embase) up to October 2009 and included 10 randomised controlled trials (RCTs) that assessed the effects of exercise training on whole bone strength. We analysed the results by age groups (childhood, adolescence, and young and older adulthood) and compared the changes to habitually active or sedentary controls. To calculate standardized mean differences (SMD; effect size), we used the follow-up values of bone strength measures adjusted for baseline bone values. An inverse variance-weighted random-effects model was used to pool the results across studies.

RESULTS

Our quality analysis revealed that exercise regimens were heterogeneous; some trials were short in duration and small in sample size, and the weekly training doses varied considerably between trials. We found a small and significant exercise effect among pre- and early pubertal boys [SMD, effect size, 0.17 (95% CI, 0.02-0.32)], but not among pubertal girls [-0.01 (-0.18 to 0.17)], adolescent boys [0.10 (-0.75 to 0.95)], adolescent girls [0.21 (-0.53 to 0.97)], premenopausal women [0.00 (-0.43 to 0.44)] or postmenopausal women [0.00 (-0.15 to 0.15)]. Evidence based on per-protocol analyses of individual trials in children and adolescents indicated that programmes incorporating regular weight-bearing exercise can result in 1% to 8% improvements in bone strength at the loaded skeletal sites. In premenopausal women with high exercise compliance, improvements ranging from 0.5% to 2.5% have been reported.

CONCLUSIONS

The findings from our meta-analysis of RCTs indicate that exercise can significantly enhance bone strength at loaded sites in children but not in adults. Since few RCTs were conducted to investigate exercise effects on bone strength, there is still a need for further well-designed, long-term RCTs with adequate sample sizes to quantify the effects of exercise on whole bone strength and its structural determinants throughout life.

Impact of dietary intake, education, and physical activity on bone mineral density among North Indian women

The aim of the study was to determine the relationship of dietary nutrients and bone mineral density (BMD) in North Indian women. This cross-sectional study was conducted from April 2006 to March 2008. Subjects included 255 healthy women, aged 20-69 years, who were relatives of patients being admitted in the hospital. Various demographic characteristics including socioeconomic status and serum parameters in relationship to BMD were evaluated. In addition, the daily dietary intake of energy, protein, fat, and calcium and the amount of physical activity were assessed. BMD at the lumbar spine, femoral neck, and Ward's triangle was measured by dual-energy X-ray absorptiometry (DXA). Body mass index (BMI), physical activity, and educational level were positively correlated with BMD. The daily intakes of energy (1563.4 +/- 267.2 kcal) and protein (48.7 +/- 8.7 g) were below the recommended dietary allowance. Daily dietary energy, protein, and calcium intakes were correlated with BMD at the lumbar spine. Stepwise multiple linear regression analyses showed that age, BMI, and physical activity were significant predictors for BMD at all sites. In addition, energy intake was also a predictor for BMD at the lumbar spine. The protein intake was associated with BMD at the spine (P = 0.02 and beta = 0.163) even after making adjustments for energy intake. Thus, dietary pattern coupled with higher education levels and greater physical activity favored bone health.

Autonomic nerve fiber function and bone mineral density in individuals with type 1 diabetes: a cross-sectional study

AIMS

Experimental models support a role for the sympathetic nervous system in bone metabolism. Beta-adrenoreceptors have been demonstrated on osteoblast-like cells. Beta-blocker use is associated with higher bone mineral density (BMD) in some epidemiologic studies. The aim of this study was to determine if measures of the autonomic nervous system (ANS) were associated with reduced BMD in type 1 diabetes.

METHODS

We studied 66 individuals with type 1 diabetes. Dual-energy X-ray absorptiometry was used to measure BMD and bone mineral content (BMC). Measures of heart rate variability (HRV) (e.g., power spectral analysis, mean circular resultant) and circulating norepinephrine levels were used to evaluate autonomic function.

RESULTS

BMD/BMC were examined by gender for individuals with a normal versus elevated low-frequency (LF) band (expressed in normalized units). No significant differences in BMD/BMC were shown for individuals with an elevated LF band. Direct-entry linear regression models with BMD/BMC as the dependent variable were performed. Duration, gender, BMI, HbA(1c), insulin dose/kg, activity energy expenditure, and measures of HRV were entered as potential independent variables. No measures of HRV, or norepinephrine, were independently associated with BMD/BMC.

CONCLUSIONS

The ANS, as assessed by measures of HRV, does not appear to impact BMD/BMC in type 1 diabetes.

Physical activity and dietary calcium interactions in bone mass in Scottish postmenopausal women

In this population-based cohort of 1,254 older Scottish women we found significant interactions between the mechanical component of self-reported habitual physical activity (PA) and dietary calcium (Ca) in BMD, independent of other risk factors. At low and/or medium Ca intakes BMD was higher amongst the most active people.

INTRODUCTION

Although there is general agreement that increased activity (PA) and dietary calcium (Ca) consumption may help maintain bone mass in later life and prevent fractures, the amount required remains uncertain.

METHODS

In 2001-2003, 1,847 postmenopausal women (mean +/- SD age: 69.3 +/- 5.5 years) underwent bone mineral density (BMD) measurement and, in 2004, 68.7% (n = 1,254) completed a bone-specific Physical Activity Questionnaire (bsPAQ) and a food frequency questionnaire. The bsPAQ measures the metabolic and mechanical components of PA. Interactions of PA and Ca in BMD were examined using ANCOVA.

RESULTS

Significant interactions were identified in the BMD of the lumbar spine (LS), right hip (RH) and left hip (LH), after adjustment for confounders, between tertiles of PA classified according to the mechanical component and tertiles of energy-adjusted Ca intake (ANCOVA p = 0.006, p = 0.004 and p = 0.013 respectively). For example, at medium Ca intakes LH BMD was higher by 7.8% in the highest tertile of PA compared with the lowest tertile of PA.

CONCLUSIONS

These data suggest that health promotion campaigns to increase PA would be most effective in populations with a low/medium calcium intake.

Role of sport and exercise in the maintenance of female bone health

Osteoporosis most commonly affects postmenopausal women, placing them at a significant risk for fractures. The strategies for preventing osteoporotic fractures are maximizing peak bone mass, counteracting age- and menopause-related bone loss, minimizing the increase in spinal kyphosis, and preventing falls. Thus, the aim of sport and exercise appears to differ among ages in the maintenance of bone health in females. Given that maximizing peak bone mass is the most important strategy for preventing fractures in later life, interventions may therefore be needed before the menarche (during the growth spurt) in children. The efficacy of sport activity and exercise in all strategies has been established, although there is no evidence that sport and exercise are able to prevent hip fractures. However, sport activity and exercise across the life span of the average female should be encouraged in the maintenance of bone health.

Influence of calcium intake and physical activity on proximal femur bone mass and structure among pre- and postmenopausal women. A 10-year prospective study

This 10-year follow-up evaluated the effect of physical activity and calcium intake on proximal femur bone mass (BMC) and structural indices (CSA and Z) and physical performance. A cohort of 133 premenopausal and 134 postmenopausal women with contrasting levels of physical activity (high [PA+]) and low [PA-]) and calcium intake (high [Ca+] and low [Ca-]) was measured with DXA at baseline and 5 and 10 years thereafter. Among premenopausal women, the mean (95% CI) femoral neck BMC was 3.8% (-0.1 to 7.8%) and the trochanter BMC 6.7% (2.4 to 11.3%) greater in the PA+ group than the PA- group. There was no difference between the Ca-intake groups. Among postmenopausal women, the mean femoral neck BMC was 4.2% (-0.2 to 8.8%) greater in the Ca+ group than in the Ca- group and 6.9% (2.2 to11.8%) greater in the PA+ group than in the PA- group. For trochanter BMC, the corresponding differences were 2.7% (-1.6 to 7.2%) and 5.5% (0.9 to 10.3%). The mean differences in CSA and Z were 3.8% (-0.9 to 8.7%) and 4.4% (-2.1 to 11.4%) in favor of the Ca+ group and 6.8% (1.9 to 12.0%) and 9.6% (2.5 to 17.1%) in favor of the PA+ group, respectively. Proximal femur BMC declined generally, but the initial differences between the physical activity and the calcium intake groups were maintained. High calcium intake seemed to slow the decline in trochanter BMC in premenopausal women, while high physical activity was beneficial for proximal femur, particularly among older women.

Bone density and young athletic women. An update

High-school girls and collegiate women have tremendous opportunities to participate in athletic teams. Young girls are also playing in club and select teams at an early age and often, year-round. There are many benefits for participating in sport and physical activity on both the physical and mental health of girls and women. Decreased risk for heart disease and diabetes mellitus, along with improved self-esteem and body-image, were among the first reported benefits of regular physical activity. In addition, sport participation and physical activity is also associated with bone health. Athletes have a greater bone mineral density compared with non-active and physically active females. The increase in bone mass should reduce the risk of fragility fractures in later life. There appears to be a window of opportunity during the development of peak bone mass in which the bone is especially responsive to weight-bearing physical activity. Impact loading sports such as gymnastics, rugby or volleyball tend to produce a better overall osteogenic response than sports without impact loading such as cycling, rowing and swimming. Relatively little is known about the impact of retiring from athletics on bone density. It appears that former athletes continue to have a higher bone density than non-athletes; however, the rate of bone loss appears to be similar in the femoral neck. The positive impact of sports participation on bone mass can be tempered by nutritional and hormonal status. It is not known whether female athletes need additional calcium compared with the general female population. Due to the increased energy expenditure of exercise and/or the pressure to obtain an optimal training bodyweight, some female athletes may develop low energy availability or an eating disorder and subsequently amenorrhoea and a loss of bone mineral density. The three inter-related clinical disorders are referred to as the 'female athlete triad'. This article presents a review of the relationship between sports training and bone health, specifically bone mineral density, in young athletic women.

Skeletal actions of intermittent parathyroid hormone: effects on bone remodelling and structure

Intermittent administration of parathyroid hormone peptides has anabolic skeletal effects and reduces fracture risk in postmenopausal women with osteoporosis but the cellular and structural mechanisms by which these effects are mediated have not been fully established. In cancellous and endocortical bone, there is evidence that both modelling and remodelling-based formation contribute to the increase in bone mass although the contribution of these at different time points in the response to PTH has not been established. Despite the large increase in spine bone mineral density, however, significant increases in iliac crest cancellous bone volume and trabecular thickness have not been consistently demonstrated, possibly reflecting site-specific differences in PTH-induced skeletal effects and/or the large sampling and measurement variance associated with assessment of iliac crest cancellous bone volume and structure. In iliac crest cortical bone, increased cortical thickness has been demonstrated, due at least in part to increased endosteal bone formation; there is also some evidence for increased formation on periosteal surfaces. At some sites an increase in cortical porosity may also occur and the overall effects on cortical bone strength, particularly at the hip, remain to be established. Studies in iliac crest bone indicate a trend towards a lower mineralisation density of bone matrix and increased heterogeneity of mineralisation, consistent with new bone formation. In addition, there is a reduction in mineral crystallinity and a shift towards more divalent collagen cross-links, indicating a change towards a younger bone profile. The potential clinical implications of these effects on bone are currently unknown. The stimulatory effect of PTH peptides on bone formation may favour their use in low turnover bone disease and in states of advanced bone loss. Furthermore, if beneficial effects on cortical bone strength are confirmed, efficacy at non-vertebral sites might be superior to those observed with antiresorptive drugs. Better definition of the effects of intermittent PTH administration on cancellous and cortical bone remodelling and structure at different skeletal sites may inform these speculations and is an important area for future research.

Geometric indices of bone strength are associated with physical activity and dietary calcium intake in healthy older women

A population-based study on 1008 postmenopausal women identified that the 24% of women achieving high levels of PA and CI had 3.4-4.4% higher femoral bone strength in axial compression and 1.7-5.2% in bending than those achieving low levels, indicating that lifestyle factors influence bone strength in the proximal femur.

INTRODUCTION

Extensive research has shown that increased physical activity (PA) and calcium intake (CI) decrease the rate of bone loss; however, there is little research on how these lifestyle variables affect bone geometry. This study was designed to investigate the effects of modifiable lifestyle variables, habitual PA and dietary CI, on femoral geometry in older women.

MATERIALS AND METHODS

Femoral geometry, habitual PA, and dietary CI were measured in a population-based sample of 1008 women (median age+/-interquartile range, 75+/-4years) enrolled in a randomized controlled trial (RCT) of calcium supplementation. Baseline PA and CI were assessed by validated questionnaires, and 1-year DXA scans (Hologic 4500A) were analyzed using the hip structural analysis technique. Section modulus (Z), an index of bending strength, cross-sectional area (CSA), an index of axial compression strength, subperiosteal width (SPW), and centroid position, the position of the center of mass, were measured at the femoral neck (NN), intertrochanter (IT), and femoral shaft (FS) sites. These data were divided into tertiles of PA and CI, and the results were compared using analysis of covariance (ANCOVA), with corrections for age, height, weight, and treatment (calcium/placebo).

RESULTS AND CONCLUSIONS

PA showed a significant dose-response effect on CSA all hip sites (p<0.03) and Z at the narrow neck and intertrochanter sites (p<0.02). For CI, there was a dose-response effect for centroid position at the intertrochanter (p=0.03). These effects were additive, such that the women (n=240) with PA in excess of 65.5 kcal/day and CI in excess of 1039 mg/day had significantly greater CSA (NN, 4.4%; IT, 4.3%; FS, 3.4%) and Z (NN, 3.9%; IT, 5.2%). These data show a favorable association between PA and aspects of bone structural geometry consistent with better bone strength. Association between CI and bone structure was only evident in 1 of 15 variables tested. However, there was evidence that there may be additive effects, whereby women with high levels of PA and CI in excess of 1039 mg/day had significantly greater CSA (NN, 0.4%; FS, 2.1%) and Z (IT, 3.0%) than women with high PA but low CI. These data show that current public health guidelines for PA and dietary CI are not inappropriate where bone structure is the health component of interest.

Effect of physical activity and nutrition on bone mineral density in young Japanese women

We explored factors that contributed to bone mineral density (BMD) in Japanese young women by quantifying the factors related to BMD. Between October 2003 and February 2004, we conducted a cross-sectional survey to study the status of nutritional intake and physical activity, and evaluated the various physical and serum parameters in relation to BMD. Subjects included 254 healthy female students who were 19-25 years old and were attending the Nursing School of Tokyo Women's Medical University, Japan. We measured the lumbar BMD (L2-L4) in these women. Multiple regression analysis was used to predict factors that contributed to current L2-L4 BMD. Our results showed that body mass index (BMI) (standardized regression coefficient = 0.45, P < 0.0001), past exercise habit (standardized regression coefficient = 0.15, P < 0.0059), and current total energy expenditure (standardized regression coefficient = 0.12, P < 0.03) were factors that significantly predicted the current L2-L4 BMD, with BMI as a key contributing factor. A BMI of 20.8 kg/m(2) allowed acquisition of young adult mean (YAM) irrespective of the total energy expenditure. In subjects with low BMI, L2-L4 BMD increased with higher current energy expenditure. A BMI of 20.8 kg/m(2) or greater and an energy expenditure of 32.9 METS-h/day or greater are required to acquire the YAM. We concluded that BMI and physical activity were factors that affected the BMD of Japanese young women.

Relationships between physical activity and physical capacity in adolescent females and bone mass in adulthood

This study investigates whether physical activity and physical performance in adolescence are positively related to adult bone mineral density (BMD). In 1974, physical activity, endurance, and muscular strength were measured in 204 randomly selected female students, age 16.1 +/- 0.3 year (range 15-17 years). Twenty years later, 36 of the women volunteered to undergo a measurement of their BMD. Women who were members in a sports club in adolescence had significantly higher adult BMD (mean differences of 5% to 17% depending on site) compared with subjects who were not engaged in a sports club. Furthermore, women with persistent weight-bearing activity in adulthood had significantly higher BMD compared with women who had stopped being active or had never been active. The differences ranged between 5% and 19% with the highest difference found in trochanter BMD. Stepwise regression analyses showed that membership in a sports club at baseline was a significant independent predictor of BMD in the total body, lumbar spine, legs, trochanter, and femoral neck, explaining 17-26% of the variation in BMD. Change in body weight was a strong independent predictor of BMD of the total body and arms, explaining 8% of the variation in both sites. In addition, running performance at baseline was an independent predictor of total body BMD, whereas the two-hand lift performance significantly predicted BMD of the total body, legs and trochanter. The hanging leg-lift and handgrip were both significant predictors of arm BMD. In conclusion, membership in a sports club and site-specific physical performance in adolescence together with the change in body weight were significantly associated with adult BMD in premenopausal women.

Long-term recreational gymnastics provides a clear benefit in age-related functional decline and bone loss. A prospective 6-year study

INTRODUCTION

Bone fragility and decreased functional performance are risk factors for osteoporotic fractures. The influence of long-term recreational gymnastics on the maintenance of bone rigidity and physical performance was evaluated.

METHODS

One hundred and seven gymnasts and 110 referents (93% of the original sample) participated in this 6-year prospective study. Analysis of covariance (ANCOVA) was used to estimate the between-group differences and changes by time, and regression analyses to find predictors for changes.

RESULTS

In both groups agility and leg extensor power decreased by over 3% and 10%, respectively, but the original between-group differences, favoring the gymnasts, persisted. Proximal femur bone mineral content (BMC) decreased approximately 0.5% per year in both groups, and femoral neck section modulus decreased. Trabecular density of the distal tibia declined only marginally, and cortical area of the tibial midshaft remained unchanged, while cortical density decreased about 2% in both groups. After adjustment by age, height, weight, change in weight, and follow-up time, antiresorptive medication and high calcium intake accounted most for the maintenance of bone rigidity.

CONCLUSIONS

In spite of similar rates of decline in bone characteristics and physical performance, the recreational gymnasts' overall physical condition was comparable to the level that their less active referents had shown approximately 5 years earlier.

Physical activity in the prevention and amelioration of osteoporosis in women : interaction of mechanical, hormonal and dietary factors

Osteoporosis is a serious health problem that diminishes quality of life and levies a financial burden on those who fear and experience bone fractures. Physical activity as a way to prevent osteoporosis is based on evidence that it can regulate bone maintenance and stimulate bone formation including the accumulation of mineral, in addition to strengthening muscles, improving balance, and thus reducing the overall risk of falls and fractures. Currently, our understanding of how to use exercise effectively in the prevention of osteoporosis is incomplete. It is uncertain whether exercise will help accumulate more overall peak bone mass during childhood, adolescence and young adulthood. Also, the consistent effectiveness of exercise to increase bone mass, or at least arrest the loss of bone mass after menopause, is also in question. Within this framework, section 1 introduces mechanical characteristics of bones to assist the reader in understanding their responses to physical activity. Section 2 reviews hormonal, nutritional and mechanical factors necessary for the growth of bones in length, width and mineral content that produce peak bone mass in the course of childhood and adolescence using a large sample of healthy Caucasian girls and female adolescents for reference. Effectiveness of exercise is evaluated throughout using absolute changes in bone with the underlying assumption that useful exercise should produce changes that approximate or exceed the absolute magnitude of bone parameters in a healthy reference population. Physical activity increases growth in width and mineral content of bones in girls and adolescent females, particularly when it is initiated before puberty, carried out in volumes and at intensities seen in athletes, and accompanied by adequate caloric and calcium intakes. Similar increases are seen in young women following the termination of statural growth in response to athletic training, but not to more limited levels of physical activity characteristic of longitudinal training studies. After 9-12 months of regular exercise, young adult women often show very small benefits to bone health, possibly because of large subject attrition rates, inadequate exercise intensity, duration or frequency, or because at this stage of life accumulation of bone mass may be at its natural peak. The important influence of hormones as well as dietary and specific nutrient abundance on bone growth and health are emphasised, and premature bone loss associated with dietary restriction and estradiol withdrawal in exercise-induced amenorrhoea is described. In section 3, the same assessment is applied to the effects of physical activity in postmenopausal women. Studies of postmenopausal women are presented from the perspective of limitations of the capacity of the skeleton to adapt to mechanical stress of exercise due to altered hormonal status and inadequate intake of specific nutrients. After menopause, effectiveness of exercise to increase bone mineral depends heavily on adequate availability of dietary calcium. Relatively infrequent evidence that physical activity prevents bone loss or increases bone mineral after menopause may be a consequence of inadequate calcium availability or low intensity of exercise in training studies. Several studies with postmenopausal women show modest increases in bone mineral toward the norm seen in a healthy population in response to high-intensity training. Physical activities continue to stimulate increases in bone diameter throughout the lifespan. These exercise-stimulated increases in bone diameter diminish the risk of fractures by mechanically counteracting the thinning of bones and increases in bone porosity. Seven principles of bone adaptation to mechanical stress are reviewed in section 4 to suggest how exercise by human subjects could be made more effective. They posit that exercise should: (i) be dynamic, not static; (ii) exceed a threshold intensity; (iii) exceed a threshold strain frequency; (iv) be relatively brief but intermittent; (v) impose an unusual loading pattern on the bones; (vi) be supported by unlimited nutrient energy; and (vii) include adequate calcium and cholecalciferol (vitamin D3) availability.

Calcium and Exercise Affect the Growing Skeleton

Adequate dietary calcium and bone-stimulating exercise during growth are known to affect skeletal development, but the combined effects of dietary calcium and osteogenic exercise have received scant attention. Animal research has showed a compensatory effect of impact loading on calcium-deprived bones, while various human studies have suggested compensatory, additive, or possibly synergistic effects in certain skeletal locations. Current evidence suggests that the best strategy for strong bones by the end of childhood may be either high-impact exercise with a moderate or greater calcium intake or a combination of moderate-impact exercise and adequate calcium during growth.

Determining the prevalence of osteoporosis and related factors using quantitative ultrasound in Vietnamese adult women

In 2003, the authors conducted a population-based, cross-sectional survey to determine the prevalence of osteoporosis and related factors in Vietnamese adult women by using quantitative ultrasound at the heel bone (calcaneus). A total of 2,232 adult women aged > or =20 years, living in Hanoi City, and free of illnesses affecting bone metabolism were randomly selected to participate in the study. Subjects' bone mass was assessed by speed of sound at the calcaneus, referred to as quantitative ultrasound measurement. The T-score threshold, defined as < or =-1.8, was used to identify subjects with osteoporosis. The crude prevalence of osteoporosis in Hanoi City was 15.4%; after adjustment for age, it was 9.0%. Among premenopausal women, the crude prevalence of osteoporosis was higher in the urban areas compared with the rural areas. By contrast, postmenopausal women in the rural areas had a higher prevalence of osteoporosis. Multiple logistic regression analysis revealed that factors associated with low speed of sound were age, menopause, educational level, lifelong occupation, recreational weight-bearing exercise, number of births, and height. Results suggest that osteoporosis is a noteworthy problem in Vietnam, and intervention strategies should be considered to control it, especially in high-risk populations.

The Canadian Health Claim for Calcium, Vitamin D and Osteoporosis

To provide evidence for or against allowing a health claim for calcium in Canada, we undertook a review of the current U.S. health claim for calcium and osteoporosis, and also reviewed the scientific literature published since that health claim was first proposed and reviewed by the U.S. Food and Drug Administration in 1991 and adopted in 1993. Our objectives were 1) to determine if the science behind the claim was still valid, and if so, 2) to recommend any new wording to the claim, if warranted, prior to implementation in Canada. Based on a review of the evidence (to May 2000) related to the various claim elements, the following health claim for calcium has been established in Canada: A healthy diet with adequate calcium and vitamin D, and regular physical activity, help to achieve strong bones and may reduce the risk of osteoporosis. The compositional criteria for foods bearing this claim are that the food must provide at least 200 mg calcium per serving and that the phosphorus content (excluding that provided by phytate) must be less than the calcium content.

Body weight change since menopause and percentage body fat mass are predictors of subsequent bone mineral density change of the proximal femur in women aged 75 years and older: results of a 5 year prospective study

Few studies have evaluated risk factors for bone loss in elderly women. We examined risk factors associated with a 5-year longitudinal change in bone mineral density (BMD) at the hip in healthy women aged 75 years and older. The BMD of 276 women from the French EPIDOS (Epidémiologie des Osteoporoses) study was assessed in Montpellier from 1992 to 1993 and again from 1997 to 1998. BMD was measured at the femoral neck, trochanter, and Ward's area using the same Lunar densitometer. We examined the relationship between clinical and behavioral factors at baseline and their variations during follow-up, with percentage BMD change adjusted for baseline BMD. Depending on the femur subregion studied, a significant decrease in BMD (exceeding the least significant difference, i.e., > 2.8 CV) was observed in 36.2% to 51.1% of women. Multivariate analysis showed that both postmenopausal weight change before baseline and baseline percentage of fat mass were positively correlated with BMD change at the Ward's triangle and the trochanter. Yearly absolute and relative weight changes over the follow-up period were significantly associated with change of trochanter and femoral neck BMD. Our results show that maintenance of body weight throughout the postmenopause period and body fat mass play protective roles against bone loss at the proximal femur in women aged 75 years and older and suggest the value in including assessment of weight change throughout postmenopause and percentage body fat mass in screening programs for elderly women who are at higher risk of accelerated bone loss.

Predictors of bone mineral density in female workers in Morelos State, Mexico

BACKGROUND

Although several studies have identified factors associated with bone mineral density (BMD), little research is available on Mexican women.

METHODS

A cross-sectional study was conducted in 1,622 female workers between 20 and 80 years of age at the Mexican Social Security Institute (IMSS), an integral part of the Mexican health system. It was carried out in Morelos, a Mexican state that borders Mexico City. Women were recruited to participate in this study from their workplaces. Body mass index (BMI) was measured and BMD was assessed using dual-energy x-ray absorptiometry of dominant forearm. Predictors of BMD (age, reproductive factors, BMI, diet, and physical activity) in pre- and postmenopausal women were assessed by questionnaire and analyzed using generalized additive models.

RESULTS

In premenopausal women, older age, higher BMI, younger age at menarche, and greater vitamin D intake were associated with higher BMD (R(2)=0.06, null deviance reduction=6.9%). In postmenopausal women, determinants of BMD were older age, higher BMI, greater height, later initiation of menopause, longer time of use of hormonal replacement therapy (HRT), and greater calcium intake from dairy products (R(2)=0.39, null deviance reduction=40.7%).

CONCLUSIONS

As observed in other populations, age, BMI, height, age at menopause, time of use of HRT, and calcium intake derived from dairy products in these Mexican women are factors associated with higher forearm BMD during postmenopausal period. Age, BMI, age at menarche, and vitamin D are associated with higher forearm BMD in premenopausal women. Some of these factors are not linearly associated with BMD. This was a limited population study carried out in a large group of female healthcare workers whose reproductive and lifestyle factors potentially agreed with those of female workers from urban areas of Mexico.

dGEMRIC (delayed gadolinium-enhanced MRI of cartilage) indicates adaptive capacity of human knee cartilage

Delayed gadolinium-enhanced MRI of cartilage (dGEMRIC) is a new imaging technique to estimate joint cartilage glycosaminoglycan content by T1-relaxation time measurements after penetration of the hydrophilic contrast agent Gd-DTPA(2-). This study compares dGEMRIC in age-matched healthy volunteers with different levels of physical activity: Group 1 (n = 12): nonexercising individuals; Group 2 (n = 16): individuals with physical exercise averaging twice weekly; Group 3 (n = 9): male elite runners. dGEMRIC was performed 2 hr after an intravenous injection of Gd-DTPA(2-) at 0.3 mmol/kg body weight. T1 differed significantly between the three different levels of physical exercise. T1 values (mean of medial and lateral femoral cartilage) for Groups 1, 2, and 3 were: 382 +/- 33, 424 +/- 22 and 476 +/- 36, respectively (ms, mean +/- SD) (P = 0.0004, 1 vs. 2 and 0.0002, 2 vs. 3). Irrespective of the exercise level, T1 was longer in lateral compared to medial femoral cartilage (P = 0.00005; n = 37). In conclusion, this cross-sectional study indicates that human knee cartilage adapts to exercise by increasing the glycosaminoglycan content. Furthermore, results suggest a compartmental difference within the knee with a higher glycosaminoglycan content in lateral compared to medial femoral cartilage. A higher proportion of extracellular water, i.e., larger distribution volume, may to some extent explain the high T1 in the elite runners.

Effects of estrogen replacement on metabolic factors that influence physical performance in female hypogonadism

There is a lack of knowledge regarding the effects of estrogens on physical performance. This is related, in part, to the challenge of isolating the effects of estrogens from those of progestins, because levels of both hormones fluctuate across the menstrual cycle, both decline during the menopausal transition, and the administration oh hormones to hypogonadal women typically involves a combination of estrogens and progestins. Some research findings suggest that fluctuations in estrogen levels acutely influence factors that may affect physical performance, such as substrate utilization or maximal aerobic power, but solid evidence is lacking. The simple observation that hypogonadism is not uncommon among elite athletes in some sports suggests that estrogen deficiency does not have a major negative impact on athletic performance. However, chronic hypogonadism may ultimately lead to impaired performance by menas that are not necessarily obvious. For example, chronic estrogen deficiency has potent, deleterious effects on the skeleton that can increase risk for stress fracture and may limit the ability to sustain a high level of physical training. Estrogen deficiency also appears to promote fat accumulation and may accelerate the loss of fat-free mass, and both of these changes in body composition could impair physical performance. There is evidence that hormone replacement attenuates the negative effects of hypogonadism on body composition and bone density, and that effects are mediated primarily by estrogens rather than progestins. Further research is necessary to broaden the understanding of the role of the estrogens in physical performance.

Bone health across the lifespan--exercising our options

Exercise is frequently extolled as an osteoporosis treatment. In reality, the use of exercise as an osteoporosis intervention lies more in its ability to: 1) maximize peak bone mass attained in youth; 2) maintain bone mass or reduce age-related bone loss; and 3) preserve muscle strength and postural stability to reduce the risk of falling and fracturing in the later years.

Effect of long-term impact-loading on mass, size, and estimated strength of humerus and radius of female racquet-sports players: a peripheral quantitative computed tomography study between young and old starters and controls

Bone characteristics of the humeral shaft and distal radius were measured from 64 female tennis and squash players and their 27 age-, height-, and weight-matched controls with peripheral quantitative tomography (pQCT) and dual energy X-ray absorptiometry (DXA). The players were divided into two groups according to the starting age of their tennis or squash training (either before or after menarche) to examine the possible differences in the loading-induced changes in bone structure and volumetric density. The following pQCT variables were used: bone mineral content, total cross-sectional area of bone (TotA), cross-sectional area of the marrow cavity (CavA) and that of the cortical bone (CoA), cortical wall thickness (CWT), volumetric density of the cortical bone (CoD) and trabecular bone (TrD), and torsional bone strength index for the shaft (BSIt) and compressional bone strength index for the bone end (BSIc). These bone strength indices were compared with the DXA-derived areal bone mineral density (aBMD) to assess how well the latter represents the effect of mechanical loading on apparent bone strength. At the humeral shaft, the loaded arm's greater bone mineral content (an average 19% side-to-side difference in young starters and 9% in old starters), was caused by an enlarged cortex (CoA; side-to-side differences 20% and 9%, respectively). The loaded humerus seemed to have grown periosteally (the CavA did not differ between the sites), leading to 26% and 11% side-to-side BSIt differences in the young and old starters, respectively. CoD was equal between the arms (-1% difference in both player groups). The side-to-side differences in the young starters' bone mineral content, CoA, TotA, CWT, and BSIt were 8-22% higher than those of the controls and 8-14% higher than those of the old starters. Old starters' bone mineral content, CoA, and BSIt side-to-side differences were 6-7% greater than those in the controls. The DXA-derived side-to-side aBMD difference was 7% greater in young starters compared with that of the old starters and 14% compared with that in controls, whereas the difference between old starters and controls was 6%, in favor of the former. All these between-group differences were statistically significant. At the distal radius, the player groups differed significantly from controls in the side-to-side bone mineral content, TrD, and aBMD differences only: the young starters' bone mineral content difference was 9% greater, TrD and aBMD differences were 5% greater than those in the controls, and the old starters' TrD and aBMD differences were both 7% greater than those in the controls. In summary, in both of the female player groups, the structural adaptation of the humeral shaft to long-term loading seemed to be achieved through periosteal enlargement of the bone cortex, although this adaptation was clearly better in the young starters. Exercise-induced cortical enlargement was not so clear at the distal radius (a trabecular bone site), and the study suggested that at long bone ends, the trabecular density could be a modifiable factor to built a stronger bone structure. Conventional DXA-based aBMD measurement detected the intergroup differences in the exercise-induced bone gains, although, because it measured two dimensions of bone only, it seemed to underestimate the effect of exercise on the apparent bone strength, especially if the playing had been started during the growing years.

Effect of long-term impact-loading on mass, size, and estimated strength of humerus and radius of female racquet-sports players: a peripheral quantitative computed tomography study between young and old starters and controls

Bone characteristics of the humeral shaft and distal radius were measured from 64 female tennis and squash players and their 27 age-, height-, and weight-matched controls with peripheral quantitative tomography (pQCT) and DXA. The players were divided into two groups according to the starting age of their tennis or squash training (either before or after menarche) to examine the possible differences in the loading-induced changes in bone structure and volumetric density. The used pQCT variables were bone mineral content (BMC), total cross-sectional area (TotA) of bone, cross-sectional area of the marrow cavity (CavA) and that of the cortical bone (CoA), cortical wall thickness (CWT), volumetric density of the cortical bone (CoD) and trabecular bone (TrD), and torsional bone strength index (BSIt) for the shaft, and compressional bone strength index (BSIc) for the bone end. These bone strength indices were compared with the DXA-derived areal bone mineral density (aBMD) to assess how well the latter represents the effect of mechanical loading on apparent bone strength. At the humeral shaft, the loaded arm's greater BMC (an average 19% side-to-side difference in young starters and 9% in old starters) was caused by an enlarged cortex (CoA; side-to-side differences 20% and 9%, respectively). The loaded humerus seemed to have grown periosteally (the CavA did not differ between the sites) leading to 26% and 11% side-to-side BSIt difference in the young and old starters, respectively. CoD was equal between the arms (-1% difference in both player groups). The side-to-side differences in the young starters' BMC, CoA, TotA, CWT, and BSIt were 8-22% higher than those of the controls and 8-14% higher than those of the old starters. Old starters' BMC, CoA, and BSIt side-to-side differences were 6-7% greater than those in the controls. The DXA-derived side-to-side aBMD difference was 7% greater in young starters compared with that of the old starters and 14% compared with that in controls, whereas the difference between old starters and controls was 6%, in favor of the former. All these between-group differences were statistically significant. At the distal radius, the player groups differed significantly from controls in the side-to-side BMC, TrD, and aBMD differences only; the young starters' BMC difference was 9% greater, TrD and aBMD differences were 5% greater than those in the controls, and the old starters' TrD and aBMD differences were both 7% greater than those in the controls. In summary, in both of the female player groups the structural adaptation of the humeral shaft to long-term loading seemed to be achievedthrough periosteal enlargement of the bone cortex although this adaptation was clearly better in the young starters. Exercise-induced cortical enlargement was not so clear at the distal radius (a trabecular bone site), and the study suggested that at long bone ends also the TrD could be a modifiable factor to build a stronger bone structure. The conventional DXA-based aBMD measurement detected the intergroup differences in the exercise-induced bone gains, although, measuring two dimensions of bone only, it seemed to underestimate the effect of exercise on the apparent bone strength, especially if the playing had been started during the growing years.

Alice in menopauseland: the jabberwocky of a medicalized middle age

Active living is being advanced in the scientific literature as an essential and effective resource to sustained health and vitality in middle-aged women, with potent benefits to biological, social, and emotional health. At the same time, menopausal women are being counseled that hormone replacement therapy (HRT) is the treatment of choice for combating symptoms and diseases that accompany female aging. Assisted by the writing of Lewis Carroll, here we gaze "through the looking glass" on women's health choices as they are relayed through current medical practice. By exploring the jabberwocky of communications experienced by women as they consider the best pathway to late life health, we show that active living is a worthy alternative--potent for health promotion, broader than hormones in its benefits, and is the more empowering and ethical route for women's long-term health.