Country-Specific Young Adult Dual-Energy X-Ray Absorptiometry Reference Data Are Warranted for T-Score Calculations in Women: Data From the Peak-25 Cohort.

The aims of this study were to provide normative data for dual-energy X-ray absorptiometry (DXA) in 25-yr-old women and evaluate whether young adult Swedish women have bone mineral density (BMD) comparable with DXA manufacturer reference values and other equivalent populations. BMD at all sites was measured in the population-based Peak-25 cohort (n = 1061 women; age, 25.5 ± 0.2yr). BMD values were standardized (sBMD) and compared against the Third National Health and Nutrition Examination Survey (NHANES III) and other cohorts. Based on the DXA manufacturer-supplied reference values, Z-scores were 0.54 ± 0.98 (femoral neck [FN]), 0.47 ± 0.96 (total hip [TH]), and 0.32 ± 1.03 (lumbar spine [LS]). In comparison with other studies, sBMD was higher in the Peak-25 cohort (FN, 1.5%-8.3%; TH, 3.9%-9.2%; and LS, 2.4%-6.5%) with the exception of trochanter-sBMD which was 2.5% lower compared with NHANES III. The concordance in identifying those in the lowest or highest quartile of BMD was highest between hip measurements (low, 71%-78% and high, 70%-84%), corresponding discordance of 0%-1%. At this age, the correlation between DXA sites was strong (r = 0.62-0.94). BMD in Swedish young adult women is generally higher than has been reported in other equivalently aged European and North American cohorts and suggests that the high fracture incidence in Sweden is not explained by lower peak bone mass. The use of nonregional-specific DXA reference data could contribute to misdiagnosed osteoporosis in elderly women

Gendered geographies and the politics of place : a comparative reading of the novels of Mariama Bâ and Chimamanda Ngozi Adichie.

This thesis is concerned with inscriptions of gender and space in the novels of two African women writers, Mariama Bâ and Chimamanda Ngozi Adichie, particularly Bâ’s So Long a Letter (1981) and Scarlet Song (1986) and Adichie’s Purple Hibiscus (2004) and Half of a Yellow Sun (2006). The exploration of representations of gendered identity is thus integrated with an awareness of space/place. By exploring the demarcation and enunciation of space within my chosen texts, I hope to provide new perspectives on the question of gendered identities and relations. The theorizing of gender identities and relations thus gains a new orientation from its application in relation to the theorizing of space and spatiality. As many theorists have argued, space is an important aspect to consider because it is not a neutral site: it becomes invested with meanings and encodes particular values and relations of power which can be contested and negotiated. This is particularly evident when looking at questions of gender identity, roles and relations. ‘Geographies of gender’ are established not only in the coding of spaces as ‘masculine’ and feminine’ but also in the kinds of sociality which they encourage and the power-relations they encode. If space is central to masculinist power, it is also important in the development of feminine resistance. Drawing on a range of theorists, I endeavour to pursue a gendered analysis of space/place through a reading of particular locations (the home, the street, the village) as expressive of power relations, gender identities and roles. I also consider how space/place is differently experienced and inhabited by men and women as well as how dominant constructions of space/place, which are also invested with meaning and power relations, come to be negotiated or contested. In all four novels explored in this thesis, the home is revealed as a dominant site of inscription, a space which tends to reflect and reinforce dominant social identities and roles. In this sense, the home is often figured as a site of patriarchal and gendered oppression, a central domain in which normative definitions of gender are established and reinforced. What is also clear, however, is that way in which the home also becomes a site for the contestation and renegotiation of gender identities and roles, a place where conventional identities can be challenged and new identities explored. In this sense, the home is revealed as a major site of contestation in which the tensions between different experiences and interpretations of space based on contrasting cultural definitions of power relations, gender identities and roles are played out. If the ordering of space is an important means of securing dominant gender relations, it also provides the means for negotiation and resistance. This is reflected not only the alternative ii examples of home explored in these novels but also in liberating spaces such as the school, the beach and the university. In the destabilisation and destruction of the home, the links between self and place becomes apparent as new identities are formed and conventional roles are redefined

Adverse Effects of Smoking on Peak Bone Mass May Be Attenuated by Higher Body Mass Index in Young Female Smokers.

Smoking is associated with postmenopausal bone loss and fracture, but the effect of smoking on bone in younger women is unclear. Peak bone mass is an important determinant for fracture risk; therefore, our aim was to evaluate the association between smoking and bone mass in 25-year-old women, specifically the influence of daily cigarette consumption and total exposure, duration, age at starting smoking, and time since smoking cessation on bone density and fracture risk. Smoking and bone mineral density (BMD) data were available for 1,054 women from the PEAK-25 cohort. Analyses comparing current smokers with women who never smoked were performed using number of cigarettes per day, pack-years, smoking duration, age smoking started, and, for former smokers, age at quitting. BMD did not differ between never, former, and current smokers; and the relative fracture risk in smokers was not significant (relative risk [RR] = 1.2, 95 % confidence interval 0.8-1.9). Among current smokers, BMD decreased with a dose response as cigarette consumption increased (femoral neck p = 0.037). BMD was not significantly lower in young women who had smoked for long duration or started smoking early (p = 0.07-0.64); long duration and early start were associated with higher body mass index (BMI; p = 0.038). Lower BMD persisted up to 24 months after smoking cessation (p = 0.027-0.050), becoming comparable to never-smokers after 24 months. Hip BMD was negatively associated with smoking and dose-dependent on cigarette consumption. Smoking duration was not associated with BMD, although young women with a long smoking history had higher BMI, which might attenuate the adverse effects from smoking

Birth weight is more important for peak bone mineral content than for bone density: the PEAK-25 study of 1,061 young adult women.

Lower birth weight has a negative association with adult BMC and body composition in young adult Swedish women. INTRODUCTION: The aim of this study was to evaluate the influence of birth weight on peak bone mass and body composition in a cohort of 25-year-old women. METHODS: One thousand sixty-one women participated in this cross-sectional population-based study using dual energy X-ray absorptiometry (DXA) to assess bone mineral content (BMC), bone mineral density (BMD), and body composition (total body (TB), femoral neck (FN), total hip (TH), lumbar spine L1-L4 (LS), and lean and fat mass). Birth weight data was available for 1,047 women and was categorized into tertiles of low (≤3,180 g), intermediate (3,181-3,620 g), and high (≥3,621 g) birth weight. RESULTS: Significant correlations were observed between birth weight and TB-BMC (r = 0.159, p < 0.001), FN-BMC (r = 0.096, p < 0.001), TH-BMC (r = 0.102, p = 0.001), LS-BMC (r = 0.095, p = 0.002), and lean mass (r = 0.215, p < 0.001). No correlation was observed between birth weight and BMD. The estimated magnitude of effect was equivalent to a 0.3-0.5 SD difference in BMC for every 1 kg difference in birth weight (151 g (TB); 0.22 g (FN); 1.5 g (TH), 2.5 kg TB lean mass). The strongest correlations between birth weight and BMC occurred in women with lowest birth weights, although excluding women who weighed <2,500 g at birth, and the correlation remained significant although slightly weaker. CONCLUSIONS: Women with lower birth weight have lower BMC and less lean and fat mass at the age of 25, independent of current body weight. Lower birth weight has a greater negative influence on bone mass than the positive influence of higher birth weight

Self-reported recreational exercise combining regularity and impact is necessary to maximize bone mineral density in young adult women : A population-based study of 1,061 women 25 years of age.

Recreational physical activity in 25-year-old women in Sweden increases bone mineral density (BMD) in the trochanter by 5.5% when combining regularity and impact. Jogging and spinning were especially beneficial for hip BMD (6.4-8.5%). Women who enjoyed physical education in school maintained their higher activity level at age 25. INTRODUCTION: The aims of this study were to evaluate the effects of recreational exercise on BMD and describe how exercise patterns change with time in a normal population of young adult women. METHODS: In a population-based study of 1,061 women, age 25 (±0.2), BMD was measured at total body (TB-BMD), femoral neck (FN-BMD), trochanter (TR-BMD), and spine (LS-BMD). Self-reported physical activity status was assessed by questionnaire. Regularity of exercise was expressed as recreational activity level (RAL) and impact load as peak strain score (PSS). A permutation (COMB-RP) was used to evaluate combined endurance and impacts on bone mass. RESULTS: More than half of the women reported exercising on a regular basis and the most common activities were running, strength training, aerobics, and spinning. Seventy percent participated in at least one activity during the year. Women with high RAL or PSS had higher BMD in the hip (2.6-3.5%) and spine (1.5-2.1%), with the greatest differences resulting from PSS (p < 0.001-0.02). Combined regularity and impact (high-COMB-RP) conferred the greatest gains in BMD (FN 4.7%, TR 5.5%, LS 3.1%; p < 0.001) despite concomitant lower body weight. Jogging and spinning were particularly beneficial for hip BMD (+6.4-8.5%). Women with high-COMB-RP scores enjoyed physical education in school more and maintained higher activity levels throughout compared to those with low scores. CONCLUSION: Self-reported recreational levels of physical activity positively influence BMD in young adult women but to maximize BMD gains, regular, high-impact exercise is required. Enjoyment of exercise contributes to regularity of exercising which has short- and long-term implications for bone health

Polymorphisms in inflammation associated genes ALOX15 and IL-6 are associated with bone properties in young women and fracture in elderly.

ALOX12 and ALOX15 encode arachidonate lipoxygenases which produce lipid metabolites involved in inflammatory processes. Metabolites generated by ALOX12 and ALOX15 can activate the expression of the potent pro-inflammatory cytokine IL-6, and produce endogenous ligands for PPARG. In this study, polymorphisms in ALOX12, ALOX15, IL6 and PPARG were investigated for association with bone properties in young and elderly Swedish women

Peak Bone Mass and Quantitative Ultrasound Bone Properties in Young Adulthood : A Study in the PEAK-25 Cohort of Women

Peak bone mass is normally reached in the third decade of life. Previously, in the population-based PEAK-25 cohort (n = 1061, age 25.5 ± 0.2), we demonstrated that bone mineral density in the population-based PEAK-25 cohort is comparatively high; therefore, this study aimed to determine if the calcaneus microarchitecture mirrored this. In the process, we describe normative quantitative ultrasound (QUS) values for 25-yr-old women and the relationship between QUS values and extremes of body weight. QUS variables speed of sound (SOS), broadband ultrasound attenuation (BUA), and stiffness index were measured. Young adult values were based on the manufacturer-supplied QUS reference values. Analyses were performed in the cohort as a whole, and additionally, to understand the relationship between body weight and QUS values in young women, the variables were categorized into octiles for weight or body mass index (BMI) and the lowest and highest octiles were compared. In the cohort, SOS values, reflecting bone density, were higher (108 ± 18%), whereas BUA values, reflecting bone complexity, were lower (90 ± 14%) compared to the young adult reference population. SOS did not correlate with body weight or BMI. In the cohort, overall correlations between BUA weight, and BMI were small and positive (Pearson's r coefficients 0.261 and 0.197, respectively; p <0.001), although in the low-weight group, r coefficients were higher (r = 0.313 and 0.268; p <0.05). In contrast, in the high-weight group, correlation with BUA values tended to be small, negative, and nonsignificant. Correlation between QUS and dual-energy X-ray absorptiometry-measured bone mineral density was low to moderate and significant at all skeletal sites (r = 0.37-0.52). Whereas coefficients tended to be higher in the low-weight group, the reverse was apparent for the low-BMI group. In these 25-yr-old women, a comparatively high dual-energy X-ray absorptiometry-measured bone mass is offset by less complex bone structures assessed by QUS. This may have implications for later osteoporosis assessment and future fracture risk

Identification of Candidate Gene Regions in the Rat by Co-Localization of QTLs for Bone Density, Size, Structure and Strength.

Susceptibility to osteoporotic fracture is influenced by genetic factors that can be dissected by whole-genome linkage analysis in experimental animal crosses. The aim of this study was to characterize quantitative trait loci (QTLs) for biomechanical and two-dimensional dual-energy X-ray absorptiometry (DXA) phenotypes in reciprocal F2 crosses between diabetic GK and normo-glycemic F344 rat strains and to identify possible co-localization with previously reported QTLs for bone size and structure. The biomechanical measurements of rat tibia included ultimate force, stiffness and work to failure while DXA was used to characterize tibial area, bone mineral content (BMC) and areal bone mineral density (aBMD). F2 progeny (108 males, 98 females) were genotyped with 192 genome-wide markers followed by sex- and reciprocal cross-separated whole-genome QTL analyses. Significant QTLs were identified on chromosome 8 (tibial area; logarithm of odds (LOD) = 4.7 and BMC; LOD = 4.1) in males and on chromosome 1 (stiffness; LOD = 5.5) in females. No QTLs showed significant sex-specific interactions. In contrast, significant cross-specific interactions were identified on chromosome 2 (aBMD; LOD = 4.7) and chromosome 6 (BMC; LOD = 4.8) for males carrying F344mtDNA, and on chromosome 15 (ultimate force; LOD = 3.9) for males carrying GKmtDNA, confirming the effect of reciprocal cross on osteoporosis-related phenotypes. By combining identified QTLs for biomechanical-, size- and qualitative phenotypes (pQCT and 3D CT) from the same population, overlapping regions were detected on chromosomes 1, 3, 4, 6, 8 and 10. These are strong candidate regions in the search for genetic risk factors for osteoporosis

Determinants of stress fracture risk in United States Military Academy cadets

Background: Prior studies have identified some risk factors for stress fracture in athletes and military recruits. Objective: To determine whether historical factors, physical measures, biochemical variables of skeletal metabolism, genetic factors, bone density (BMD) and bone size could predict risk of stress fracture over 4 years in physically fit cadets at the US Military Academy (USMA). Methods: Baseline surveys, assessments of height, weight, scores on the Army Physical Fitness Test, and peripheral BMD were obtained in all cadets (755 men, 136 women), and central BMD in a subset. Blood samples were analyzed for variables of calcium homeostasis, bone turnover, and selected hormones and genetic factors. Stress fractures were adjudicated by review of orthopedic notes and imaging reports. Results: 5.7% of male and 19.1% of female cadets had at least 1 stress fracture (58% metatarsal and 29% tibial), most within 3 months of entry to USMA. In males, risk of stress fracture was higher in those who exercised <7 h per week during the prior year (RR 2.31; CI 1.29,4.12), and in those with smaller tibial cortical area (RR 1.12; CI 1.03,1.23), lower tibial bone mineral content (RR 1.11; CI 1.03,1.20) and smaller femoral neck diameter (RR 1.35, CI 1.01, 1.81). In women, higher stress fracture risk was seen in those with shorter time since menarche (RR 1.44 per year; Cl 1.19, 1.73) and smaller femoral neck diameter (RR 1.16; Cl 1.01, 1.33.). Conclusion: Although prior physical training in men, length of prior estrogen exposure in women and leg bone dimensions in both genders played a role, the maximum variance explained by all of these factors was below 10%. We conclude these factors play a minor role in the development of stress fractures in physically fit USMA cadets. (C) 2013 Elsevier Inc. All rights reserved