Genetic influence on bone phenotypes and body composition: a Swedish twin study

Causal associations of anthropometric measurements with osteoarthritis: A Mendelian randomization study

OBJECTIVE

We believe that there is a causal relationship between waist circumference and knee osteoarthritis. To confirm the hypothesis, we have conducted this study.

METHODS

Genetic variants associated with the five anthropometric variables were obtained from previous large-scale genomewide association studies. Summary-level data on osteoarthritis were obtained from the UK Biobank. The univariable and multivariable MR framework were used to evaluate the associations. The two-sided p value was considered to be statistically significant at 0.01 (where p = 0.05/5) after Bonferroni correction for the five exposure variables.

RESULTS

In the univariable MR, there was evidence of a detrimental effect of height, weight, BMI, waist circumference, and hip circumference on osteoarthritis risk in the main IVW analyses (height: OR 1.115, 95% CI 1.054-1.180; weight: OR 1.765, 95% CI 1.650-1.889; BMI: OR 1.952, 95%CI 1.841-2.068; waist circumference: OR 2.140, 95% CI 1.994-2.296; hip circumference: OR 1.719, 95% CI 1.600-1.846). And the analyses on knee osteoarthritis and hip osteoarthritis yielded similar results. However, the multivariable MR showed that only waist circumference was causally associated with osteoarthritis, after adjusting for the confounding exposure effects (waist circumference: OR 1.877, 95% CI 1.286-2.739). Such association was also repeated in the analyses on knee osteoarthritis but not hip osteoarthritis.

CONCLUSION

Our study highlighted the causal associations between waist circumference and knee osteoarthritis risk.

Aging and Bone Metabolism

Changes in bone architecture and metabolism with aging increase the likelihood of osteoporosis and fracture. Age-onset osteoporosis is multifactorial, with contributory extrinsic and intrinsic factors including certain medical problems, specific prescription drugs, estrogen loss, secondary hyperparathyroidism, microenvironmental and cellular alterations in bone tissue, and mechanical unloading or immobilization. At the histological level, there are changes in trabecular and cortical bone as well as marrow cellularity, lineage switching of mesenchymal stem cells to an adipogenic fate, inadequate transduction of signals during skeletal loading, and predisposition toward senescent cell accumulation with production of a senescence-associated secretory phenotype. Cumulatively, these changes result in bone remodeling abnormalities that over time cause net bone loss typically seen in older adults. Age-related osteoporosis is a geriatric syndrome due to the multiple etiologies that converge upon the skeleton to produce the ultimate phenotypic changes that manifest as bone fragility. Bone tissue is dynamic but with tendencies toward poor osteoblastic bone formation and relative osteoclastic bone resorption with aging. Interactions with other aging physiologic systems, such as muscle, may also confer detrimental effects on the aging skeleton. Conversely, individuals who maintain their BMD experience a lower risk of fractures, disability, and mortality, suggesting that this phenotype may be a marker of successful aging. © 2023 American Physiological Society. Compr Physiol 13:4355-4386, 2023.

Current use of bone turnover markers in the management of osteoporosis

The adult bone is continuously being remodelled to repair microdamage, preserve bone strength and mechanical competence as well as maintain calcium homeostasis. Bone turnover markers are products of osteoblasts (bone formation markers) and osteoclasts (bone resorption markers) providing a dynamic assessment of remodelling (turnover). Resorption-specific bone turnover markers are typically degradation products of bone collagen molecules (N- [NTX] and C-telopeptide cross-linked type 1 collagen [CTX]), which are released into the circulation and excreted in urine; or enzymatic activities reflecting osteoclastic resorption, tartrate-resistant acid phosphatase [TRACP]. Formation-specific bone turnover markers embrace different osteoblastic activities: type 1 collagen synthesis (Procollagen type I N- propeptide [PINP]), osteoblast enzymes (bone-specific alkaline phosphatase [BALP]), or bone matrix proteins [osteocalcin]. Among individuals not receiving osteoporosis treatment, resorption and formation markers are tightly linked and highly correlated (r= 0.6-0.8). Significant biological variability was reported in the past, but these issues have been greatly improved with automated assays and attention to pre-analytical and analytical factors that are known to influence bone turnover marker levels. Bone turnover markers are not useful in the diagnosis of osteoporosis, the individual prediction of bone loss, fracture, or rare complications, or in the selection of pharmacological treatment. Despite remaining issues with reference intervals and assays harmonization, bone turnover markers have proven to be useful in elucidating the pharmacodynamics and effectiveness of osteoporosis medications in clinical trials. As an alternative to BMD testing, BTMs may be useful to monitor osteoporosis therapies.

Body Mass Index Differentially Moderates Heritability of Total Joint Replacement Due to Hip and Knee Osteoarthritis: A Cohort Study of 29,893 Swedish Twin Pairs

BACKGROUND

Osteoarthritis and obesity are diseases with high prevalence, and they share common etiologies. We investigated the sex-specific genetic susceptibility to hip and knee osteoarthritis necessitating total joint replacement (TJR), and how body mass index (BMI) moderated the heritability of these osteoarthritis phenotypes.

METHODS

We linked 29,893 twin pairs with information on BMI in the Swedish Twin Registry with the Swedish National Patient Register to identify twins who underwent primary TJR of the hip or knee combined with a concomitant diagnosis of primary osteoarthritis of these joints. Structural equation modeling was used to calculate the heritability of hip and knee osteoarthritis treated with TJR, with estimates adjusted for the first available BMI, birth year, and sex. We also investigated how heritability varied with BMI treated as a continuous variable.

RESULTS

Similar heritability estimates for hip replacement (0.65 [95% confidence interval (CI), 0.59 to 0.70]) and knee replacement (0.57 [95% CI, 0.50 to 0.64]) were found. Heritability decreased with higher BMI in both sexes for hip replacement and in men for knee replacement. In contrast, heritability for knee replacement increased with higher BMI in women; the estimate was 0.37 (90% likelihood interval [LI], 0.25 to 0.49) for a BMI of 20 kg/m2 and 0.87 (90% LI, 0.68 to 0.94) for a BMI of 35 kg/m2.

CONCLUSIONS

In our population, heritability explained, on average, about half of the susceptibility to undergo primary TJR of the hip or knee with the indication of primary osteoarthritis, but it varied with BMI and sex. We demonstrated substantial heritability for knee replacement in obese women.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

The Impact of Different Modes of Exercise Training on Bone Mineral Density in Older Postmenopausal Women: A Systematic Review and Meta-analysis Research

Effectiveness of exercise on bone mass is closely related to the mode of exercise training regimen, as well as the study design. This study aimed to determine the effect of different modes of exercise training on lumbar spine and femoral neck bone mineral density (BMD) in older postmenopausal women (PMW). PubMed, CINAHL, Medline, Google Scholar, and Scopus databases and reference lists of included studies were searched up until March 25, 2019 for randomized controlled trials (RCTs) that evaluated the effectiveness of various modes of exercise training in PMW. Sixteen RCTs with 1624 subjects were included. Our study found no significant change in both lumbar spine and femoral neck BMD following exercise training (MD: 0.01 g/cm²; 95% confidence interval (CI) [- 0.01, 0.02] and MD: 0.00 g/cm²; 95% CI [- 0.01, 0.01], respectively). However, subgroup analysis by type of exercise training revealed that lumbar spine BMD (MD: 0.01; 95% CI [0.00, 0.02]) raised significantly when whole-body vibration (WBV) was employed as intervention compared with RCTs that utilized aerobic (MD: - 0.01; 95% CI [- 0.02, - 0.01]), resistance (MD: 0.01; 95% CI [- 0.04, 0.06]), and combined training (MD: 0.03; 95% CI [- 0.01, 0.08]). On the other hand, lumbar spine BMD (MD: - 0.01; 95% CI [- 0.02, - 0.01]) reduced significantly when aerobic exercise training was used as intervention compared with RCTs that utilized resistance training, combined training, and WBV. By contrast, these analyses did not have significant effect on change in femoral neck BMD. WBV is an effective method to improve lumbar spine BMD in older PMW.

A High-Intensity Jump-Based Aquatic Exercise Program Improves Bone Mineral Density and Functional Fitness in Postmenopausal Women

The aim of this study was to verify the effects of a high-intensity jump-based aquatic exercise (HIIAE) program on bone mass and functional fitness in postmenopausal women. We randomly assigned 25 women (65 ± 7 years) into two groups: Training group (T, n = 15) and Untrained group (Un, n = 10). The T group was submitted to 24 weeks of HIIAE program, where each session lasted for 30 minutes. The following parameters were assessed before and 6 months following the intervention: bone and physical fitness; lumbar spine (LS), total femur (TF), and whole body (WB) bone mineral density (BMD); agility (time up-and-go, TUG); and leg strength (chair stand test, CS). We observed a significant increase (p < 0.01) in LS, (Un: -0.88 ± 3.55, T: 3.71 ± 3.68; %), TF (Un: -1.38 ± 17.76, T: 6.52 ± 2.71; %), and WB (Un: 2.09 ± 3.17, T: 3.23 ± 4.18) BMD in the T group. Regarding functional fitness, the T group showed improvements in both TUG (before: 6.86 ± 1.24 vs. after: 6.22 ± 1.13 seconds; p < 0.05) and CS (before: 16 ± 4 vs. after: 19 ± 5 repetitions; p > 0.05) tests when compared with the U group's TUG (before: 5 ± 1, after: 6 ± 1 seconds; p < 0.05) and CS (before: 20 ± 2, after: 19 ± 2 repetitions; p > 0.05) scores. Our data suggest that a high-intensity, jump-based interval aquatic exercise program is able to improve BMD and functional fitness parameters in postmenopausal women.

Bone Turnover in Young Adult Men: Cross-Sectional Determinants and Associations With Prospectively Assessed Bone Loss

Biochemical markers of bone turnover are higher in young adult men than in middle-aged men or young adult women. Nonetheless, little is known about the determinants and clinical significance hereof. The present study examined determinants of serum bone turnover markers in men around peak bone mass age, and explored whether bone turnover at this age predicts subsequent changes in bone mass. We used cross-sectional and longitudinal data from 973 and 428 healthy men, respectively, aged 25 to 45 years at baseline, including baseline procollagen type I amino-terminal propeptide (P1NP), osteocalcin, and C-terminal telopeptide of type I collagen (CTX) from fasting serum samples, baseline questionnaire-assessed physical activity levels, and baseline and follow-up dual-energy X-ray absorptiometry-derived areal bone mineral density (aBMD) and body composition. Mean follow-up time was 12.4 ± 0.4 years. At baseline, all bone turnover markers were inversely associated with total body fat mass (β ≤ -0.20, p < 0.001), and positively with physical activity during sports activities (β ≥ 0.09, p ≤ 0.003), and, albeit not independently from fat mass, total body lean mass (β ≥ 0.20, p ≤ 0.003). Mean annual aBMD changes in the longitudinal cohort were -0.19% ± 0.24% at the total body, -0.14% ± 0.42% at the spine, -0.49% ± 0.47% at the femoral neck, and -0.25% ± 0.37% at the total hip (all p < 0.001). Higher bone turnover markers at baseline were associated with larger decreases in aBMD at all measurement sites (β ≤ -0.08, p ≤ 0.081 for P1NP; β ≤ -0.16, p ≤ 0.002 for osteocalcin; and β ≤ -0.21, p < 0.001 for CTX). In conclusion, our findings show that sports activities and body composition, primarily fat mass, are the main identified determinants of bone turnover in men around peak bone mass age. Further, bone turnover at this age is an important determinant of subsequent changes in bone mass, with higher levels of bone turnover markers being associated with greater decreases in aBMD. © 2017 American Society for Bone and Mineral Research.

Exploring correlation between bone metabolism markers and densitometric traits in extended families from Spain

Osteoporosis is a common multifactorial disorder characterized by low bone mass and reduced bone strength that may cause fragility fractures. In recent years, there have been substantial advancements in the biochemical monitoring of bone metabolism through the measurement of bone turnover markers. Currently, good knowledge of the genetics of such markers has become an indispensable part of osteoporosis research. In this study, we used the Genetic Analysis of Osteoporosis Project to study the genetics of the plasma levels of 12 markers related to bone metabolism and osteoporosis. Plasma phenotypes were determined through biochemical assays and log-transformed values were used together with a set of covariates to model genetic and environmental contributions to phenotypic variation, thus estimating the heritability of each trait. In addition, we studied correlations between the 12 markers and a wide variety of previously described densitometric traits. All of the 12 bone metabolism markers showed significant heritability, ranging from 0.194 for osteocalcin to 0.516 for sclerostin after correcting for covariate effects. Strong genetic correlations were observed between osteocalcin and several bone mineral densitometric traits, a finding with potentially useful diagnostic applications. In addition, suggestive genetic correlations with densitometric traits were observed for leptin and sclerostin. Overall, the few strong and several suggestive genetic correlations point out the existence of a complex underlying genetic architecture for bone metabolism plasma phenotypes and provide a strong motivation for pursuing novel whole-genome gene-mapping strategies.

Osteoporosis: the emperor has no clothes

Current prevention strategies for low-trauma fractures amongst older persons depend on the notions that fractures are mainly caused by osteoporosis (pathophysiology), that patients at high risk can be identified (screening) and that the risk is amenable to bone-targeted pharmacotherapy (treatment). However, all these three notions can be disputed.

PATHOPHYSIOLOGY

Most fracture patients have fallen, but actually do not have osteoporosis. A high likelihood of falling, in turn, is attributable to an ageing-related decline in physical functioning and general frailty.

SCREENING

Currently available fracture risk prediction strategies including bone densitometry and multifactorial prediction tools are unable to identify a large proportion of patients who will sustain a fracture, whereas many of those with a high fracture risk score will not sustain a fracture.

TREATMENT

The evidence for the viability of bone-targeted pharmacotherapy in preventing hip fracture and other clinical fragility fractures is mainly limited to women aged 65-80 years with osteoporosis, whereas the proof of hip fracture-preventing efficacy in women over 80 years of age and in men at all ages is meagre or absent. Further, the antihip fracture efficacy shown in clinical trials is absent in real-life studies. Many drugs for the treatment of osteoporosis have also been associated with increased risks of serious adverse events. There are also considerable uncertainties related to the efficacy of drug therapy in preventing clinical vertebral fractures, whereas the efficacy for preventing other fractures (relative risk reductions of 20-25%) remains moderate, particularly in terms of the low absolute risk reduction in fractures with this treatment.

Genetic analysis of bone quality traits and growth in a random mating broiler population

We report the genetic relationship between growth and bone quality traits in a random mating broiler control population. Traits studied were growth rates from week 0 to 4 [body weight gain (BWG) 0 to 4], from week 0 to 6 (BWG 0 to 6), and residual feed intake (RFI) from week 5 to 6 (RFI 5 to 6). Bone quality traits were obtained at 6 weeks of age. These traits were shank weight (SW), shank length (SL), shank diameter (SDIAM), tibia weight (TW), tibia length (TL), and tibia diameter (TDIAM). Likewise, tibia was used to obtain the tibia density (TDEN), tibia breaking strength (TBS), tibia mineral density (TMD), tibia mineral content (TMC), and tibia ash content (TAC). At the phenotypic level, growth traits were positively correlated with most of the bone quality traits except with TDEN and TAC which tended to show unfavorable associations (-0.04 to -0.31). Heritability of bone quality traits ranged from 0.08 to 0.54. The additive genetic associations of growth traits with weight, length, and diameter of shank and tibia were positive (0.37 to 0.80). A similar pattern was observed with TMD and TMC (0.06 to 0.65). In contrast, growth traits showed unfavorable genetic associations with TDEN, TBS, and TAC (-0.03 to -0.18). It was concluded that bone quality traits have an additive genetic background and they can be improved by means of genetic tools. It appears that selection for growth is negatively correlated with some traits involved in the integrity, health, and maturity of leg bones.

Genetic and environmental variances of bone microarchitecture and bone remodeling markers: a twin study

All genetic and environmental factors contributing to differences in bone structure between individuals mediate their effects through the final common cellular pathway of bone modeling and remodeling. We hypothesized that genetic factors account for most of the population variance of cortical and trabecular microstructure, in particular intracortical porosity and medullary size - void volumes (porosity), which establish the internal bone surface areas or interfaces upon which modeling and remodeling deposit or remove bone to configure bone microarchitecture. Microarchitecture of the distal tibia and distal radius and remodeling markers were measured for 95 monozygotic (MZ) and 66 dizygotic (DZ) white female twin pairs aged 40 to 61 years. Images obtained using high-resolution peripheral quantitative computed tomography were analyzed using StrAx1.0, a nonthreshold-based software that quantifies cortical matrix and porosity. Genetic and environmental components of variance were estimated under the assumptions of the classic twin model. The data were consistent with the proportion of variance accounted for by genetic factors being: 72% to 81% (standard errors ∼18%) for the distal tibial total, cortical, and medullary cross-sectional area (CSA); 67% and 61% for total cortical porosity, before and after adjusting for total CSA, respectively; 51% for trabecular volumetric bone mineral density (vBMD; all p < 0.001). For the corresponding distal radius traits, genetic factors accounted for 47% to 68% of the variance (all p ≤ 0.001). Cross-twin cross-trait correlations between tibial cortical porosity and medullary CSA were higher for MZ (rMZ  = 0.49) than DZ (rDZ  = 0.27) pairs before (p = 0.024), but not after (p = 0.258), adjusting for total CSA. For the remodeling markers, the data were consistent with genetic factors accounting for 55% to 62% of the variance. We infer that middle-aged women differ in their bone microarchitecture and remodeling markers more because of differences in their genetic factors than differences in their environment.

Family resemblance of bone turnover rate in mothers and daughters--the MODAM study

We studied bone turnover markers (BTM) and bone microarchitecture (using high-resolution peripheral quantitative computed tomography (HR-pQCT)) in 171 postmenopausal women and their 210 premenopausal daughters. BTM levels correlated positively between mothers and daughters. The mother-daughter pairs with high BTM levels had lower cortical density than those with low BTM levels.

INTRODUCTION

We assessed the correlation of serum bone turnover markers (BTM) between postmenopausal mothers and their premenopausal daughters as well as possible determinants of this association and its impact on resemblance of bone microarchitecture between mothers and their daughters.

METHODS

Cross-sectional analysis was performed in 171 untreated postmenopausal mothers (54 sustained fragility fractures) and their 210 premenopausal daughters. Intact N-terminal propeptide of type I collagen (PINP) and β-isomerized C-terminal crosslinking telopeptide of type I collagen (CTX-I) were measured in the fasting status. Bone microarchitecture was assessed using HR-pQCT.

RESULTS

After adjustment for age, weight, lifestyle factors, hormones, and mother's fracture status, BTM levels correlated positively between mothers and daughters (Intraclass Correlation Coefficient = 0.22-0.27, p <0.005). Average BTM levels were ∼ 0.6 SD higher among daughters of mothers in the highest BTM quartile vs. the ones in the lowest BTM quartile. The variability of BTM levels explained ≤ 10 and ≤ 14% of variability of bone microarchitecture in the daughters and mothers, respectively. Cortical density was lower by 2.3-2.9% (0.6 SD, p <0.05 to <0.005) in the daughters from the mother-daughter pairs with high BTM levels (defined by generation-specific quartiles) than in the daughters from the pairs with low BTM levels. Corresponding differences for the mothers were 4.5-4.8% (0.5 SD, p <0.05 to <0.01).

CONCLUSION

BTM levels correlated between postmenopausal mothers and their premenopausal daughters after adjustment for age, weight, mother's fracture status, lifestyle, and hormonal factors. Family resemblance of BTM levels may contribute to family resemblance of some bone microarchitectural parameters, especially of cortical density.

(Patho)physiology of cross-sex hormone administration to transsexual people: the potential impact of male-female genetic differences

There is a limited body of knowledge of desired and undesired effects of cross-sex hormones in transsexual people. Little attention has been given to the fact that chromosomal configurations, 46,XY in male-to-female transsexuals subjects (MtoF) and 46,XX in female-to-male transsexual subjects (FtoM), obviously, remain unchanged. These differences in their genomes cause sex differences in the functions of cells. This study reviews sex differences in metabolism/cardiovascular pathology, immune mechanisms, bone (patho)physiology and brain functions and examines whether they are, maybe partially, determined by genetic mechanisms rather than by (cross-sex) hormones. There do not appear to be major genetic impacts on the changes in bone physiology. Also immune functions are rather unaffected and the evidence for an increase of autoimmune disease in MtoF is preliminary. Brain functions of transsexuals may have differed from controls before cross-sex hormones; they do undergo shifts upon cross-sex hormone treatment, but there is no evidence for changes in sex-specific brain disease. The prevalence of cardiovascular disease is higher in MtoF receiving oestrogens than in FtoM receiving androgens. While type of oestrogen and route of administration might be significant, it is reasonable to speculate that nonhormonal/genetic factors play a role.

Birth weight is not associated with risk of fracture: results from two Swedish cohort studies

Development and growth in utero has been suggested to influence bone health. However, the relationship with risk of fracture in old age is largely unknown. Using Cox proportional hazards regression, we studied the association between birth weight and fractures at ages 50-94 among 10,893 men and women (48% women) from the Uppsala Birth Cohort Study (UBCoS, born 1915-29) and 1334 men from the Uppsala Longitudinal Study of Adult Men (ULSAM, born 1920-24). Measured birth weight was collected from hospital or midwives' records and fractures from the Swedish National Patient Register. We observed 2796 fractures (717 of these were hip fractures) in UBCoS and 335 fractures (102 hip fractures) in ULSAM. In UBCoS, the hazard ratio (HR) per 1 kg increase in birth weight, adjusted for sex and socioeconomic status at birth, was 1.01 [95% confidence interval (CI), 0.94-1.09] for any fracture and 1.06 (95% CI, 0.91-1.23) for hip fracture. Estimates in ULSAM were similar. We did not observe a differential association of birth weight with fractures occurring before age 70 or after age 70 years. Neither birth weight standardized for gestational age nor gestational duration was associated with fracture rate. In linear regression, birth weight was not associated with bone mineral density among 303 men who were 82-years-old in ULSAM but showed positive associations with total body bone mineral content (β per kg increase in birth weight, adjusted for social class and age, 133; 95% CI, 30-227). This association was attenuated after further adjustment for body mass index and height (β, 41; 95% CI, -43-126). We conclude that birth weight is associated with bone mineral content but this association does not translate into an association with risk of fracture in men and women aged 50-94 years.

Genotype by energy expenditure interaction and body composition traits: The Portuguese Healthy Family Study

Background and Aims. Energy expenditure has been negatively correlated with fat accumulation. However, this association is highly variable. In the present study we applied a genotype by environment interaction method to examine the presence of Genotype x by Total Daily Energy Expenditure and Genotype x by Daily Energy Expenditure interactions in the expression of different body composition traits. Methods and Results. A total of 958 subjects from 294 families of The Portuguese Healthy Family Study were included in the analysis. TDEE and DEE were assessed using a physical activity recall. Body fat percentages were measured with a bioelectrical impedance scale. GxTDEE and GxDEE examinations were performed using SOLAR 4.0 software. All BC traits were significantly heritable, with heritabilities ranging from 21% to 34%. The GxTDEE and GxDEE interaction models fitted the data better than the polygenic model for all traits. For all traits, a significant GxTDEE and GxDEE interaction was due to variance heterogeneity among distinct levels of TDEE and DEE. For WC, GxTDEE was also significant due to the genetic correlation function. Conclusions. TDEE and DEE are environmental constraints associated with the expression of individuals' BC genotypes, leading to variability in the phenotypic expression of BC traits.

Impact of hip fracture on mortality: a cohort study in hip fracture discordant identical twins

Several studies have shown a long-lasting higher mortality after hip fracture, but the reasons for the excess risk are not well understood. We aimed to determine whether a higher mortality after hip fracture exists when controlling for genetic constitution, shared environment, comorbidity, and lifestyle by use of a nationwide cohort study in hip fracture discordant monozygotic twins. All 286 identical Swedish twin pairs discordant for hip fracture (1972 to 2010) were identified. Comorbidity and lifestyle information was retrieved by registers and questionnaire information. We used intrapair Cox regression to compute multivariable-adjusted hazard ratios (HRs) for death. During follow-up, 143 twins with a hip fracture died (50%) compared with 101 twins (35%) without a hip fracture. Through the first year after hip fracture, the rate of death increased fourfold in women (HR = 3.71; 95% confidence interval [CI] 1.32-10.40) and sevenfold in men (HR = 6.67; 95% CI 1.47-30.13). The increased rate in women only persisted during the first year after hip fracture (HR after 1 year = 0.99; 95% CI 0.66-1.50), whereas the corresponding HR in men was 2.58 (95% CI 1.02-6.62). The higher risk in men after the hip fracture event was successively attenuated during follow-up. After 5 years, the hazard ratio in men with a hip fracture was 1.19 (95% CI 0.29-4.90). On average, the hip fracture contributed to 0.9 years of life lost in women (95% CI 0.06-1.7) and 2.7 years in men (95% CI 1.7-3.7). The potential years of life lost associated with the hip fracture was especially pronounced in older men (>75 years), with an average loss of 47% (95% CI 31-61) of the expected remaining lifetime. We conclude that both women and men display a higher mortality after hip fracture independent of genes, comorbidity, and lifestyle.

Effects of life-long fluoride intake on bone measures of adolescents: a prospective cohort study

Controversy persists concerning the impact of community water fluoridation on bone health in adults, and few studies have assessed relationships with bone at younger ages. Ecological studies of fluoride's effects showed some increase in bone mineral density of adolescents and young adults in areas with fluoridated water compared with non-fluoridated areas. However, none had individual fluoride exposure measures. To avoid ecological fallacy and reduce bias, we assessed associations of average daily fluoride intake from birth to age 15 yr for Iowa Bone Development Study cohort members with age 15 yr dual-energy x-ray absorptiometry (DXA) bone outcomes (whole body, lumbar spine, and hip), controlling for known determinants (including daily calcium intake, average daily time spent in moderate-to-vigorous intensity physical activity, and physical maturity). Mean (SD) daily fluoride intake was 0.66 mg (0.24) for females and 0.78 mg (0.30) for males. We found no significant relationships between daily fluoride intake and adolescents' bone measures in adjusted models (for 183 females, all p values ≥ .10 and all partial R(2) ≤ 0.02; for 175 males, all p values ≥ .34 and all partial R(2) ≤ 0.01). The findings suggest that fluoride exposures at the typical levels for most US adolescents in fluoridated areas do not have significant effects on bone mineral measures.