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Background and Aims Bone fragility fractures (bone fractures) are extremely frequent in haemodialysis (HD) patients. Serum phosphate (P) has been suggested as a risk factor for bone fracture, nonetheless, evidence is poor. The aim of this study was to assess the association between incidence of bone fractures and serum phosphate (P), calcium (Ca) and parathyroid hormone (PTH) in patients from the COSMOS study. Method COSMOS is an observational, prospective, open cohort study with 3 years of follow-up including 6797 haemodialysis patients from 227 centres randomly selected from 20 European countries. At baseline, demographics, comorbidities, treatments, serum biochemical parameters of the previous six months and bone fractures of the previous 12 months were collected. Every 6 months, all these variables, outcomes, and incident bone fractures, were collected. Patients who had at least one bone fracture during follow-up were compared with those who had not. Multivariate binary logistic regression and Poisson regression were used to assess the association between incidence of bone fractures and serum P, Ca and PTH. Time to fracture (and possible re-fracture) was also evaluated using Cox regression and Cox regression for recurrent events. All the results were adjusted by 23 variables including Ca, P, PTH, albumin and haemoglobin (full adjusted model). Results Analysis included 6274 patients who had follow-up data and non-missing information regarding bone fractures at baseline and during follow-up; 252 patients (4.0%), suffered at least one incident bone fracture. The fractured patients were older (68.1±12.9 vs. 63.8±14.5 years, p Multivariate binary logistic regression showed that “well known risk factors for bone fracture”, such as a previous bone fracture (OR: 7.78[95%CI:4.83-12.55], p 800 pg/mL (OR: 1.60[95%CI: 1.01-2.55], p=0.047), were associated with a higher incidence of follow-up bone fractures. In addition to the “well known bone risk factors for fracture”, serum P > 6.1 mg/dL (OR: 1.50[95% CI: 1.07-2.11], p=0.02) and serum Ca > 9.7 mg/dL (OR: 1.42[95%CI: 1.01-2.03], p=0.043), were also associated with a higher incidence of bone fractures in the full-adjusted model. These findings were partly consistent with Poisson regression for serum P >6.1 mg/dL (IRR: 1.46[95% CI: 1.00-2.13], p=0.0085) and serum Ca > 9.7 mg/dL (IRR: 1.49[95%CI: 1.06-2.08], p=0.0047), but not for PTH. In addition, Cox regression analysis showed association between bone fractures and serum P >6.1 mg/dl (HR: 1.61 [95%CI: 1.16-2.24], p=0.0049) and 1.60 [95%CI: 1.14-2.24] (p=0.0066) for simple and recurrent events respectively, but no association was found with serum Ca and PTH in the 2 full-adjusted models for the Cox regression analyses. Conclusion In COSMOS, a large haemodialysis patient’s cohort with 3 years follow up, serum P was the only biochemical parameter that remained as a significant risk factor for bone fractures after 4 statistic approaches. Thus, for the first time, in a large scale well controlled study, high serum P has been identified as a new independent potential risk factor for incident bone fractures in haemodialysis patients.

Background. Vascular calcifications and the bone fractures caused by abnormal bone fragility, also called osteoporotic fractures, are frequent complications associated with chronic kidney diseases (CKD). The aim of this study was to investigate the association between vascular calcifications, osteoporotic bone fractures and survival in haemodialysis (HD) patients. Methods. A total of 193 HD patients were followed up to 2 years. Vascular calcifications and osteoporotic vertebral fractures (quoted just as vertebral fractures in the text) were assessed by thoracic, lumbar spine, pelvic and hand X-rays and graded according to their severity. Clinical, biochemical and therapeutic data gathered during the total time spent on HD were collected. Results. The prevalence of aortic calcifications was higher in HD patients than in a random-based general population (79% versus 37.5%, P < 0.001). Total time on any renal replacement therapy (RRT) and diabetes were positively associated with a higher prevalence of vascular calcifications. In addition to these factors, time on HD was also positively associated with the severity of vascular calcifications, and higher haemoglobin levels were associated with a lower prevalence of severe vascular calcifications in large and medium calibre arteries. The prevalence of vertebral fractures in HD patients was similar to that of the general population (26.5% versus 24.1%). Age and time on HD showed a positive and statistically significant association with the prevalence of vertebral fractures. Vascular calcifications in the medium calibre arteries were associated with a higher rate of prevalent vertebral fractures. In women, severe vascular calcifications and vertebral fractures were positively associated with mortality [RR = 3.2 (1.0–10.0) and RR = 4.8 (1.7–13.4), respectively]. Conclusions. Positive associations between vascular calcifications, vertebral fractures and mortality have been found in patients on HD.