Associations between adverse social position and bone mineral density in women aged 50 years or older: data from the Manitoba bone density program

The authors examined the independent contribution of income to low bone mineral density in women aged 50 years and older. A significant dose–response association was observed between low income and low (bone mineral density) BMD, which was not explained by clinical risk factors or osteoporotic treatment in the year prior.

The association between social disadvantage and osteoporosis is attracting increased attention; however, little is known of the role played by income. We examined associations between income and bone mineral density (BMD) in 51,327 women aged ≥50 years from Manitoba, Canada.

Optimization of MLP parameters on mineral potential mapping tasks

Mineral potential mapping is the process of combining a set of input maps, each representing a distinct geo-scientific variable, to produce a single map which ranks areas according to their potential to host deposits of a particular type. The maps are combined using a mapping function which must be either provided by an expert (knowledge-driven approach), or induced from sample data (data-driven approach). Current data-driven approaches using multilayer perceptrons (MLPs) to represent the mapping function have several inherent problems: they rely heavily on subjective judgment in selecting training data and are highly sensitive to this selection; they do not utilize the contextual information provided by unlabeled data; and, there is no objective interpretation of the values output by the MLP. This paper presents a novel approach which overcomes these three problems.

Comparison of MLP and Bayesian approaches on mineral prospectivity mapping tasks

Mineral Prospectivity Mapping is the process of combining maps containing different geoscientific data sets to produce a single map depicting areas ranked according to their potential to host mineral deposits of a particular type. This paper outlines two approaches for deriving a function which can be used to assign to each cell in the study area a value representing the posterior probability that the cell contains a deposit of the sought-after mineral. One approach is based on estimating probability density functions (pdfs); the second uses multilayer perceptrons (MLPs). Results are provided from applying these approaches to geoscientific datasets covering a region in North Western Victoria, Australia. The results demonstrate that while both the Bayesian approach and the MLP approach yield similar results when the number of input dimensions is small, the Bayesian approach rapidly becomes unstable as the number of input dimensions increases, with the resulting maps displaying high sensitivity to the number of mixtures used to model the distributions. However, despite the fact that Bayesian assigned values cannot be interpreted as posterior probabilities in high dimensional input spaces, the pixel favorability rankings produced by the two methods is similar.

Pregnancy and lactation have no long-term deleterious effect on measures of bone mineral in healthy women: a twin study

BACKGROUND: The long-term effects of pregnancy and lactation on measures of bone mineral in women remain unclear.

OBJECTIVE: We studied whether pregnancy or lactation has deleterious long-term effects on bone mineral in healthy women.

DESIGN: We measured bone mineral density (BMD; g/cm(2)) in women aged > or = 18 y. Analyses were performed on 3 data sets: study 1, 83 female twin pairs (21 monozygous and 62 dizygous) aged (x +/- SD) 42.2 +/- 15.5 y who were discordant for ever having been pregnant beyond 20 wk; study 2, 498 twin pairs aged 42.3 +/- 15.0 y; and study 3, 1354 individual twins, their siblings, and family members.

RESULTS: In study 1, there were no significant within-pair differences in unadjusted BMD or BMD adjusted for age, height, and fat mass at the lumbar spine or total-hip or in total-body bone mineral content (BMC; kg) (paired t tests). In study 2, there was no significant within-pair difference in measures of bone mineral or body composition related to the within-pair difference in number of pregnancies. In study 3, subjects with 1 or 2 (n = 455) and > or = 3 pregnancies (n = 473) had higher adjusted lumbar spine BMD (2.9% and 3.8%, respectively; P = 0.001) and total-body BMC (2.2% and 3.1%; P < 0.001) than did nulliparous women (n = 426). Parous women who breast-fed had higher adjusted total-body BMC (2.6%; P = 0.005), total-hip BMD (3.2%; P = 0.04), and lower fat mass (10.9%; P = 0.01) than did parous non-breast-feeders.

CONCLUSION: We found no long-term detrimental effect of pregnancy or breast-feeding on bone mineral measures.

Depression and bone mineral density in a community sample of men : Geelong Osteoporosis Study

Background : Previous research in psychiatric and community samples has demonstrated reduced bone mineral density (BMD) in individuals with both clinical depression and depressive symptoms, although the findings are equivocal. This study aimed to investigate the association between self-reported depression and BMD in a community sample of men aged 20–96 years enrolled in the Geelong Osteoporosis Study.

Methods : A self-report questionnaire based on DSM-IV criteria was used to determine lifetime prevalence rates of depression within the study sample at baseline. Those currently taking oral glucocorticoids, testosterone or bisphosphonates were excluded from the analysis (n = 23) resulting in a sample of 1279 men.

Results : In this sample, 155 men reported a lifetime history of depression (LHX). There were no differences in age, weight, height, calcium intake, smoking rates or unadjusted BMD at the femoral neck between the cases and the controls, whereas unadjusted BMD at the spine was significantly lower in those with a LHX (1.254 ± 0.187 vs 1.293 ± 0.194 g/cm2). BMD adjusted for age, weight, calcium intake and smoking was 3.6% lower at the spine (1.255 ± 0.016 vs 1.295 ± 0.006 g/cm2) and 3.4% lower at the femoral neck (0.973 ± 0.011 vs 1.007 ± 0.004 g/cm2) in those with a LHX compared to controls.

Conclusion : These data are consistent with previous findings of diminished BMD in people with depressive disorders and symptoms and suggest that depression may be a risk factor for reduced BMD in community-dwelling adult men.

Socioeconomic status and bone mineral density in a population-based sample of men

Overall, socioeconomic status (SES) is inversely associated with poorer health outcomes. However, current literature provides conflicting data of the relationship between SES and bone mineral density (BMD) in men. In an age-stratified population-based randomly selected cross-sectional study of men (n = 1467) we assessed the association between SES and lifestyle exposures in relation to BMD. SES was determined by matching the residential address for each subject with Australian Bureau of Statistics 2006 census data for the study region. BMD was measured at the spine and femoral neck by dual energy X-ray absorptiometry. Lifestyle variables were collected by self-report. Regression models were age-stratified into younger and older groups and adjusted for age, weight, dietary calcium, physical activity, and medications known to affect bone. Subjects with spinal abnormalities were excluded from analyses of BMD at the spine. In younger men, BMD was highest at the spine in the mid quintiles of SES, where differences were observed compared to quintile 1 (1–7%, p < 0.05). In older men, the pattern of BMD across SES quintiles was reversed, and subjects from mid quintiles had the lowest BMD, with differences observed compared to quintile 5 (1–7%, p < 0.05). Differences in BMD at the spine across SES quintiles represent a potential 1.5-fold increase in fracture risk for those with the lowest BMD. There were no differences in BMD at the femoral neck. Further research is warranted which examines the mechanisms that may underpin differences in BMD across SES quintiles and to address the current paucity of data in this field of enquiry.

Bone mineral density reference ranges for Australian men : Geelong Osteoporosis Study

Summary : A large population-based random sample of Australian white men was used to provide normative bone mineral density (BMD) data at multiple anatomical sites. The femoral neck BMD data are very similar to those obtained in USA non-Hispanic white males participating in the National Health and Nutrition Examination Survey III (NHANES III). The reference ranges will be suitable for similar populations.

Introduction : To provide normative BMD data for Australian men derived from a large population-based random sample.

Methods : An age-stratified random sample of men was recruited from the Australian electoral rolls (n = 1,467 aged 20–97 years). BMD was quantified at multiple sites using Lunar densitometers.

Results : Age-related differences in BMD were best predicted by linear relationships at the spine and hip and by quadratic functions at the whole body and forearm. At the spine, a small age-related increase in mean BMD was observed. Although in the subset with no spinal abnormalities, there was a decrease of 0.003 g/cm² per year from age 20. At the hip sites, mean BMD decreased at 0.001–0.006 g/cm² per year from age 20. At the forearm and whole body, BMD peaked at 41–47 years. Apart from a small difference in men greater than or equal to 80 years, the Australian femoral neck BMD data are not different to those obtained in USA non-Hispanic white males participating in NHANES III and were generally similar to those of large studies from Canada (CaMos) and Spain.

Conclusions : These data supply BMD reference ranges at multiple anatomical sites that will be applicable to white Australian men and similar populations such as USA non-Hispanic white men.

β-Adrenergic blockers reduce the risk of fracture partly by increasing bone mineral density : Geelong Osteoporosis Study

This population-based study documented β-blocker use in 59/569 cases with incident fracture and 112/775 controls. OR for fracture associated with β-blocker use was 0.68 (95%CI, 0.49–0.96). β-Blockers were associated with higher BMD at the total hip (2.5%) and UD forearm (3.6%) after adjusting for age, anthropometry, and thiazide use. β-Blocker use is associated with reduced fracture risk and higher BMD.

Introduction: Animal data suggests that bone formation is under β-adrenergic control and that β-blockers stimulate bone formation and/or inhibit bone resorption.

Materials and Methods: We evaluated the association between β-blocker use, bone mineral density (BMD), and fracture risk in a population-based study in Geelong, a southeastern Australian city with a single teaching hospital and two radiological centers providing complete fracture ascertainment for the region. β-Blocker use was documented for 569 women with radiologically confirmed incident fractures and 775 controls without incident fracture. Medication use and lifestyle factors were documented by questionnaire.

Results: Odds ratio for fracture associated with β-blocker use was 0.68 (95% CI, 0.49–0.96) for any fracture. Adjusting for age, weight, medications, and lifestyle factors had little effect on the odds ratio. β-Blocker use was associated with a higher BMD at the total hip (2.5%, p = 0.03) and ultradistal forearm (3.6%, p = 0.04) after adjustment for age, anthropometry, and thiazide use.

Conclusion: β-Blockers are associated with a reduction in fracture risk and higher BMD.

Statin use, bone mineral density, and fracture risk: Geelong Osteoporosis Study

Background Recent data suggest that 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) decrease fracture risk and increase bone mineral density (BMD).

Methods This cross-sectional study is set in southeastern Australia. We evaluated the association between statin use, fracture risk, and BMD in 1375 women (573 with incident fractures and 802 without incident fracture, all drawn from the same community). Fractures were identified radiologically. Medication use and lifestyle factors were documented by questionnaire.

Results Unadjusted odds ratio for fracture associated with statin use was 0.40 (95% confidence interval [CI], 0.23-0.71). Adjusting for BMD at the femoral neck, spine, and whole body increased the odds ratio to 0.45 (95% CI, 0.25-0.80), 0.42 (95% CI, 0.24-0.75), and 0.43 (95% CI, 0.24-0.78), respectively. Adjusting for age, weight, concurrent medications, and lifestyle factors had no substantial effect on the odds ratio for fracture. Statin use was associated with a 3% greater adjusted BMD at the femoral neck (P = .08), and BMD tended to be greater at the spine and whole body but did not achieve statistical significance.

Conclusion The substantial 60% reduction in fracture risk associated with statin use is greater than would be expected from increases in BMD alone.

Reasons for referral to bone densitometry in men and women aged 20-49 years : population-based data

Introduction Osteoporosis poses a significant public health problem for ageing Australians. However, approximately 25 % of Australian adults aged 20–49 years have osteopenia, a precursor condition to osteoporosis. Despite this, little is known about bone density testing in this age group.

Methods Reasons for referral to dual energy X-ray absorptiometry (DXA) were examined in 2,264 patients aged 20–49 years, referred in 2001–2010 to the Geelong Bone Densitometry Service, Geelong Hospital, Victoria. Referral reasons were determined from clinical indication codes derived from patient records. Age, sex and bone mineral density (BMD) T scores were ascertained for each patient.

Results The most common reason for referral for women reflected glucocorticoid use, and for men reflected fracture. Compared to women, men were more likely to have been referred because of minimal trauma fracture or low BMD (41.7 versus 27.1 %, p < 0.001). No further differences were identified between the sexes, with similar numbers of referral observed for secondary osteoporosis, and monitoring of drug therapy. At the spine, and for all indications, men had a significantly greater BMD deficit compared to women (all p ≤ 0.002). After age adjustment, men who were tested due to fracture or glucocorticoid reasons had significantly greater BMD at the total hip (p ≤ 0.03). No further associations were seen after age adjustment between referral reason and BMD.

Conclusions Our study presents the first data examining reasons for referral to DXA among Australians aged 20–49 years. Understanding health service utilisation regarding bone health in young adults is fundamental to understanding future risk, informing effective public health messages and raising awareness of osteoporosis.

Social disadvantage, bone mineral density and vertebral wedge deformities in the Tasmanian Older Adult Cohort

Summary The relationship between social disadvantage and bone mineral density (BMD) is complex and remains unclear; furthermore, little is known of the relationship with vertebral deformities. We observed social disadvantage to be associated with BMD for females, independent of body mass index (BMI). A lower prevalence of vertebral deformities was observed for disadvantaged males.

Introduction The relationship between social disadvantage and BMD appears complex and remains unclear, and little is known about the association between social disadvantage and vertebral wedge deformities. We examined the relationship between social disadvantage, BMD and wedge deformities in older adults from the Tasmanian Older Adult Cohort.

Methods BMD and wedge deformities were measured by dual-energy X-ray absorptiometry and associations with extreme social disadvantage was examined in 1,074 randomly recruited population-based adults (51 % female). Socioeconomic status was assessed by Socio-economic Indexes for Areas values derived from residential addresses using Australian Bureau of Statistics 2001 census data. Lifestyle variables were collected by self-report. Regression models were adjusted for age, BMI, dietary calcium, serum vitamin D (25(OH)D), smoking, alcohol, physical inactivity, calcium/vitamin D supplements, glucocorticoids and hormone therapy (females only).

Results Compared with other males, socially disadvantaged males were older (65.9 years versus 61.9 years, p = 0.008) and consumed lower dietary calcium and alcohol (both p ≤ 0.03). Socially disadvantaged females had greater BMI (29.9 ± 5.9 versus 27.6 ± 5.3, p = 0.002) and consumed less alcohol (p = 0.003) compared with other females. Socially disadvantaged males had fewer wedge deformities compared with other males (33.3 % versus 45.4 %, p = 0.05). After adjustment, social disadvantage was negatively associated with hip BMD for females (p = 0.02), but not for males (p = 0.70), and showed a trend for fewer wedge deformities for males (p = 0.06) but no association for females (p = 0.85).

Conclusions Social disadvantage appears to be associated with BMD for females, independent of BMI and other osteoporosis risk factors. A lower prevalence of vertebral deformities was observed for males of extreme social disadvantage. Further research is required to elucidate potential mechanisms for these associations.

Who are the older Australians referred for a bone density scan? Data from the Barwon region

We investigated the reasons for referral of older Australians aged 70 years and older to dual energy X-ray absorptiometry (DXA). The most common clinical indication was being aged 70 years and older, followed by monitoring for fracture or low bone mineral density (BMD). Compared to males, females were twice as likely to have osteoporotic BMD.

Poor agreement between self-reported diagnosis and bone mineral density results in the identification of osteoporosis.

Osteoporosis is a major health concern, estimated to affect millions worldwide. Bone mineral density (BMD) assessment is not practical for many large-scale epidemiological studies resulting in the reliance of self-report methods to ascertain diagnostic information. The aim of the study was to assess the validity of self-reported diagnosis of osteoporosis in a population-based study. This study examined data collected from 906 men and 843 women participating in the Geelong Osteoporosis Study. Osteoporosis was self-reported and compared against results of BMD scans of the hip and spine. Validity was examined by calculating sensitivity, specificity, positive predictive value, negative predictive value, and kappa statistic. Osteoporosis was self-reported by 118 (6.7%) participants and identified using BMD results for 64 (3.7%) participants. Specificity and negative predictive value were good (95.1% and 96.0%, respectively), whereas sensitivity and positive predictive value were poor (35.9% and 31.4%, respectively). The overall level of agreement (kappa) was 0.29. The results changed only slightly when we included participants with osteopenia and adult fracture as osteoporotic. Reliance on self-report methods to ascertain osteoporosis status is not recommended.

Is there an interaction between socioeconomic status and FRAX 10-year fracture probability determined with and without bone density measures? Data from the Geelong Osteoporosis Study of female cohort.

FRAX(©) evaluates 10-year fracture probabilities and can be calculated with and without bone mineral density (BMD). Low socioeconomic status (SES) may affect BMD, and is associated with increased fracture risk. Clinical risk factors differ by SES; however, it is unknown whether aninteraction exists between SES and FRAX determined with and without the BMD. From the Geelong Osteoporosis Study, we drew 819 females aged ≥50 years. Clinical data were collected during 1993-1997. SES was determined by cross-referencing residential addresses with Australian Bureau of Statistics census data and categorized in quintiles. BMD was measured by dual energy X-ray absorptiometry at the same time as other clinical data were collected. Ten-year fracture probabilities were calculated using FRAX (Australia). Using multivariable regression analyses, we examined whether interactions existed between SES and 10-year probability for hip and any major osteoporotic fracture (MOF) defined by use of FRAX with and without BMD. We observed a trend for a SES * FRAX(no-BMD) interaction term for 10-year hip fracture probability (p = 0.09); however, not for MOF (p = 0.42). In women without prior fracture (n = 518), we observed a significant SES * FRAX(no-BMD) interaction term for hip fracture (p = 0.03) and MOF (p = 0.04). SES does not appear to have an interaction with 10-year fracture probabilities determined by FRAX with and without BMD in women with previous fracture; however, it does appear to exist for those without previous fracture.

Muscle strength and areal bone mineral density at the hip in women: a cross-sectional study

BACKGROUND: Muscle strengthening exercises are promoted for building and maintaining a healthy skeleton. We aimed to investigate the relationship between muscle strength and areal bone mineral density (BMD) at the hip in women aged 26-97 years.

METHODS: This cross-sectional study utilises data from 863 women assessed for the Geelong Osteoporosis Study. Measures of hip flexor and abductor strength were made using a hand-held dynamometer (Nicholas Manual Muscle Tester). The maximal measure from three trials on each leg was used for analyses. BMD was measured at the hip using dual energy x-ray absorptiometry (DXA; Lunar DPX-L). Total lean mass, body fat mass and appendicular lean mass were determined from whole body DXA scans. Linear regression techniques were used with muscle strength as the independent variable and BMD as the dependent variable. Models were adjusted for age and indices of body composition.

RESULTS: Measures of age-adjusted hip flexor strength and hip abductor strength were positively associated with total hip BMD. For each standard deviation (SD) increase in hip flexor strength, the increase in mean total hip BMD (SD) was 10.4 % (p = 0.009). A similar pattern was observed for hip abductor strength, with an increase in mean total hip BMD of 22.8 % (p = 0.025). All associations between hip muscle strength and total hip BMD were independent of height, but were nullified after adjusting for appendicular lean mass or total lean mass.

CONCLUSIONS: There was a positive association observed between muscle strength and BMD at the hip. However, this association was explained by measures of lean mass.