Osteoporotic Fractures In Later Life Research Articles

Impact of Exercises on Bone Health of Pre-Menopausal Female

The process of bone resorption and creation, in which osteoclasts destroy old bone and osteoblasts produce new bone, causes the living tissue of bone to continually degrade. Bone is a dynamic tissue that adjusts to the accompanying mechanical forces that are put on it, such as exercise. In order to lower the risk of osteoporosis and resultant fractures during the postmenopausal years, with relative-risk rises, it is crucial to maintain appropriate bone mineral density (BMD) levels throughout the premenopausal years. Pre-menopausal women have been found to have osteopenia and osteoporosis at prevalence rates of 15% and 0.6%, respectively [1]. In addition, it has been found that premenopausal women lose between 0.25 and 1% of their bone mineral density per year [2]. In Pakistan, the long-life expectancy after menopause, multiparity, lack of a calcium-rich diet, vitamin D deficiency, physical inactivity, as well as socio-demographic factors, all contribute to an increase in the prevalence of primary, type II osteoporosis and its associated complications. According to a local survey, it affects postmenopausal women 20-49.3% of the time [3]. Although pre-menopausal women are often unsuitable for pharmaceutical treatment, relying on lifestyle factors is virtually always advised. Exercise, a low-cost, non-pharmacologic intervention that is accessible to the great majority of the population, is one potentially successful lifestyle strategy for accomplishing this aim. During youth, exercise improves bone growth and increases BMD, and it may help older people avoid osteoporosis and fractures. Regular exercise, particularly weight-bearing and high-impact exercises, helps the body build high peak bone mass and may lower the risk of falls and osteoporotic fractures in later life. Regarding femoral neck BMD, high-impact exercise was shown to be most beneficial, and it has also been hypothesized that gains brought on by high-impact exercise are retained after intervention. In healthy pre-menopausal women, high-impact exercise increases the bone mineral density in the upper femur and the lumbar spine. This kind of exercise could be an effective, secure, and affordable strategy to prevent osteoporosis later in life if done regularly. Progressive resistance strength training for the lower limbs is the kind of exercise that have the greatest impact on BMD for the neck of the femur and should be taken into consideration in clinical practice. The multicomponent training exercise programme has been recommended as the most effective intervention for BMD at the spine. Aerobic exercises involving weight bearing and training on vibrating platforms may also improve BMD.

What Are the Barriers to Adoption of a Lifestyle Associated with Optimal Peak Bone Mass Acquisition? A Qualitative Study of Young Adults in New Zealand

Objective: This study aimed to investigate the barriers to adopting lifestyle factors other than physical activity important for optimal peak bone mass (PBM) acquisition—namely, dietary factors, avoidance of cigarette smoking, and keeping alcohol consumption within recommended limits. Materials and Methods: University students and staff aged 18–35 years were recruited. Six semi-structured, in-depth focus group interviews were conducted with a total of 28 participants. The interviews were digitally recorded and transcribed. A thematic approach for data analysis using a constant comparative method was performed using NVivo software. Results: Three major themes emerged: socio-cultural barriers (peer pressure and cultural norms); personal barriers (time, cost, and diet preferences); and other barriers (medical illness and lack of symptoms associated with low bone mass density). Conclusions: We identified several barriers to adoption of lifestyle behaviours that might be beneficial to PBM acquisition. These data might facilitate the development of public health interventions designed to help young adults embrace osteoprotective lifestyles, and hence reduce the burden of osteoporotic fracture in later life.

Dietary patterns with special reference to calcium intake in 2-16-year-old Urban Western Indian children.

It is important to establish good dietary practices in childhood that promote adequate calcium intake throughout life and reduce the risk of osteoporotic fractures in later life. To assess dietary patterns of 2-16-year-old children with special reference to calcium and suggest strategies and develop recipes suitable to identified patterns to increase dietary calcium intake. We studied 220 schoolchildren (2-16 years) around Pune city, India. The study duration was June 2013-July 2014. Height and weight were measured using standard protocols. Dietary intake was assessed by 24-h diet recall on 3 nonconsecutive days. Dietary patterns were derived by cluster analysis in two age groups; children (2-9 years) and adolescents (10-16 years). As per the dietary patterns, calcium-rich recipes were developed. Among children, "rice-pulse" (RP) and "wheat, milk, and milk products" (WM) patterns were observed. Among adolescents, RP, "wheat, milk, and bakery" (WMB), and "mixed food" patterns were observed. Children who consumed "WM" and "WMB" patterns had greater intake of calcium (P < 0.05) than children consuming other dietary patterns. The daily calcium intake of whole group was 53% of the recommended dietary allowance. From this, 30% calcium came from milk. Each serve of the developed recipe provided an average of 254 mg of calcium. Majority of children had cereal-pulse-based dietary patterns. By replacing foods from existing dietary patterns with calcium-rich foods, the dietary calcium content may be increased in a sustainable manner.

Reference values of bone stiffness index and C-terminal telopeptide in healthy European children.

Quantitative ultrasound measurements and bone metabolic markers can help to monitor bone health and to detect impaired skeletal development. Population-based reference values for children may serve as a basis for preventive measures to reduce the risk of osteoporosis and osteoporotic fractures in later life. This is the first paper providing age-, sex- and height-specific reference values for bone stiffness index (SI) and serum carboxy-terminal cross-linking telopeptide of type I collagen (CTX) in healthy, apparently prepubertal children. In the population-based IDEFICS baseline survey (2007-2008) and follow-up (2009-2010), 18,745 children from eight European countries were newly recruited. A total of 10,791 2-10.9-year-old and 1646 3-8.9-year-old healthy children provided data on SI of the right and left calcaneus and serum CTX, respectively. Furthermore, height and weight were measured. Percentile curves were calculated using the General Additive Model for Location Scale and Shape (GAMLSS) to model the distribution of SI and CTX depending on multiple covariates while accounting for dispersion, skewness, and the kurtosis of this distribution. SI was negatively associated with age and height in children aged 2-5 years, whereas a positive association was observed in children aged 6-10 years. The dip in SI occurred at older age for higher SI percentiles and was observed earlier in taller children than in smaller children. The CTX reference curves showed a linear-positive association with age and height. No major sex differences were observed for the SI and CTX reference values. These reference data lay the ground to evaluate bone growth and metabolism in prepubertal children in epidemiological and clinical settings. They may also inform clinical practice to monitor skeletal development and to assess adverse drug reactions during medical treatments.

Calcium and bone

Evaluate the role of calcium on bone health. Review of literatures on calcium and bone development during childhood and bone health in adulthood and older age. Calcium intake influences skeletal calcium retention during growth and thus affects peak bone mass achieved in early adulthood. Increased calcium intake is associated with increased bone mineral accretion rate up to a threshold level in all ethnic groups. The minimum intake to achieve maximal retention is 1140 mg/day for white boys and 1300 mg/day for white girls. Calcium also plays a role in preventing bone loss and osteoporotic fractures in later life. Meta-analyses report that calcium supplementation reduce bone loss by 0.5-1.2% and the risk of fracture of all types by at least 10% in older people. Low calcium intake is a widespread problem across countries and age groups. Adequate calcium intake throughout lifetime is important for bone health and the prevention of osteoporosis and related fractures.

Association between bone mass and injuries in professional jumpers

The health benefits of exercise are well established. Research has shown that exercise has a positive effect on bone health. Sport injuries are associated with several physical and physiological changes...

Vitamin D deficiency in Indian adolescents

In humans, the main source of vitamin D comes from photoconversion of 7-dehydrocholesterol in the skin to cholecalciferol (vitamin D3) by solar ultraviolet radiation (UVB: 290-320 nm). Vitamin D formed in the skin or the small amount absorbed from the diet is hydroxylated at the 25 position to produce 25 hydroxyvitamin D (25OHD), which is considered to be a reliable index of an individual’s vitamin D status. Vitamin D is crucial for calcium homeostasis and musculoskeletal health. Adequate vitamin D status during adolescence might help to reduce the risk of osteoporotic fractures in later life. There is also a growing body of evidence linking vitamin D status with non-skeletal disorders including autoimmune disorders (Crohn’s disease, multiple sclerosis, rheumatoid arthritis, and type 1 diabetes), infections, and risk of developing cancers of the breast, colon, prostate and ovaries(1).

Replication of previous genome-wide association studies of bone mineral density in premenopausal American women.

Bone mineral density (BMD) achieved during young adulthood (peak BMD) is one of the major determinants of osteoporotic fracture in later life. Genetic variants associated with BMD have been identified by three recent genome-wide association studies. The most significant single-nucleotide polymorphisms (SNPs) from these studies were genotyped to test whether they were associated with peak BMD in premenopausal American women. Femoral neck and lumbar spine BMD were determined by dual-energy X-ray absorptiometry in two groups of premenopausal women: 1524 white women and 512 black women. In premenopausal white women, two SNPs in the C6orf97/ESR1 region were significantly associated with BMD (p < 4.8 × 10−4), with suggestive evidence for CTNNBL1 and LRP5 (p < .01). Evidence of association with one of the two SNPs in the C6orf97/ESR1 region also was observed in premenopausal black women. Furthermore, SNPs in SP7 and a chromosome 4 intergenic region showed suggestive association with BMD in black women. Detailed analyses of additional SNPs in the C6orf97/ESR1 region revealed multiple genomic blocks independently associated with femoral neck and lumbar spine BMD. Findings in the three published genome-wide association studies were replicated in independent samples of premenopausal American women, suggesting that genetic variants in these genes or regions contribute to peak BMD in healthy women in various populations. © 2010 American Society for Bone and Mineral Research.

Educational achievement and fracture risk: response to Clark and Tobias

Dear Editors,WethankDrsClarkandTobias[1]fortheircommentregarding our systematic review, which examined the roleof socioeconomic status (SES) of the individual adult aged>55 years and their risk of osteoporotic fracture [2]. Thestrict eligibility criteria of our review meant that studiesthat had examined the role of parents’ SES upon bonemass acquisition by their offspring did not fulfil theinclusion criteria.The findings of this review were based upon the dataprovided by 11 eligible studies ranked as high quality.Three of the studies ranked as high quality had examinededucation as a prime predictor [3–5]. Of these, only onewas a cohort study from which causality could be inferred[3]; however, it did not adjust for height and weight.Further, of the two cross-sectional studies that assessededucation and were deemed as high quality, only one hadaccounted for body mass index (BMI) in the final model[5]. Thus, we confirm that not all the reviewed studies hadaccounted for weight or height within the final model,although they had adjusted for various combinations ofother risk factors for low bone mass, including age, gender,smoking, physical activity, medications, and prior fracture.The additional explanation for the conflicting associationbetween educational attainment and fracture suggested byClark and Tobias [6] may be plausible. However, since thelead time between bone mass of children and osteoporoticfracture in later life is considerable, the strength of thisassociation may be attenuated by many other influencesduring the intervening years, including co-morbidities,medication use, smoking, alcohol, diet, physical activity,and the occupational environment. Thus, the complexinterrelationship between bone area and bone mass inadulthood in relation to SES may differ from that inchildhood. However, that being said, the alternativeexplanation provided by Clark and Tobias suggests aconceivable explanation and offers an additional and veryinteresting area of further enquiry.References

Strategies to reverse bone loss in women with functional hypothalamic amenorrhea: a systematic review of the literature

Functional hypothalamic amenorrhea (FHA) impairs the attainment of peak bone mass and as such can increase the risk of fractures later in life. To document available treatment strategies, we conducted a systematic review of the literature. We report that hormonal therapies have limited effectiveness in increasing bone mass, whereas increased caloric intake resulting in weight gain and/or resumption of menses is an essential strategy for restoring bone mass in women with FHA. Women with functional hypothalamic amenorrhea (FHA) may not achieve peak bone mass (PBM), which increases the risk of stress fractures, and may increase the risk of osteoporotic fractures in later life. To identify effective treatment strategies for women with FHA, we conducted a systematic review of the literature. We included randomized controlled trials (RCTs), cross-sectional studies, and case studies that reported on the effects of pharmacological and non-pharmacological interventions on bone mineral density (BMD) or bone turnover in women with FHA. Most published studies (n=26) were designed to treat the hormonal abnormalities observed in women with FHA (such as low estrogen, leptin, insulin-like growth factor-1, and DHEA); however none of these treatments demonstrated consistent improvements in BMD. Therapies containing an estrogen given for 8-24 months resulted in variable improvements (1.0-19.0%) in BMD, but failed to restore bone mass to that of age-matched controls. Three studies reported on the use of bisphosphonates (3-12 months) in anorexic women, which appear to have limited effectiveness to improve BMD compared to nutritional treatments. Another three investigations showed no improvements in BMD after androgen therapy (DHEA and testosterone) in anorexic women. In contrast, reports (n=9) describing an increase in caloric intake that results in weight gain and/or the resumption of menses reported a 1.1-16.9% increase in BMD concomitant with an improvement in bone formation and reduction in bone resorption markers. Our literature review indicates that the most successful, and indeed essential strategy for improving BMD in women with FHA is to increase caloric intake such that body mass is increased and there is a resumption of menses. Further long-term studies to determine the persistence of this effect and to determine the effects of this and other strategies on fracture risk are needed.

The association between non-melanoma skin cancer and osteoporotic fractures—a population-based record linkage study

We studied the association between osteoporotic fractures and prior non-melanoma skin cancer (NMSC, a biomarker for cumulative sun exposure). The risk of prior NMSC in our fracture cohort was significantly reduced (standardised incidence ratio 0.69, 95% CI 0.61, 0.78). Adequate lifetime sun exposure may be necessary to protect against osteoporotic fractures in later life. The relationship between cumulative sun exposure and osteoporotic fractures is uncertain. We aimed to study the association between non-melanoma skin cancer (NMSC), a marker of cumulative sun exposure, and osteoporotic fractures in an older cohort. A retrospective cohort study in southern Tasmania in people aged at least 50 years with incident radiographic fracture (n = 2,283) was carried out. By record linkage to the Tasmanian Cancer Registry the cohort was followed backwards through time until the occurrence of NMSC or end-of follow-up. Relative risk was estimated by the standardised incidence ratio (SIR) using sex-, age- and calendar year-specific cancer incidence rates in southern Tasmania as reference. The incidence of prior NMSC in the fracture cohort was 31% lower than for the general population (SIR 0.69, 95% CI 0.61, 0.78). This effect was significant for most fracture subtypes except pelvic and wrist fractures and observed for both NMSC subtypes, squamous cell carcinoma and basal cell carcinoma. Older people with osteoporotic fractures may have had lifestyles linked to lower cumulative sunlight exposure. Achieving a balance between adequate lifetime sun exposure and protection against its adverse effects (such as fractures and skin cancer) may require assessment of individual risks.

Polymorphisms in the bone morphogenetic protein 2 (BMP2) gene do not affect bone mineral density in white men or women

Peak bone mineral density (BMD) achieved during adulthood is a major determinant of osteoporotic fracture in later life. Although environmental factors affect peak BMD, it is a highly heritable trait. Recently, bone morphogenetic protein 2 (BMP2) was reported as a susceptibility gene for osteoporotic fractures and low BMD in Icelandic and Danish populations. To determine whether polymorphisms in the BMP2 gene contribute to BMD variation in our population of healthy American whites, we tested seven single nucleotide polymorphisms (SNPs), four of which were associated with osteoporotic phenotypes in the previous study. BMD at the femoral neck and lumbar spine (L2-L4) were measured by dual energy X-ray absorptiometry (DXA) in 411 men (age 18-61) and 1,291 pre-menopausal women (age 20-50). SNP genotypes/haplotypes were tested for population-based association with BMD using analysis of variance. None of the polymorphisms tested reached statistical significance (all p values >0.05) for BMD at the femoral neck or lumbar spine in either gender. Two of the SNP haplotypes spanning the entire BMP2 gene were marginally associated with BMD in men (p values=0.019-0.043). However, these haplotypes would account for only a small, if any, portion of BMD variation and would not be significant after adjustment for multiple comparisons. These results demonstrate that genetic variations in BMP2 do not substantially contribute to BMD variation in our population of healthy American whites.

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

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

PTH/PTHrP activity and the programming of skeletal development in utero.

There is increasing evidence that nutritional deficiency in utero adversely affects bone development and the risk of developing osteoporosis in later life. Although the mechanisms involved are unknown, circumstantial evidence points to an important role of PTH/PTHrP activity. It is recognized that PTH and PTHrP are critically involved in regulating fetal calcium homeostasis, actions that are mediated at least in part by PPR. As well as playing a central role in the maintenance of calcium homeostasis in the fetus, studies in transgenic mice show that PTH, PTHrP, and PPR exert similar effects on skeletal development in utero, acting to increase the size of the trabecular envelope and decrease that of the cortical envelopes. Taken together, these observations raise the possibility that stimulation of PTH/PTHrP activity in the fetus in response to calcium deficiency acts to increase the size of the trabecular envelope but to reduce that of the cortical envelope. Although any increase in trabecular bone at birth is likely to be relatively transient, a decrease in size of the cortical envelope may have a persistent effect on the trajectory of bone growth in subsequent childhood. Consistent with this proposal, preliminary findings from birth cohort studies suggest that maternal calcium intake and cord blood calcium levels are positively related to bone mass of the offspring as assessed later in childhood. Further studies are justified to determine whether alterations in fetal PTH/ PTHrP activity caused by calcium stress lead to a reduction in size of the cortical envelope at birth that persists into childhood and later adult life and to identify modifiable maternal factors that are responsible for these changes.

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

Eighty-six healthy, young Caucasian 18-year-old men with no known disease or bone injury were recruited to this study at the United States Naval Academy. Change in bone mineral density (BMD) of the hip, lumbar spine, and distal tibia, and total body bone mineral content (TBMC) was measured by dual-energy X-ray absorptiometry (DXA). BMD and TBMC of these men were measured within 2 months (67 ± 3 days) of entering the Academy, and, at the end of their first, second, and fourth years. Hip BMD was unchanged during the study period ( p > 0.05). Lumbar spine BMD increased 3% ( p < 0.001) and distal tibia BMD increased 5% ( p < 0.001). TBMC showed a 7.5% increase over the study period. In this group of young men, gain in BMD and TBMC is greatest to age 21 years, with minimal further increase after age 21. The significance of this rise in bone mass during early adulthood on risk for osteoporotic fractures in later life or its impact on exercise-related bone injuries is unknown and warrants further examination.

An early-life femoral shaft fracture and bone mineral density at adulthood.

High peak bone mass and density in early adulthood is an important protective factor against osteoporotic fractures in later life, but it is not known whether injuries to growing bones adversely affect the attainment of peak bone mass and density. The purpose of this study was therefore to examine with dual-energy X-ray absorptiometry the areal bone mineral density (BMD) of the injured and uninjured extremity (the femoral neck, trochanter area of the femur, distal femur, patella, proximal tibia and distal tibia), lumbar spine and distal radius of young adults with a history of an early-life femoral shaft fracture and to find out whether the fracture had affected the attainment of peak bone density of these patients. Thus, the BMD and clinical status of 41 patients (28 men, 13 women) who had sustained a femoral shaft fracture in childhood or adolescence (between 7 and 15 years of age, average 13 years before the study) were examined. The fracture had led to a statistically significant difference in BMD between the injured and uninjured side distal to the fracture site (men/women: distal femur, -3.7%/-3.9%; patella, -3.1%/-5.9%; proximal tibia, -2.0%/-4.6%; distal tibia, -3.4%/-5.2%), whereas the proximal femur did not show such differences. The male patients' spinal BMD was significantly lower (-7.9%) than that in their age-, height- and weight-matched healthy controls. The female patients' spinal BMD tended to be fairly comparable (-1.6%) to that of the controls (NS). In summary, this study indicates that early-life femoral shaft fracture results in a moderate (-2% to -6%) long-term side-to-side BMD difference distal to the fracture site. Patients' spinal BMD values also tend to be lower than that of controls. Thus, a femoral shaft fracture sustained in childhood or adolescence seems to disturb somewhat the attainment of peak bone density, the important predictor of osteoporotic fractures in later life.

A tibial shaft fracture sustained in childhood or adolescence does not seem to interfere with attainment of peak bone density.

High peak bone mass or density in early adulthood is an important protective factor against osteoporotic fractures in later life, but it is not known whether injuries on growing bones affect the attainment of peak bone mass and density. The purpose of this study was therefore to examine with dual-energy X-ray absorptiometry the areal bone mineral density (BMD) of the injured and uninjured extremity (the femoral neck, trochanter area of the femur, distal femur, patella, proximal tibia, and distal tibia), lumbar spine, and distal radius of young adults with a history of early life tibial shaft fracture and to find out whether the fracture had affected the attainment of peak bone density of these patients. The second objective was to clarify whether any background or clinical follow-up variable would predict the BMD difference between the affected and unaffected extremity. Thus, the BMD and clinical status of 45 patients (34 men and 11 women), who had sustained a tibial shaft fracture in childhood or in adolescence (between 7 and 15 years of age) an average 11 years before the study, were examined. The results showed that the fracture had created a small but statistically significant injured-to-uninjured side BMD difference (proximal tibia -1.7%; p = 0.011, and distal tibia 2.6%; p = 0.014), while the other sites showed no significant side-to-side differences. There were neither significant differences in the spinal or radial BMDs between the patients and their age-, height-, and weight-matched healthy controls. A further analysis of the data showed that the better the muscle strength in the injured lower limb, the lower the side-to-side BMD deficit in the proximal tibia of the same limb (r = 0.51; p < 0.001). Smoking had a significant association with the relative BMD in the injured distal tibia (mean injured-to-uninjured side BMD difference: smokers 6.1% vs. nonsmokers -0.6%, p = 0.016). Also patient's age at the time of the injury showed an association: the younger the patient at the time of the injury, the lower the side-to-side BMD deficit in the injured distal tibia (r = -0.35; p = 0.048). In conclusion, this study indicates that early life tibial fracture leads to a small long-term BMD deficit in the fractured bone while the other sites of the skeleton seem not to be affected. Thus, a tibial shaft fracture sustained in childhood or adolescence seems to only marginally interfere the attainment of peak bone density, the important predictor of the osteoporotic fractures in later life.

Randomised controlled trial of effect of high-impact exercise on selected risk factors for osteoporotic fractures

Osteoporotic fractures among the elderly are common, and without preventive measures the burden of these fractures on health-care systems will increase further. The purpose of this randomised controlled study was to evaluate, in premenopausal women, the effects of high-impact loading on several determinants osteoporotic fractures. 98 healthy, sedentary female volunteers aged 35-45 years were randomly assigned to either a training (n = 49) or a control group (n = 49). Progressive high-impact exercises were done three times per week for 18 months. We measured bone mineral density (BMD) in specific axial and lower-limb sites, by dual-energy X-ray absorptiometry, at baseline and after 12 and 18 months. Maximum isometric strength, muscular and cardiovascular performance, and dynamic balance were also assessed. BMD at the femoral neck, a weightbearing site, increased significantly more in the training group (mean 1.6% [95% CI 0.8-2.4]) than in the control group (0.6% [-0.2 to 1.4], p = 0.006). By contrast, at non-weightbearing sites, such as the distal radius, there was no significant difference between the training and control groups (-1.5% [-2.7 to -0.3] vs -0.7% [-1.9 to -0.5], p = 0.60). In the training group there was a significant improvement in vertical jump and predicted oxygen consumption per min at maximum exercise compared with controls. High-impact exercises that load bones with a rapidly rising force profile in versatile movements improve skeletal integrity, muscular performance, and dynamic balance in premenopausal women. If done on a regular basis, this type of exercise may help decrease the risk of osteoporotic fractures in later life. Long-term studies are required to show whether these 18-month results can be translated into long-term benefit.

Bone density and milk Consider fat as well as calcium intake Consider fat as well as calcium intake

EDITOR, - Sean Murphy and colleagues concluded that milk consumption should be encouraged during childhood and adolescence to prevent osteoporotic fractures in later life.1 This, however, prompts several questions. Firstly, the subjects in the authors' study were asked to categorise their milk consumption without estimating their past total calcium intake. It is known that many subjects who do not drink milk consume other dairy products (cheese and ice cream). Secondly, the subjects had to recall their milk consumption up to age 25, which was a long time before the study (50 years for the 74 year old woman). It could as well be concluded that good memory makes strong bones or vice versa. If the results are reliable they lead to an interesting speculation. It is known that calcium supplementation increases bone mass in childhood.2 This does not occur later in life. Might calcium, or some other agent in dairy products, affect the developing bone in a way that later in life allows calcium intake and maintains high mineral density? I strongly disagree with the public health implications cited by Murphy and colleagues. Dietary habits are learnt in childhood and adolescence and commonly …

The site-specific effects of long-term unilateral activity on bone mineral density and content

This study assessed the site-specific effects of long-term tennis playing on the bone mineral density (BMD) and content (BMC) of upper extremities in male Finnish top-level players using a dual energy x-ray absorptiometric (DXA) scanner. In players ( n = 20), the BMDs and BMCs were significantly higher in each bone of the playing right extremity ( p < 0.05–0.001), the side-to-side difference being largest in the humeral shaft (BMD +25.4%, BMC +28.7%) and proximal humerus (BMD +14.4%, BMC +20.5%), and smallest in the ulnar shaft (BMD +3.1%, BMC +7.5%) and distal ulna (BMD +6.3%, BMC +7.8%). In sex-, age-, weight-, and height-matched controls ( n = 20), the right-to-left differences were small ranging from 0.0% to +6.4% (average +3%). The number of training sessions per week was the only variable in muscle strength and training history assessment which showed, in several anatomic sites, a significant correlation with the relative bone mineral variables ( r = 0.460–0.627, p < 0.05–0.001). In conclusion, long-term unilateral tennis activity had a clearly positive effect on the BMD and BMC of the bones of the playing extremity. The effect was very site-specific, being greatest in the humerus and smallest in the ulna. The effect was always greater in BMC than BMD indicating that the excess mineral was used not only for condensation of the bone tissue, but also for enlargement of bone dimensions. The magnitude of the benefit for the playing extremity (average +13%) is clinically important when estimating that the arm is more than 10 years ahead of its less active counterpart in the prevention of bone loss. This advantage may, in turn, be crucial in prevention of osteoporotic fractures in later life.