Medical Journal of Babylon

ORIGINAL ARTICLE
Year
: 2018  |  Volume : 15  |  Issue : 4  |  Page : 267--270

Prevalence and risk factors of osteoporosis in kidney transplant recipients: Dual-Energy x-ray absorptiometry scan study


Esra Omar Hameed1, Hussein Yousif Sinjari2,  
1 Department of Medicine, Nephrology Unit, Hawler Teaching Hospital, Erbil, Iraq
2 Department of Medicine, College of Medicine, Hawler Medical University, Erbil, Iraq

Correspondence Address:
Esra Omar Hameed
Nephrology Unit, College of Medicine, Hawler Medical University, Erbil
Iraq

Abstract

Background: Osteoporosis is one of the major bone diseases that affect kidney transplant (KT) recipients; it causes significant long-term morbidity and increases the risk of fractures. The aim of this study was to investigate the prevalence and risk factors of osteoporosis in KT recipients. Materials and Methods: A cross-sectional study enrolled 70 KT recipients followed in the Nephrology Unit at Hawler Teaching Hospital, Erbil, Iraq, over a period of 6 months from December 15, 2017, to June 14, 2018. All patients were subjected to comprehensive history, clinical examination, relevant investigations, and measurement of bone mineral density (BMD) in the hip and lumbar spines using dual-energy X-ray absorptiometry. A T-score of –1 to + 1 standard deviation (SD) indicates normal BMD whereas a T-score of −1 to −2.5 SD was considered as osteopenia and T-score of <−2.5 SD was regarded as osteoporosis. Results: Osteoporosis was seen in 52.9% of the studied patients; statistically significant positive associations were detected between osteoporosis and low body mass index (BMI), diabetes mellitus (DM), second KT, pretransplant steroid treatment, and Vitamin D deficiency (P < 0.05), whereas no significant relationship was observed with age, gender, smoking, hypertension, and serum levels of calcium, phosphate, and parathyroid hormone. Conclusion: Osteoporosis is common among KT recipients. Low BMI, Vitamin D deficiency, DM, pretransplant steroid therapy, and second KT are the contributing factors. BMD measurement at pre- and post-transplant period is warranted for early recognition and management of this condition.



How to cite this article:
Hameed EO, Sinjari HY. Prevalence and risk factors of osteoporosis in kidney transplant recipients: Dual-Energy x-ray absorptiometry scan study.Med J Babylon 2018;15:267-270


How to cite this URL:
Hameed EO, Sinjari HY. Prevalence and risk factors of osteoporosis in kidney transplant recipients: Dual-Energy x-ray absorptiometry scan study. Med J Babylon [serial online] 2018 [cited 2019 Mar 20 ];15:267-270
Available from: http://www.medjbabylon.org/text.asp?2018/15/4/267/248054


Full Text



 Introduction



Posttransplant bone disease is a major cause of morbidity in kidney transplant (KT) recipients, with a fundamentally higher risk of fractures, as well as expanded healthcare costs, hospitalization, and mortality.[1] The range of bone diseases in KT recipients includes renal osteodystrophy, osteoporosis, bone fracture, and osteonecrosis characterized by decreased bone mass, impeded bone quality, and inclination to fracture.[2] Back pain, vertebral fractures, and osteopenia on plain films are recognized as the clinical characteristics of osteoporosis. After transplantation, bone mineral density (BMD) declines by 4%–10% in the first 6 months with a further decrease of 0.4%–4.5% in lumbar BMD between 6 and 12 months as reported by earlier studies.[2],[3] BMD remains relatively stable with no more declines after 1 year but at significantly lower levels than healthy people.[2] Osteopenia after renal transplantation has been demonstrated to be associated with several factors, including preexisting bone diseases, low BMD due to advanced age and/or Vitamin D deficiency, secondary hyperparathyroidism as well as posttransplant immunosuppressive therapy, dose of steroid, and ongoing disorder in the phosphate-calcium-parathyroid hormone-Vitamin D axis.[4],[5] Dual-energy X-ray absorptiometry (DXA) scan is generally a noninvasive, accurate, cost-effective screening technique for evaluating bone mass, and it appears to help expecting fracture risk in KT recipients.[6] The aim of this study was to investigate the prevalence and risk factors of osteoporosis in KT recipients.

 Materials and Methods



This cross-sectional study enrolled 70 KT recipients in the Nephrology Unit at Hawler Teaching Hospital in Erbil, Iraq, over a period of 6 months from December 15, 2017, to June 14, 2018.

The patients were randomly assigned with a transplantation vintage of at least 1 year. The exclusion criteria were age below 18 years, pregnancy, abnormal renal indices, history of pretransplantation osteoporosis, and postmenopausal women. The data were collected through direct interview using a special questionnaire, and the following information was obtained from each patient: age, gender, history of smoking, hypertension and diabetes mellitus (DM), existence of pretransplant steroid therapy, and hyperparathyroid bone disease. Clinical examination was done including height and weight to calculate body mass index (BMI) (normal range [NR] 18.5–24.9 kg/m2). All participants were subjected to serum measurements of creatinine (NR 0.6–1.3 mg/dL), calcium (NR 8.5–10.5 mg/dL), phosphate (NR 2.48–4.34 mg/dL), parathyroid hormone (NR 16–75 pg/ml), and 25 OH-Vitamin D (NR >50 nmol/L). BMD was measured in the hip and lumbar spines using DXA scan. A T-score of –1 to +1 standard deviation (SD) indicate a normal BMD. A T-score of −1 to −2.5 SD was considered as osteopenia and T-score of [7]

The study was conducted according to the Helsinki ethical guidelines and has been approved by the Ethical Committee of Kurdistan Board of Medical Specialties. The written consent forms were obtained from all patients before recruitment and guarantees were given for confidentiality of their personal information.

The data were analyzed using Statistical Package for the Social Sciences version 25 (SPSS, IBM Company, Chicago, USA). The data were presented as mean, SD, and ranges. Categorical data were presented by frequencies and percentages. Pearson's Chi-square test was used to assess statistical association between bone density levels (BDLs) and studied variables. A P < 0.05 was considered statistically significant.

 Results



This study included 70 KT recipients. The mean age of them were 48.9 ± 11.8 years. The participants' characteristics are presented in [Table 1].{Table 1}

Laboratory investigations revealed that the highest proportion of patients had normal level of serum calcium, phosphorus, and 25 OH-Vitamin D (61.4%, 87.1%, and 54.3%, respectively), whereas 57.1% of them showed high parathyroid hormone level. According to the DXA scan results, the patients were distributed according to BDL, and more than half of them have osteoporosis [Table 2].{Table 2}

Regarding immunosuppressive drugs, all participants were on steroid, mycophenolate mofetil, and calcineurin inhibitors (either cyclosporine or tacrolimus). However, 13 patients (18.6%) were on pretransplantation steroid therapy.

The highest prevalence of osteoporosis was found among underweight patients, diabetics, second renal transplantation, pre transplantation steroid therapy and those with vitamin D deficiency (P < 0.05) [Table 3].{Table 3}

 Discussion



Post-KT bone diseases commonly develop, with a significantly higher risk of morbidity and mortality. Osteoporosis is associated with low bone mass and enhanced skeletal fragility.

The current study demonstrates a high prevalence (52.9%) of osteoporosis among Iraqi KT recipients, which was comparable with studies conducted in Turkey (42.9%)[8] and South Korea (47.3%)[9] but higher than that reported in other studies as 26% in Iran[10] and 26.4% in Thailand,[11] which may be explained by complex pathophysiology underlying bone disorders, including preexisting renal osteodystrophy.[6] Our results showed that low BMI level was positively associated with osteoporosis that is in line with some studies[11],[12] and disagreed with others.[10],[13]

The present study revealed that Vitamin D deficiency had significant impact on the development of osteoporosis; a similar finding was reported in other regions across the world, as in Turkey,[8] the UK,[14] Denmark,[15] the Netherlands,[16] and the USA.[17] Vitamin D deficiency may be due to the low sunlight exposure, using sun protectors and immunosuppressive drugs, especially high doses of steroid and impaired kidney function.[18]

This study showed that osteoporosis associated significantly with pretransplant steroid treatment, this is consistent with a China study[13] but disagreed with other,[10] and this might be explained by the fact that corticosteroid can suppress bone formation, inhibit osteoblastogenesis, stimulate bone resorption, promote osteoblast apoptosis, and attenuate calcium absorption from the intestine.[19]

In congruence with our observation, other study showed a high rate of osteoporosis among diabetics.[6] Cumulative dosage of steroid may explain the high prevalence of osteoporosis in second KT recipients.[2],[11]

In agreement with other studies, no significant relationship was observed between osteoporosis and age, gender, smoking, hypertension, and serum levels of calcium, phosphate, and parathyroid hormone.[8],[10],[13] The sample size of the present study does not allow us to generalize the findings to patients in other settings across the country.

 Conclusion



Osteoporosis is common among Iraqi KT recipients. Low BMI, Vitamin D deficiency, DM, pretransplant steroid therapy, and second KT are the contributing factors. BMD measurement at pre- and post-transplant period is warranted for early recognition and management of this condition.

Acknowledgments

We wish to thank the staff of radiology at Hawler Teaching Hospital, Erbil, Iraq, for their help and support.

Financial support and sponsorship

The authors were the only supporters of the research.

Conflicts of interest

There are no conflicts of interest.

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