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Research Article| Volume 74, 104726, June 2023

Screening for osteoporosis in people with MS: A new risk score

Open AccessPublished:April 17, 2023DOI:https://doi.org/10.1016/j.msard.2023.104726

      Highlights

      • Osteoporosis is more frequent in postmenopausal female and male patients with MS.
      • Disability is a MS specific risk factor for osteoporosis.
      • A new risk score allows to estimate the individual probability of osteoporosis.
      • This risk score enables individual screening recommendation and prevent osteoporosis-associated morbidity.

      Abstract

      Background

      Due to the demographic development and improved treatment options, the role of comorbidities is of increasing importance in the medical care of people with MS (pwMS). A higher risk of osteoporosis is well known in chronic autoimmune diseases, and is also described in MS. While there are several screening guidelines in the elderly or in patients with rheumatoid arthritis, there are no generally accepted recommendations when to perform bone mineral testing in pwMS under the age of 65 years. We aimed to determine risk factors of osteoporosis in pwMS and to develop a risk score which can be applied in daily clinical routine.

      Methods

      Densitometry (hip and lumbar spine) was performed in 159 pwMS aged ≤65 years and in 81 age- and sex-matched healthy controls (HC). Osteoporosis was defined according to WHO criteria as a bone density 2.5 standard deviation or more below the mean of young adults. Risk factors were identified by logistic regression analysis.

      Results

      Osteoporosis occurred more frequently in postmenopausal pwMS and male pwMS as compared to HC. Besides age, sex, menopausal status in females, body-mass-index and smoking, a higher degree of disability - as assessed by the Expanded Disability Status Scale - was identified as MS specific risk factor for osteoporosis, whereas the cumulative glucocorticoid dose was not associated with osteoporosis risk. Based on these risk factors, we developed an MS-specific risk score which allows to estimate the individual probability of osteoporosis.

      Conclusion

      This risk score enables individual screening recommendation for pwMS and, subsequently, early prevention of osteoporosis which probably should result in reduction of fractures and morbidity.

      Keywords

      Abbreviations

      BMD
      bone mass density
      BMI
      body-mass-index
      DMT
      disease-modifying treatment
      DXA
      dual-energy X ray absorptiometry
      EDSS
      Expanded Disability Status Scale
      FSH
      follicle-stimulating hormone
      FSS
      functional system score
      GC
      glucocorticoid
      HC
      healthy controls
      LH
      luteinizing hormone
      MS
      multiple sclerosis
      P1NP
      aminoterminal propeptide of type I collagen
      pwMS
      people with multiple sclerosis

      1. Introduction

      Comorbidities in multiple sclerosis (MS) are of increasing interest and can affect not only the quality of life, but also MS outcome (
      • Lo L.M.P.
      • Taylor B.V.
      • Winzenberg T.
      • Palmer A.J.
      • Blizzard L.
      • van der Mei I.
      Change and onset-type differences in the prevalence of comorbidities in people with multiple sclerosis.
      ). Therefore, early screening and prevention is crucial throughout the disease course (
      • Lo L.M.P.
      • Taylor B.V.
      • Winzenberg T.
      • Palmer A.J.
      • Blizzard L.
      • van der Mei I.
      Change and onset-type differences in the prevalence of comorbidities in people with multiple sclerosis.
      ). In people with MS (pwMS), a higher incidence of osteoporosis is a consistent finding, and a recent systematic review revealed a pooled osteoporosis prevalence of 17% in pwMS (
      • Azadvari M.
      • Mirmosayyeb O.
      • Hosseini M.
      • Vaheb S.
      • Razavi S.Z.E.
      The prevalence of osteoporosis/osteopenia in patients with multiple sclerosis (MS): a systematic review and meta-analysis.
      ). Prevalence of osteoporosis varied according to included study population from 5 to 29% and is a risk factor for fragility-related fractures (
      • Dobson R.
      • Ramagopalan S.
      • Giovannoni G.
      Bone health and multiple sclerosis.
      ). Several studies reported that disability, i.e. Expanded Disability Status Scale (EDSS), - besides age and low body mass index (BMI) - significantly correlates with low bone mass density (BMD) and, respectively, osteoporosis in pwMS (
      • Olsson A.
      • Oturai D.B.
      • Sørensen P.S.
      • Oturai P.S.
      • Oturai A.B.
      Short-term, high-dose glucocorticoid treatment does not contribute to reduced bone mineral density in patients with multiple sclerosis.
      ;
      • Ozgocmen S.
      • Bulut S.
      • Ilhan N.
      • Gulkesen A.
      • Ardicoglu O.
      • Ozkan Y.
      Vitamin D deficiency and reduced bone mineral density in multiple sclerosis: effect of ambulatory status and functional capacity.
      ;
      • Weinstock-Guttman B.
      • Gallagher E.
      • Baier M.
      • et al.
      Risk of bone loss in men with multiple sclerosis.
      ;
      • Huang Z.
      • Qi Y.
      • Du S.
      • Chen G.
      • Yan W.
      BMI levels with MS Bone mineral density levels in adults with multiple sclerosis: a meta-analysis.
      ). Although long-term glucocorticoid (GC) treatment is a well-known risk factor for osteoporosis, the role of short-term GC treatment as used for relapse treatment in MS is under debate. Despite evidence of an association of a high cumulative GC dose (>15 gr) with low BMD in pwMS (
      • Huang Z.
      • Qi Y.
      • Du S.
      • Chen G.
      • Yan W.
      BMI levels with MS Bone mineral density levels in adults with multiple sclerosis: a meta-analysis.
      ), other studies showed no correlation (
      • Olsson A.
      • Oturai D.B.
      • Sørensen P.S.
      • Oturai P.S.
      • Oturai A.B.
      Short-term, high-dose glucocorticoid treatment does not contribute to reduced bone mineral density in patients with multiple sclerosis.
      ;
      • Weinstock-Guttman B.
      • Gallagher E.
      • Baier M.
      • et al.
      Risk of bone loss in men with multiple sclerosis.
      ). Furthermore, reduced bone mass (osteopenia and osteoporosis) was also observed in half of patients with clinically isolated syndrome and early MS with a low cumulative GC dose and no or only minimal disability (
      • Moen S.M.
      • Celius E.G.
      • Sandvik L.
      • Nordsletten L.
      • Eriksen E.F.
      • Holmøy T.
      Low bone mass in newly diagnosed multiple sclerosis and clinically isolated syndrome.
      ) suggesting that there might be a shared pathogenetic mechanism.
      Even in the general population, there is a “treatment gap” of osteoporosis in Europe that is associated with a high socioeconomic burden by fragility fractures (
      • Hernlund E.
      • Svedbom A.
      • Ivergård M.
      • et al.
      Osteoporosis in the European Union: medical management, epidemiology and economic burden. A report prepared in collaboration with the International Osteoporosis Foundation (IOF) and the European Federation of Pharmaceutical Industry Associations (EFPIA).
      ;
      • Fuggle N.R.
      • Curtis B.
      • Clynes M.
      • et al.
      The treatment gap: the missed opportunities for osteoporosis therapy.
      ). Based on a literature review, in 2010 an osteoporosis screening algorithm was proposed for pwMS fulfilling either of the following criteria: i) postmenopausal women; ii) EDSS score ≥6; iii) EDSS score <6, but fractures; or iv) >3 month GC therapy or antiepileptic therapy (
      • Hearn A.P.
      • Silber E.
      Osteoporosis in multiple sclerosis.
      ). Despite these recommendations, in 2019 only thirteen percent of pwMS underwent BMD screening (
      • Bisson E.J.
      • Ekuma O.
      • Marrie R.A.
      • Leslie W.D.
      • Finlayson M.L.
      Factors associated with receiving bone mineral density screening among people with multiple sclerosis.
      ). There is still a lack of evidence regarding the degree of disability where osteoporosis risk is markedly increased and limited data are available for male individuals with MS. Recently, the development of more proactive and easily applicable screening guideline was recommended (
      • Bisson E.J.
      • Ekuma O.
      • Marrie R.A.
      • Leslie W.D.
      • Finlayson M.L.
      Factors associated with receiving bone mineral density screening among people with multiple sclerosis.
      ).
      As there is a general screening recommendation for women aged ≥65 years and men aged ≥70 years (
      • Cosman F.
      • de Beur S.J.
      • LeBoff M.S.
      • et al.
      Clinician's guide to prevention and treatment of osteoporosis.
      ), we aimed to determine risk factors of osteoporosis in pwMS under the age of 65 years and to develop a risk score which can be applied in daily clinical routine for these patients.

      2. Methods

      2.1 Study population

      For this study, premenopausal women, postmenopausal women, and men with MS aged between 18 and 65 years, as well as age-, sex- and in case of women menopausal status-matched healthy controls (HC) (2:1) were prospectively included at the Department of Neurology of the Medical University Innsbruck between March 2020 and October 2021. All pwMS were diagnosed according to 2017 McDonald criteria (
      • Thompson A.J.
      • Banwell B.L.
      • Barkhof F.
      • et al.
      Diagnosis of multiple sclerosis: 2017 revisions of the McDonald criteria.
      ). Patients with different disease courses (relapsing-remitting, secondary or primary progressive multiple sclerosis) were included (
      • Lublin F.D.
      • Reingold S.C.
      • Cohen J.A.
      • et al.
      Defining the clinical course of multiple sclerosis: the 2013 revisions.
      ).
      Disability was determined by EDSS, pyramidal functional system score (FSS) and ambulation score at inclusion by the treating neurologist. In addition, the treating neurologist documented disease course, comorbidities, concomitant medication, disease duration in years and past and/ or current disease-modifying treatment (DMT). DMT was categorized in moderately effective treatment (glatiramer acetate, interferon-beta, teriflunomide, dimethyl fumarate), highly active treatment (alemtuzumab, cladribine, fingolimod, natalizumab, ocrelizumab, rituximab), depleting DMTs (alemtuzumab, cladribine, ocrelizumab, rituximab) or no treatment. Furthermore, demographic data, weight, height, BMI, abdominal circumference, smoking status, alcohol consumption, date of menopause, family status, occupational status, education, parental hip fracture, and familiar osteoporosis were collected.
      Postmenopausal status was defined as a 12-month primary amenorrhea and confirmed by hormonal status. To assess activity the Baecke questionnaire was used (
      • Baecke J.A.
      • Burema J.
      • Frijters J.E.
      A short questionnaire for the measurement of habitual physical activity in epidemiological studies.
      ). Exposure to GC was assessed as cumulative lifetime methylprednisolone dose. Exposure of GC and number of relapses were collected by retrospectively reviewing the prospectively collected Innsbruck MS data base by the study investigators and medical files of the patients (AZ, FDP).
      Exclusion criteria comprised a history of osteoporosis, an ongoing pregnancy as a contraindication for densitometry, and conditions that confound dual-energy X ray absorptiometry (DXA) such as a lumbar spinal fusion surgery, and lack of documented history of cumulative GC dose.

      2.2 Densitometry

      Every study participant underwent BMD measurement of lumbar spine (L1-L4) and right hip (femoral neck, Ward`s triangle, trochanteric, intertrochanteric, and total hip) by DXA (Hologic Discovery™ A) at the Department of Nuclear Medicine, Medical University Innsbruck according to standard protocol. Analysis of results was performed by a blinded rater of the Department of Nuclear Medicine (ED and AK). Osteoporosis was defined according to the WHO criteria (
      Report of a WHO Study Group
      Assessment of fracture risk and its application to screening for postmenopausal osteoporosis.
      ;
      • Kanis J.A.
      • McCloskey E.V.
      • Johansson H.
      • Oden A.
      • Melton L.J.
      • Khaltaev N.
      A reference standard for the description of osteoporosis.
      ) in study participants with T score ≤ −2.5 in at least one skeletal site.

      2.3 X-Ray

      To detect vertebral osteoporotic fractures a thoracic and lumbar spine X-Ray was performed in all study participants.

      2.4 Laboratory analysis

      Laboratory analysis included hemoglobin A1c (HbA1c), total cholesterol, high density lipoprotein (HDL) cholesterol, low density lipoprotein (LDL) cholesterol, calcium, phosphate, alkaline phosphatase, C-reactive protein (CRP), interleukin-6 (IL-6), thyroid-stimulating hormone (TSH), parathyroid hormone (PTH), 25-hydroxyvitamin D (measured by high performance liquid chromatography), osteopontin, osteoprotegerin, aminoterminal propeptide of type I collagen (P1NP), Beta-Crosslaps (CTX), luteinizing hormone (LH), follicle-stimulating hormone (FSH), 7-beta estradiol, progesterone, prolactin, androstenedione, dehydroepiandrosterone, testosterone, sex-hormone-binding globulin, free androgen index, estrone, inhibin B, anti-Mullerian hormone. All analysis except osteopontin were performed by the Central Institute of Medical and Chemical Laboratory Diagnostics (ZIMCL), University Hospital of Innsbruck, according to routine laboratory standards (eTable 1). Osteopontin was measured with the commercially available human ProcartaPlex simplex kit (Thermo Fisher Scientific, Waltham, MA, USA) according to the manufacturer's instructions. Measurements were performed on a MagPix (Luminex Corporation; Software: xPonent 4.2) reader.

      2.5 Statistical analysis

      Statistical analysis was performed using the statistical software R (

      R Core Team Vienna A. A language and environment for statistical computing. R Foundation for Statistical Computing 2021.

      ). Distribution of data was assessed graphically and by the Kolmogorov-Smirnov test and data were displayed as mean ± standard deviation, or as median and interquartile range or range, as appropriate. For group comparisons, Mann-Whitney-U test or χ2 test was applied.
      To identify predictors of osteoporosis, logistic regression was employed with osteoporosis as the dependent variable and current smoking status, BMI, parental hip fractures, cumulative GC dose, disease duration, EDSS score, spasmolytic treatment, DMT, Vitamin D intake and patient group (premenopausal women, postmenopausal women, men ≤ 45 and men > 45 years) as independent variables. In addition, logistic regression was employed with FSS as well as ambulation score instead of EDSS score. McFadden's R square, accuracy, sensitivity and specificity were the model quality criteria.
      To provide a practical risk score, we dropped the insignificant variables, categorized BMI (as <20, 20–30 and >30) and EDSS score (as <4.5/ ≥4.5) and re-computed the logistic regression. The corresponding odds ratios were used to compute the risk score. Various ranges of the risk score with its associated probability for osteoporosis were summarized for practical use.
      A-priori power analysis with a significance level of 5%, a power of 80%, and 8 independent variables was computed. According to previous findings in the literature (
      • Hearn A.P.
      • Silber E.
      Osteoporosis in multiple sclerosis.
      ) we assumed a medium effect size of the parameter of interest, i.e. a Cohen f2 of 0.15 was used (

      Cohen J. Statistical Power Analysis for the Behavioral Sciences. 1988.

      ). The analysis revealed a necessary sample size of 109 patients for the logistic regression with all independent variables.

      2.6 Ethics and consent

      The study was approved by the ethics committee of the Medical University of Innsbruck (approval number: 1261/2018). Written informed consent was obtained from all study participants.

      2.7 Data availability statement

      Data supporting the findings of this study are available from the corresponding author upon reasonable request by a qualified researcher and upon approval by the ethics committee of the Medical University of Innsbruck.

      3. Results

      A total of 159 pwMS and 81 age- and sex-matched controls with a median age of 48 years and a female predominance of 68% were included in the study. Detailed demographic and clinical characteristics of pwMS and controls are displayed in Table 1. PwMS had higher abdominal circumference, lower grade of activity and had more often a history of smoking compared to controls. There was also a trend for a higher BMI and a higher frequency of hyperlipidemia and arterial hypertension in pwMS. PwMS suffered more frequently from depression compared to controls, were more often retired or unemployed and had a lower educational level.
      Table 1Characteristics of pwMS and controls at study inclusion.
      PwMSControlsP value
      No. of patients15981
      Demographics
      Age, years48 (37–55)48 (35–57)0.686
      Sex (females), n (%)107 (67.3)55 (67.9)0.925
      Clinical characteristics
      BMI25 (21–29)23 (21–27)0.069
      Abdominal circumference (cm)91 (80–102)83 (76–93)0.006
      Alcohol consumption (glasses per week)0 (0–2)2 (0–4)<0.001
      Current smoking, n (%)42 (26.4)18 (22.2)0.478
      Ever smoking, n (%)108 (67.9)38 (46.9)0.002
      Socioeconomic status
      Occupational status, n (%)

       working

       retired

       unemployed


      103 (64.8)

      42 (26.4)

      14 (8.8)


      77 (95.1)

      3 (3.7)

      1 (1.2)
      <0.001
      Family status, n (%)

       single

       divorced

       widowed

       relationship

       married


      43 (27.2)

      18 (11.4)

      3 (1.9)

      16 (10.1)

      78 (49.4)


      24 (30.8)

      7 (9.0)

      0 (0)

      16 (20.5)

      31 (39.7)


      0.126
      Educational grade, n (%)

       ≤9 years of schooling

       secondary schooling

       apprenticeship

       tertiary degree

       others


      25 (15.7)

      43 (27.0)

      48 (30.2)

      37 (23.3)

      6 (3.8)


      4 (4.9)

      21 (25.9)

      14 (17.3)

      42 (51.9)

      0 (0)


      <0.001
      Baecke questionnaire total

       Work activity

       Sport activity

       Nonsport leisure activity
      2.69 (2.09–3.17)

      2.14 (1.14–2.71)

      3 (1.75–3.75)

      3 (2–3.33)
      3.25 (2.87–3.57)

      2.57 (2.14–3.14)

      3.75 (3.25–4)

      3.33 (3–4)
      <0.001

      <0.001

      <0.001

      <0.001
      Comorbidities and concomitant medication
      Depression, n (%)27 (17.0)1 (1.2)<0.001
      Diabetes type I, n (%)1 (0.6)0 (0)NA
      Diabetes type II, n (%)1 (0.6)1 (1.2)NA
      Insulin-dependent diabetes, n (%)1 (0.6)0 (0)NA
      Hyperlipidemia, n (%)16 (10.1)3 (3.7)0.084
      Arterial hypertension, n (%)25 (15.7)6 (7.4)0.069
      Thyroid disease, n (%)32 (20.1)14 (17.3)0.597
      Rheumatoid arthritis, n (%)0 (0)0 (0)NA
      Cardiovascular disease, n (%)7 (4.4)2 (2.5)0.456
      Antiepileptic treatment, n (%)17 (10.4)0 (0)0.002
      Antispasmodic treatment, n (%)20 (12.6)0 (0)<0.001
      Vitamin D intake24 (15.1)7 (8.6)0.159
      Familial osteoporosis, n (%)55 (34.6)27 (33.3)0.846
      Fractures in the last 12 months, n (%)1 (0.6)3 (3.7)0.079
      Ever fractures85 (53.5)31 (38.3)0.026
      Parental hip fracture, n (%)16 (10.1)9 (11.1)0.802
      MS characteristics
      Disease duration, years10 (3–17, range 0–37)NANA
      EDSS score2.5 (1.5–4.5, range 0–8)NANA
      Pyramidal FSS1 (0–3, range 0–5)NANA
      Ambulation Score0 (0–2, range 0–12)NANA
      Relapses since diagnosis3 (1–6, range 0–21)NANA
      Cumulative lifetime GC dose in gr12 (4.5–20, range 0–56)NANA
      Number of different DMT1 (1–2, range 0–6)NANA
      DMT, n (%)

       No DMT

       Moderately effective

       Highly effective


      55 (34.6)

      39 (24.5)

      65 (40.9)
      NANA
      Depleting DMT, n (%)38 (23.9)NANA
      Legend:.
      Data are given as median and interquartile range unless specified otherwise. For group comparisons, Mann-Whitney-U test or χ2 test was applied as appropriate.
      Abbreviations: BMI, body-mass index; DMT, disease-modifying treatment; EDSS, Expanded Disability Status Scale; FSS, Functional System Score; GC, glucocorticoid; MS, multiple sclerosis; n, number; NA, not appropriate; PwMS, people with multiple sclerosis.
      Overall, 115 (72%) of 159 pwMS had a relapsing disease course, while 44 (28%) showed a progressive disease course. The median disease duration was 10 (range 0–37) years and the median EDSS score was 2.5 (range 0–8). There was a high correlation between pyramidal FSS and EDSS score (Spearman r = 0.75), as well as between ambulation score and EDSS score (Spearman r = 0.88). We provide a mosaic plot that shows these correlations (eFigure 1). Fifty-five (34.6%) patients had no DMT, whereas 39 (24.5%) and 65 (40.9%) patients were treated with a moderately and highly effective DMT, respectively. Depleting agents were used in 38 (23.9%) patients. The median cumulative lifetime GC dose was 12 g (maximum 56 g). No study participant used low dose long-term GC treatment.

      4. Osteoporosis is increased in PWMS

      Osteoporosis was detected in 47 (30%) of 159 pwMS, while in 7 (9%) of 81 controls (Fig. 1A). In the group of pwMS, several characteristics differed between patients with and without osteoporosis (Table 2). Patients with osteoporosis were older, had lower BMI and lower abdominal circumference, showed longer disease duration, higher EDSS score, higher pyramidal FSS, higher ambulation score, more frequently a progressive disease course and received less frequently DMT but more frequently antispasmodic treatment. In female patients, postmenopausal status was associated with the occurrence of osteoporosis.
      Fig 1:
      Fig. 1Osteoporosis frequency in pwMS and controls. Legend: y-axis shows percentage of osteoporosis frequency.
      Table 2Characteristics in pwMS with and without osteoporosis.
      OsteoporosisNo osteoporosisP value
      No. of patients47112
      Demographics
      Age, years55 (47–59)45 (36–53)<0.001
      Female sex, n (%)31 (66.6)76 (67.9)0.816
      Clinical characteristics
      Menopausal25 (80.6)25 (32.9)<0.001
      BMI22 (20–25)26 (22–30)<0.001
      Abdominal circumference (cm)85 (77–96)95 (84–104)0.006
      Alcohol consumption (glasses per week)0 (0–1)1 (0–2)0.045
      Current smoking, n (%)16 (34.0)26 (23.2)0.150
      Ever smoking, n (%)34 (72.3)74 (66.1)0.597
      Socioeconomic status
      Occupational status, n (%)

       working

       retired

       unemployed


      20 (42.6)

      23 (48.9)

      4 (8.5)


      83 (74.1)

      19 (17.0)

      10 (8.9)
      <0.001
      Family status, n (%)

       single

       divorced

       widowed

       relationship

       married


      9 (19.1)

      3 (6.4)

      1 (2.1)

      3 (6.4)

      31 (66.6)


      34 (30.6)

      15 (13.5)

      2 (1.8)

      13 (11.7)

      47 (42.3)


      0.101

      Educational grade, n (%)

       ≤9 years of schooling

       secondary schooling

       apprenticeship

       tertiary degree

       others


      7 (14.9)

      10 (21.3)

      15 (31.9)

      12 (25.5)

      3 (6.4)


      18 (16.1%)

      33 (29.5%)

      33 (29.5%)

      25 (22.3%)

      3 (2.7%)
      0.687
      Baecke questionnaire total

       Work activity

       Sport activity

       Non-sport leisure activity
      2.25 (1.61–3.25)

      2 (1–2.86)

      2,5 (1.25–3.5)

      2.33 (1.33–3.33)
      2.79 (2.19–3.17)

      2.14 (1.43–2.57)

      3 (2–3.75)

      3 (2.33–3.67)
      0.041

      0.848

      0.029

      0.003
      Comorbidities and concomitant medication
      Depression, n (%)10 (21.3)17 (15.20)0.350
      Diabetes type I, n (%)0 (0)1 (0.9)NA
      Diabetes type II, n (%)0 (0)1 (0.9)NA
      Insulin-dependent diabetes, n (%)0 (0)1 (0.9)NA
      Hyperlipidemia, n (%)7 (14.9)9 (8)0.190
      Arterial hypertension, n (%)6 (12.8)19 (17.0)0.507
      Thyroid disease, n (%)9 (19.1)23 (20.5)0.842
      Rheumatoid arthritis, n (%)0 (0)0 (0)NA
      Cardiovascular disease, n (%)5 (10.6)2 (1.8)0.013
      Antiepileptic treatment, n (%)7 (14.9)10 (8.9)0.267
      Antispasmodic treatment, n (%)11 (23.4)9 (8.0)0.008
      Vitamin D intake10 (21.3)14 (12.5)0.158
      Familial osteoporosis, n (%)17 (36.2)38 (33.9)0.786
      Fractures in the last 12 months, n (%)01 (0.9)0.516
      Ever fractures29 (61.7)56 (50.0)0.177
      Parental hip fracture, n (%)5 (8.9)20 (10.9)0.677
      Osteoporotic fractures in patients with osteoporosis detected by X-Ray, n (%)11 (23.4)NANA
      MS characteristics
      Disease duration, years15 (10–22)8 (3–14)<0.001
      EDSS score3.5 (2–6)2 (1–4)<0.001
      Pyramidal FSS2 (0–3)1 (0–1.5)<0.001
      Ambulation Score1 (0–7)0 (0–1)<0.001
      Relapses since diagnosis3 (2–8)3 (1–6)0.463
      Cumulative lifetime GC dose in g14 (7–21)11 (4–19)0.179
      Number of different DMT2 (1–2)1 (1–2)0.863
      DMT, n (%)

       No DMT

       Moderately effective

       Highly effective


      22 (46.8)

      17 (36.2)

      8 (17.0)


      28 (25.0)

      33 (29.5)

      51 (45.5)
      <0.001
      Depleting DMT, n (%)14 (29.8)24 (21.4)0.259
      Legend:.
      Data are given as median and interquartile range unless specified otherwise. For group comparisons, Mann-Whitney-U test or χ2 test was applied as appropriate.
      Abbreviations: BMI, body-mass index; DMT, disease-modifying treatment; EDSS, Expanded Disability Status Scale; FSS, Functional System Score; GC, glucocorticoid; MS, multiple sclerosis; n, number; NA, not appropriate; PwMS, people with multiple sclerosis.
      In subgroup analysis, osteoporosis was detected in 6/57 (10.5%) of premenopausal pwMS and in 1/28 (3.6%) of premenopausal HC; in 25/50 (50%) of postmenopausal pwMS, but only in 4/27 (14.8%) of postmenopausal controls. In male pwMS aged ≤45 years osteoporosis was detected in 7/28 (25.0%), while in none of the controls ≤45 years, but in 9/24 (37.5%) pwMS >45 years and 2/11 (18.2%) controls >45 years (Fig. 1B-E). For further details please refer to eTable 2.
      Logistic regression analysis including current smoking status, BMI, parental hip fractures, cumulative GC dose, disease duration, EDSS score, antispasmodic treatment, DMT, vitamin D intake and patient group (premenopausal women, postmenopausal women, men ≤45 and men >45 years) as independent variables revealed that BMI, smoking status, EDSS score and allocation into one of the four patient groups were statistically significant predictors of osteoporosis (eTable 3). Similar to the EDSS score, the pyramidal FSS (eTable 4 A) as well as the ambulation score (eTable 4 B) predicted osteoporosis.
      To simplify the risk assessment of osteoporosis, we dropped statistically non-significant variables (Table 3) and used categorized variables of BMI and EDSS score (eTable 5). The cut-point of 4.5 for the EDSS score was derived from the estimated osteoporosis probability dependent on the EDSS score (Fig. 2). The quality of the model with the variables on their original scale and the one of the model with the two categorized variables and without statistically insignificant variables (simplified model) were quite similar (eTable 6). With the simplified model (eTable 5), the calculation steps to obtain patients’ risk probability are: i) the total risk score of a patient is calculated as the product of the odds ratios of applicable risk factors multiplied with the normalization factor (Fig. 3A) and ii) the risk score gives the corresponding risk probability (Fig. 3B). Three computational examples are provided.
      Table 3Logistic regression analysis with the significant risk factors of osteoporosis in MS.
      EstimateStd.ErrorP valueOdds ratio
      Constant2.8931.3940.01918.055
      Current smoking = yes0.8330.4940.0462.300
      BMI−0.2670.060<0.0010.765
      Postmenopausal women
      reference category = premenopausal women Std. Error denotes standard error. BMI, body-mass index; EDSS, Expanded Disability Status Scale.
      2.5940.621<0.00113.390
      Men ≤ 45 years
      reference category = premenopausal women Std. Error denotes standard error. BMI, body-mass index; EDSS, Expanded Disability Status Scale.
      1.7300.7040.0075.639
      Men > 45 years
      reference category = premenopausal women Std. Error denotes standard error. BMI, body-mass index; EDSS, Expanded Disability Status Scale.
      1.9220.7180.0046.833
      EDSS score0.2930.1110.0041.341
      McFadden's R square = 0.329.
      1 reference category = premenopausal women Std. Error denotes standard error.BMI, body-mass index; EDSS, Expanded Disability Status Scale.
      Fig 2:
      Fig. 2Probability of osteoporosis depends on disability. Legend: Probability estimated by logistic regression () is provided for patients with differing EDSS scores. For group comparisons, Mann-Whitney-U test or χ2 test was applied as appropriate.
      Fig 3:
      Fig. 3Calculating osteoporosis risk. Legend: Reference categories are1 non-smokers,2 BMI of 20–30,3 premenopausal women, and 4 EDSS score ≤4.5,5 If all risk factors are set to the reference category, the risk score equals the normalization factor of 0.04 (as shown in Example 1). BMI, body-mass index; EDSS, Expanded Disability Status Scale.

      5. Laboratory analysis

      Laboratory analysis revealed higher LDL levels, slightly lower HDL and phosphate levels in pwMS compared to HC. In addition, 25-hydroxyvitamin D levels were significantly decreased in patients with MS (eTable 7). In pwMS/controls with osteoporosis compared to pwMS/controls without osteoporosis, total cholesterol, alkaline phosphatase, P1NP, CTX, LH and FSH were significantly increased, whereas, 17-beta estradiol, progresterone, prolactin, dehydroepiandrosterone, androstenedione, estrone, inhibin B and anti-Mullerian hormone were significantly decreased. There was a trend to higher osteopontin levels in pwMS/controls with osteoporosis compared to pwMS/controls without osteoporosis (eTable 8). In eTable 9, laboratory analysis in controls without or with osteoporosis and in MS patients without or with osteoporosis were compared.

      6. Discussion

      Osteoporosis is an underestimated comorbidity in MS associated with an increased morbidity and mortality. Early identification of patients at risk is crucial as an effective prophylactic treatment is available. In this study, we determined risk factors for osteoporosis in pwMS and propose a prospectively developed and highly accurate risk score as an easy screening tool in pwMS under the age of 65 years. Osteoporosis detected by DXA was found in approximately 30% of pwMS patients under 65 years. In a recent meta-analysis, a pooled prevalence of 17% was described (
      • Azadvari M.
      • Mirmosayyeb O.
      • Hosseini M.
      • Vaheb S.
      • Razavi S.Z.E.
      The prevalence of osteoporosis/osteopenia in patients with multiple sclerosis (MS): a systematic review and meta-analysis.
      ), which may be explained by the different study population regarding age, disability, and BMI. Furthermore, most studies included a relatively small number of patients. In addition, not all studies screened patients with DXA. The largest study included in the meta-analysis detected low bone mass only by a voluntary self-report registry (reporting 15.4%) (
      • Marrie R.A.
      • Cutter G.
      • Tyry T.
      • Vollmer T.
      A cross-sectional study of bone health in multiple sclerosis.
      ), whereas a similar prevalence as in our study was observed by a number of other studies in pwMS using DXA screening (
      • Weinstock-Guttman B.
      • Gallagher E.
      • Baier M.
      • et al.
      Risk of bone loss in men with multiple sclerosis.
      ;
      • Bisson E.J.
      • Ekuma O.
      • Marrie R.A.
      • Leslie W.D.
      • Finlayson M.L.
      Factors associated with receiving bone mineral density screening among people with multiple sclerosis.
      ;
      • Simonsen C.S.
      • Celius E.G.
      • Brunborg C.
      • et al.
      Bone mineral density in patients with multiple sclerosis, hereditary ataxia or hereditary spastic paraplegia after at least 10 years of disease - a case control study.
      ;
      • Bisson E.J.
      • Finlayson M.L.
      • Ekuma O.
      • Leslie W.D.
      • Marrie R.A.
      Multiple sclerosis is associated with low bone mineral density and osteoporosis.
      ).
      Several factors were suggested to be associated with osteoporosis, low BMD or pronounced bone loss in pwMS. In our study, risk factors for osteoporosis were age, sex, postmenopausal status in females, BMI and smoking corroborating well to known risk factors in the general population (
      • Raisz L.G.
      Clinical practice. Screening for osteoporosis.
      ). In male pwMS, the frequency of osteoporosis is less clear. In our study, risk was already increased in young male pwMS compared to premenopausal women and male HC and further increased with age. This is consistent with a high prevalence of osteoporosis in male individuals with MS (37.5%) disproportionate to their age (
      • Weinstock-Guttman B.
      • Gallagher E.
      • Baier M.
      • et al.
      Risk of bone loss in men with multiple sclerosis.
      ).
      In addition, a higher degree of physical disability - as assessed by the EDSS - was identified as an independent MS specific risk factor. A cut-off of a clinically relevant EDSS score >4.5 was determined. Greater disability was also associated with osteoporosis in a recent population-based study, however, this study considered use of home care services as a proxy for disability and did not determine EDSS score (
      • Bisson E.J.
      • Finlayson M.L.
      • Ekuma O.
      • Leslie W.D.
      • Marrie R.A.
      Multiple sclerosis is associated with low bone mineral density and osteoporosis.
      ). Other studies showed that ambulatory status, higher disability or severe MS course were associated with bone loss, low BMD and osteopenia or osteoporosis (
      • Olsson A.
      • Oturai D.B.
      • Sørensen P.S.
      • Oturai P.S.
      • Oturai A.B.
      Short-term, high-dose glucocorticoid treatment does not contribute to reduced bone mineral density in patients with multiple sclerosis.
      ;
      • Ozgocmen S.
      • Bulut S.
      • Ilhan N.
      • Gulkesen A.
      • Ardicoglu O.
      • Ozkan Y.
      Vitamin D deficiency and reduced bone mineral density in multiple sclerosis: effect of ambulatory status and functional capacity.
      ;
      • Cosman F.
      • Nieves J.
      • Komar L.
      • et al.
      Fracture history and bone loss in patients with MS.
      ;
      • Schwid S.R.
      • Goodman A.D.
      • Puzas J.E.
      • McDermott M.P.
      • Mattson D.H.
      Sporadic corticosteroid pulses and osteoporosis in multiple sclerosis.
      ;
      • Tüzün S.
      • Altintaş A.
      • Karacan I.
      • Tangürek S.
      • Saip S.
      • Siva A.
      Bone status in multiple sclerosis: beyond corticosteroids.
      ;
      • Tyblova M.
      • Kalincik T.
      • Zikan V.
      • Havrdova E.
      Impaired ambulation and steroid therapy impact negatively on bone health in multiple sclerosis.
      ;
      • Coskun Benlidayi I.
      • Basaran S.
      • Evlice A.
      • Erdem M.
      • Demirkiran M
      Prevalence and risk factors of low bone mineral density in patients with multiple sclerosis.
      ;
      • Nieves J.
      • Cosman F.
      • Herbert J.
      • Shen V.
      • Lindsay R.
      High prevalence of vitamin D deficiency and reduced bone mass in multiple sclerosis.
      ). Even though one study in male patients reported that osteoporosis is more likely diagnosed with an EDSS score ≥5.5, bone loss was detected in up to 60% of patients with a lower EDSS score (
      • Weinstock-Guttman B.
      • Gallagher E.
      • Baier M.
      • et al.
      Risk of bone loss in men with multiple sclerosis.
      ). Further studies showed bone loss in fully ambulatory pwMS (
      • Steffensen L.H.
      • Mellgren S.I.
      • Kampman M.T.
      Predictors and prevalence of low bone mineral density in fully ambulatory persons with multiple sclerosis.
      ;
      • Terzi T.
      • Terzi M.
      • Tander B.
      • Cantürk F.
      • Onar M.
      Changes in bone mineral density and bone metabolism markers in premenopausal women with multiple sclerosis and the relationship to clinical variables.
      ), newly diagnosed MS or even clinically isolated syndrome (
      • Moen S.M.
      • Celius E.G.
      • Sandvik L.
      • Nordsletten L.
      • Eriksen E.F.
      • Holmøy T.
      Low bone mass in newly diagnosed multiple sclerosis and clinically isolated syndrome.
      ), but manifest osteoporosis as measured by DXA was low in these studies. Altogether, these results are consistent with ours showing osteoporosis risk increased by 34% per increase of one point in EDSS score.
      In contrast to disability, lifetime cumulative GC dose was not associated with an increased osteoporosis risk. Evidence of the influence of short-term GC administration on osteoporosis development in pwMS is inconsistent and a cumulative dose of > 15 gr was suggested to negatively influence bone mass (
      • Huang Z.
      • Qi Y.
      • Du S.
      • Chen G.
      • Yan W.
      BMI levels with MS Bone mineral density levels in adults with multiple sclerosis: a meta-analysis.
      ). In most studies, no independent correlation of GC use and osteoporosis was reported (
      • Olsson A.
      • Oturai D.B.
      • Sørensen P.S.
      • Oturai P.S.
      • Oturai A.B.
      Short-term, high-dose glucocorticoid treatment does not contribute to reduced bone mineral density in patients with multiple sclerosis.
      ;
      • Weinstock-Guttman B.
      • Gallagher E.
      • Baier M.
      • et al.
      Risk of bone loss in men with multiple sclerosis.
      ;
      • Schwid S.R.
      • Goodman A.D.
      • Puzas J.E.
      • McDermott M.P.
      • Mattson D.H.
      Sporadic corticosteroid pulses and osteoporosis in multiple sclerosis.
      ;
      • Tüzün S.
      • Altintaş A.
      • Karacan I.
      • Tangürek S.
      • Saip S.
      • Siva A.
      Bone status in multiple sclerosis: beyond corticosteroids.
      ;
      • Ayatollahi A.
      • Mohajeri-Tehrani M.R.
      • Nafissi S.
      Factors affecting bone mineral density in multiple sclerosis patients.
      ;
      • Zengin Karahan S.
      • Boz C.
      • Kilic S.
      • et al.
      Lack of association between pulse steroid therapy and bone mineral density in patients with multiple sclerosis.
      ), indeed, even a protective effect of short-term GC treatment was suggested due to the prevention of disability (
      • Zorzon M.
      • Zivadinov R.
      • Locatelli L.
      • et al.
      Long-term effects of intravenous high dose methylprednisolone pulses on bone mineral density in patients with multiple sclerosis.
      ). Our study includes patients with a median cumulative lifetime GC dose of 12 gr and a maximum of 56 gr; therefore, it can be regarded as representative.
      It has been suggested that DMT may have a beneficial effect on bone density in pwMS patients (
      • Shuhaibar M.
      • McKenna M.J.
      • Au-Yeong M.
      • Redmond J.M.
      Favorable effect of immunomodulator therapy on bone mineral density in multiple sclerosis.
      ;
      • Miyazaki Y.
      • Niino M.
      • Kanazawa I.
      • et al.
      Fingolimod suppresses bone resorption in female patients with multiple sclerosis.
      ). Accordingly, an association of no DMT with higher risk of osteoporosis was observed. However, in multivariate analysis including confounding factors such as age and EDSS score, use of DMT was no longer associated with reduced osteoporosis risk. This reflects that patients with more progressed disease are less likely to receive DMT.
      Laboratory analysis revealed lower 25-hydroxyvitamin D levels in pwMS compared to HC. However, there was no association of low 25-hydroxyvitamin D levels and osteoporosis in our study. Whereas in some studies lower 25-hydroxyvitamin D levels were associated with low BMD and a faster bone loss (
      • Cosman F.
      • Nieves J.
      • Komar L.
      • et al.
      Fracture history and bone loss in patients with MS.
      ;
      • Nieves J.
      • Cosman F.
      • Herbert J.
      • Shen V.
      • Lindsay R.
      High prevalence of vitamin D deficiency and reduced bone mass in multiple sclerosis.
      ;
      • Terzi T.
      • Terzi M.
      • Tander B.
      • Cantürk F.
      • Onar M.
      Changes in bone mineral density and bone metabolism markers in premenopausal women with multiple sclerosis and the relationship to clinical variables.
      ), other studies support our finding and found no correlation between BMD and 25-hydroxyvitamin D levels in pwMS (
      • Olsson A.
      • Oturai D.B.
      • Sørensen P.S.
      • Oturai P.S.
      • Oturai A.B.
      Short-term, high-dose glucocorticoid treatment does not contribute to reduced bone mineral density in patients with multiple sclerosis.
      ;
      • Ozgocmen S.
      • Bulut S.
      • Ilhan N.
      • Gulkesen A.
      • Ardicoglu O.
      • Ozkan Y.
      Vitamin D deficiency and reduced bone mineral density in multiple sclerosis: effect of ambulatory status and functional capacity.
      ;
      • Tüzün S.
      • Altintaş A.
      • Karacan I.
      • Tangürek S.
      • Saip S.
      • Siva A.
      Bone status in multiple sclerosis: beyond corticosteroids.
      ;
      • Coskun Benlidayi I.
      • Basaran S.
      • Evlice A.
      • Erdem M.
      • Demirkiran M
      Prevalence and risk factors of low bone mineral density in patients with multiple sclerosis.
      ;
      • Triantafyllou N.
      • Lambrinoudaki I.
      • Thoda P.
      • et al.
      Lack of association between vitamin D levels and bone mineral density in patients with multiple sclerosis.
      ;
      • Assadi M.
      • Salimipour H.
      • Akbarzadeh S.
      • et al.
      Correlation of circulating omentin-1 with bone mineral density in multiple sclerosis: the crosstalk between bone and adipose tissue.
      ;
      • Kirbas A.
      • Kirbas S.
      • Anlar O.
      • Turkyilmaz A.K.
      • Cure M.C.
      • Efe H.
      Investigation of the relationship between vitamin D and bone mineral density in newly diagnosed multiple sclerosis.
      ). Furthermore, randomized trials showed no effect of high dose Vitamin D intake on BMD or biochemical markers of bone formation in pwMS (
      • Steffensen L.H.
      • Jørgensen L.
      • Straume B.
      • Mellgren S.I.
      • Kampman M.T.
      Can vitamin D supplementation prevent bone loss in persons with MS? A placebo-controlled trial.
      ;
      • Holmøy T.
      • Lindstrøm J.C.
      • Eriksen E.F.
      • Steffensen L.H.
      • Kampman M.T.
      High dose vitamin D supplementation does not affect biochemical bone markers in multiple sclerosis - a randomized controlled trial.
      ).
      In participants with osteoporosis, known bone turn over markers such as alkaline phosphatase, P1NP, and CTX were increased and typical postmenopausal, respectively age-related, hormonal changes (increase of LH and FSH, decrease of 17-beta estradiol, progresterone, prolactin, dehydroepiandrosterone, androstenedione, estrone, inhibin B and anti-Mullerian hormone) were observed compared to participant without osteoporosis. However, no additional effect in pwMS with osteoporosis was detected regarding bone metabolism markers. This is in line with previous results that showed that low testosterone levels alone did not explain the bone loss in male pwMS (
      • Weinstock-Guttman B.
      • Gallagher E.
      • Baier M.
      • et al.
      Risk of bone loss in men with multiple sclerosis.
      ), while disease duration and disability instead of bone markers were the main drivers of low bone mass in pwMS (
      • Terzi T.
      • Terzi M.
      • Tander B.
      • Cantürk F.
      • Onar M.
      Changes in bone mineral density and bone metabolism markers in premenopausal women with multiple sclerosis and the relationship to clinical variables.
      ), and there is a lack of difference in bone-related cytokines between pwMS and controls (
      • Assadi M.
      • Salimipour H.
      • Akbarzadeh S.
      • et al.
      Correlation of circulating omentin-1 with bone mineral density in multiple sclerosis: the crosstalk between bone and adipose tissue.
      ). However, this study detected a correlation of Omentin-1 with BMD in pwMS and osteopontin levels suggesting a cross-talk between adipose tissue and bone in MS. Further studies are needed to elucidate a possible shared pathophysiological mechanism between osteoporosis and MS.
      Based on a literature review, in 2010 an osteoporosis screening algorithm was proposed for pwMS with an EDSS score ≥6; postmenopausal women; an EDSS score <6 with a fracture; >3 month GC therapy or on antiepileptic therapy (
      • Hearn A.P.
      • Silber E.
      Osteoporosis in multiple sclerosis.
      ). However, in our study, neither fracture during the last 12 month nor ever fracture, antiepileptic or antispasmodic treatment was significant in the multivariate analysis. Therefore, in contrast to this review-based recommendation, we developed a MS-specific osteoporosis risk score based on a prospective study, which allows to determine the individual probability of osteoporosis in patients under 65 years. Importantly, EDSS score of 4.5 was identified as a relevant cut-point, which corresponds to an impaired ambulation status. The risk-score is an easily applicable tool as it only requires sex, age, smoking status, BMI, (post)menopausal status, and EDSS score as necessary parameters. With this newly developed score, the probability of osteoporosis can be predicted with an accuracy of 84%, a sensitivity of 62% and a specificity of 94% in pwMS under 65 years.
      A limitation of this study is that alcohol consumption and long-term low dose GC treatment could not be considered, due to the low alcohol consumption rate in pwMS and higher alcohol consumption in postmenopausal healthy women and male HC as well as the lack of participants using low dose long-term GC treatment. In addition, history of falls was not assessed, however, disability measured by EDSS considers gait disturbance and may be indirect evidence for the risk of falls. Data whether regular physiotherapy was done was not assessed in this study. This is probably another risk factor and should be considered by further research. Recent fractures were identified as relevant risk factor for osteoporosis prediction in MS (
      • Hearn A.P.
      • Silber E.
      Osteoporosis in multiple sclerosis.
      ). The number of fractures in the last year was very low and was not included in the proposed risk score. A possible explanation may be that we excluded patients with known osteoporosis and in most patients with fragility fracture osteoporosis screening is performed, this may be a bias underestimating the relevance of fragility fractures as relevant risk factor. However, as in the case of a fragility fracture DXA is recommended, it is not a relevant limitation for the application of the risk score.
      In conclusion, this study identified risk factors of osteoporosis and provides for an easily applicable risk score that allows the identification of even young pwMS with a high probability of osteoporosis and provides a rationale for osteoporosis screening, e.g., by DXA.
      Anne Zinganell, designed study, data acquisition, writing - review & editing
      Harald Hegen, designed study, data acquisition, formal analysis, drafted paper, writing - review & editing
      Janette Walde, formal analysis, writing - review & editing
      Angelika Bauer, data acquisition, writing - review & editing
      Klaus Berek, data acquisition, writing - review & editing
      Robert Barket, data acquisition, writing - review & editing
      Michael Auer, data acquisition, writing - review & editing
      Gabriel Bsteh, designed study, writing - review & editing
      Evelin Donnemiller, data acquisition, writing - review & editing
      Alexander Egger, data acquisition, writing - review & editing
      Astrid Grams, data acquisition, writing - review & editing
      Andrea Griesmacher, data acquisition, writing - review & editing
      Alexander Stephan Kroiss, data acquisition, writing - review & editing
      Florian Rettenwander, data acquisition, writing - review & editing
      Maximillian Tschallener, data acquisition, writing - review & editing
      Alexander Tschoner, data acquisition, writing - review & editing
      Thomas Berger, designed study, writing - review & editing
      Florian Deisenhammer, designed study, data acquisition, writing - review & editing
      Franziska Di Pauli, designed study, data acquisition, analysed data, drafted paper, writing - review & editing

      Disclosures

      AZ has participated in meetings sponsored by, received speaking honoraria or travel funding from Biogen, Merck, Sanofi-Genzyme and Teva; HH has participated in meetings sponsored by, received speaker honoraria or travel funding from Bayer, Biogen, Celgene, Merck, Novartis, Sanofi-Genzyme, Siemens, Teva, and received honoraria for acting as consultant for Biogen, Celgene, Novartis and Teva: JW has nothing to disclose; MA received speaker honoraria and/or travel grants from Biogen, Merck, Novartis and Sanofi; RB has participated in meetings sponsored by or received travel grants from Biogen, Novartis and Sanofi; AB has participated in meetings sponsored by or received travel funding from Novartis, Sanofi-Genzyme, Merck, Almirall and Biogen; KB has participated in meetings sponsored by and received travel funding from Roche and Biogen; GB has participated in meetings sponsored by, received speaker honoraria or travel funding from Biogen, Celgene/BMS, Lilly, Merck, Novartis, Roche, Sanofi-Genzyme and Teva, and received honoraria for consulting Biogen, Celgene/BMS, Novartis, Roche, Sanofi-Genzyme and Teva. He has received unrestricted research grants from Celgene/BMS and Novartis; ED has nothing to disclose; AE has nothing to disclose; AGra has nothing to disclose; AGri has nothing to disclose; ASK has nothing to disclose; FR has nothing to disclose; MT has nothing to disclose; AT has nothing to disclose; TB has participated in meetings sponsored by and received honoraria (lectures, advisory boards, consultations) from pharmaceutical companies marketing treatments for MS: Allergan, Bayer, Biogen, Bionorica, BMS/Celgene, Genesis, GSK, GW/Jazz Pharma, Horizon, Janssen-Cilag, MedDay, Merck, Novartis, Octapharma, Roche, Sandoz, Sanofi-Genzyme, Teva and UCB. His-institution has received financial support in the past 12 months by unrestricted research grants (Biogen, Bayer, BMS/Celgene, Merck, Novartis, Roche, Sanofi-Genzyme, Teva and for participation in clinical trials in multiple sclerosis sponsored by Alexion, Bayer, Biogen, Merck, Novartis, Octapharma, Roche, Sanofi-Genzyme, Teva; FD has participated in meetings sponsored by or received honoraria for acting as an advisor/speaker for Almirall, Alexion, Biogen, Celgene, Genzyme-Sanofi, Janssen, Merck, Novartis Pharma, Roche, and TEVA ratiopharm. His-institution has received research grants from Biogen and Genzyme Sanofi. He is section editor of the MSARD Journal (Multiple Sclerosis and Related Disorders); FDP has participated in meetings sponsored by, received honoraria (lectures, advisory boards, consultations) or travel funding from Bayer, Biogen, Janssen-Cilag, Merck, Novartis, Sanofi-Genzyme, Teva, Celgene and Roche. Her institution has received research grants from Roche.

      Acknowledgement

      We thank Markus Reindl for his advice and guidance in study design.
      The study was supported by Roche.

      Appendix. Supplementary materials

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