Fracture risk based on HR-pQCT measures does not vary with age in older adults - the bone microarchitecture international consortium (BoMIC) prospective cohort study

Fracture risk increases with lower areal BMD (aBMD); however, aBMD-related estimate of risk may decrease with age. This may depend on technical limitations of 2-dimensional (2D) DXA which are reduced with 3D high-resolution peripheral quantitative computed tomography (HR-pQCT). Our aim was to examine whether the predictive utility of HR-pQCT measures with fracture varies with age. We analyzed associations of HR-pQCT measures at the distal radius and distal tibia with two outcomes: incident fractures and major osteoporotic fractures. We censored follow-up time at first fracture, death, last contact or 8 years after baseline. We estimated hazard ratios (HR) and 95%CI for the association between bone traits and fracture incidence across age quintiles. Among 6835 men and women (ages 40-96) with at least one valid baseline HR-pQCT scan who were followed prospectively for a median of 48.3 months, 681 sustained fractures. After adjustment for confounders, bone parameters at both the radius and tibia were associated with higher fracture risk. The estimated HRs for fracture did not vary significantly across age quintiles for any HR-pQCT parameter measured at either the radius or tibia. In this large cohort, the homogeneity of the associations between the HR-pQCT measures and fracture risk across age groups persisted for all fractures and for major osteoporotic fractures. The patterns were similar regardless of the HR-pQCT measure, the type of fracture, or the statistical models. The stability of the associations between HR-pQCT measures and fracture over a broad age range shows that bone deficits or low volumetric density remain major determinants of fracture risk regardless of age group. The lower risk for fractures across measures of aBMD in older adults in other studies may be related to factors which interfere with DXA but not with HR-pQCT measures.

Quality of life in sarcopenia measured with the SarQoL questionnaire: A meta-analysis of individual patient data

Age-related sarcopenia, resulting from a gradual loss in skeletal muscle mass and strength, is pivotal to the increased prevalence of functional limitation among the older adult community. The purpose of this meta-analysis of individual patient data is to investigate the difference in health-related quality of life between sarcopenic individuals and those without the condition using the Sarcopenia Quality of Life (SarQoL) questionnaire. A protocol was published on PROSPERO. Multiple databases and the grey literature were searched until March 2023 for studies reporting quality of life assessed with the SarQoL for patients with and without sarcopenia. Two researchers conducted the systematic review independently. A two-stage meta-analysis was performed. First, crude (mean difference) and adjusted (beta coefficient) effect sizes were calculated within each database; then, a random effect meta-analysis was applied to pool them. Heterogeneity was measured using the Q-test and I2 value. Subgroup analyses were performed to investigate the source of potential heterogeneity. The strength of evidence of this association was assessed using GRADE. From the 413 studies identified, 32 were eventually included, of which 10 were unpublished data studies. Sarcopenic participants displayed significantly reduced health-related quality of life compared with non-sarcopenic individuals (mean difference = -12.32; 95 % CI = [-15.27; -9.37]). The model revealed significant heterogeneity. Subgroup analyses revealed a substantial impact of regions, clinical settings, and diagnostic criteria on the difference in health-related quality of life between sarcopenic and non-sarcopenic individuals. The level of evidence was moderate. This meta-analysis of individual patient data suggested that sarcopenia is associated with lower health-related quality of life measured with SarQoL.

Prevalence of bone complications in young patients with sickle cell disease presenting low bone mineral density

PURPOSE

Bone fragility in sickle cell disease (SCD) has been previously reported even in young patients, but the clinical consequences and specific management remain unclear. The objective of this study was to assess the prevalence of bone fragility in sickle cell patients and to evaluate the potential risk factors and associated complications.

METHODS

We conducted a single-center cross-sectional study. Bone mineral densitometry (BMD) at the lumbar spine and the hip, Vertebral Fracture Assessment (VFA) and biological measurements were performed in patients aged between 20 and 40 years.

RESULTS

One hundred and thirty-eight patients with sickle cell disease were included between June 2020 and December 2021. One hundred and one patients (73.2 %) were from Sub-Saharan Africa, 13 from North Africa (9.4 %), 11 from the Caribbean (7.9 %), 6 from the Indian Ocean. A Z-score < -2 was found in 43 patients (31.2 %) at the lumbar spine, in 4 patients (3 %) at the total hip, and in 5 patients (3.7 %) at the femoral neck. 59 patients (46.8 %) had vertebral deformities. Fragility fractures were recorded in 9 patients (10.8 %). Patients with low BMD had lower BMI (21.3 (19.0, 24.0) versus 24.0 (20.7, 26.1) Kg/m2, p = 0.003), lower osteonecrosis history (7 % versus 25.3 %, p = 0.011) and lower hemoglobin levels (9.0 (8.0, 10.0) versus 10.0 (9.0, 11.0) g/dL, p < 0.01). No association was found between history of fracture and low BMD.

CONCLUSION

Young patients with SCD commonly have low BMD at the lumbar spine, but the prevalence of fragility fracture was low. Low BMD - specifically at the spine - may not be tantamount to bone fragility.

Dysregulation of MicroRNAs in Adult Osteogenesis Imperfecta: The miROI Study

As epigenetic regulators of gene expression, circulating micro-RiboNucleic Acids (miRNAs) have been described in several bone diseases as potential prognostic markers. The aim of our study was to identify circulating miRNAs potentially associated with the severity of osteogenesis imperfecta (OI) in three steps. We have screened by RNA sequencing for the miRNAs that were differentially expressed in sera of a small group of OI patients versus controls and then conducted a validation phase by RT-qPCR analysis of sera of a larger patient population. In the first phase of miROI, we found 79 miRNAs that were significantly differentially expressed. We therefore selected 19 of them as the most relevant. In the second phase, we were able to validate the significant overexpression of 8 miRNAs in the larger OI group. Finally, we looked for a relationship between the level of variation of the validated miRNAs and the clinical characteristics of OI. We found a significant difference in the expression of two microRNAs in those patients with dentinogenesis imperfecta. After reviewing the literature, we found 6 of the 8 miRNAs already known to have a direct action on bone homeostasis. Furthermore, the use of a miRNA-gene interaction prediction model revealed a 100% probability of interaction between 2 of the 8 confirmed miRNAs and COL1A1 and/or COL1A2. This is the first study to establish the miRNA signature in OI, showing a significant modification of miRNA expression potentially involved in the regulation of genes involved in the physiopathology of OI. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Value of rare diseases reference centers: impact on diagnosis and access to specialized care in fibrous dysplasia of bone

INTRODUCTION

Reference Centers and Rare Disease Health Networks aim to improve the management of patients with rare diseases. The French reference center for Fibrous Dysplasia was certified in 2006.

OBJECTIVE

The objective of our study was to assess the effectiveness of our reference center since its constitution.

METHODS

In a retrospective cohort study, we compared the activity of our center, including the time elapsed between access to the center and the diagnostic delay of patients with Fibrous Dysplasia between two periods, 1994-2006 (before certification) and 2007-2019 (after certification). Data were extracted from patients' records (Easily®). Wilcoxon and Fisher tests were performed, using R®.

RESULTS

Our cohort included 527 patients with Fibrous Dysplasia/Mc Cune Albright syndrome. The activity of the Fibrous Dysplasia center increased from 139 patients in the first period (1994-2006) to an additional 388 patients for the second period (2007-2019). Mean time elapsed to diagnosis of Fibrous Dysplasia was 1.5 years before 2007 and 1.9 years after 2007 (p = 0.12). Diagnosis was made before referral in over 80% of patients. There was a non-significant decrease in the number of patients with delayed diagnosis: 37 patients (44%) in the first period had a diagnostic delay and 94 patients (33%) in the second period (p = 0.07). Patients were referred to our center on average 6.8 years (before 2007) and 7.9 years (after 2007) after their diagnosis (p = 0.77).

CONCLUSION

Healthcare organization with reference centers significantly impacted the management of patients with Fibrous Dysplasia/Mc Cune Albright syndrome, with a substantial increase in the activity of our center, that roughly tripled since certification. This healthcare organization was also associated with a trend toward decreasing diagnostic delay. However, diagnostic delay affected more than a third of patients and the time to access to the center remained extended (≈7-8 years after diagnosis). The current challenge lies in informing primary care providers and patients about education to rare diseases and existence of reference centers for earlier and more effective specialized management.

[Nutrition and age-related macular degeneration]

Age-related macular degeneration (AMD) is the leading cause of vision loss in France and in other industrialized countries. AMD affects around 20 % of the population over the age of 80 years. This complex and multifactorial disease involves both genetic susceptibility and environmental factors. Smoking and nutrition are well-known modifiable risk factors for AMD. Numerous studies provide convincing arguments in favor of micronutrients to encourage dietary advice and the prescription of nutritional supplements containing antioxidant vitamins, lutein and omega-3 fatty acids. Attention to modifiable risk factors is of utmost importance to reduce progression to advanced AMD and associated medical and societal burdens.

A Fracture Risk Assessment Tool for High Resolution Peripheral Quantitative Computed Tomography

Most fracture risk assessment tools use clinical risk factors combined with bone mineral density (BMD) to improve assessment of osteoporosis; however, stratifying fracture risk remains challenging. This study developed a fracture risk assessment tool that uses information about volumetric bone density and three-dimensional structure, obtained using high-resolution peripheral quantitative compute tomography (HR-pQCT), to provide an alternative approach for patient-specific assessment of fracture risk. Using an international prospective cohort of older adults (n = 6802) we developed a tool to predict osteoporotic fracture risk, called μFRAC. The model was constructed using random survival forests, and input predictors included HR-pQCT parameters summarizing BMD and microarchitecture alongside clinical risk factors (sex, age, height, weight, and prior adulthood fracture) and femoral neck areal BMD (FN aBMD). The performance of μFRAC was compared to the Fracture Risk Assessment Tool (FRAX) and a reference model built using FN aBMD and clinical covariates. μFRAC was predictive of osteoporotic fracture (c-index = 0.673, p < 0.001), modestly outperforming FRAX and FN aBMD models (c-index = 0.617 and 0.636, respectively). Removal of FN aBMD and all clinical risk factors, except age, from μFRAC did not significantly impact its performance when estimating 5-year and 10-year fracture risk. The performance of μFRAC improved when only major osteoporotic fractures were considered (c-index = 0.733, p < 0.001). We developed a personalized fracture risk assessment tool based on HR-pQCT that may provide an alternative approach to current clinical methods by leveraging direct measures of bone density and structure. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Spondyloarthritis and Sarcopenia: Prevalence of Probable Sarcopenia and its Impact on Disease Burden: The Saspar Study

To evaluate the prevalence of probable, confirmed, and severe sarcopenia in spondyloarthritis (SpA), according to the European Working Group on Sarcopenia in Older People 2019 (EWGSOP2) definition. A total of 103 patients (51% women) with SpA, mean age 47.1 ± 13.7 years, were included and compared to 103 age- and sex-matched controls. Grip strength was measured by dynamometry. Body composition was assessed by whole-body densitometry. In SpA patients gait speed was measured by the 4-m-distance walk test and quality of life was evaluated with a specific health-related questionnaire for sarcopenia (SaRQoL®). Twenty-two SpA patients (21%) versus 7 controls (7%) had a low grip strength, i.e., probable sarcopenia (p < 0.01), 15 SpA (15%) patients and 7 controls (7%) had low Skeletal Muscle mass Index (SMI) (ns), respectively, and 5 and 2% of SpA patients and controls had low grip strength and low SMI, i.e., confirmed sarcopenia (ns). All the sarcopenic SpA patients had a low gait speed, i.e., severe sarcopenia. Finally, probable sarcopenic SpA patients had significantly higher C-Reactive Protein (CRP, p < 0.001) and Bath Ankylosing Spondylitis Disease Activity Index (BASDAI score, p < 0.01), lower gait speed (p < 0.001), and SarQoL® score (p < 0.001) than SpA patients with normal grip strength. According to EWGSOP2 definition, the prevalence of probable sarcopenia was significantly higher in SpA patients compared to controls. Probable sarcopenia was associated with higher inflammation and disease activity, impaired muscle performance, and quality of life. These results suggest that muscle strength may be a salient hallmark in SpA.

The disability associated with hand osteoarthritis is substantial in a cohort of post-menopausal women: the QUALYOR study

OBJECTIVES

Our primary aims were to assess current prevalence of HOA and the disability associated with this condition, in the group usually most affected, i.e., women older than 55.

METHODS

We performed hand radiographs, clinical examination, grip strength measurement, AUSCAN and COCHIN questionnaires in a cohort of postmenopausal women aged at least 55. Radiographic hand OA (RHOA) was defined as at least 2 affected joints among 30, grading 2 or more using the Kellgren Lawrence score but without any HOA symptom. Symptomatic HOA (OA ACR) was defined according to ACR criteria for hand OA. Moderate to severe symptomatic HOA was defined as having OA ACR and AUSCAN total score of >43/100.

RESULTS

We enrolled 1,189 participants. The mean age was 71.7 years. Inter-reader reliability of radiographs reading was good (ICC = 0.86) and intra-reader reliability was excellent (ICC = 0.97). Among the 1,189 women, 333 (28.0%) had RHOA, 482 (40.5%) patients fulfilled the ACR criteria for symptomatic HOA and 82 of these (17% of OA ACR population) had moderate to severe symptomatic HOA. The prevalence of symptomatic erosive osteoarthritis was 11.8%. Mean AUSCAN and Cochin scores were higher and grip strength lower in patients with symptomatic HOA compared to patient without HOA. Differences were more noticeable in patients with moderate to severe HOA.

CONCLUSIONS

We have assessed disability associated with HOA in greater detail than previously and found that a third of postmenopausal women had RHOA, two fifths had symptomatic HOA and one sixth of symptomatic patients had moderate to severe HOA related disability and a tenth had symptomatic erosive osteoarthritis, representing a substantial burden of disease in our population-based cohort.

Bone Microarchitecture Phenotypes Identified in Older Adults Are Associated With Different Levels of Osteoporotic Fracture Risk

Prevalence of osteoporosis is more than 50% in older adults, yet current clinical methods for diagnosis that rely on areal bone mineral density (aBMD) fail to detect most individuals who have a fragility fracture. Bone fragility can manifest in different forms, and a "one-size-fits-all" approach to diagnosis and management of osteoporosis may not be suitable. High-resolution peripheral quantitative computed tomography (HR-pQCT) provides additive information by capturing information about volumetric density and microarchitecture, but interpretation is challenging because of the complex interactions between the numerous properties measured. In this study, we propose that there are common combinations of bone properties, referred to as phenotypes, that are predisposed to different levels of fracture risk. Using HR-pQCT data from a multinational cohort (n = 5873, 71% female) between 40 and 96 years of age, we employed fuzzy c-means clustering, an unsupervised machine-learning method, to identify phenotypes of bone microarchitecture. Three clusters were identified, and using partial correlation analysis of HR-pQCT parameters, we characterized the clusters as low density, low volume, and healthy bone phenotypes. Most males were associated with the healthy bone phenotype, whereas females were more often associated with the low volume or low density bone phenotypes. Each phenotype had a significantly different cumulative hazard of major osteoporotic fracture (MOF) and of any incident osteoporotic fracture (p < 0.05). After adjustment for covariates (cohort, sex, and age), the low density followed by the low volume phenotype had the highest association with MOF (hazard ratio = 2.96 and 2.35, respectively), and significant associations were maintained when additionally adjusted for femoral neck aBMD (hazard ratio = 1.69 and 1.90, respectively). Further, within each phenotype, different imaging biomarkers of fracture were identified. These findings suggest that osteoporotic fracture risk is associated with bone phenotypes that capture key features of bone deterioration that are not distinguishable by aBMD. © 2021 American Society for Bone and Mineral Research (ASBMR).

A Signature of Circulating miRNAs Associated With Fibrous Dysplasia of Bone: the mirDys Study

Fibrous dysplasia (FD) is a rare bone disease caused by activating mutations of GNAS encoding the Gsα protein, enhancing cyclic adenosine monophosphate (cAMP) production by overstimulation of adenylyl cyclase and impairing osteoblastic differentiation. The clinical presentation ranges from asymptomatic to polyostotic forms with severe disability, explained by the mosaic distribution of the GNAS mutation. Physicians have to deal with the gap of knowledge in FD pathogenesis, the absence of prognostic markers and the lack of specific treatment. The identification of specific biomarkers for FD is an important step to improve the clinical and therapeutic approaches. An epigenetic regulation driven by microRNAs (miRNAs), known as promising biomarkers in bone disease, could be involved in FD. We have sought circulating miRNAs that are differentially expressed in FD patients compared to controls and would reflect dysregulations of osteogenesis-related genes and bone disorder. The global miRNA profiling was performed using Next Generation Sequencing in patient serum collected from a discovery cohort of 20 patients (10 polyostotic and 10 monostotic) and 10 controls. From these, we selected 19 miRNAs for a miRNA validation phase from serum of 82 patients and 82 controls, using real-time qPCR. Discovery screening identified 111 miRNAs differentially expressed in patient serum, after adjusting for the false discovery rate (FDR). Among the 82 patients, 55% were polyostotic, and 73% were women with a mean age of 42 years. Six miRNAs (miR-25-3p, miR-93-5p, miR-182-5p, miR-324-5p, miR-363-3p, and miR-451a) were significantly overexpressed in serum, with FDR <0.05. The expression level of these six miRNAs was not associated with the FD severity. In conclusion, we identified a signature of circulating miRNAs associated with FD. These miRNAs are potential negative regulators of gene expression in bone cell progenitors, suggesting their activity in FD by interfering with osteoblastic and osteoclastic differentiation to impair bone mineralization and remodeling processes. © 2020 American Society for Bone and Mineral Research.

Genetic testing is useful in adults with limited phenotypes of genetic skeletal conditions

We show the value of genetic screening in 3 adults with limited phenotypes of three bone sclerosing genetic disease (GD): osteopetrosis (OPT), Camurati-Engelmann disease (CED) and pycnodysostosis.

INTRODUCTION

OPT, CED and pycnodysostosis are three rare bone diseases often diagnosed in childhood. However, some atypical phenotypes raise the problem of delayed diagnosis in adults. Genetic tests may then be useful to establish a formal diagnosis.

METHODS

We report 3 cases of adult patients with symptomatic or asymptomatic bone sclerosing lesions for whom the clinical, radiological and biological explorations were atypical and did not allow a formal diagnosis. These unusual descriptions led to the search for genetic mutations.

RESULTS

These 3 cases of limited phenotypes were associated with unknown or poorly described variants of 3 rare bone genetic diseases.

CONCLUSIONS

Genetic tests proved useful to establish the diagnosis and manage the condition of adults with rare bone sclerosing GD.

Interventions to improve osteoporosis care: a systematic review and meta-analysis

Osteoporosis (OP) is a major public health concern, but still OP care does not meet guidelines. Interventions have been developed to improve appropriate OP management. The objective of the present study was to systematically review the current literature to ascertain the efficacy of interventions to improve OP care and characterize interventions taking into account elements related to their potential cost and feasibility. Studies published from 2003 to 2018 were retrieved from PubMed/MEDLINE, Science Direct, Web of Science, Cochrane, and Wiley Online Library databases. Screening of references and quality assessment were independently performed by two reviewers. We classified interventions into three types according to the target of the intervention: health system (structural interventions), healthcare professional (HCP), and patient. Meta-analysis was performed by type of intervention and their effect on two outcomes: prescription of BMD measurement and prescription of OP therapy. A total of 4268 records were screened; 32 studies were included in the qualitative analysis and 29 studies in the quantitative analysis. Structural interventions strongly and significantly improved prescription of BMD measurement (OR = 9.99, 95% CI 2.05; 48.59) and treatment prescription (OR = 3.82, 95% CI 2.16; 6.75). The impact of HCP-centered interventions on BMD measurement prescription did not reach statistical significance (OR = 2.19, 95% CI 0.84; 5.73) but significantly improved treatment prescription (OR = 3.82, 95% CI 2.16; 6.75). Interventions involving patients significantly improved the prescription of BMD measurement (OR = 2.16, 95% CI 1.62; 2.89) and treatment prescription (OR = 1.70, 95% CI 1.35; 2.14). Interventions to improve OP management had a significant positive impact on prescription of BMD measurement but a more limited impact on treatment prescription.

Serum periostin levels and severity of fibrous dysplasia of bone

Fibrous dysplasia of bone (FD) is a rare congenital bone disease, characterized by a fibrous component in the bone marrow. Periostin has been extensively researched because of its implication in various fibrotic or inflammatory diseases. Periostin may be associated with the burden or the severity of FD. The case control PERIOSDYS study aimed at assessing serum periostin levels in FD patients. Sixty four patients with monostotic or polyostotic disease were included, in order to evaluate whether the concentrations were greater in patients than in 128 healthy age, BMI and sex-matched controls and if they were more elevated in patients with the more severe phenotypes. We found that periostin levels were greater in patients with FD compared to controls (mean = 1085 vs 958 pmol/l, p = 0.026), especially in those with a history of fracture (mean = 1475 vs 966 pmol/l, p = 0.0005), polyostotic forms (mean = 1214 vs 955 pmol/l, p = 0.004) or McCune-Albright syndrome (mean = 1585 vs 1023 pmol/l, p = 0.0048). In contrast, high pain levels were not associated with periostin levels (mean = 1137 vs 1036 pmol/l, p = 0.445). Furthermore, patients undergoing bisphosphonate therapy had significantly lower levels than treatment naïve patients (mean = 953 vs 1370 pmol/l, p = 0.002). In conclusion, periostin may be a biochemical marker indicative of the most severe forms of FD and could be used to monitor patients treated with bisphosphonates.

Osteoporosis prevention: where are the barriers to improvement in a French general population? A qualitative study

We conducted a qualitative study with French men and women in order to provide insight into individuals' experiences, behaviors, and perceptions about osteoporosis (OP) and OP care. The data showed that both sexes, but especially men, were unfamiliar with OP, did not always feel concerned, and mistrusted pharmacological treatments.

INTRODUCTION

To engage actively in osteoporosis (OP) prevention, people need to have basic knowledge about the disease. The aim of this qualitative study was to explore knowledge and representations of OP care and prevention among both men and women.

METHODS

Focus groups were conducted in the Rhône-Alpes Region, France, with women aged 50-85 years and men aged 60-85 years, with or without a history of fragility fracture and/or an OP diagnosis (respectively referred to as "aware" or "unaware"). A total of 45 women (23 "aware" and 22 "unaware" in 5 and 4 focus groups, respectively) and 53 men (19 "aware" and 34 "unaware" in 3 and 4 focus groups, respectively) were included. A thematic analysis of transcripts was performed to explore knowledge and representations about OP, risk factors, prevention, and treatment.

RESULTS

The data showed that both sexes, but especially men, had limited knowledge of OP and considered it as a natural aging process not related to fragility fractures. They generally did not feel concerned by OP and no important difference was observed between "aware" and "unaware" patients. Women expressed their fear of the disease, associated with aging and the end of life, while men considered it to be a women's disease only. Both sexes were aware of OP risk factors, but were suspicious towards treatments because of the associated side effects.

CONCLUSION

Understanding people's representation of OP might help to provide patients with relevant information in order to optimize their preventive behavior and decrease the burden of the disease.

Cortical and trabecular bone microarchitecture as an independent predictor of incident fracture risk in older women and men in the Bone Microarchitecture International Consortium (BoMIC): a prospective study

BACKGROUND

Although areal bone mineral density (aBMD) assessed by dual-energy x-ray absorptiometry (DXA) is the clinical standard for determining fracture risk, most older adults who sustain a fracture have T scores greater than -2·5 and thus do not meet the clinical criteria for osteoporosis. Importantly, bone fragility is due to low BMD and deterioration in bone structure. We assessed whether indices of high-resolution peripheral quantitative CT (HR-pQCT) were associated with fracture risk independently of femoral neck aBMD and the Fracture Risk Assessment Tool (FRAX) score.

METHODS

We assessed participants in eight cohorts from the USA (Framingham, Mayo Clinic), France (QUALYOR, STRAMBO, OFELY), Switzerland (GERICO), Canada (CaMos), and Sweden (MrOS). We used Cox proportional hazard ratios (HRs) to estimate the association between HR-pQCT bone indices (per 1 SD of deficit) and incident fracture, adjusting for age, sex, height, weight, and cohort, and then additionally for femoral neck DXA aBMD or FRAX.

FINDINGS

7254 individuals (66% women and 34% men) were assessed. Mean baseline age was 69 years (SD 9, range 40-96). Over a mean follow-up of 4·63 years (SD 2·41) years, 765 (11%) participants had incident fractures, of whom 633 (86%) had femoral neck T scores greater than -2·5. After adjustment for age, sex, cohort, height, and weight, peripheral skeleton failure load had the greatest association with risk of fracture: tibia HR 2·40 (95% CI 1·98-2·91) and radius 2·13 (1·77-2·56) per 1 SD decrease. HRs for other bone indices ranged from 1·12 (95% CI 1·03-1·23) per 1 SD increase in tibia cortical porosity to 1·58 (1·45-1·72) per 1 SD decrease in radius trabecular volumetric bone density. After further adjustment for femoral neck aBMD or FRAX score, the associations were reduced but remained significant for most bone parameters. A model including cortical volumetric bone density, trabecular number, and trabecular thickness at the distal radius and a model including these indices plus cortical area at the tibia were the best predictors of fracture.

INTERPRETATION

HR-pQCT indices and failure load improved prediction of fracture beyond femoral neck aBMD or FRAX scores alone. Our findings from a large international cohort of men and women support previous reports that deficits in trabecular and cortical bone density and structure independently contribute to fracture risk. These measurements and morphological assessment of the peripheral skeleton might improve identification of people at the highest risk of fracture.

FUNDING

National Institutes of Health National Institute of Arthritis Musculoskeletal and Skin Diseases.

The QUALYOR (QUalité Osseuse LYon Orléans) study: a new cohort for non invasive evaluation of bone quality in postmenopausal osteoporosis. Rationale and study design

The diagnostic performance of densitometry is inadequate. New techniques of non-invasive evaluation of bone quality may improve fracture risk prediction. Testing the value of these techniques is the goal of the QUALYOR cohort.

INTRODUCTION

The bone mineral density (BMD) of postmenopausal women who sustain osteoporotic fracture is generally above the World Health Organization definition for osteoporosis. Therefore, new approaches to improve the detection of women at high risk for fracture are warranted.

METHODS

We have designed and recruited a new cohort to assess the predictive value of several techniques to assess bone quality, including high-resolution peripheral quantitative computerized tomography (HRpQCT), hip QCT, calcaneus texture analysis, and biochemical markers. We have enrolled 1575 postmenopausal women, aged at least 50, with an areal BMD femoral neck or lumbar spine T-score between - 1.0 and - 3.0. Clinical risk factors for fracture have been collected along with serum and blood samples.

RESULTS

We describe the design of the QUALYOR study. Among these 1575 women, 80% were aged at least 60. The mean femoral neck T-score was - 1.6 and the mean lumbar spine T-score was -1.2. This cohort is currently being followed up.

CONCLUSIONS

QUALYOR will provide important information on the relationship between bone quality variables and fracture risk in women with moderately decreased BMD.

Post-fracture care: do we need to educate patients rather than doctors? The PREVOST randomized controlled trial

We conducted a multicenter, randomized controlled trial to evaluate the impact of a population-based patient-centered post-fracture care program with a dedicated case manager, PREVention of OSTeoporosis (PREVOST), on appropriate post-fracture osteoporosis management. We showed that, compared to usual care, BMD investigation post-fracture was significantly improved (+20%) by our intervention program.

INTRODUCTION

Our study aims to evaluate the impact of a population-based patient-centered post-fracture care program, PREVOST, on appropriate post-fracture care.

METHODS

Multicenter, randomized controlled trial enrolling 436 women aged 50 to 85 years and attending a French hospital, for a low-energy fracture of the wrist or humerus. Randomization was stratified by age, hospital department, and site of fracture. The intervention was performed by a trained case manager who interacted only with the patients, with repeated oral and written information about fragility fractures and osteoporosis management, and prompting them to visit their primary care physicians. Control group received usual care. The primary outcome was the initiation of an appropriate post-fracture care defined by Bone Mineral Density (BMD) and/or anti-osteoporotic treatment prescription at 6 months.

RESULTS

At 6 months, 53% of women in intervention group initiated a post-fracture care versus 33% for usual care (adjOR 2.35, 95%CI [1.58-3.50], p < 0.001). Post-fracture care was more frequent after wrist than humerus fracture (adjOR 1.93, 95%CI [1.14-3.30], p = 0.015) and decreased with age (adjOR for 10 years increase 0.76, 95%CI [0.61-0.96], p = 0.02). The intervention resulted in BMD prescription in 50% of patients (adjOR 2.10, 95%CI [1.41-3.11], p < 0.001) and in BMD performance in 41% of patients (adjOR 2.12, 95%CI [1.40-3.20], p < 0.001) versus 33 and 25% for usual care, respectively. Having performed a BMD increased treatment prescription; however, only 46% of women with a low BMD requiring a treatment according to the French guidelines received a prescription.

CONCLUSION

A patient-centered care program with a dedicated case manager can significantly improve post-fracture BMD investigation.

Periostin and transforming growth factor β-induced protein (TGFβIp) are both expressed by osteoblasts and osteoclasts

Periostin (Postn) and transforming growth factor β-induced protein (TGFβIp) are two closely related extracellular matrix (ECM) proteins predominantly distributed in collagen-rich connective tissues submitted to mechanical strain, including bone and more specifically the periosteum. We have investigated the expression of Postn and TGFβIp mRNA by primary osteoblasts isolated from mouse periosteum and calvaria, or by the osteoblast-like MC3T3-E1 cell line, and by osteoclasts from mouse long bones differentiated in vitro. Secretion of Postn was measured with a specific ELISA. Postn and TGFβIp mRNA were concomitantly expressed in all three osteoblast models all along the differentiation process in a time-dependent manner. Both Postn and TGFβIp transcripts appeared early in osteoblast differentiation, and their expression increased 3-10 times in mature osteoblast cells. Expression decreased after differentiation was achieved and when the cultures mineralised. ELISA for secreted Postn showed a similar pattern. When MC3T3-E1 cells were treated with TGF-β, Postn and TGFβIp mRNA expression and secretion were stimulated, whereas 1.25(OH)(2)D(3) had no detectable effect. Osteoclasts also expressed both Postn and TGFβIp during in vitro differentiation. Expression of both Postn and TGFβIp peaks in the early phases of osteoblast differentiation, and decreases later at the start of mineralisation. A novel finding is that Postn and TGFβIp are expressed by osteoclasts in vitro. Therefore Postn and TGFβIp proteins are potential biomarkers of early osteoblast differentiation and new bone formation.

The multiple facets of periostin in bone metabolism

Periostin is a matricellular glutamate-containing protein expressed during ontogenesis and in adult connective tissues submitted to mechanical strains including bone and, more specifically, the periosteum, periodontal ligaments, tendons, heart valves, or skin. It is also expressed in neoplastic tissues, cardiovascular and fibrotic diseases, and during wound repair. Its biological functions are extensively investigated in fields such as cardiovascular physiology or oncology. Despite its initial identification in bone, investigations of periostin functions in bone-related physiopathology are less abundant. Recently, several studies have analyzed the potential role of periostin in bone biology and suggest that periostin may be an important regulator of bone formation. The aim of this article is to provide an extensive review on the implications of periostin in bone biology and its potential use in benign and metabolic bone diseases.

[Spontaneous spinal epidural haematoma during pregnancy]

Spontaneous spinal epidural haematomas are quite rare. We report here the case of a 27-year-old woman, without previous history of relevant medical disorder, who presented with acute paraplegia at 36 weeks of gestation. MRI performed in emergency revealed a T8 epidural haematoma. The management consisted in an emergency Caesarean section under general anaesthesia, followed immediately by a T8 laminectomy allowing the spinal cord decompression 14 hours after the first symptoms. Neurologic recovery was rapid and complete, except for bladder dysfunction persisting one month later. Spontaneous spinal epidural haematomas require a prompt diagnosis because neurologic prognosis essentially depends on the interval of time between onset of symptoms and surgical decompression. Obstetrical management especially depends on the term of pregnancy. For the anaesthesiologist, the difficulty is the management of both pregnant condition (full stomach general anaesthesia) and spinal cord compression (maintenance of spinal cord perfusion pression and limitation of ischaemia and oedema).

Non-enzymatic glycation of bone collagen modifies osteoclastic activity and differentiation

Type I collagen, the major organic component of bone matrix, undergoes a series of post-translational modifications that occur with aging, such as the non-enzymatic glycation. This spontaneous reaction leads to the formation of advanced glycation end products (AGEs), which accumulate in bone tissue and affect its structural and mechanical properties. We have investigated the role of matrix AGEs on bone resorption mediated by mature osteoclasts and the effects of exogenous AGEs on osteoclastogenesis. Using in vitro resorption assays performed on control- and AGE-modified bone and ivory slices, we showed that the resorption process was markedly inhibited when mature osteoclasts were seeded on slices containing matrix pentosidine, a well characterized AGE. More specifically, the total area resorbed per slice, and the area degraded per resorption lacuna created by osteoclasts, were significantly decreased in AGE-containing slices. This inhibition of bone resorption was confirmed by a marked reduction of the release of type I collagen fragments generated by the collagenolytic enzymes secreted by osteoclasts in the culture medium of AGE-modified mineralized matrices. This effect is likely to result from decreased solubility of collagen molecules in the presence of AGEs, as documented by the reduction of pepsin-mediated digestion of AGE-containing collagen. We found that AGE-modified BSA totally inhibited osteoclastogenesis in vitro, most likely by impairing the commitment of osteoclast progenitors into pre-osteoclastic cells. Although the mechanisms remain unknown, AGEs might interfere with osteoclastic differentiation and activity through their interaction with specific cell-surface receptors, because we showed that both osteoclast progenitors and mature osteoclasts expressed different AGEs receptors, including receptor for AGEs (RAGEs). These results suggest that AGEs decreased osteoclast-induced bone resorption, by altering not only the structural integrity of bone matrix proteins but also the osteoclastic differentiation process. We suggest that AGEs may play a role in the alterations of bone remodeling associated with aging and diabetes.

Expression of Semaphorin-3A and its receptors in endochondral ossification: potential role in skeletal development and innervation

Bone tissue is densely innervated, and there is increasing evidence for a neural control of bone metabolism. Semaphorin-3A is a very important regulator of neuronal targeting in the peripheral nervous system as well as in angiogenesis, and knockout of the Semaphorin-3A gene induces abnormal bone and cartilage development. We analyzed the spatial and temporal expression patterns of Semaphorin-3A signaling molecules during endochondral ossification, in parallel with the establishment of innervation. We show that osteoblasts and chondrocytes differentiated in vitro express most members of the Semaphorin-3A signaling system (Semaphorin-3A, Neuropilin-1, and Plexins-A1 and -A2). In vitro, osteoclasts express most receptor chains but not the ligand. In situ, these molecules are all expressed in the periosteum and by resting, prehypertrophic and hypertrophic chondrocytes in ossification centers before the onset of neurovascular invasion. They are detected later in osteoblasts and also osteoclasts, with differences in intensity and regional distribution. Semaphorin-3A and Neuropilin-1 are also expressed in the bone marrow. Plexin-A3 is not expressed by bone cell lineages in vitro. It is detected early in the periosteum and hypertrophic chondrocytes. After the onset of ossification, this chain is restricted to a network of cell processes in close vicinity to the cells lining the trabeculae, similar to the pattern observed for neural markers at the same stages. After birth, while the density of innervation decreases, Plexin-A3 is strongly expressed by blood vessels on the ossification front. In conclusion, Semaphorin-3A signaling is present in bone and seems to precede or coincide at the temporal but also spatial level with the invasion of bone by blood vessels and nerve fibers. Expression patterns suggest Plexin-A3/Neuropilin-1 as a candidate receptor in target cells for the regulation of bone innervation by Semaphorin-3A.

NMDA glutamate receptors are expressed by osteoclast precursors and involved in the regulation of osteoclastogenesis

We previously identified functional N-methyl-D-aspartate (NMDA) glutamate receptors in mature osteoclasts and demonstrated that they are involved in bone resorption in vitro. In the present work, we studied the expression of NMDA receptors (NMDAR) by osteoclast precursors and their role in osteoclastogenesis using two in vitro models, the murine myelomonocytic RAW 264.7 cell line and mouse bone marrow cells, both of which differentiate into osteoclasts in the presence of macrophage colony-stimulating factor (M-CSF) and Rank ligand (RankL). Using RT-PCR analysis with specific probes, we showed that RAW 264.7 cells and mouse bone marrow cells express mRNA of NMDAR subunits NMDA receptor 1 (NR1) and NMDA receptor 2 (NR2) A, B, and D. These subunits are expressed all along the differentiation sequence from undifferentiated precursors to mature resorbing osteoclasts. Semi-quantitative PCR analysis showed no regulation of the expression of these subunits during the differentiation process. Two specific non competitive antagonists of NMDAR, MK801 and DEP, dose-dependently inhibited osteoclast formation in both models, indicating that osteoclastogenesis requires the activation of NMDAR expressed by osteoclast precursors. MK801 had no effect when added only during the first 2 days of culture, suggesting that NMDAR are rather involved in the late stages of osteoclast formation. Finally, we demonstrated using Western-blotting and immunofluorescence that activation of NMDAR in RAW 264.7 cells by specific agonists induces nuclear translocation of NF-kappa B, a factor required for osteoclast formation. Altogether, our results indicate that osteoclast precursors express NMDAR that are involved in the osteoclast differentiation process through activation of the NF-kappa B pathway.

Molecular identification of NMDA glutamate receptors expressed in bone cells

The N-methyl-D-aspartate (NMDA) subtype of the glutamate receptor has recently been identified in bone, but the molecular composition of this receptor expressed by bone cells is unknown. NMDA receptor (NMDAR) is a hetero-oligomeric protein composed of two classes of subunits, the essential subunit NR1 and NR2A to D subunits that do not by themselves produce functional channels but potentiate NR1 activity and confer functional variability to the receptor. These subunits coassemble in different combinations to form functionally distinct NMDAR. In this study, we have investigated the molecular composition of NMDAR expressed by osteoblasts and osteoclasts in culture, using RT-PCR analysis, in situ hybridization and immunocytochemistry. Specific probes were designed for the different subunits of the NMDAR, and we showed by RT-PCR analysis that mammalian osteoclasts expressed NR2B and NR2D subunits mRNAs but not NR2A and NR2C mRNAs. Rat calvaria and MG63 osteoblastic cells also expressed several NR2 subunits mRNAs, namely NR2A, NR2B, and NR2D. In situ hybridization on isolated rabbit osteoclasts and MG63 cells has confirmed the localization of NR1, NR2B, and NR2D transcripts in osteoclasts and NR1, NR2A, NR2B, and NR2D transcripts in MG63 cells. The expression of NR2D protein by bone cells was shown by immunofluorescence. These results demonstrate for the first time that osteoblasts and osteoclasts express several NR2 subunits, suggesting a molecular diversity of NMDAR channels similar to what was shown for brain. The presence of distinct functional NMDAR on bone cells may be associated with various states of bone cell differentiation and function.

Decorin inhibits cell migration through a process requiring its glycosaminoglycan side chain

Several studies overwhelmingly support the notion that decorin (DCN) is involved in matrix assembly, and in the control of cell adhesion and proliferation. However, nothing is known about the role of DCN during cell migration. Cell migration is a tightly regulated process which requires both adhesion (at the leading edge of the cell) and de-adhesion (at the trailing edge of the cell) from the substratum. We have determined in this study the effect of DCN on MG-63 osteosarcoma cell migration and have analyzed whether its effect is mediated by the protein core and/or the glycosaminoglycan side chain. DCN impeded the migration-promoting effect of matrix molecules (fibronectin, collagen type I) known to interact with the proteoglycan. Conversely, DCN did not counteract the migration-promoting effect of fibrinogen lacking proteoglycan affinity. DCN bearing dermatan-sulfate chains (i.e., skin and cartilage DCN) was about 20-fold more effective in inhibiting cell migration than DCN bearing chondroitin-sulfate chains (i.e., bone DCN). In addition, chondroitinase AC-treatment of cartilage DCN (which specifically removes chondroitin-sulfate chains) did not attenuate the inhibitory effect of this proteoglycan, while cartilage DCN deprived of both chondroitin- and dermatan-sulfate chains failed to alter cell migration promoted by either fibronectin or its heparin- and cell-binding domains. These data assert that the dermatan-sulfate chains of DCN are responsible for a negative influence on cell migration. However, isolated glycosaminoglycans failed to alter cell migration promoted by fibronectin, indicating that strongly negatively charged glycosaminoglycans alone cannot account for the impaired cell motility seen with DCN. Overall, these results show that the inhibitory action of DCN is dependent of substratum binding, is differentially mediated by its glycosaminoglycan side chains (chondroitin-sulfate vs. dermatan-sulfate chains), and is independent of a steric hindrance effect exerted by its glycosaminoglycan side chains.

Decorin inhibits cell attachment to thrombospondin-1 by binding to a KKTR-dependent cell adhesive site present within the N-terminal domain of thrombospondin-1

Skin decorin (DCN) is an antiadhesive dermatan sulfate-rich proteoglycan that interacts with thrombospondin-1 (TSP) and inhibits fibroblast adhesion to TSP [Winnemöller et al., 1992]. Molecular mechanisms by which DCN interacts with TSP and inhibits cell adhesion to TSP are unknown. In the present study, we showed that skin DCN and bone DCN (chondroitin sulfate-rich proteoglycan) were quantitatively identical with respect to their ability to interact with TSP. Using a series of fusion proteins corresponding to the different structural domains of TSP, binding of [125I]DCN to TSP was found to be dependent of the N-terminal domain and, to a lesser extent, of the type 1 repeats and the C-terminal domain of TSP. In addition, heparan sulfate drastically inhibited [125I]DCN binding to solid-phase adsorbed TSP (80% inhibition), suggesting that DCN could bind to the N-terminal domain of TSP through interaction with heparin-binding sequences. To address this question, a series of synthetic peptides, overlapping heparin-binding sequences ARKGSGRR (residues 22-29), KKTR (residues 80-83) and RLRIAKGGVNDN (residues 178-189), were synthesized and tested for their ability to interact with DCN. [125I]DCN interacted only with peptides VDAVRTEKGFLLLASLRQMKKTRGT and KKTRGTLLALERKDHS containing the heparin-binding consensus sequence KKTR. These peptides contained glycosaminoglycan-dependent and -independent binding sites because [125I]DCN binding to VDAVRTEKGFLLLASLRQMKKTRGT and KKTRGTLLALERKDHS was partially reduced upon removal of the glycosaminoglycan chain (65% and 46% inhibition, respectively). [125I]DCN poorly bound to subpeptide MKKTRG and did not bind at all to subpeptides VDAVRTEKGFLLLASLRQ and TLLALERKDHS, suggesting that heparin-binding sequence MKKTRG constituted a DCN binding site when flanked with peptides VDAVRTEKGFLLLASLRQ and TLLALERKDHS. The sequence VDAVRTEKGFLLLASLRQMKKTRGTLLALERKDHS constitutes a cell adhesive active site in the N-terminal domain of TSP [Clezardin et al., 1997], and DCN inhibited the attachment of fibroblastic and osteoblastic cells to peptides VDAVRTEKGFLLLASLRQMKKTRGT and KKTRGTLLALERKDHS by about 50 and 80%, respectively. Although fibroblastic cells also attached to type 3 repeats and the C-terminal domain of TSP, DCN only inhibited cell attachment to the C-terminal domain. Overall, these data indicate that modulation by steric exclusion of cell adhesion to a KKTR-dependent cell adhesive site present within the N-terminal domain of TSP could explain the antiadhesive properties of DCN.

Normal carboxylation of circulating osteocalcin (bone Gla-protein) in Paget's disease of bone

Serum osteocalcin (bone Gla-protein), a specific marker of osteoblastic activity, is only moderately increased in patients with active Paget's disease of bone, despite biochemical evidence of increased bone turnover. Because pagetic bone has an abnormal texture, such a discrepancy could be due to an abnormal carboxylation of osteocalcin. To test this hypothesis, we measured the fraction of decarboxylated osteocalcin in the serum of 11 patients with active Paget's disease of bone by the hydroxyapatite binding technique and the data were compared to those obtained in 10 controls and in 10 patients on vitamin K antagonist therapy. In contrast to the decreased decarboxylated fraction of osteocalcin in warfarin-treated patients (27 +/- 2.2%, P less than 0.01 vs controls), the fraction of decarboxylated osteocalcin was normal in pagetic patients (8.9 +/- 2.2% vs 6.5 +/- 1.7% in controls, n.s.). These data suggest that there is no abnormality of the osteocalcin carboxylation in Paget's disease. The disproportionate levels of circulating osteocalcin compared to the marked elevation of alkaline phosphatase in that disease could be due to other factors such as an increased binding of the protein to the woven bone matrix.

Serum bone-gla protein after fracture

Serum bone Gamma-carboxyglutamic acid (bone-gla) protein (BGP), a marker of bone formation, was measured in serial blood samples drawn from 14 patients who had fractured at least one of their tibial or femoral diaphyses and from two other patients who had sustained major trauma without fracture but who had been immobilized. A total of 85 samples were taken and analyzed during the first three months after the fractures occurred. Serum BGP significantly increased and positively correlated with the time that had elapsed after the fracture, with an average twofold increase after two months. The fracture site and the duration of immobilization had no influence on the serum BGP levels. Serum BGP levels from the two non-fractured cases increased in the first two weeks with no subsequent consistent trend. These data suggest that serum BGP increases one to two months after a major fracture, possibly as a manifestation of bone repair. Further studies are required to determine the potential clinical value of serum BGP in the management of such patients.

Influence of experimental conditions on osteoblast activity in human primary bone cell cultures

Primary bone cell cultures were derived from human bone explants. Cellular activity was characterized by the alkaline phosphatase (AP) activity, osteocalcin, and type I and III collagen secretions in the supernatant. The determination of bone cell activity was performed in three different wells. No significant difference was noted between wells: the coefficient of variation was 8.0 +/- 2.9% for AP activity, 18.3 +/- 1.9% for osteocalcin secretion, and 22.5 +/- 14.3% for collagen. The AP activity and osteocalcin secretion significantly decreased with the number of passages: they were the highest after the first passage. Between each subject, the coefficient of variation was 85% for AP activity and osteocalcin secretion and 63 and 57% for type I and III collagen secretion, respectively. The AP activity did not differ with the age or sex of the donor. In contrast, osteocalcin secretion was significantly lower in females than in males. In males, osteocalcin significantly decreased with the age of the donor (r = -0.61; p less than 0.05). Cellular activity did not depend on the site of the biopsy. When bone explants from one donor were cultured in two different petri dishes, the activity of cells was similar in both dishes, except in one case. Primary cell cultures derived from human bone explants are the only model providing untransformed osteoblastlike cells of human origin. Because of the experimental conditions, some factors may have influenced the cellular activity and they must be taken into account to validate further in vitro studies.

Specific radioimmunoassay for ovine bone gla-protein (osteocalcin)

We developed a sensitive and specific radioimmunoassay for ovine bone gla-protein (osteocalcin) using a polyclonal rabbit antibody raised against ovine bone gla-protein. Bone from lambs was extracted in 0.5 mol/l EDTA and desalted on Sephadex G-25. Bone gla-protein was purified by gel filtration chromatography over Sephadex G-100 and ion-exchange chromatography on DEAE-Sephadex A-25. The protein, subjected to monodimensional electrophoresis migrated as a single spot in SDS PAGE with the same apparent molecular weight of 12 kD as bovine bone gla-protein. The amino acid composition of purified bone gla-protein was in agreement with a previous publication. The competitive RIA uses 125I-labelled bone gla-protein as a tracer and a complex of a second antibody and polyethylene glycol to separate free and antibody-bound 125I-labelled bone gla-protein. The intra- and inter-assay variations are less than 6 and 10%, respectively. There is no reactivity of our antisera with dog sera. The cross-reactivity is only partial with calf and human sera and complete with ovine sera. We measured bone gla-protein levels in serum of 96 normal male sheep of different ages. Serum bone gla-protein rapidly and significantly (P less than 0.001) decreased from 535 +/- 169 microgram/l at birth, to 240 +/- 43 microgram/l at 45 days, 152 +/- 44 micrograms/l at 90 days, and 5.9 +/- 0.7 microgram/l at 7 years of age.(ABSTRACT TRUNCATED AT 250 WORDS)

Circadian rhythms (temperature, heart rate, vigilance, mood) of short and long sleepers: effects of sleep deprivation

Seven long sleepers (LS) (sleep greater than or equal to 9 h) and seven short sleepers (SS) (sleep less than or equal to 7 h), aged 20 to 23 years, were selected among medical students. They measured their axillary temperature (T), heart rate (HR) and self-estimated their vigilance (V) and mood (M) every 4 h from awakening to bed time during a ten-day control span and during the two sleep deprived nights. Polygraphic sleep recordings were performed on 3 control days and recovery from 24 h (day sleep) or 36 h (night sleep) sleep deprivations. For the 4 variables (T, HR, V and M), group circadian patterns were analyzed by means of the cosinor method for the control span and after both types of sleep deprivation. The acrophases of the 4 variables clustered more in LS than in SS. The acrophases of V and M were found to be more closely related to the sleep/wake rhythm than those of T and HR. Sleep deprivation resulted in a large change of the circadian rhythms in LS but had little effect in SS as indicated by the non detection of most acrophases in LS and the persistence of such acrophases in SS. This difference might be explained by the large interindividual variability of changes induced by the sleep deprivation in LS. Moreover, day sleep recovery was more disturbed in LS than in SS.

Diurnal rhythm of axillary temperature in long and short sleepers: effects of sleep deprivation and sleep displacement

Six habitual long (greater than or equal to 9 hr) sleepers (LS) and 6 habitual short (less than or equal to 6.5 hr) sleepers (SS) measured their diurnal axillary temperature (T) every 4 hr from awakening time to bedtime. For the control span of 10 days, temperature peak time was similar in both groups but occurred later in SS than in LS when measured from midsleep. Bedtime was closer to temperature peak time in LS than in SS. While experiencing the same sleep deprivations (SD 24 hr with morning sleep recovery and SD 36 hr with nocturnal sleep recovery). SS maintained a more stable body temperature curve than LS. After the nights of sleep deprivation, morning temperature increased in LS but not in SS. In both experimental conditions LS tended to advance their temperature peaks. This shift resulted in a statistically significant difference between the groups' T peaks for the 36-hour sleep deprivation. These results suggest that coupling between sleep/activity rhythm and temperature rhythm probably is different in LS and in SS, being stronger in LS.

Habitual sleep length and patterns of recovery sleep after 24 hour and 36 hour sleep deprivation

Five long sleepers (LS) and 5 short sleepers (SS) were selected from 310 medical students. Nine regular sleepers (RS) were used as a control. The sleep was recorded during 3 reference nights, one recovery night after a 36 h sleep deprivation (R2), one morning sleep after a 24 h sleep deprivation (D1) and the night following D1(R1). According to previous data slow wave sleep (SWS) amounts were the same in the 3 groups while stage 2 and paradoxical sleep (PS) amounts increased with the sleep duration. The hourly distribution of intervening wakefulness and SWS were similar for all groups. When compared to RS or SS the hourly distribution in LS of PS was lower until the sixth hour. As a function of experimental conditions, sleep patterns of LS were the most affected. In R2 the sleep of LS more closely resembled that of RS or SS than in reference nights, while in R1 LS' sleep was the most disturbed. Morning sleep durations were very similar for all groups, but in LS intervening wakefulness was increased and PS was decreased when compared to RS and SS. Negative correlations (Spearman rank test) were found between the morning increase of body temperature after a sleep-deprived night and both TST and PS durations. In all recorded sleep periods, SWS amounts were positively correlated with prior wakefulness duration and the PS amount with TST.