Vitamin D levels and comorbidities in ambulatory and hospitalized patients in Austria

Wien Klin Wochenschr DOI 10.1007/s00508-015-0824-5 Vitamin D levels and comorbidities in ambulatory and hospitalized patients in Austria Christian Muschitz Roland Kocijan Verena Stütz Alexandra Kaider Gabriela Katharina Muschitz Heinrich Resch Stylianos Kapiotis Received: 24 October 2014 / Accepted: 28 May 2015 Springer-Verlag Wien 2015 Summary Vitamin D in its hormonal active form, 1,25-dihydroxyvitamin D (calcitriol), has a major impact on bone turnover by regulating calcium and phosphate homoeostasis. By binding the active vitamin D hormone to the vitamin D receptor (VDR), it acts as a nuclear transcription factor (Bouillon et al., Endocr Rev 29(6):726 776, 2008). The discovery that almost all tissues and cells in the body express the VDR and that several tissues possess the enzymatic capability to convert 25-hydroxyvitamin D (25(OH)-D3; cholecalciferol) to the active form, suggests that vitamin D fulfills various extraosseous functions (Bouillon et al., Endocr Rev 29(6):726 776, 2008; Holick, N Engl J Med 357(3):266 281, 2007). For example, VDR ensures adequate intestinal calcium absorption by regulating the synthesis of several calcium transport proteins in the duodenum (Bouillon et al., C. Muschitz, MD ( ) R. Kocijan, MD H. Resch, MD St. Vincent Hospital, Medical Department II, Academic Teaching Hospital of the Medical University of Vienna, Stumpergasse 13, 1060 Vienna, Austria e-mail: christian.muschitz@bhs.at V. Stütz, MSc Department of Controlling and Medical Statistics, St. Vincent Hospital Vienna, Vienna, Austria A. Kaider, MSc Center for Medical Statistics, Informatics and Intelligent Systems, Medical University of Vienna, Vienna, Austria G. K. Muschitz, MD, PhD Division of Plastic and Reconstructive Surgery, Department of Surgery, Medical University of Vienna, Vienna, Austria S. Kapiotis, MD Labcon Medical Laboratories Ltd., St. Vincent Group, Vienna, Austria Endocr Rev 29(6):726 776, 2008). Additionally, vitamin D is important for proper muscle function, and some studies suggest it may contribute to prevent type 1 diabetes mellitus, certain autoimmune diseases, hypertension, and several types of cancer (Holick, N Engl J Med 357(3):266 281, 2007). Keywords Vitamin D deficiency Comorbidities Age groups Cross-sectional study Introduction Vitamin D in its hormonal active form, 1,25-dihydroxyvitamin D (calcitriol), has a major impact on bone turnover by regulating calcium and phosphate homoeostasis. By binding the active vitamin D hormone to the vitamin D receptor (VDR), it acts as a nuclear transcription factor [1]. The discovery that almost all tissues and cells in the body express the VDR and that several tissues possess the enzymatic capability to convert 25-hydroxyvitamin D (25(OH)-D3; cholecalciferol) to the active form, suggests that vitamin D fulfills various extra-osseous functions [1, 2]. For example, VDR ensures adequate intestinal calcium absorption by regulating the synthesis of several calcium transport proteins in the duodenum [1]. Additionally, vitamin D is important for proper muscle function, and some studies suggest it may contribute to prevent type 1 diabetes mellitus, certain autoimmune diseases, hypertension, and several types of cancer [2]. It has been observed that serum 25(OH)-D3 is the best indicator of vitamin D status among individuals without kidney disease [3]. However, there is an ongoing debate on the optimum cut-off for 25(OH)-D3 depending on the evaluation criteria applied the optimum suppression of serum intact parathyroid hormone (ipth) levels, optimum enteral absorption of calcium, highest bone mineral density (BMD), lowest rate of BMD loss, or lowest 1 3 Vitamin D levels and comorbidities in ambulatory and hospitalized patients in Austria 1

fracture rate [4]. Despite this, there is growing consensus that serum 25(OH)-D3 levels of 30 ng/ml ( 75 nmol/l) are optimal for bone health and extraskeletal effects [5 7]. Concentrations between 20 and 29 ng/ml (50 74 nmol/l) are considered insufficient, and serum levels below 20 ng/ml (< 50 nmol/l) indicate vitamin D deficiency. Likewise, the guidelines of the Dachverband Osteologie (DVO; Germany, Austria, Switzerland) state that 25(OH)-D3 concentrations should be > 20 ng/ml to prevent osteoporosis [8]. According to the International Osteoporosis Foundation, vitamin D levels above 30 ng/ ml are considered sufficient, whereas the American Society for Bone and Mineral Research is less restrictive in this respect, leaving it up to the treating physician to decide whether 20 or 30 ng/ml is to be the lower normal limit [9]. In addition, there is no consensus on how to rapidly correct severe deficiencies [2, 10]. In Europe, vitamin D deficiency is prevalent among all age groups, and it might affect more than 50 % of the population depending on the time of the year [7, 11 14]. Inadequate 25(OH)-D3 levels adversely affect calcium metabolism leading to diminished bone mineralization [15]. In children, this is related to rickets, and in adults osteomalacia is a result of pronounced hypovitaminosis D. Some studies showed an association between low 25(OH)-D3 concentrations and reduced BMD [16, 17], whereas other studies could not determine such a relationship [18, 19]. A meta-analysis of 23 randomized, controlled studies demonstrated only a weak influence of vitamin D supplementation on femoral BMD and no effect on other skeletal sites [20]. However, two meta-analyses showed that 25(OH)-D3 supplementation may result in a significant reduction of hip fractures and non-vertebral fractures [21, 22]. In one of these analyses, there was a nonsignificant reduction in hip fractures and a significant reduction in non-vertebral fractures of 10 and 7 %, respectively [22]. When subdivided by vitamin D intake, there was a significant reduction in fractures at hip of 30 % for patients taking daily doses above 792 IU vs. control group. Vertebral fractures were reduced by 11 % in those patients taking more than 400 IU per day. In contrast to this, previous meta-analyses could not demonstrate reduced fracture rates by vitamin D supplementation [23 25]. Other studies indicated that adequate 25(OH)-D3 supplementation in elderly subjects can maintain muscle strength and reduce the risk of falls [26 28]. The objective of this cross-sectional study was to investigate the prevalence of 25(OH)-D3 deficiency in both genders and all age groups of a Central European population. In addition, an association of 25(OH)-D3 deficiency with different comorbidities was tested. Patients, material, and methods This retrospective study was conducted at seven hospitals of the Vincent Group Austria (VGÖ) between 2012 and 2013. These were the St. Vincent Hospitals (Barmherzige Schwestern) in Linz, Ried and Vienna, the Hospital Divine Saviour (Göttlicher Heiland), the Orthopaedic Hospital Speising, St. Josephs Hospital Vienna, and the Hospital Sacred Heart of Jesus (Herz Jesu KH), Vienna. In these centers, available serum 25(OH)-D3 levels from patients were retrieved anonymously. In case of multiple (outpatient or stationary) treatments by one of these hospitals, only the very first available serum value was evaluated. Reasons for vitamin D measurement were not available. Measurement of vitamin D levels were performed by determining serum 25(OH)-D3 concentrations. Fasting blood samples were drawn from patients between 8:00 and 10:00 a.m. Routine blood analyses included whole blood count and the following lab parameters: calcium, phosphate, ipth, 25(OH)-D3, thyroid-stimulating hormone (TSH) levels as well as parameters of kidney and liver function. All were measured on the Abbott Architect platform (Abbott GmbH, Vienna, Austria). Beta- CrossLaps (CTX) indicating osteoclast activity and intact N-terminal type 1 procollagen propeptide (intact P1NP) indicating osteoblast activity were measured by electrochemiluminescence immunoassays using the isys device (IDS-iSYS; Immunodiagnostic Systems Inc., Gaithersburg, MD, USA). Limits of detection were: 25(OH)D: 1 ng/ml, total CV 3.3 4.9 %; P1NP: 1 ng/ml, total CV 4.2 5.3 %; CTX: 0.023 ng/ml, total CV 2.1 4.9 %. Quality assurance was controlled by regular Round Robin Tests in all centers of the Vincent Group. The primary study endpoint was to gather vitamin D levels in female and male patients treated in hospitals of the VGÖ. All patients were grouped according to their age decade: group 1: 0 10 years, group 2: 11 20 years, group 3: 21 30 years, etc. Secondary endpoints included a potential correlation of vitamin D levels with age, common serum markers, and established bone turnover markers. For this analysis, the following serum markers were determined: albumin, alkaline phosphatase, bilirubin, C-reactive protein (CRP), total protein, glomerular filtration rate (egfr), hemoglobin, creatinin, creatine kinase (CK), lactate dehydrogenase (LDH), TSH. Markers of bone turnover included: P1NP, S-CTX, calcium, phosphate, ipth. Additionally, in those patients treated at the St. Vincent Hospital in Vienna, vitamin D levels were compared with the patients diagnoses according to the medical reports. Statistical analysis All statistical data were calculated by the Center for Medical Statistics, Informatics and Intelligent Systems of the Medical University of Vienna, Austria. Continuous variables are described by the median [interquartile range]. The non-parametric Spearman correlation coefficient was used to describe the correlation of vitamin D levels 2 Vitamin D levels and comorbidities in ambulatory and hospitalized patients in Austria 1 3

with patient age and selected serum parameters. Comparisons between groups of patients with respect to the vitamin D level were performed using the non-parametric Mann Whitney U test. The chi-square test was used to compare frequencies of vitamin D insufficiency and deficiency between male and female patients, and in selected disease groups compared with the whole patient sample. The SAS software (version 9.3, SAS Institute Inc., 2002 2010; Cary, NC, USA) was used for data analyses. Results Patient characteristics In total, data sets from 16,412 patients with 25(OH)-D3 levels treated in a center of the VGÖ between 2012 and 2013 were analyzed. Of these patients, 33 % were male and 67 % female patients. Patients age ranged from 3 to 102 years with a median value of 67 [IQR: 51 78] years. Vitamin D levels A total of 71 and 42 % of the patients analyzed had vitamin D concentrations < 30 and < 20 ng/ml, respectively. The median 25(OH)-D3 level in the female study population was 23.0 [IQR 15.0; 32.7] and 20.6 [IQR 13.5; 29.3] ng/ ml for male patients (p < 0.0001). According to the higher number of women analyzed, the amount of women in the 25(OH)-D3 insufficiency/ deficiency group was higher, but the percentage of persons with vitamin D insufficiency or deficiency was higher among male compared with female individuals: 75.8 and 47.2 % of male and 68.5 and 40.1 % of female individuals had vitamin D levels < 30 and < 20 ng/ml (p < 0.0001 for all comparisons between both genders), respectively (Table 1). Vitamin D concentrations in different age groups Allocation of patients to their respective age decade revealed that in every group more than half of the patients had 25(OH)-D3 concentrations below 30 ng/ml. In the age group 91 100 years, more than 50 % had concentrations below 20 ng/ml (Fig. 1a). In age group 2 (11 20 years), 4 (31 40 years), 9 (81 90 years), and 10, at least 75 % of all patients analyzed had insufficient vitamin D levels or even a deficiency. Gender-specific analysis of median and IQR values of vitamin D concentrations showed that insufficient levels were more frequent in male patients than in female patients, with the exception of the first two and the fourth age decades (Fig. 1b, Table 2). This was even more pronounced in male patients from the sixth age decade onward, i.e., patients older than 50 years. Table 1 25(OH)-D3 concentrations with a cut-off of 30 and 20 ng/ml Males n (%) Females n (%) Bone turnover parameters p Values The majority of patients in every age decade had ipth concentrations within the normal range. From decade 8 onward (71 80 years), there is a shift toward increased ipth values even above the upper normal limit (Fig. 2). Likewise, serum levels of P1NP and S-CTX were within the normal range in patients of all age decades, except for patients at the age of 0 10 years, corresponding to the increased bone formation and turnover during child growth (Fig. 2). Calcium and phosphate concentrations were in the normal range in most patients of all age groups. Creatinine concentrations were in the normal range in most patients. However, in patients older than 70 years, there was a trend toward increased concentrations. Comparison of the seven hospitals revealed no marked variations in these parameters with regard to the vitamin D levels, hence excluding a geographical impact. Correlation analysis of vitamin D levels with age and serum markers Correlation coefficients of 25(OH)-D3 levels with age and serum parameters (bone turnover markers, calcium, phosphate, albumin, bilirubin, CK, CRP, TSH, egfr, hemoglobin, LDH) were statistically significant, but showed weak values ranging from 0.24 for serum calcium to 0.31 for albumin levels (data not shown). Vitamin D concentration and diagnoses Total n (%) Vitamin D 4.119 (75.8) 7.513 (68.5) < 0.0001 11.632 (70.9) insufficiency (< 30 ng/ml) Vitamin D 2.565 (47.2) 4.400 (40.1) < 0.0001 6.965 (42.4) deficiency (< 20 ng/ml) Total 5.437 (100) 10.975 (100) 16.412 (100) Major and secondary diagnoses with high evidence of increased risk for osteoporosis were evaluated in a subgroup of patients treated in the St. Vincent Hospital Vienna (n = 3.136). Most common diagnoses were arterial hypertension (23.5 %), osteoporosis with or without prevalent fracture (8.6 and 11.8 %), adipositas (11.3 %), and diabetes mellitus type 2 (7.1 %). 25(OH)-D3 insufficiency, i.e., levels < 30 ng/ml were most frequently observed in patients with type 1 and type 2 diabetes mellitus, adipositas, chronic kidney disease, and chronic inflammatory bowel disease. At least three quarters of these patients showed vitamin D insufficiency. 1 3 Vitamin D levels and comorbidities in ambulatory and hospitalized patients in Austria 3

Fig. 1 Box plots of vitamin D concentrations in the separate age decades (N = 16.412). Horizontal lines indicate the 20 and 30 ng/ml thresholds. Panel a both genders; panel b separated by gender median, interquartile ranges, and p values are presented in Table 2 By comparing patients with specific disease groups to the whole study population at the St. Vincent Hospital, we discovered a statistically significantly higher proportion of patients with insufficient or deficient 25(OH)-D3 levels compared with the whole group of patients. This deficiency, i.e., levels < 20 ng/ml, was seen in more than half of the patients with the following diagno- 4 Vitamin D levels and comorbidities in ambulatory and hospitalized patients in Austria 1 3

Table 2 25(OH)-D3 concentrations of female and male patients, subdivided by age decades Age (years) Males Females p Value n Median [IQR] n Median [IQR] Study population 5.437 20.6 [13.5; 29.3] 10.975 23.0 [15.0; 32.7] < 0.0001 0 10 23 27.6 [20.0; 39.6] 15 23.8 [9.1; 34.7] 0.232 11 20 111 21.0 [15.3; 29.0] 152 23.5 [16.0; 31.8] 0.406 21 30 277 20.7 [15.0; 28.0] 495 23.5 [15.9; 33.6] 0.007 31 40 430 20.3 [13.2; 29.2] 634 21.9 [15.4; 29.9] 0.033 41 50 671 22.0 [14.8; 30.8] 1.098 23.0 [16.0; 31.4] 0.140 51 60 938 21.1 [14.2; 29.4] 1.567 24.0 [16.5; 33.3] < 0.0001 61 70 1.082 21.5 [13.8; 30.4] 1.984 24.3 [16.4; 33.9] < 0.0001 71 80 1.110 20.2 [13.0; 29.0] 2.448 23.8 [14.7; 33.5] < 0.0001 81 90 712 17.6 [11.4; 26.6] 2.246 21.5 [12.8; 31.4] < 0.0001 91 100 78 15.2 [10.2; 26.3] 331 20.2 [11.7; 31.3] 0.015 > 100 0 1 29.9 ses: type 1 diabetes mellitus, adipositas, chronic kidney disease, and liver cirrhosis. The same pattern for patients with certain diseases was also observed in vitamin D-deficient patients. In contrast, vitamin D deficiency was less frequently recognized in patients with arthritis and osteoporosis. However, even in these groups 20 % (arthritis) and 25 % (osteoporosis) of the patients were affected (Table 3, Fig. 3). Discussion In this cross-sectional study, 25(OH)-D3 levels were evaluated in patients of all age groups, who were treated in seven large Austrian hospitals. Inadequate vitamin D concentrations are clearly very common among Austrian patients. Independent of age, more than 40 % of patients had a deficiency (i.e., 25(OH)-D3 < 20 ng/ml), and for some diseases approximately 75 % of patients had vitamin D concentrations below 30 ng/ml. It can be assumed that the proportion is somewhat higher in patients treated in hospital compared with the general population. However, a study in healthy Austrian adults showed that 26 % of the subjects had 25(OH)-D3 levels < 12 ng/ml [29]. Between 1992 and 2001, the National Diet and Nutrition Survey collected vitamin D levels in all age groups between 18 and 85 years in Great Britain [30]. This study showed that 20 60 % of the general population had a vitamin D deficiency (< 50 nmol/l/20 ng/ml) and even 90 % had insufficient levels (< 80 nmol/l/32 ng/ml). Deficiency was particularly frequent in young adults and elderly people, with approximately 75 % of them affected. A European study on vitamin D status in adolescents revealed that 42 and 81 % had 25(OH)-D3 concentrations < 50 and < 75 nmol/l, respectively [31]. In the Longitudinal Aging Study Amsterdam (LASA), serum 25(OH) D concentrations < 50 nmol/l were observed in 45 and 56 % of all male and female individuals, respectively [32]. Despite prevalent vitamin D insufficiency in the general population, levels seem to vary between different European countries [14, 33]. There is still a debate on potential medical consequences of this prevalent deficiency, but an association of vitamin D deficiency with an increased incidence of fractures could be shown in older adults of both sexes [34]. Additionally, a link between vitamin D deficiency and the risk of stress fractures in young adults at the age of 18 44 years has been described [35 37]. However, a study on the association of 25(OH)-D3 levels and fracture risk in different ethnic groups revealed divergent associations, suggesting that the optimal level of vitamin D for skeletal health may differ in white, black, and Asian women [38]. We could not show any correlation between vitamin D levels and age or any serum or bone turnover parameter in this study population. The observed significant findings with weak correlation coefficients are mainly caused by the large number of patients, but do not provide any reasonable data in this context. If a vitamin D insufficiency is suspected, determination of the 25(OH)-D3 concentrations is absolutely necessary. Despite the high prevalence of vitamin D deficiency, available and reliable tests and efficient treatment options, general examination of vitamin D levels is currently not recommended by national guidelines. In this study, we observed that 25(OH)-D3 deficiency and insufficiency were particularly more frequent in patients with certain diseases to be known to negatively affect bone metabolism, such as diabetes mellitus, adipositas, and chronic renal failure. Vitamin D deficiency [25(OH)-D3 < 20 ng/ml] is possibly an important etiological factor in the pathogenesis of many chronic diseases. These include autoimmune diseases such as multiple sclerosis and type 1 diabetes, inflammatory bowel disease, immune deficiency, cardiovascular diseases, certain cancers (colon cancer, breast cancer, non-hodgkin s lymphoma), and neurocognitive disorders (Alzheimer disease) [2, 39]. The role of vitamin D in the pathogenesis of these diseases remains to be clarified in detail, 1 3 Vitamin D levels and comorbidities in ambulatory and hospitalized patients in Austria 5

Fig. 2 Serum markers of bone turnover parameters, expressed as box plots of patients allocated to their age decade (N = 16.412). Horizontal lines indicate the normal range; ipth, intact parathyroid hormone; P1NP, intact N-terminal type 1 procollagen propeptide; CTX, beta crosslaps 6 Vitamin D levels and comorbidities in ambulatory and hospitalized patients in Austria 1 3

Table 3 25(OH)-D3 concentrations signifying a higher proportion of insufficient or deficient patients, when subdivided by different diseases. Eating disorder anorexia and bulimia; heart arterial hypertension, heart failure, coronary heart disease and myocardial infarction; lung asthma and COPD; stomach/intestine all chronic inflammatory bowel diseases (Crohn s disease, ulcerative colitis); liver liver cirrhosis (ASH, NASH); arthritis rheumatoid arthritis; kidney chronic kidney disease stage II IV; osteoporosis osteoporosis with/without fracture. p Values indicate comparisons of patients with available 25(OH)-D3 and the respective disease against the whole patient population at the St. Vincent Hospital Vienna, Austria (n = 3.136) Liver Arthritis Osteoporosis Kidney Heart/Hypert Lung Stomach/ Intestine Adipositas Dementia Eating disorder Type 2 diabetes Type 1 diabetes Subjects with 25(OH)-D 3 levels, < 30 ng/ml n (%) With specific diagnosis 28 (90.3) 165 (74.0) 312 (87.9) 66 (72.5) 36 (52.2) 692 (69.8) 146 (72.6) 38 (77.6) 20 (64.5) 20 (41.7) 417 (52.3) 163 (80.3) Without diagnosis 2.073 (66.7) 1.936 (66.5) 1.789 (64.3) 2.035 (66.83) 2.065 (67.3) 1.409 (65.7) 1.955 (66.6) 2.063 (66.8) 2.081 (67.0) 2.081 (67.4) 1.684 (72.0) 1.938 66.1 p Value 0.006 0.021 < 0.0001 0.255 0.008 0.022 0.079 0.113 0.768 0.001 < 0.0001 < 0.0001 Subjects with 25(OH)-D3 levels, < 20 ng/ml n (%) With specific diagnosis 23 (74.2) 105 (47.1) 210 (59.2) 37 (40.7) 21 (30.4) 411 (41.5) 92 (45.8) 22 (44.9) 16 (51.6) 10 (20.8) 197 (24.7) 109 (53.7) Without diagnosis 1.180 (38.8) 1.098 (37.7) 993 (35.7) 1.166 (38.3) 1.182 (38.5) 792 (36.9) 1.111 (37.9) 1.181 (38.3) 1.187 (38.3) 1.193 (38.6) 1.006 (43.0) 1.094 37.3) p Value < 0.0001 0.005 < 0.0001 0.647 0.171 0.015 0.026 0.343 0.127 0.012 < 0.0001 < 0.0001 but vitamin D is known to regulate more than 200 genes [2]. These include genes involved in the regulation of cell proliferation, differentiation, and apoptosis, as well as angiogenesis [2, 40]. Furthermore, vitamin D is a potent immunomodulator [2, 41]. Two studies on structural bone alterations in patients with type 2 diabetes mellitus suggested diminished cortical bone quality rather than lower BMD and a continuous low grade inflammation caused by the disease as the main reason for increased fracture risk in these patients. In this context, vitamin D is considered to exert positive effects [42, 43]. Patients with diseases, which are associated with structural alterations of the bone require adequate 25(OH)-D3 levels to be successfully treated with antiresorptives or osteoanabolic agents. Interestingly, patients with rheumatoid arthritis or evident osteoporosis had better median vitamin D levels than patients with other diseases, suggesting a better awareness of vitamin D supplementation. However, even many of these patients had insufficient 25(OH)-D3 levels. To rapidly correct vitamin D insufficiency, 50,000 IU of vitamin D 2 (ergocalciferol) every week for 8 weeks are recommended in the USA, irrespective of the degree of vitamin D deficiency or body weight [2]. In Europe, other loading regimens are proposed as well, such as vitamin D3 (cholecalciferol) supplementation based on the equation: dose (IU) = 40 (75 serum 25(OH)-D3) body weight. The calculated dose (nmol/l) should then be given in weekly portions of 25,000 IU [10]. One advantage of this study was the large number of patients studied during a 2-year period in different hospitals and regions of Austria. In addition, the study covered a wide range of ages from children less than 10 years up to 100-year-old senior patients of both genders. However, there was no information on prevalent vitamin D substitution or on the reason for the vitamin D test. In addition, as there were no available DXA scans, a potential association of vitamin D deficiency and BMD could not be analyzed. It would be of great interest to investigate 25(OH)-D3 levels and low traumatic osteoporotic fractures in this study population in the context of age, gender, and concomitant diseases. As none of the seven hospitals has a trauma department and previous fractures were not separately recorded in the patients medical history, we cannot draw any conclusions on this specific question. Another possible limitation despite the large number of patients is high percentage of urban dwellers and potential geographical differences across Austria due to the distribution of the seven hospitals of the Vinzenz Group Austria. Conclusion This study supports previous data indicating that vitamin D insufficiency and deficiency is very frequent in the Central European population, independent of age and gender. As hypovitaminosis D is easy to detect and treat, 25(OH)-D3 levels should be integrated into routine 1 3 Vitamin D levels and comorbidities in ambulatory and hospitalized patients in Austria 7

Fig. 3 Box plots of vitamin D status subdivided by different diseases. Horizontal lines indicate the respective vitamin D thresholds of 20 and 30 ng/ml. Diagnoses are grouped as follows: eating disorder anorexia and bulimia; heart arterial hypertension, heart failure, coronary heart disease, and myocardial infarction; lung asthma and COPD; stomach/intestine all chronic inflammatory bowel diseases (Crohn s disease, ulcerative colitis); liver liver cirrhosis (ASH, NASH); arthritis rheumatoid arthritis; kidney chronic kidney disease stage II IV; osteoporosis osteoporosis with/without fracture medical examination. Despite a broadly accepted lower normal limit, the optimal serum 25(OH)-D3 concentration is still under debate. Acknowledgments The authors cordially thank Mr. Wolfgang Sischka for the electronic extraction of all laboratory data. 8 Vitamin D levels and comorbidities in ambulatory and hospitalized patients in Austria 1 3

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