Age-related bone changes

Age estimation using medial clavicle by histomorphometry method with artificial intelligence: A review

This review research critically assesses the evolving landscape of age estimation methodologies, with a particular focus on the innovative integration of histomorphometry and artificial intelligence (AI) in the analysis of the medial clavicle. The medial clavicle emerges as a crucial skeletal feature for predicting age, offering valuable insights into the morphological changes occurring throughout an individual's lifespan. Through an in-depth exploration of histological complexities, including variations in osteons, trabecular structures, and cortical thickness, this review elucidates their utility as viable indicators for age-related evaluations. This framework is augmented by the incorporation of AI technology, which enables automatic picture identification, feature extraction, and complicated pattern analysis. Our review of previous research highlights the promise of AI in improving prediction models for nuanced age estimates, highlighting the importance of large-scale, diversified datasets and thorough cross-validation. This thorough study, which addresses ethical concerns as well as the influence of population-specific characteristics, moves the debate around age estimate ahead, presenting insights with consequences for forensic anthropology, clinical diagnoses, and future research avenues.

Respiratory dysfunction in old mice could be related to inflammation and lung fibrosis induced by hyperphosphatemia

BACKGROUND

With age, lungs undergo typical changes that lead to a deterioration of respiratory function. Our aim was to assess the role of age-associated hyperphosphatemia in these changes.

METHODS

We used C57BL6 mice to study an ageing model in vivo and human lung fibroblasts were treated with a phosphate donor, beta-glycerophosphate (BGP), to explore mechanisms involved. Respiratory function was registered with a double chamber plethysmograph. Lung structure was analysed by different staining, phosphate and cytokines levels by colorimeric kits, expression of fibrosis, inflammation and ET-1 system by western blot or RT-PCR.

RESULTS

Old mice showed hyperphosphatemia, along with lung fibrosis, loss of elastin, increased expression of pro-inflammatory cytokines and impaired respiratory function. BGP induced inflammation and fibrosis in fibroblasts through the activation and binding of NFkB to the MCP-1 or FN promoters. BGP increased ECE-1 expression by inducing NFkB binding to the ECE-1 promoter. QNZ, an NFkB inhibitor, blocked these effects. When ECE-1 was inhibited with phosphoramidon, BGP-induced inflammation and fibrosis were significantly reduced, suggesting a role for ET-1 in BGP-mediated effects.ET-1 produced effects similar to those of BGP, which were also dependent on NFkB. To study the pathophysiological relevance of hyperphosphatemia in vivo, a low-P diet was administered to a group of old animals, showing an improvement in fibrosis, inflammation and respiratory function compared to old mice on a standard diet.

CONCLUSION

These results suggest that age-related hyperphosphatemia induces inflammation, fibrosis, and impaired respiratory function in old mice; these effects appear to be mediated by ET-1 and NFkB activation.

A statistical shape analysis for the assessment of the main geometrical features of the distal femoral medullary canal

Statistical Shape Models (SSMs) are widely used in orthopedics to extract the main shape features from bone regions (e.g., femur). This study aims to develop an SSM of the femoral medullary canal, investigate its anatomical variability, and assess variations depending on canal length. The canals were isolated from 72 CT femur scans, through a threshold-based segmentation. A region of interest (ROI) was selected; sixteen segments were extracted from the ROI, ranging from 25% of the full length down to the most distal segment. An SSM was developed to identify the main modes of variation for each segment. The number of Principal Components (PCs) needed to explain at least 90% of the shape variance were three/four based on the length of the canal segment. The study examined the relationship between the identified PCs and geometric parameters like length, radius of curvature, ellipticity, mean diameter, and conicity, reporting range and percentage variation of these parameters for each segment. The SSMs provide insights into the anatomical variability of the femoral canal, emphasizing the importance of considering different segments to capture shape variations at various canal length. These findings can contribute for the design of personalized orthopedic implants involving the distal femur.

Age estimation in the combined long bones and ribs by histomorphometry: Past, present, and future

Numerous age estimation methods in unidentified bone have been a long time developing for application in forensic anthropology. The histomorphometric technique is one of the alternative methods that relied upon the evaluation of the cortical bone microstructure over the lifespan as a result of the remodeling process in bone. Remodeling is a sophisticated event occurring from the coupled function of bone formation and resorption cells for maintaining mineral homeostasis and repairment of microdamage in bone tissue. Products derived from remodeling are primary changes in the osteon or haversian system in various regions in the cortical bone, including periosteum, endosteum, and trabecular bone. Throughout life, bone remodeling rate with osteon alteration can be predictable. In the forensic field, histological methods are getting more attention due to the unavailability of macroscopic methods. Histomorphometry approach can be accomplished in fragmentary or incomplete bone remains indicating the limited use of gross morphological methods. In addition, the microscopic methods can aid to increase the more accuracy of analyses and diminish the biased subjective assessment for determining age. Most histomorphometry method utilizes a cross-section of the midshaft of the long bones including the mandible, rib, and clavicle. This review provides the basic knowledge of bone biology and anatomy, several age-estimating methods of histology, and crucial factors for age methods. Studies regarding overall age determination methods from the past until now contribute to obtaining more benefits for developing methods of histomorphometry using human bone in forensic identification.

Effect of immunology biomarkers associated with hip fracture and fracture risk in older adults

Osteoporosis is a skeletal disease that can increase the risk of fractures, leading to adverse health and socioeconomic consequences. However, current clinical methods have limitations in accurately estimating fracture risk, particularly in older adults. Thus, new technologies are necessary to improve the accuracy of fracture risk estimation. In this observational study, we aimed to explore the association between serum cytokines and hip fracture status in older adults, and their associations with fracture risk using the FRAX reference tool. We investigated the use of a proximity extension assay (PEA) with Olink. We compared the characteristics of the population, functional status and detailed body composition (determined using densitometry) between groups. We enrolled 40 participants, including 20 with hip fracture and 20 without fracture, and studied 46 cytokines in their serum. After conducting a score plot and two unpaired t-tests using the Benjamini-Hochberg method, we found that Interleukin 6 (IL-6), Lymphotoxin-alpha (LT-α), Fms-related tyrosine kinase 3 ligand (FLT3LG), Colony stimulating factor 1 (CSF1), and Chemokine (C-C motif) ligand 7 (CCL7) were significantly different between fracture and non-fracture patients (p < 0.05). IL-6 had a moderate correlation with FRAX (R2 = 0.409, p < 0.001), while CSF1 and CCL7 had weak correlations with FRAX. LT-α and FLT3LG exhibited a negative correlation with the risk of fracture. Our results suggest that targeted proteomic tools have the capability to identify differentially regulated proteins and may serve as potential markers for estimating fracture risk. However, longitudinal studies will be necessary to validate these results and determine the temporal patterns of changes in cytokine profiles.

Biomarkers of aging

Aging biomarkers are a combination of biological parameters to (i) assess age-related changes, (ii) track the physiological aging process, and (iii) predict the transition into a pathological status. Although a broad spectrum of aging biomarkers has been developed, their potential uses and limitations remain poorly characterized. An immediate goal of biomarkers is to help us answer the following three fundamental questions in aging research: How old are we? Why do we get old? And how can we age slower? This review aims to address this need. Here, we summarize our current knowledge of biomarkers developed for cellular, organ, and organismal levels of aging, comprising six pillars: physiological characteristics, medical imaging, histological features, cellular alterations, molecular changes, and secretory factors. To fulfill all these requisites, we propose that aging biomarkers should qualify for being specific, systemic, and clinically relevant.

Age-related low skeletal muscle mass correlates with joint space narrowing in knee osteoarthritis in a South Korean population: a cross-sectional, case-control study

Background

This study was conducted to analyze the effects of low skeletal muscle mass index (SMI) and obesity on aging-related osteoarthritis (OA) in the Korean population.

Methods

A total of 16,601 participants who underwent a dual-energy X-ray absorptiometry and 3,976 subjects with knee X-rays according to the modified Kellgren-Lawrence (KL) system were enrolled. Knees of ≥KL grade 2 were classified as radiologic OA. The severity of joint space narrowing (JSN) was classified by X-rays as normal, mild-to-moderate, and severe JSN in radiologic OA. The subjects were grouped as normal SMI (SMI of ≥–1 standard deviation [SD] of the mean), low SMI class I (SMI of ≥–2 SDs and <–1 SD), and low SMI class II (SMI of <–2 SDs). Obesity was defined as a body mass index (BMI) of ≥27.5 kg/m².

Results

The modified KL grade and JSN severity were negatively correlated with the SMI and positively correlated with BMI and age. The SMI was negatively correlated with age. JSN severity was significantly associated with a low SMI class compared to a normal SMI, which was more prominent in low SMI class II than class I. Obesity was significantly associated with more severe JSN, only for obesity with a low SMI class. Furthermore, patients with a low SMI class, regardless of obesity, were prone to having more severe JSN.

Conclusion

This study suggested that a low SMI class was associated with aging and that an age-related low SMI was more critically related to the severity of JSN in OA.

A Pilot Study to Assess Opportunistic Use of CT-Scan for Osteoporosis Screening in Chronic Pancreatitis

Objectives: CT scans are commonly performed in patients with chronic pancreatitis (CP). Osteopathy and fractures are recognized in CP but no osteoporosis screening guidelines are recommended. "Opportunistic" CT scan-derived bone density thresholds are assessed for identifying osteoporosis in CP. Methods: Retrospective pilot cohort study. CP subjects who had CT scans and dual-energy x-ray absorptiometry (DXA) within 1 year were included. CT-derived bone density was measured at the L1 level. Pearson's correlation was performed between age and CT-derived bone density in Hounsfield unit (HU). Univariate analysis using HU to identify osteoporosis was performed at various thresholds of bone density. The discriminatory ability of the model was evaluated with the area under the receiver operating characteristic (ROC) curve (AUC). Several HU thresholds were tested. Results: Twenty-seven CP subjects were included, of whom 11 had normal bone density, 12 osteopenia, and four osteoporosis on DXA. The mean age was 59.9 years (SD 13.0). There was a negative correlation of age with HU (r = -0.519, p = 0.006). CT-derived bone density predicted DXA-based osteoporosis in the univariable analysis (Odds Ratio (OR) = 0.97 95% Confidence Interval (CI) 0.94-1.00, p = 0.03). HU thresholds were tested. A threshold of 106 HU maximized the accuracy (AUC of 0.870). Conclusions: CT scan may be repurposed for "opportunistic" screening to rule out osteoporosis in CP. A larger study is warranted to confirm these results.

Diffusion-weighted magnetic resonance imaging of mandibular bone marrow: do apparent diffusion coefficient values of the cervical vertebrae and mandible correlate with age?

OBJECTIVES

The objective of this investigation was to assess the correlation between the mandible and cervical vertebrae bone marrow apparent diffusion coefficient (ADC), obtained by diffusion-weighted magnetic resonance imaging (DWI), with age; to verify the correlation between ADC values from the mandible and the cervical vertebrae; to describe and assess the differences between ADC values obtained from DWI examinations of distinct mandible areas as well as cervical vertebrae.

METHODS

Thirty imaging examinations with DWI for that included the mandible and C1, C2, C3, and C4 vertebrae in the same examination were included. ADC values were collected from 7 distinct areas in the mandible and the cervical vertebrae. Differences between ADC values and non-parametric correlations were performed.

RESULTS

A total of 270 regions were assessed. No significant difference was found between ADC values of all areas tested. An inverse correlation was found between C2, C3, and C4 vertebrae ADC values and age. The significant correlation of anatomic area ADC values and age were presented as graphics to verify if the linear trend of ADC values and age are in accordance with the literature CONCLUSIONS: The mandible area that most correlates with the cervical vertebrae, using ADC values, is the posterior trabecular area, below the inferior molars. Also, C2, C3, and C4 vertebrae ADC values inversely correlate with age, which demonstrates the bone qualitative changes in bone composition. ADC values may be useful for the qualitative assessment of bone quality to screen patients at osteoporosis risk.

Association of Low Bone Mass with Decreased Skeletal Muscle Mass: A Cross-Sectional Study of Community-Dwelling Older Women

This study aimed to investigate the characteristics of skeletal muscle mass, muscle strength, and physical performance among community-dwelling older women. Data were collected from 306 older adults, and the data of 214 older women were included in the final analysis. Participants' calcaneus bone mass was measured using ultrasonography. Based on their T-scores, participants were divided into the following three groups: normal (T-score > -1), low (-2.5 < T-score ≤ -1), and very low (T-score ≤ -2.5) bone mass. Further, participants' skeletal muscle mass, muscle strength (grip and knee extension strength), and physical performance [gait speed and timed up and go (TUG)] were measured. Arm skeletal muscle index (SMI, skeletal muscle mass/height2), leg SMI, and appendicular SMI in the very low bone mass group were low compared to those of the low bone mass group (p = 0.034, p = 0.011, and p = 0.009, respectively). Grip and knee extension strength, gait speed, and TUG were not significantly different between the groups. These findings suggest that older women with low bone density had decreased skeletal muscle mass. Therefore, maintaining or improving skeletal muscle mass may prevent low bone mass.

Auditory Processing Deficits Are Selectively Associated with Medial Temporal Lobe Mnemonic Function and White Matter Integrity in Aging Macaques

Deficits in auditory function and cognition are hallmarks of normative aging. Recent evidence suggests that hearing-impaired individuals have greater risks of developing cognitive impairment and dementia compared to people with intact auditory function, although the neurobiological bases underlying these associations are poorly understood. Here, a colony of aging macaques completed a battery of behavioral tests designed to probe frontal and temporal lobe-dependent cognition. Auditory brainstem responses (ABRs) and visual evoked potentials were measured to assess auditory and visual system function. Structural and diffusion magnetic resonance imaging were then performed to evaluate the microstructural condition of multiple white matter tracts associated with cognition. Animals showing higher cognitive function had significantly better auditory processing capacities, and these associations were selectively observed with tasks that primarily depend on temporal lobe brain structures. Tractography analyses revealed that the fractional anisotropy (FA) of the fimbria-fornix and hippocampal commissure were associated with temporal lobe-dependent visual discrimination performance and auditory sensory function. Conversely, FA of frontal cortex-associated white matter was not associated with auditory processing. Visual sensory function was not associated with frontal or temporal lobe FA, nor with behavior. This study demonstrates significant and selective relationships between ABRs, white matter connectivity, and higher-order cognitive ability.

Radiological and Clinical Outcomes of Anterior Cervical Discectomy and Fusion in Older Patients: A Comparative Analysis of Young-Old Patients (Ages 65-74 Years) and Middle-Old Patients (Over 75 Years)

Objective

Anterior cervical discectomy and fusion (ACDF) is the most commonly performed procedure for degenerative cervical spondylosis. Because of its relatively low invasiveness and surgical procedure, old age is not regarded as an exclusion criterion for ACDF. However, very few studies have been conducted on the radiological and clinical outcomes of ACDF in older patients. The purpose of this study was to evaluate the radiological and clinical outcomes of ACDF in older patients.

Methods

We retrospectively analyzed 48 patients (> 65 years) who underwent ACDF from January 2011 to December 2015. We divided the patients into 2 groups: young-old age group (65–74 years) and middle-old age group (≥ 75 years). Cervical lateral radiographs taken in the neutral standing position were evaluated preoperatively (PRE), on postoperative day 7 (POST), and at the 1-year follow-up (F/U). The radiological parameters included cervical angle (CA: C2–7 Cobb angle), segmental angle, total intervertebral height, disc height, sagittal vertical axis (SVA), T1 slope (T1s), and range of cervical motion (extension CA minus flexion CA). Postoperative hospital days, comorbidities, complications, and clinical outcomes were also analyzed.

Results

We analyzed data from 48 patients (group A: n = 30 patients, 46 segments, mean age, 68.60 ± 3.36 years; group B: n = 18 patients, 23 segments, mean age, 79.22 ± 2.63 years). The surgical levels were as follows: C3/4, 4; C4/5, 7; C5/6, 10; C6/7, 29; and C7/ T1, 6 levels, and there were no significant between-group differences in the distribution. There were no significant between-group differences in the fusion and subsidence rates (fusion rate: group A, 76.2%; group B, 71.4%; p = 0.732; subsidence rate: group A, 34.8%; group B, 26.1%; p = 0.587). There was no longitudinal trend in the repeated-measurements analysis of variance test of the 2 groups of the PRE, POST, and F/U data for each radiological parameter. According to the paired t-test, T1 slope (T1s), SVA, and CA did not differ preoperatively and postoperatively. There was no statistically significant difference in visual analogue scale scores (axial, arm), the Neck Disability Index, or Odom’s criteria between the 2 groups (p = 0.448, p = 0.357, and p = 0.913).

Conclusion

There was no significant difference in radiological and clinical outcomes between young-old and middle-old patients. Middle-old age does not seem to be a limitation to ACDF, but larger-scale and longer-term studies are needed to confirm the findings of this study.

The importance of being amorphous: calcium and magnesium phosphates in the human body

This article focuses on the relevance of amorphous calcium (and magnesium) phosphates in living organisms. Although crystalline calcium phosphate (CaP)-based materials are known to constitute the major inorganic constituents of human hard tissues, amorphous CaP-based structures, often in combination with magnesium, are frequently employed by Nature to build up components of our body and guarantee their proper functioning. After a brief description of amorphous calcium phosphate (ACP) formation mechanism and structure, this paper is focused on the stabilization strategies that can be used to enhance the lifetime of the poorly stable amorphous phase. The various locations of our body in which ACP (pure or in combination with Mg²⁺) can be found (i.e. bone, enamel, small intestine, calciprotein particles and casein micelles) are highlighted, showing how the amorphous nature of ACP is often of paramount importance for the achievement of a specific physiological function. The last section is devoted to ACP-based biomaterials, focusing on how these materials differ from their crystalline counterparts in terms of biological response.

Targeting Cell Senescence for the Treatment of Age-Related Bone Loss

PURPOSE OF REVIEW

We review cell senescence in the context of age-related bone loss by broadly discussing aging mechanisms in bone, currently known inducers and markers of senescence, the senescence-associated secretory phenotype (SASP), and the emerging roles of senescence in bone homeostasis and pathology.

RECENT FINDINGS

Cellular senescence is a state of irreversible cell cycle arrest induced by insults or stressors including telomere attrition, oxidative stress, DNA damage, oncogene activation, and other intrinsic or extrinsic triggers and there is mounting evidence for the role of senescence in aging bone. Cellular aging also instigates a SASP that exerts detrimental paracrine and likely systemic effects. With aging, multiple cell types in the bone microenvironment become senescent, with osteocytes and myeloid cells as primary contributors to the SASP. Targeting undesired senescent cells may be a favorable strategy to promote bone anabolic and anti-resorptive functions in aging bone, with the possibility of improving bone quality and function with normal aging and/or disease.

Hypertension and its Correlates in the Oldest Old Population Aged 80 Years and Above in Urban South India

BACKGROUND

Hypertension is a major problem among the geriatric population, presenting the risk of multiple associated co-morbidities and organ system damage. Data related to the epidemiology of controlled and uncontrolled hypertension among the oldest old population is sparse, more so from developing countries. The objectives of the present paper were to identify the prevalence and correlates of hypertension according to gender among the urban community-dwelling healthy oldest old population.

METHODS

200 healthy people aged 80 years and above were recruited by random selection from Hyderabad city of South India in 2017. A trained investigator collected data on background history, history of hypertension and other co-morbidities, medications and sleep. Participants were tested for muscle strength, gait speed, and SPPB and cognitive impairment.

RESULTS

The prevalence of hypertension was 83.5%; 81.6% among men and 84.7% among women. 64.5% was self-reported. Hypertension was controlled with treatment among only 46.2%. In 74.6%, it was controlled even without treatment. The independent correlates were BMI per SD increase (OR: 1.92, 95% CI: 1.17-3.16), diabetes (OR: 6.02, 95% CI: 1.24-29.11) and asthma (OR: 3.59, 95% CI: 1.05-12.29). Among men, BMI per SD increase was significantly associated while hemoglobin per SD increase, height per SD decrease, and arthritis were positively associated among women. Increasing heart rate among total subjects (OR: 0.44, 95% CI: 0.27-0.71), and among women (OR: 0.47, 95% CI: 0.24-0.92) showed a negative association.

CONCLUSION

The prevalence of hypertension was high. The correlates were different for men and women. Subjects were unaware of their control status which posed an increased risk for organ damage, and development of co-morbidities. Policies aimed at improving quality of life of the oldest old should place due stress on appropriate hypertension management in developing countries.

Assessment of cortical bone fracture resistance curves by fusing artificial neural networks and linear regression

Bone injures (BI) represents one of the major health problems, together with cancer and cardiovascular diseases. Assessment of the risks associated with BI is nontrivial since fragility of human cortical bone is varying with age. Due to restrictions for performing experiments on humans, only a limited number of fracture resistance curves (R-curves) for particular ages have been reported in the literature. This study proposes a novel decision support system for the assessment of bone fracture resistance by fusing various artificial intelligence algorithms. The aim was to estimate the R-curve slope, toughness threshold and stress intensity factor using the two input parameters commonly available during a routine clinical examination: patients age and crack length. Using the data from the literature, the evolutionary assembled Artificial Neural Network was developed and used for the derivation of Linear regression (LR) models of R-curves for arbitrary age. Finally, by using the patient (age)-specific LR models and diagnosed crack size one could estimate the risk of bone fracture under given physiological conditions. Compared to the literature, we demonstrated improved performances for estimating nonlinear changes of R-curve slope (R² = 0.82 vs. R² = 0.76) and Toughness threshold with ageing (R² = 0.73 vs. R² = 0.66).

Implant-Supported Immediately Loaded Fixed Full-Arch Dentures: Evaluation of Implant Survival Rates in a Case Cohort of up to 7 Years

BACKGROUND

The treatment of severely atrophied and edentulous jaws by means of fixed implant supported solutions is a challenging procedure.

PURPOSE

The immediate loading of four to six axial and tilted implants offers the possibility to overcome elaborate hard tissue augmentation procedures but lacks implant and patient related data on implant survival rates.

MATERIALS AND METHODS

This retrospective 7-years clinical trial investigated the implant survival rates of 2,081 implants (380 patients, 482 jaws) using an immediate loading protocol with either 4, 5, or 6 implants per restoration. Survival rates were calculated concerning implantation related factors (jaws/number of supporting implants/angulations/diameters/lengths) and patient related factors (medical status/smoking).

RESULTS

Overall survival of 2,081 implants was 97.0% on implant level. Survival rates of implantation related factors did not yield significant differences. Significant differences were yield between healthy patients and patients with osteoporosis (p = .002) and the medical status group "other" (p = .032), respectively. Smokers yielded a significantly higher survival than nonsmokers (p = .002).

CONCLUSIONS

It is assumed that four implants per jaw serve as a sufficient implant number for full arch restorations in both, the mandible and the maxilla. Osteoporosis under the medication with bisphosphonates seems to be a risk factor for implant survival. The authors suggest that the effect of smoking on ISRs remains controversial within this treatment concept.

An analysis of age-related loss of skeletal muscle mass and its significance on osteoarthritis in a Korean population

BACKGROUND/AIMS

This study was conducted in order to analyze the effects of sarcopenia on age-related osteoarthritis (OA) of the knee in a Korean population.

METHODS

All the Korean subjects who visited the Yeungnam University Medical Center Health Promotion Center between 2008 and 2012 in order to undergo a routine medical examination were enrolled. A total of 5,723 young, healthy people (2,959 males, 2,764 females) enrolled as normal subjects and 23,473 subjects (13,006 males and 10,467 females) were included for evaluation of the effects of sarcopenia on OA. There were 266 subjects who followed-up bioelectrical impedance analysis at a 4-year interval. Of 327 subjects enrolled in this study, knees with anteroposterior X-rays were assessed according to the Kellgren-Lawrence (K/L) grade.

RESULTS

Skeletal muscle mass index (SMI) and basal metabolic rate (BMR) showed a steady decrease with the advance of age (p < 0.01), but SMI showed strong positive correlation with BMR (r = 0.72, β = 30.96, p < 0.01). During the 4-year interval, BMR showed a significant decrease with aging (p < 0.01), consistently with the decrease of SMI. Knees with normal SMI were prone to be designated as K/L grade 0 or 1; however, subjects with sarcopenia showed a trend toward the higher K/L grade, classified as knee radiological osteoarthritis (ROA) (p < 0.01).

CONCLUSIONS

The results of this study may indicate that sarcopenia as age-related loss of skeletal muscle mass is interactively correlated with the presence and severity of age-related OA.

The persistence of epiphyseal scars in the distal radius in adult individuals

The use of radiographic imaging in the estimation of chronological age facilitates the analysis of structures not visible on gross morphological inspection. Following the completion of epiphyseal fusion, a thin radio-opaque band, the epiphyseal scar, may be observed at the locus of the former growth plate. The obliteration of this feature has previously been interpreted as the final stage of skeletal maturation and consequently has been included as a criterion in several methods of age estimation, particularly from the distal radius. Due to the recommendations relating to age estimation in living individuals, accurate assessment of age from the distal radius is of great importance in human identification; however, the validity of the interpretation of the obliteration of the epiphyseal scar as an age-related process has not been tested. A study was undertaken to assess the persistence of epiphyseal scars in adults between 20 and 50 years of age through the assessment of 616 radiographs of left and right distal radii from a cross-sectional population. This study found that 86% of females and 78% of males retained some remnant of the epiphyseal scar in the distal radius. The relationships between chronological age, biological sex and the persistence of the epiphyseal scar were not statistically significant. The findings of this study indicate that the epiphyseal scars may persist in adult individuals until at least 50 years of age. No maximum age should therefore be applied to the persistence of an epiphyseal scar in the distal radius.

Adaptive properties of human cementum and cementum dentin junction with age

OBJECTIVES

The objective of this study was to evaluate age related changes in physical (structure/mechanical properties) and chemical (elemental/inorganic mineral content) properties of cementum layers interfacing dentin.

METHODS

Human mandibular molars (N=43) were collected and sorted by age (younger=19-39, middle=40-60, older=61-81 years). The structures of primary and secondary cementum (PC, SC) types were evaluated using light and atomic force microscopy (AFM) techniques. Chemical composition of cementum layers were characterized through gravimetric analysis by estimating ash weight and concentrations of Ca, Mn, and Zn trace elements in the analytes through inductively coupled plasma mass spectroscopy. The hardness of PC and SC was determined using microindentation and site-specific reduced elastic modulus properties were determined using nanoindentation techniques.

RESULTS

PC contained fibrous 1-3 µm wide hygroscopic radial PDL-inserts. SC illustrated PC-like structure adjacent to a multilayered architecture composing of regions that contained mineral dominant lamellae. The width of the cementum dentin junction (CDJ) decreased as measured from the cementum enamel junction (CEJ) to the tooth apex (49-21 µm), and significantly decreased with age (44-23 µm; p<0.05). The inorganic ratio defined as the ratio of post-burn to pre-burn weight increased with age within primary cementum (PC) and secondary cementum (SC). Cementum showed an increase in hardness with age (PC (0.40-0.46 GPa), SC (0.37-0.43 GPa)), while dentin showed a decreasing trend (coronal dentin (0.70-0.72 GPa); apical dentin (0.63-0.73 GPa)).

SIGNIFICANCE

The observed physicochemical changes are indicative of increased mineralization of cementum and CDJ over time. Changes in tissue properties of teeth can alter overall tooth biomechanics and in turn the entire bone-tooth complex including the periodontal ligament. This study provides baseline information about the changes in physicochemical properties of cementum with age, which can be identified as adaptive in nature.

Bone Regeneration Based on Tissue Engineering Conceptions - A 21st Century Perspective

The role of Bone Tissue Engineering in the field of Regenerative Medicine has been the topic of substantial research over the past two decades. Technological advances have improved orthopaedic implants and surgical techniques for bone reconstruction. However, improvements in surgical techniques to reconstruct bone have been limited by the paucity of autologous materials available and donor site morbidity. Recent advances in the development of biomaterials have provided attractive alternatives to bone grafting expanding the surgical options for restoring the form and function of injured bone. Specifically, novel bioactive (second generation) biomaterials have been developed that are characterised by controlled action and reaction to the host tissue environment, whilst exhibiting controlled chemical breakdown and resorption with an ultimate replacement by regenerating tissue. Future generations of biomaterials (third generation) are designed to be not only osteoconductive but also osteoinductive, i.e. to stimulate regeneration of host tissues by combining tissue engineering and in situ tissue regeneration methods with a focus on novel applications. These techniques will lead to novel possibilities for tissue regeneration and repair. At present, tissue engineered constructs that may find future use as bone grafts for complex skeletal defects, whether from post-traumatic, degenerative, neoplastic or congenital/developmental "origin" require osseous reconstruction to ensure structural and functional integrity. Engineering functional bone using combinations of cells, scaffolds and bioactive factors is a promising strategy and a particular feature for future development in the area of hybrid materials which are able to exhibit suitable biomimetic and mechanical properties. This review will discuss the state of the art in this field and what we can expect from future generations of bone regeneration concepts.

Theories and mechanisms of aging

This article discusses various theories of aging and their relative plausibility related to the human aging process. Structural and physiologic changes of aging are discussed in detail by organ system. Each of the organ systems is discussed when applicable to the various theories of aging. Normal versus abnormal aging is discussed in the context of specific aging processes, with atypical presentations of disease and general links to life expectancy. Life expectancy and lifespan are discussed in the context of advances in medical science and the potential ultimate link to human life span.

Porous tantalum stimulates the proliferation and osteogenesis of osteoblasts from elderly female patients

Porous tantalum (Ta) implants have been successful in various orthopedic procedures for patients with compromised bone-forming abilities. Previous studies demonstrated that human osteoblast (HOB) cultures from older female patients produced less bone on implant materials in vitro compared to HOBs from age-matched male and younger female patients. In this study, the responses of HOBs from younger (< 45) and older (> 60 years old) female patients were compared on Ta, titanium fiber mesh (TFM) and tissue culture plastic. Adhesion, proliferation, and mineralization were greater in cells from younger patients than from older patients. Cell adhesion was slightly higher on Ta than TFM or plastic. However, Ta highly stimulated cell proliferation with a 4- and 6-fold increase compared to TFM for cells from younger and older patients, respectively, and 12- and 16-fold increase in proliferation compared to cells on plastic (p ≤ 0.001). At 3 weeks, mineralization was significantly higher on Ta compared to TFM for HOBs from older patients (p ≤ 0.05). Expression levels of bone matrix markers demonstrated differences dependent on age and substrate. Scanning electron micrographs revealed HOBs covering the surfaces and entering the pores of both Ta and TFM. In conclusion, tantalum greatly stimulates cell proliferation, and improves the ability of HOBs from older patients to form bone.

Age-related differences of bone mass, geometry, and strength in treatment-naïve postmenopausal women. A tibia pQCT study

Most studies addressing the effects of aging on bone strength have focused mainly on (areal) bone mineral densities and bone mineral content (BMC) and less on bone geometry. We assessed age-related differences of bone mass (grams of bone mineral), geometry, and derived strength in 219 treatment-naïve postmenopausal women using peripheral quantitative computed tomography of the load-bearing tibia. Subjects were separated in 3 age groups: A=48-59yr (N=80), B=60-69yr (N=84), C=70-80yr (N=55). Three slices were obtained for each individual, at the 4% (trabecular), 14% (subcortical and cortical), and 38% (cortical bone) of tibia length sites. Trabecular, subcortical, and cortical BMC (mg per 1-mm slice), volumetric bone mineral densities (mg/cm(3)), bone cross-sectional areas (mm(2)), periosteal (PERI_C, mm) and endosteal circumference (ENDO_C, mm), mean cortical thickness (CRT_THK, mm), and Stress Strain Indexes (SSIs, mm(3)) were studied. Trabecular and cortical BMC and volumetric densities were significantly lower in the elder subjects (group C) compared with younger subjects (groups A and B), p<0.0005. Cortical area and CRT_THK were significantly lower in group C (vs A and B, p<0.0005), whereas total cross-sectional area was higher in group C compared with A and B. ENDO_C was significantly higher in older subjects (group C vs A and B, p<0.0005), whereas PERI_C did not differ significantly between the age groups. SSIs were significantly lower in older subjects at the 14% site (group C vs A, p<0.0005 and C vs B, p<0.005), and at the 38% site (group C vs group A, p<0.01). Our results indicate that age-induced differences on bone strength entail significant alterations not only of bone mass, but also of bone geometry.

Sinus floor augmentation surgery using autologous bone grafts from various donor sites: a meta-analysis of the total bone volume

BACKGROUND

To date, no studies have been published that evaluated histomorphometric data from a large number of patients while comparing different sites and methods of autologous bone grafting in sinus floor augmentation procedures. A meta-analysis of the English literature from January 1995 till April 2009 was carried out.

MATERIALS AND METHODS

PubMed search engine and the following journals were explored: Clinical Oral Implant Research, International Journal of Oral and Maxillofacial Implants, International Journal of Periodontics and Restorative Dentistry, and the Journal of Periodontology.

RESULTS

Out of 147 titles, according to our criteria, 25 articles were left for analysis. The majority were prospective controlled studies (21) and 2 randomized clinical trials, 1 pilot study and 1 case series. A reference value of 47% for total bone volume (TBV) was found while using iliac bone grafting as a standard. Use of intraoral bone grafts increases the TBV, with 11% for chin bone and 14% for bone grafted from other intraoral sites. Particulation of the bone graft has a negative effect on the TBV of 18%. Surprisingly, no correlation between TBV and the time of graft healing was found. Histological section thickness seemed to be a significant variable, as every micron increase of section thickness leads to an increase of 0.4% of TBV.

CONCLUSIONS

Bone grafting from the iliac crest resulted in a significantly lower TBV compared with intraoral bone grafting. However, due to the limited availability of intraoral bone to be harvested, iliac grafts still have to be considered the gold standard in augmenting the severely atrophic maxilla.

How does human bone resist fracture?

The fracture of bone is clearly a major health concern, especially for the elderly. Medical therapies to reduce the possibility of bone fracture to date have principally centered on treating the loss in bone mass (bone mineral density) that accompanies aging (i.e., addressing the loss in bone quantity). However, it is now known that there is an additional, perhaps more significant, effect of the degradation in the inherent properties of bone (i.e., a loss in bone quality) with age. To address this issue, we review here the structure and properties of bone, focusing on its strength and fracture resistance from the perspective of the multidimensional hierarchical nature of its structure. We show that bone derives its resistance to fracture from a multitude of deformation and toughening mechanisms at many of these size-scales, ranging from the nanoscale structure of its protein molecules to its macroscopic physiological state.

On the increasing fragility of human teeth with age: a deep-UV resonance Raman study

UV resonance Raman spectroscopy (UVRRS) using 244-nm excitation was used to study the impact of aging on human dentin. The intensity of a spectroscopic feature from the peptide bonds in the collagen increases with tissue age, similar to a finding reported previously for human cortical bone.

INTRODUCTION

The structural changes that lead to compromised mechanical properties with age in dentin and bone are under intense study. However, in situ analyses of the content and distribution of the mineral phase are more highly developed at present than equivalent probes of the organic phase.

MATERIALS AND METHODS

Thirty-five human molars were divided into three groups: young/normal (23.3 +/- 3.8 years); aged/transparent (74.3 +/- 6.0 years), which had become transparent because of filling of the tubule lumens with mineral deposits; and aged/nontransparent (73.3 +/- 5.7 years). Control experiments were performed by demineralizing normal dentin.

RESULTS

Spectral features caused by both the amide backbone and resonance-enhanced side-chain vibrations were observed. This finding contrasts with reported Raman spectra of proteins in solution excited with similar UV wavelengths, where side chain vibrations, but not strong amide features, are observed. The strong intensity of the amide features observed from dentin is attributed to broadening of the resonance profile for the amide pi --> pi* transition caused by the environment of the collagen molecules in dentin. With increasing age, the height of one specific amide vibration (amide I) becomes significantly higher when comparing teeth from donors with an average age of 23 years to those of 73 years (p < 0.001). This trend of increasing amide I peak height with age is similar to that previously reported for human cortical bone. The amide I feature also increased in dentin that had been demineralized and dehydrated.

CONCLUSIONS

The similar trend of increasing amide I peak height with age in the UVRR spectra of both teeth and bone is surprising, given that only bone undergoes remodeling. However, by considering those observations together with this study of demineralized/dehydrated dentin and our prior work on dentin dehydrated with polar solvents, a consistent relationship between changes in the UVRR spectra and the collagen environment in the tissue can be developed.

MR imaging and osteoporosis: fractal lacunarity analysis of trabecular bone

We develop a method of magnetic resonance (MR) image analysis able to provide parameter(s) sensitive to bone microarchitecture changes in aging, and to osteoporosis onset and progression. The method has been built taking into account fractal properties of many anatomic and physiologic structures. Fractal lacunarity analysis has been used to determine relevant parameter(s) to differentiate among three types of trabecular bone structure (healthy young, healthy perimenopausal, and osteoporotic patients) from lumbar vertebra MR images. In particular, we propose to approximate the lacunarity function by a hyperbola model function that depends on three coefficients, alpha, beta, and gamma, and to compute these coefficients as the solution of a least squares problem. This triplet of coefficients provides a model function that better represents the variation of mass density of pixels in the image considered. Clinical application of this preliminary version of our method suggests that one of the three coefficients, beta, may represent a standard for the evaluation of trabecular bone architecture and a potentially useful parametric index for the early diagnosis of osteoporosis.

Aortic valve calcification: association with bone mineral density and cardiovascular risk factors

BACKGROUND

Cardiovascular risk factors are reported to increase the incidence of aortic valve calcification. Among older women, low bone mineral density appears to be associated with increased prevalence of aortic calcification. We aimed to assess and compare cardiovascular risk factors and bone mineral density of patients with and without aortic valve calcification.

MATERIALS AND METHODS

Cardiovascular risk factors and bone mineral density measurements have been assessed in 49 patients with aortic valve calcification and in 65 patients without aortic valve calcification. All patients were subsequently referred to the nuclear medicine department to measure bone mineral density after echocardiographic evaluation.

RESULTS

No statistically significant differences were observed between the two groups with respect to sex, body mass index, history of coronary artery disease, diabetes mellitus, hypercholesterolemia, and smoking status. Although height and weight of the patients with aortic valve calcification were significantly lower than those of patients without aortic valve calcification, they were not independent risk factors. Age and hypertension were found to be independent positive risk factors for aortic valve calcification, whereas T score was found to be negatively associated with aortic valve calcification.

CONCLUSION

We have shown that aortic valve calcification is positively associated with age and hypertension, whereas bone mineral density is negatively associated with aortic valve calcification. The mechanism underlying the association between decreased bone mineral density and aortic valve calcification remains to be clarified in further studies.

Deep-ultraviolet Raman spectroscopy study of the effect of aging on human cortical bone

The age-related deterioration in bone quality and consequent increase in fracture incidence is an obvious health concern that is becoming increasingly significant as the population ages. Raman spectroscopy with deep-ultraviolet excitation (244 nm) is used to measure vibrational spectra from human cortical bone obtained from donors over a wide age range (34-99 years). The UV Raman technique avoids the fluorescence background usually found with visible and near-infrared excitation and, due to resonance Raman effects, is particularly sensitive to the organic component of bone. Spectral changes in the amide I band at 1640 cm(-1) are found to correlate with both donor age and with previously reported fracture toughness data obtained from the same specimens. These results are discussed in the context of possible changes in collagen cross-linking chemistry as a function of age, and are deemed important to further our understanding of the changes in the organic component of the bone matrix with aging.

Fixation principles in metaphyseal bone--a patent based review

Osteoporotic changes start in cancellous bone due to the underlying pathophysiology. Consequently, the metaphyses are at a higher risk of "osteoporotic" fracture than the diaphysis. Furthermore, implant purchase to fix these fractures is also affected by the poor bone quality. In general, researchers and developers have worked on three different approaches to address the problem of fractures to osteoporotic bone: adapted anchoring techniques, improved load distribution as well as transfer with angular stable screws, and augmentation techniques using bone substitutes. A patent-based review was performed to evaluate which ideas were utilized to improve fixation in osteoporotic, metaphyseal bone, especially in the proximal femur, and to analyze whether the concept had entered clinical use. Anchoring devices that are either extramedullary or intramedullary have a long clinical history. However, demanding surgical techniques and complications, especially in poor quality bone, are justification that such implants and their corresponding surgical techniques need to be improved upon. Expanding elements have been evaluated in the laboratory. The results are promising and the potential of this approach has yet to be fully exploited in the clinics. Internal fixators with angular stable screws open the door for many new anchorage ideas and have great potential for further optimization of load distribution and transfer. Augmentation techniques may improve anchorage in osteoporotic bone. However, the properties of bone substitute materials will need to be modified and improved upon in order to meet the demanding requirements. If we summarise the development process and the clinical use of implants to date, we have to clearly state that more factors than simply biomechanical advantage will determine the clinical success of a new fixation principle or a new implant. Instead, fracture treatment of patients with osteoporosis really needs an interdisciplinary approach!

Genetic epidemiology of skeletal system aging in apparently healthy human population

The study of our team was driven by a clinical problem of age-dependent chronic degenerative disease of skeleton that includes osteoporosis (OP) and osteoarthritis (OA)-related phenotypes. The major aims of the study included evaluation of the putative genetic factors determining the rate and pattern of the bone and cartilage loss and identification of the specific genes involved in this process. In addition, we examined genetic effects on circulating molecular factors involved in bone and cartilage metabolism. The skeletal phenotypes were assessed from hand radiographs, in total on about 1200 individuals belonging to ethnically homogeneous nuclear and complex three-generational pedigrees of European origin. The results obtained until now can be divided into three sections: (1) genetic analysis of bone mass/size/geometry characteristics (OP) and traits related to hand OA; (2) pedigree-based investigation of circulating levels of calciotropic hormones, growth factors, cytokines, and biochemical indices of bone and cartilage remodelling; (3) linkage and linkage disequilibrium study of several candidate genes, such as estrogen receptor alpha, collagen type I alpha 1, genes related to extracellular inorganic pyrophosphate transport and OP/OA phenotypes, including biochemical variables. The study provides compelling evidence to suggest strong involvement of the genetic factors in determination of variation of the majority of the examined OP- and OA-related phenotypes.

Fall-related upper body injuries in the older adult: a review of the biomechanical issues

Although the epidemiology of fall-related injuries is well established for the elderly population over 65 years of age, the biomechanics of how, when and why injuries do and do not occur when arresting a fall have received relatively little attention. This paper reviews the epidemiological literature in the MEDLINE data base pertinent to the biomechanics of fall-related injuries, including data on fall rates, fall-related injury rates, fall directions and types of injuries available. It also covers primary sources not listed on MEDLINE, along with the pertinent biomechanics literature. Many falls in older adults are in a forward direction, and as a result the upper extremities are one of the most commonly injured structures, presumably in protecting the head and torso. In this review emphasis is placed on what is, and what is not, known of the biomechanical factors that determine the impact forces and injury risk associated with upper extremity injuries in forward falls. While decreased bone mineral density may be contributory, it is not a reliable predictor of fracture risk. Evidence is presented that fall-related impact forces can be reduced by appropriate volitional arrest strategies. Further theoretical and experimental research is needed to identify appropriate fall-arrest strategies for the elderly, as well as the physical capacities and skills required to do so. Inexpensive interventions might then be developed to teach safe fall-arrest techniques to older individuals.

Collagen and bone viscoelasticity: a dynamic mechanical analysis

The purpose of this study was to explore the effects of changes in Type I collagen on the viscoelasticity of bone. Bone coupons were heated at either 100 or 200 degrees C to induce the thermal denaturation of Type I collagen. Half of these specimens were rehydrated after heat treatment; the other half were tested in a dry condition. The degree of denatured collagen (DC%) was analyzed by a selective digestion technique with the use of alpha-chymotrypsin. Isothermal (37 degrees C) and variable temperature tests (scans from 35 to 200 degrees C) were performed with the use of a dynamic mechanical analyzer to evaluate changes in bone viscoelastic properties as a function of collagen damage, specifically, changes in the loss factor (tan delta) and storage modulus (E') were assessed. Significant collagen denaturation occurred only when bone was heated at 200 degrees C irrespective of the hydration condition. Also, DC% did not show a significant effect on tan delta. However, higher values of tan delta were observed in wet samples compared to dry specimens. The temperature-scan tests revealed that the hydration condition, but not DC%, significantly affected the behavior of tan delta. However, E' was not strongly influenced either by DC% or by water content. These results suggest that at a constant frequency the denaturation of collagen triple-helical molecules may have few effects on the viscoelasticity of bone, but moisture may play a prominent role in determining this property.

Interrelationship between bone aging traits and basic anthropometric characteristics

Using plain hand radiographs, the age dependence of various bone-aging traits (bone mineral density [BMD], cortical index [CI], osteoarthritis [OA], and osseographic [OSS] scores) was evaluated to test whether the correlation among these traits is an individual- or population-based phenomenon. In addition, the effect of anthropometric features on variation of bone-aging traits was estimated. The study included 1,295 individuals from Chuvasha, Russia, 18 to 89 years. BMD was measured from the compact compartment of the middle and distal phalanges of both 3(rd) fingers. The CI of the II-IV metacarpal bones and II-IV proximal phalanges was obtained. The development of OA was based on the standard Kellgren and Lawrence grading scheme for 28 hand joints. OSS score, a surrogate measure that takes into account different kinds of bone changes, was also obtained for each individual. Body weight and height, eight skinfold thicknesses on the trunk and extremities, and breadths of the long bones were measured. Sex-based univariate analyses and multivariate statistical analysis showed the following: 1) Age dependence was defined more strongly in "OA-linked" compared to "osteoporosis (OP)-linked" traits; 2) While "OP-linked" bone-aging traits correlated with age differently between sexes, "OA-linked" traits did not; 3) The strong interrelationship between OA-linked and OP-linked traits in both sexes became very weak and statistically insignificant (P > 0.10) after adjustment for age. Thus, OA and OP conditions in the same individual develop independently and probably reflect different underlying physiological mechanisms. 4) Anthropometric characteristics were significantly correlated with bone-aging traits, but correlations were low (r < 0.20). Thus, the contribution of anthropometric characteristics to the rate and pattern of bone aging of the hand was to relatively small.

Microstructural heterogeneity and the fracture toughness of bone

Age-related changes in the skeleton often lead to an increase in the susceptibility of bone to fracture. The purpose of this study was to determine whether differences in material properties between the osteonal and interstitial regions of bone have an effect on bone fracture properties. Parameters such as longitudinal fracture toughness, transverse fracture toughness, porosity, interstitial microhardness, osteonal microhardness, bone density, and weight fractions of the mineral and organic phases of bone were examined as a function of age using female baboon femurs. With increasing age, the longitudinal fracture toughness decreased significantly as did transverse fracture toughness, whereas the interstitial microhardness increased. However, no significant differences in the other parameters were observed as a function of age. Using the ratio of interstitial microhardness to osteonal microhardness as a measure of the differences in the material properties in these two regions, correlation analysis revealed that the longitudinal fracture toughness of bone has a significant correlation with the microhardness ratio. Localized differences in material properties between osteonal and interstitial regions of bone increase with age; such differences may result in high stress concentrations at cement lines and facilitate longitudinal crack propagation.

Hormonal changes in humans during spaceflight

Readers of this review may feel that there is much more that we do not know about space endocrinology than what we know. Several reasons for this state of affairs have been given: 1. the complexity of the field of endocrinology with its still increasing number of known hormones, releasing factors and precursors, and of the interactions between them through various feedback mechanisms 2. the difficulty in separating the microgravity effects from the effects of stress from launch, isolation and confinement during flight, reentry, and postflight re-adaptation 3. the experimental limitations during flight, such as limited number of subjects, limited number of samples, impossibility of collecting triple samples for pulsatile hormones like growth hormone 4. the disturbing effects of countermeasures used by astronauts 5. the inadequacy of postflight samples for conclusions about inflight values 6. limitations of conclusions from animal experiments and space simulation studies The endocrinology field is divided in to nine systems or axes, which are successively reviewed: 1. Rapid bone demineralization in the early phase of spaceflight that, when unopposed, leads to catastrophic effects after three months but that slows down later. The endocrine mechanism, apart from the effect of exercise as a countermeasure, is not yet understood. 2. The hypothalamic-pituitary-adrenal axis is involved in stress reactions, which complicate our understanding and makes postflight analysis dubious. 3. In the hypothalamic-pituitary-gonadal axis, pulsatility poses a problem for obtaining representative values (e.g., for luteinizing hormone). Reproduction of rats in space is possible, but much more needs to be known about this aspect, particularly in women, before the advent of space colonies, but also in males because some evidence for reversible testicular dysfunction in space has been found. 4. The hypothalamic-pituitary-somato-mammotrophic axis involves prolactin and growth hormone. The latter also acts as a stress hormone and its secretion is greatly decreased in spaceflown rats, but not in astronauts, which may be due to differences in the regulation of growth hormone secretion between rats and humans. 5. The hypothalamic-pituitary-thyroid axis involves the thyroid hormones thyroxine and triiodothyronine, which are lowered in space, suggesting mild hypothyroidism. 6. The renin-angiotensin-aldosterone axis, which regulates water and electrolytes, involves antidiuretic hormone and two natriuretic peptides and shows paradoxical behavior in space. 7. Erythrocyte mass regulation involves erythropoietin, and space anemia is still not explained. 8. The endocrine pancreas involves insulin and glucagon, with loss of insulin sensitivity in space due to lack of exercise, which phenomenon requires more study before the advent of space colonies. 9. The sympathetic system acts through epinephrine, norepinephrine and dopamine and seems to have an increased activity in space in contrast to what had been widely believed. From the foregoing conclusions, it is clear that much further study is needed in all fields of space endocrinology. On the other hand, future studies will allow us to understand what happens in a given endocrine subsystem in the absence of the "gravity factor", the perturbing factor to which the human race has become adapted through thousands of years of evolution. This should provide us with a fuller understanding of the internal homeostatic mechanisms. An important point is that some endocrine systems seem to undergo changes in space that resemble those observed during senescence, but after spaceflight, recovery always occurs within weeks or months after return. This is particularly true for the systems regulating bone and muscle metabolism and reproduction, exactly as happens with the immune, neurosensory, and cardiovascular systems. Further space research may help us find new insights in the pathophysiology of aging and hopefully define novel prev

Body composition in 85 year-old women: effects of increased physical activity

This study explores whether regular training alters body composition and resting metabolism in the very old. A total of 55 community-dwelling women, 85 years old, were enrolled in a training group (N = 22) and a control group (N = 33). Training was performed once a week for eight months, and consisted of various exercises with particular attention to movements important for everyday activities. Before, immediately after, and one year after cessation of training, body composition was evaluated both by an impedance measurement and a whole body scan by dual-photon X-ray absorptiometry. Resting metabolism, assessed as energy expenditure at rest, was measured with standardized protocols by analyzing oxygen consumption and carbon dioxide production. Height declined in both groups throughout the study. Immediately after the training period, body weight showed a trend towards reduced levels in the training group, and an opposite trend in the control group. The control group showed an increased body mass index (p < 0.05) related to an increase in fat mass immediately after the training period; these parameters were unaltered in the training group. A reduction in fat free mass (p < 0.05) and bone mineral content (p < 0.05), and unaltered energy expenditure at rest were evident in both groups during the course of the study. These results suggest that regular training can counteract the age-related accumulation of fat in the very old. Physical reactivation, therefore, may possess an important potential for reducing morbidity in the very old by lowering fat mass, and thereby reducing the risk of acquiring several age-related diseases.

Changes in the fracture toughness of bone may not be reflected in its mineral density, porosity, and tensile properties

Age-related changes in the skeleton often lead to an increase in the susceptibility of bone to fracture. Such changes most likely occur in the constituents of bone, namely, the mineral and organic phases, and in their spatial arrangement manifested as orientation and microstructure. In the past, however, bone loss or decline in bone mineral density has been considered to be the major contributing factor for the increased risk of bone fractures, and elastic modulus and ultimate strength have been commonly used to assess bone quality and strength. However, whether these properties provide sufficient information regarding the likelihood of bone to fracture remains debatable. Using a novel fracture toughness test, which measures the energy or stress intensity required to propagate a crack within a material, the objective of this study was to investigate if the mineral density and mechanical properties of bone can accurately predict bone fragility as measured by fracture toughness. Changes in fracture toughness (K(IC)), bone mineral density (BMD), elastic modulus (E), yield and ultimate strength (sigma y and sigma s), porosity (P0), and microhardness (Hv) of bone were examined as a function of age in a baboon model. With increasing age, the fracture toughness of bone decreased, and its microhardness increased. However, no significant changes were found in BMD, E, P0, sigma y, and sigma s as a function of age. In addition, simple regression analyses revealed no significant correlation between bone fracture toughness and the other parameters, except for microhardness of bone. The results of this study indicate that changes in bone fracture toughness may not be necessarily reflected in its mineral density, porosity, elastic modulus, yield strength, and ultimate strength.

Genes play an important role in bone aging

Pathological changes in bones like osteoarthritis and osteoporosis are among the most frequent outcomes of age and aging. Presently, little is known about the genetic basis of peak bone mass or rate of bone loss, or on the genetics of bone formation and resorption. This paper reviews modern studies, dealing with the genetic aspects of bone formation and bone aging. The currently most popular measures of bone aging are: osteometric measurements (OSM) including measures of cortical thickness, bone mineral density (BMD), and osteographic scores (OSS) basing on descriptive criteria of bone age. These three are important clinical tools for predicting chronic degenerative disease and estimating biological age of individuals. Despite abundant data on ethnic and racial differences in these bone aging measures, modern knowledge regarding the genetics of the processes came primarily from family studies of BMD which point to strong familial and probably also genetic effects on bone mass. Regardless of the measurement technique or skeletal site selected, heritability estimates of BMD in most studies account for about 60% of the total variation in bone mass. Similarity of heritability estimates in most studies suggests that the same genetic factors operate on both weight-bearing and nonweight-bearing bones. However, genetic heritability may be overestimated in some family studies due to underestimation of common environmental effects. Segregation analysis, performed to date, reveals strong effect of potential major locus on BMD of both compact and trabecular bone, but much remains to be clarified. Genetic factors affecting BMD may be mediated through biochemical turnover of bone. Hence, segregation, linkage, and molecular biology are the staples of any genetic analysis of BMD, while the study of biochemical factors regulating bone turnover should elucidate the full picture of bone formation and aging. Am. J. Hum. Biol. 10:421-438, 1998. © 1998 Wiley-Liss, Inc.

Clinical factors associated with calcific aortic valve disease. Cardiovascular Health Study

OBJECTIVES

The aim of this study was to determine the prevalence of aortic sclerosis and stenosis in the elderly and to identify clinical factors associated with degenerative aortic valve disease.

BACKGROUND

Several lines of evidence suggest that degenerative aortic valve disease is not an inevitable consequence of aging and may be associated with specific clinical factors.

METHODS

In 5,201 subjects > or = 65 years of age enrolled in the Cardiovascular Health Study, the relation between aortic sclerosis or stenosis identified on echocardiography and clinical risk factors for atherosclerosis was evaluated by using stepwise logistic regression analysis.

RESULTS

Aortic valve sclerosis was present in 26% and aortic valve stenosis in 2% of the entire study cohort; in subjects > or = 75 years of age, sclerosis was present in 37% and stenosis in 2.6%. Independent clinical factors associated with degenerative aortic valve disease included age (twofold increased risk for each 10-year increase in age), male gender (twofold excess risk), present smoking (35% increase in risk) and a history of hypertension (20% increase in risk). Other significant factors included height and high lipoprotein(a) and low density lipoprotein cholesterol levels.

CONCLUSIONS

Clinical factors associated with aortic sclerosis and stenosis can be identified and are similar to risk factors for atherosclerosis.

Alveolar bone turnover in male rats: site- and age-specific changes

BACKGROUND

This study compares alveolar bone turnover adjacent to distally drifting maxillary first molar teeth of rapidly and slowly growing rats.

METHODS

Two groups of forty male rats (1 and 3 months) were sacrificed. Sera were analyzed for acid (AcP), alkaline (AlkP), and tartrate-resistant acid phosphatase (TRAP). Bone histomophometry was done on parasagittal sections of maxillary molars. Molar drift was quantified cephalometrically.

RESULTS

Distal surface contained more osteoclasts and higher osteoclast percents than mesials at both ages (P < 0.001). There were also more osteoclasts on the distals of the older rats as compared to the young (P < 0.001). Osteoblast percents were higher (P < 0.001) in the older rats on both surfaces. Mesials had higher double-labeled surface, MAR and BFR than distals in the younger rats (P < 0.001). The younger rats had higher (P < 0.001) AlkP, AcP, and TRAP. There were no age-specific differences in rate of molar drift. A model of rate of molar drift (P < 0.0015) containing bone formation measures accounts for 54.9% of the variability.

CONCLUSIONS

We conclude that the bone turnover dynamics adjacent to maxillary first molars represent predominantly remodeling on the distal in both groups and modeling on the mesial only in the young rats, that distal molar tooth drift reflects alveolar bone turnover, and that alveolar bone manifests the marked reduction in bone cell activity that occurs in the rat skeleton after 8 weeks but that this reduction is compensated by recruitment or maintenance of more bone cells at these sites.

Determinants of bone mass in the Chinese old-old population

One hundred and eighty-eight elderly men and women were included in a study of bone mass at the neck of femur and its related factors. The study subjects were a subsample of a Hong Kong wide study of the elderly population aged 70 years and above. The study variables included age, sex, body measurements of height, weight, body mass index, dietary calcium intake, grip strength, 16 feet (5 m) gait speed, smoking, drinking, and years since menopause among women. The neck of femur bone mineral density among elderly men was about 1 standard deviation higher than that of women. Subjects aged 85 years and above had about 20% lower bone mineral density at the neck of femur when compared with those in the age group 70-74 years. Mean dietary calcium intake ranged between 300 and 430 mg/day and was not associated with bone mass. Multiple regression analysis showed that body weight, 16 feet gait speed, sex and alcohol consumption explained 46% of the total variance of femoral neck bone mineral density. Body weight was the most significant predictor of bone mineral density, with a partial correlation coefficient of 0.5. The maintenance of body weight within the acceptable weight range and promotion of physical fitness may be important measures in reducing bone loss in the elderly population.