International Journal of Rheumatology
Volume 2017 (2017), Article ID 5491676, 8 pages
https://doi.org/10.1155/2017/5491676

Research Article

Evaluation of Vitamin D Status in Rheumatoid Arthritis and Its Association with Disease Activity across 15 Countries: “The COMORA Study”

Najia Hajjaj-Hassouni,1,2,3 Nada Mawani,1,2 Fadoua Allali,1,2 Hanan Rkain,1,2,4 Kenza Hassouni,⁵ Ihsane Hmamouchi,1,2 and Maxime Dougados⁶

¹LIRPOS-URAC30, Faculty of Medicine and Pharmacy, Mohammed V University, Rabat, Morocco
²Department of Rheumatology, El Ayachi Hospital, Ibn Sina University Hospital, Rabat-Salé, Morocco
³Innovation Center, Mohammed VI University for Health Sciences, Casablanca, Morocco
⁴Department of Physiology, Faculty of Medicine and Pharmacy, Mohammed V University, Rabat, Morocco
⁵International School for Public Health, Mohammed VI University for Health Sciences, Casablanca, Morocco
⁶Department of Rheumatology, Hôpital Cochin, Paris Descartes University, Assistance Publique-Hôpitaux de Paris, EULAR Center of Excellence, INSERM (U1153): Clinical Epidemiology and Biostatistics, PRES Sorbonne Paris-Cité, Paris, France

Correspondence should be addressed to Najia Hajjaj-Hassouni; nhajjajhassouni@gmail.com

Received 9 February 2017; Accepted 2 May 2017; Published 1 June 2017

Academic Editor: Bruce M. Rothschild

Copyright © 2017 Najia Hajjaj-Hassouni et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

The aims of this study are to evaluate vitamin D status in 1413 RA patients of COMORA study from 15 countries and to analyze relationship between patients’ RA characteristics and low levels of vitamin D. All demographic, clinical, and biological data and RA comorbidities were completed. The results showed that the average of vitamin D serum dosage was 27.3 ng/mL ± 15.1 0.1–151. Status of vitamin D was insufficient in 54.6% and deficient in 8.5% of patients. 43% of RA patients were supplemented with vitamin D and absence of supplementation on vitamin D was related to higher prevalence of vitamin D deficiency (). Finally, our study shows that the status of low levels of vitamin D is common in RA in different countries and under different latitudes. Absence of supplementation on vitamin D was related to higher prevalence of vitamin D deficiency. Low levels of vitamin D were associated with patients characteristics (age, BMI, and educational level), RA (disease activity and corticosteroid dosage), and comorbidities (lung disease and osteoporosis therapy). This suggests the need for a particular therapeutic strategy to improve vitamin D status in RA patients.

1. Background

In the last few years, vitamin D has been the subject of a spectacular interest and a renewed debate. Among all the topics involved, a great number of papers dealing with vitamin D relationships with autoimmune diseases have been published [1, 2]. Particularly, its role in the pathogenesis, activity, and treatment of rheumatoid arthritis (RA) has been raised, based on the observations and results of clinical and laboratory studies [1–12].

In fact, RA is an autoimmune disorder with a very complex physiopathology. The first triggering event could be the activation of antigen-dependent T cells leading to an essentially Th1 type immune response. The subsequent effects are multiple, including the activation and the proliferation of endothelial and synovial cells, recruitment and activation of proinflammatory cells, secretion of cytokines and proteases by macrophages and fibroblast-like synovial cells, and production of autoantibodies [1].

Vitamin D, as a prohormone, is considered to be able to play potential immune-suppressive roles and to exert an endocrine action on the immune system cells, generating anti-inflammatory and immunoregulatory effects [3, 4].

The rationale behind relating vitamin D and RA is based on two facts. The first one is that there is evidence indicating that patients with RA have low levels of vitamin D [5, 7, 8]. The second one is that the presence of vitamin D and VDR in macrophages, chondrocytes, and synovial cells in the joints of those patients has also been demonstrated [1].

Thus, relationship between RA and vitamin D has been extensively studied, and the results remain controversial. Several studies show that RA patients have lower levels of vitamin D [5, 6]. Either vitamin D insufficiency or deficiency was also described to be associated with higher risks of bone loss, disease activity, and disability [7–10]. However, other studies did not detect any association between RA and vitamin D concentration [12, 13].

The aims of this study are to evaluate vitamin D status in RA population of COMORA study and to analyze related factors between patients and their RA characteristics and low levels of vitamin D. We also aimed to compare vitamin D status between patients with and without vitamin D supplementation.

2. Patients and Methods

2.1. Data Source

This study is a post hoc analysis of COMORA (COMOrbidities in Rheumatoid Arthritis) cohort [14], an observational, cross-sectional, multicenter, international study. In our study, we have included patients who had a serum dosage of vitamin D among 3920 patients of COMORA study. Then 1431 were eligible to inclusion criteria.

2.2. Patient Recruitment

Consecutive patients visiting the participating rheumatologists were invited to enroll them in this study, only if they were at least 18 years old, if patients fulfilled the 1987 American College of Rheumatology (ACR) classification criteria for RA [15], and also if patients were able to understand and complete questionnaires that were administered to them. Written informed consent was obtained from all subjects before enrollment. The scientific committee chose national principal investigators for this study. Their task was to select rheumatologists who would be representative of their country and to conduct the study in accordance with good clinical practice. The protocol was reviewed and approved by all local institutional review boards or ethics committees.

2.3. Methods of Data Collection and Measurements

The details of the data collected have been published previously [1].

2.3.1. Patient’s Characteristics

In this study, 1413 patients from 15 countries were included. Demographic characteristics and disease-specific variables (age, gender, BMI, educational level, smoking status, and disease duration) were reported. The data of drug use and vitamin D supplementation were collected. Comorbidities (hypertension, diabetes, cancer, lung, liver and renal diseases, anemia and blood diseases, hepatitis B and C, ulcer, and stomach diseases) were documented for each patient.

2.3.2. Clinical Evaluation

Disease activity evaluated by DAS28 score (high > 5.1; 3.2 < moderate ≤ 5.1; 2.6 < low ≤ 3.2; and remission ≤ 2.6), functional impact of the disease evaluated by health assessment questionnaire (HAQ), and therapy (glucocorticoid intake, DMARDs, and biotherapy), and drugs affecting bone metabolism including bisphosphonates, calcium, and vitamin D supplements were described and compared according to vitamin “D” status.

2.3.3. Vitamin D Status

The data of current vitamin D levels (1 ng/mL = 2.5 nmol/L) were collected. Laboratory evaluation and method of measuring serum concentration of 25-hydroxyvitamin D (25 (OH) D) were not specified in the COMORA database. It should be noted that there is no perfect consensus today on the subject of the recommended thresholds to define the limit values of serum vitamin D levels, and those that are currently recognized by a panel of experts are very variable [16–18]. In our study, vitamin D status was defined according to the Group for Research and Information on Osteoporosis (GRIO), as normal when vitamin D levels ≥ 30 ng/mL, insufficient when 10 ng/mL ≤ vitamin D levels < 30 ng/mL, and deficient when ≤ 10 ng/mL [19].

2.4. Statistical Analysis

Continuous variables were expressed by median ± standard deviation or median (interquartile ranges) and categorical variables as number (percentage). Comparison of categorical variables was done by chi-square or Fisher’s exact test. Continuous variables were compared by Student’s -test. Comparison of continuous variables between normal, deficient, and insufficient vitamin D groups was done using ANOVA test. Furthermore, we used correlation analysis to compare between continuous variables. Linear regression models were performed, where factors were found to be significant to the level in univariate analysis. Odds ratios (OR) with 95% confidence interval (95% CI) were calculated. Statistical analysis was performed using the SPSS 18.0 for Windows (SPSS 18, Chicago, IL, USA).

3. Results

3.1. Patients and Disease Characteristics

Demographic and disease characteristics of RA patients are summarized on Table 1. The average age of patients was years. High education level was received by 67.2% of patients. Most of the patients were female (83%). The median DAS28 was [0–8.2].

Table 1: Demographic and disease characteristics of rheumatoid arthritis patients.

Characteristics

Age (years)
57.9 ± 12.8 18–88]

Female sex
1172 (82.9)

High educational level

(≥secondary)
950 (67.2)

BMI (kg/m²)
26.3 ± 5 15–53.1]

Current/past smoking
214 (15.1)

Disease duration (years)
8.3 (3.6–15.2)

DAS 28
3.5 ± 1.4 0–8.2]

Disease activity

    High
231 (16.3)

    Moderate
576 (40.8)

    Low
208 (14.7)

    Remission
398 (28.2)

Vitamin D level
27.3 ± 15.1 0.1–151]

HAQ
1 ± 0.6 0.4–1]

Glucocortocoid therapy intake
691 (48.9)

Current dose of glucocortocoid (mg/day)
0 0–5]

DMARDs

Immunosuppressor
17 (1.2)

APS
238 (16.8)

Salazopyrin
70 (4.9)

Golds
57 (4)

Methotrexate
763 (54)

Biotherapy
173 (12.2)

Comorbidities

Hypertension
494 (35)

Diabetes
133 (9.4)

Cancer
42 (3)

Lung diseases
110 (7.8)

Renal diseases
40 (2.8)

Anemia and blood diseases
165 (11.8)

Hepatitis B
39 (2.8)

Hepatitis C
18 (1.3)

Liver diseases
51 (3.6)

Ulcer and stomach diseases
166 (11.8)

Mean ± DS; number and percentage; median; BMI: body mass index; DAS28: Disease Activity Score using 28 joints; HAQ: health assessment questionnaire; APS: antimalarial drug, DMARDs: Disease-Modifying Antirheumatic Drugs.

3.2. Vitamin D Status

The mean vitamin “D” serum dosage was 27.3 ng/mL ± 15.1 0.1–151]. Status of vitamin D was normal, insufficient, and deficient in, respectively, 36.9, 54.6, and 8.5% of patients. Table 2 illustrated vitamin D status in different countries of COMORA study.

Table 2: Vitamin D status according to countries.

(%)
Vitamin D normal 
(%)
Vitamin D insufficiency 
(%)
Vitamin D deficiency 
(%)

Argentina
120 (100)
33 (27.5)
71 (59.2)
16 (13.3)

Austria
120 (100)
37 (30.8)
68 (56.7)
15 (12.5)

Egypt
1 (100)
0 (0)
1 (100)
0 ( 0)

France
309 (100)
146 (47.2)
152 (49.2)
11 ( 3.6)

Germany
45 (100)
13 (28.9)
30 (66.7)
2 (4.4)

Hungary
87 (100)
25 (28.7)
53 (60.9)
9 (10.3)

Italy
81 (100)
46 (56.8)
29 (35.8)
6 (7.4)

Korea
111 (100)
23 (20.7)
79 (71.2)
9 (8.1)

Morocco
34 (100)
8 (23.5)
20 (58.8)
6 (17.6)

Netherlands
3 (100)
0 (0)
2 (66.7)
1 (33.3)

Spain
133 (100)
37 (27.8)
83 (62.4)
13 ( 9.8)

Taiwan
88 (100)
7 (8.0)
58 (65.9)
23 (26.1)

UK
1 (100)
0 (0)
1 (100)
0 (0)

Uruguay
9 (100)
3 (33.3)
5 (55.6)
1 (11.1)

USA
271 (100)
143 (52.8)
120 (44.3)
8 ( 3)

Total
1413 (100)
521 (36.9)
772 (54.6)
120 (8.5)

Number and percentage; vitamin D ≥ 30 ng/mL, 10 ng/mL ≤ Vitamin D < 30 ng/mL, and vitamin D < 10 ng/mL.

3.3. Patients’ Comorbidities

Hypertension, anemia, blood diseases, ulcer, and stomach diseases were the most common comorbidities in our study (Table 1). Patients with vitamin D insufficiency had more comorbidities and were significantly associated with lung diseases and osteoporosis therapy ( and , resp.) (Table 4).

3.4. Association Analysis between Vitamin D Status and Patients RA Characteristics

In univariate analysis (Tables 3 and 4), low levels of vitamin D were associated with higher age (), higher BMI (), higher disease activity (), more current daily dose of corticosteroids (), lower level of education (), antiosteoporotic treatment (), and presence of lung diseases (). The vitamin D levels were inversely correlated with disease activity assessed by DAS28 (; ).

Table 3: Relationship between demographic and disease characteristics of RA patients and vitamin D status.

Vitamin D normal
Vitamin D insufficiency
Vitamin D deficiency

Age (years)
57.2 ± 12.7 19–86]
56.4 ± 12.8 [18–88]
59.2 ± 12.8 [19–88]
<0.001

Female sex
426 (36.3)
640 (54.6)
106 (9)
0.27

BMI (kg/m)
26.9 ± 5.7 15.1–53.9]
26.4 ± 5.7 [15.6–50.2]
25.9 ± 5.2 [16.1–47.2]
0.02

Smoking current/past
204 (35.8)
152 (26.7)
214 (37.5)
0.8

High educational level
377 (39.7)
509 (53.6)
64 (6.7)
<0.001

Disease duration (years)
11.8 ± 10 0.02–56.2]
10.1 ± 0.02–56.2]
10.3 ± 9.2 0–54]
1.0

Glucocorticoid intake
249 (36)
208 (30.1)
234 (33.9)
0.04

DAS28
3.3 ± 0.06 0–8.2]
3.5 ± 0.05 0.4–8.1]
3.6 ± 0.1 1.1–7.3]
0.01

HAQ
0.9 ± 0.6 [0.4–3]
1.02 ± 0.6 [0.4–3]
1.02 ± 0.6 0.4–2.9]
0.5

Mean ± DS; number and percentage; vitamin D ≥ 30 ng/mL, 10 ng/mL ≤ vitamin D < 30 ng/mL, and vitamin D < 10 ng/mL; BMI: body mass index; DAS28: Disease Activity Score using 28 joints; HAQ: health assessment questionnaire; significant if ≤0.05.

Table 4: Association analysis between comorbidities and vitamin D status.

Comorbidities
Vitamin D
normal
Vitamin D
insufficiency
Vitamin D
deficiency

Hypertension
181 (36.6)
272 (55.1)
41 (8.3)
0.9

Diabetes
46 (34.6)
76 (57.1)
11 (8.3)
0.8

Dyslipidemia
41 (33.6)
66 (54.1)
15 (12.3)
0.2

Renal deficiency
15 (37.5)
21 (52.5)
4 (10)
0.9

Anemia and blood diseases
66 (40)
88 (53.3)
11 (6.7)
0.5

Cancer
18 (42.9)
21 (50)
3 (7.1)
0.7

Osteoporosis therapy
124 (42.6)
150 (51.5)
17 (5.8)
0.04

Lung diseases (COPD, asthma, cancer)
50 (45.5)
45 (40.9)
15 (13.6)
0.006

Liver diseases
20 (39.2)
26 (51)
5 (9.8)
0.8

Ulcer and stomach disease
156 (33.7)
91 (54.8)
19 (11.4)
0.3

Number and percentage; vitamin D ≥ 30 ng/mL, 10 ng/mL ≤ vitamin D < 30 ng/mL, and vitamin D < 10 ng/mL; significant if ≤0.05.

In multivariate analysis, all those variables except presence of lung diseases remain significantly associated with a bad status of vitamin D. Association analysis between vitamin D status and patients RA characteristics is summarized in Table 5.

Table 5: Multivariate analysis between vitamin D levels and characteristics of RA patients.

IC

Age (years)
0.14
0.10; 0.23]
<0.001

BMI (kg/m²)
−0.07
−0.35; −0.06]
0.004

High educational level
0.12
2.39; 5.85]
<0.001

DAS28
−0.05
−1.21; −0.05]
0.03

Glucocorticoid intake (mg/day)
−0.08
−0.30; −0.06]
0.003

Osteoporotic therapy intake
−0.07
−4.53; −0.65]
0.009

Lung diseases
−0.01
−4.82; −2.74]
0.58

significant 0.05.

3.5. Relationship between Vitamin D Supplementation and Vitamin D Status

In this cohort, 43% of RA patients were supplemented with vitamin D (Table 6). Comparing vitamin D status between patients with and without vitamin D supplementation showed that deficiency on vitamin D was more prevalent in patients without vitamin D supplementation (). Prevalence of a normal status of vitamin D was significantly higher in patients with vitamin D supplementation (). Table 7 illustrated those findings.

Table 6: Vitamin D intake according to countries.

Country
Patients with vitamin D supplementation
Patients without vitamin D supplementation
Total

Argentina
72 (60)
48 (40)
120 (100)

Austria
37 (30.8)
83 (69.2)
120 (100)

Egypt
0 (0)
1 (100)
1 (100)

France
99 (32)
210 (68)
309 (100)

Germany
21 (46.7)
24 (53.3)
45 (100)

Hungary
46 (52.9)
41 (47.1)
87 (100)

Italy
44 (54.3)
37 (45.7)
81 (100)

Korea
58 (52.3)
53 (47.7)
111 (100)

Morocco
12 (35.5)
22 (64.7)
34 (100)

Netherlands
2 (66.7)
1 (33.3)
3 (100)

Spain
57 (42.9)
76 (57.1)
133 (100)

Taiwan
64 (72.7)
24 (27.3)
88 (100)

UK
1 (100)
0 (0)
1 (100)

Uruguay
1 (11.1)
8 (88.9)
9 (100)

USA
94 (34.7)
177 (65.3)
271 (100)

Total
608 (43)
805 (57)
1413 (100)

Number and percentage.

Table 7: Vitamin D status according to vitamin D supplementation.

Patients with vitamin D supplement 
()
Patients without vitamin D supplement 
()
value

Vitamin D normal ()
353 (43.9)
168 (27.6)
<0.001

Vitamin D insufficiency ()
403 (50.1)
369 (60.7)
<0.001

Vitamin D deficiency ()
49 (6.1)
71 (11.7)
<0.001

Number and percentage; vitamin D ≥ 30 ng/mL, 10 ng/mL ≤ vitamin D < 30 ng/mL, and vitamin D < 10 ng/mL; significant ≤ 0.05.

4. Discussion

This study showed that prevalence of low vitamin D levels is common in RA patients. This prevalence was really varied between countries, with the highest rates found in Korea and the lowest rates in Italy (71% and 36%, resp.). This variability may be explained by some differences among the populations, such as racial/ethnic differences, regional climates, lack of sun exposure, veiled clothing style, or latitude [7, 20, 21]. Indeed we have long considered that vitamin D insufficiency and deficiency were the preserve of the few sunny countries, particularly in Northern Europe, with a North-South gradient in Europe. In fact, recent data shows that the tropicals or subtropicals, such as Central America and the Middle East, particularly Asia, are also widely affected [22]. This has several explanations: no sun exposure in hot countries, coloured skin which synthesizes less vitamin D, and wearing protective clothing. This variability could also be related to the well-known vitamin D receptor (VDR) gene polymorphism and its expression across different populations, able to influence RA severity [20, 23, 24].

Current epidemiological data indicates a high prevalence of vitamin D insufficiency in patients with autoimmune diseases and especially in RA when compared to the general population [25, 26]. However according to some studies, there is a great variability most likely because of the size and the methodology used in these studies or according to the characteristics of the populations. In Turkey and India, the prevalence of vitamin D insufficiency was, respectively, about 68% and 90% [20, 27]. In Denmark, Haga et al. evaluated it up to 33.4% [28]. This prevalence was around 43% in an Italian cohort [8]. In the USA, the prevalence ranges from 41% up to 84% [5, 29], and it was common in African Americans with recent-onset RA, affecting approximately half of this population [7]. When considering countries latitudes, some studies have shown that vitamin D insufficiency, together with a higher prevalence of RA, was more common among Northern patients than in Southern European patients [21]. Even in northern latitudes, vitamin D insufficiency has been linked to higher latitude as it further characterizes Greenlanders versus Danes [30].

Although the primary determinant of vitamin D status is sunlight exposure [31], the prevalence of vitamin D deficiency is paradoxically higher in sunny countries [31]. In Morocco, in spite of the sunny climate, prevalence of vitamin D insufficiency has been demonstrated as exceeding that of the European cohorts, as it affects about 91% of Moroccan women [32, 33].

One hypothesis for vitamin D insufficiency throughout the countries may be latitude. Indeed it has been described that prevalence of RA increases with higher latitude [34, 35]. However, it has been described that vitamin D levels are low in RA patients in low latitude [9, 19], especially in above latitude 33° (north of a line through the North of Morocco, Northern Algeria, Iran, Iraq, Japan, and Los Angeles). It was considered that it is not possible to synthesize vitamin D by exposure to sunlight for some winter months [19]. Unfortunately, in our study, this status of latitude could not be studied to verify this relationship.

In this study, vitamin D status was associated with several independent factors that have previously been shown to affect vitamin D [23]. We found a significant association with low levels of vitamin D and age, educational level, and BMI. This correlation remained significant even after multivariate adjustment (Table 6). In fact, regardless of the disease, the dietary intake and cutaneous production of vitamin D decreases with age and adiposity [35, 36]. Also patients, who had a high educational level, had better vitamin D status, with a higher prevalence of normal vitamin D level. This is probably due to their better understanding of their disease and its complications, as well as their greater ability to perform the dosage of vitamin D.

There was a negative relationship between vitamin D levels and RA disease activity in our study. After multivariate adjustment, this correlation between vitamin D levels and DAS28 scores persisted. That is to say, DAS28 scores increase when vitamin D levels decrease.

In fact, the association between low vitamin D levels and active RA is widely debated in the literature with conflicting data. Our results are consistent with some studies [5, 8–10, 12, 21, 29, 37, 38], while others did not find any significant relationship between RA and low vitamin D levels [7, 11, 39, 40]. This relationship may be related to latitude as it was described. In low-latitude regions, there is not a lot of sun exposure because of the months of rain, which could exacerbate joint pain and increase the DAS28 scores [9].

Osteoporosis, whose prevalence was estimated by percentage of patients taking a specific antiosteoporotic drug in our study, was significantly higher in patients with low vitamin D levels. This is probably related to RA which generates bone loss and corticosteroids use which increases bone remodeling and decreases bone density. This can also be explained by the fact that a low vitamin D level is involved in the pathogenesis of osteoporosis [15, 41, 42]. Indeed, it has been shown that low vitamin D levels may be the result of changes in cortical bone and lead to bone fragility [22].

In our study, vitamin D insufficiency was also significantly associated with other comorbidities in RA mostly lung diseases. In fact, it was described that patients with respiratory disease are frequently deficient in vitamin D [43]. This is probably related to the fact that respiratory monocytes/macrophages and epithelial cells constitutively express the vitamin D receptor. Smoking also may lead to the deficiency of vitamin D, but in our study, there was no significant association between smoking and vitamin D status. Other studies have shown that lower vitamin D levels increase the VDR gene mutations. This could be an explanation of increase risk of lung cancer [44, 45]. This was not found in our study.

Glucocorticoids intake remains independently and inversely associated with low vitamin D levels in our study. The GRIO had already recommended a systematic supplementation in patients using a long-term corticotherapy [19]. Recently, corticosteroids and vitamin “D” have been subjects to experimental studies and clinical trials in a plethora of autoimmune diseases. These molecules are ligands for the nuclear receptor, which results in a direct regulation of transcription of genes involved in the immune system. This eventually leads to an immune response less proinflammatory and, therefore, beneficial in autoimmune diseases [46].

In our study, 43% of the patients were supplemented with vitamin D. This prevalence varied widely between countries. This is could be explained by the variability in the number of patients included in each country. Patients, who were supplemented by vitamin D in our study, had a better vitamin D status than those who had no vitamin D supplementation. And the opposite, patients who were not supplied had a vitamin D deficiency. This implies necessity to optimize doses of vitamin D supplementation in RA patients. Some studies have concluded that clinical improvement in RA patients treated with vitamin D was strongly correlated with the immunomodulating potential of vitamin D administration [3, 47], while others suggest that antirheumatic drugs combined with vitamin D should be recommended for RA patients, in order to prevent and treat osteoporosis and improve its effect on disease activity [46].

Our study had some limitations. Firstly, our data included 1413 RA patients that are corresponding to 36% of the COMORA study population. This is reflecting the rheumatologist practice in real life regarding prescription of vitamin D dosage in RA patients. This lack of vitamin D dosage might be related to the difference in attitudes of health practitioners on the request of the dosage of vitamin D or to the cost of this assay and its repayment by the health insurance in some countries.

Secondly, the method of vitamin D dosing was not specified in the COMORA database. Certainly, there is variability in methods of assay in each country. In fact there are several ways to measure 25 (OH) D (radio-immunoassays, enzyme-linked assays, and liquid chromatography with mass spectrometry). The precision and accuracy of the assays especially in nonreference laboratories remain problematic. There is also no reference method or international standard today for the determination of the 25 (OH) vitamin D. The characteristics required to define future reference method, which will probably be mass spectrometry after chromatography gas or liquid, have been proposed recently [48].

Thirdly, the association between vitamin D status and osteoporosis in our study is to some extent unsatisfying. In fact, the prevalence of osteoporosis has been estimated on the basis of percentage of patients taking antiosteoporotic drugs. We have certainly omitted patients with osteoporosis without any antiosteoporotic treatment.

Finally, schemes of vitamin D supplementation were not available in COMORA database. Consequently, it is not clear at all if those schemes were really adequate or not.

Despite those limitations, our data has several strengths. Comparing to other studies focusing on vitamin D status and RA, our data has the advantage to include a large number of patients. We have described vitamin D in 15 countries. Prevalence of low vitamin D levels seems to be high in most of them. Nevertheless, we are not able to make any adequate comparison on vitamin D status between the 15 countries as well. This is due to discrepancies in population number, age, and other RA and disease characteristics. In addition to this, our study showed that status on vitamin D was better in patients who have vitamin D supplementation.

5. Conclusion

A status of low level of vitamin D is common in RA in different countries and under different latitudes. Absence of supplementation on vitamin D is related to higher prevalence of vitamin D deficiency. Many factors related to patients and their diseases seem to be associated with low level of vitamin D.

Vitamin D supplementation by active natural or synthetic analogs could possibly be used as an adjunct therapy with DMARDs in patients with active RA. Moreover, it can be considered as an inexpensive, potentially safe, and beneficial adjuvant aimed to reducing disease severity as well as joint and bone destruction. Nevertheless, randomized and controlled trials are necessary to determine from which reference levels deficiency or insufficiency should be considered. It is also necessary to evaluate which mechanism and which dosing of drug to choose. All this is to achieve pharmacological and clinical efficacy and safety, suggesting specific treatment strategies especially in RA patients.

Abbreviations

ACR: | American College of Rheumatology
APS: | Antimalarial drug
BMI: | Body mass index
CRP: | Creative reactive protein
CI: | Confidence interval
DAS28: | Disease Activity Score using 28 joints
DMARDs: | Disease-Modifying Antirheumatic Drugs
ESR: | Erythrocyte sedimentation rate
GRIO: | Group for Research and Information on Osteoporosis
HAQ: | Health assessment questionnaire
SD: | Standard deviation
SJC: | Swollen joint count
TJC: | Tender joint count
PhGA: | Physician global assessment
RA: | Rheumatoid arthritis
UVR: | Ultraviolet ray
VDR: | Vitamin D receptor.

Data Access

The database is available from Pr. Najia Hajjaj-Hassouni.

Ethical Approval

The ethics committee of Rabat University Mohamed V approved the study protocol.

Consent

All patients gave informed written consent prior to their inclusion in the study.

Disclosure

This work was supported by Roche Pharmaceuticals. Roche Pharmaceuticals had no role in the study design, data collection, data analysis, or writing of this manuscript. Publication of this article was not contingent on the approval of this study sponsor.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

Authors’ Contributions

Najia Hajjaj-Hassouni made substantial contributions to the conception and design of the study and to the interpretation of data, helped to draft the article and to review it critically for important intellectual content, and gave final approval of the version to be published. Nada Mawani and Ihsane Hmamouchi made substantial contributions to collecting the data and interpreting them, performed the analyses, and helped to draft the article. Fadoua Allali and Hanan Rkain made substantial contribution to the conception and design of the study and helped to draft the article and to critically review it. Kenza Hassouni made substantial contribution to interpreting the data and to critically reviewing the draft. Maxime Dougados made substantial contributions to the conception and design of the study after having set up the whole cohort, organized the collection of the data and their interpretation, helped to critically review for important intellectual content, and gave final approval of the version to be published.

Acknowledgments

The authors would like to thank Pr. Maxime Dougados, the René Descartes University Paris, the Mohammed V University, Rabat, Morocco, and the Mohammed VI University for Health Sciences for having made this collaboration possible. They also would like to thank all the patients and investigators who participated in this study.

References

C. D. L. Marques, A. T. Dantas, T. S. Fragoso, and Â. L. B. P. Duarte, “The importance of vitamin D levels in autoimmune diseases,” Bras J Rheumatol, vol. 50, no. 1, pp. 67–80, 2010.

A. Antico, M. Tampoia, R. Tozzoli, and N. Bizzaro, “Can supplementation with vitamin D reduce the risk or modify the course of autoimmune diseases? A systematic review of the literature,” Autoimmunity Reviews, vol. 12, no. 2, pp. 127–136, 2012.

M. Cutolo, K. Otsa, M. Uprus, S. Paolino, and B. Seriolo, “Vitamin D in rheumatoid arthritis,” Autoimmunity Reviews, vol. 7, no. 1, pp. 59–64, 2007.

P. Welsh, M. J. L. Peters, and N. Sattar, “Is vitamin D in rheumatoid arthritis a magic bullet or a mirage? the need to improve the evidence base prior to calls for supplementation,” Arthritis and Rheumatism, vol. 63, no. 7, pp. 1763–1769, 2011.

G. S. Kerr, I. Sabahi, J. S. Richards et al., “Prevalence of vitamin D insufficiency/deficiency in rheumatoid arthritis and associations with disease severity and activity,” The Journal of Rheumatology, vol. 38, no. 1, pp. 53–59, 2011.

M. Varenna, M. Manara, F. Cantatore et al., “Determinants and effects of vitamin D supplementation on serum 25-Hydroxy-vitamin levels in patients with rheumatoid arthritis,” Clinical and Experimental Rheumatology, vol. 30, no. 5, pp. 714–719, 2012.

S. M. Craig, F. Yu, J. R. Curtis et al., “Vitamin D status and its associations with disease activity and severity in African Americans with recent-onset rheumatoid arthritis,” Journal of Rheumatology, vol. 37, no. 2, pp. 275–281, 2010.

M. Rossini, S. Maddali Bongi, G. La Montagna et al., “Vitamin D deficiency in rheumatoid arthritis: prevalence, determinants and associations with disease activity and disability,” Arthritis Research & Therapy, vol. 12, pp. 216–223, 2010.

Y. H. Lee and Bae S. C., “Vitamin D level in rheumatoid arthritis and its correlation with the disease activity: a meta-analysis,” Clinical and Experimental Rheumatology, vol. 34, pp. 827–833, 2016.

J. Lin, J. Liu, M. L. Davies, and W. Chen, “Serum Vitamin D level and rheumatoid arthritis disease activity: Review and meta-analysis,” PLoS ONE, vol. 11, no. 1, Article ID e0146351, 2016.

T. Baykal, K. Senel, F. Alp, A. Erdal, and M. Ugur, “Is there an association between serum 25-hydroxyvitamin D concentrations and disease activity in rheumatoid arthritis?” Bratislava Medical Journal, vol. 113, no. 10, pp. 610-611, 2012.

S. M. Attar, “Vitamin D deficiency in rheumatoid arthritis. Prevalence and association with disease activity in Western Saudi Arabia,” Saudi Med J, vol. 33, no. 5, pp. 520–525, 2012.

F. C. Arnett, S. M. Edworthy, D. A. Bloch et al., “The American Rheumatism Association 1987 revised criteria for the classification of rheumatoid arthritis,” Arthritis & Rheumatism, vol. 31, no. 3, pp. 315–324, 1988.

M. Dougados, M. Soubrier, A. Antunez et al., “Prevalence of comorbidities in rheumatoid arthritis and evaluation of their monitoring: Results of an international, cross-sectional study (COMORA),” Annals of the Rheumatic Diseases, vol. 73, no. 1, pp. 62–68, 2014.

K. Briot, M. Audran, B. Cortet et al., “Vitamin D: skeletal and extra skeletal effects; recommendations for good practice,” Presse Medicale, vol. 38, no. 1, pp. 43–54, 2009.

R. Rizzoli, S. Boonen, M. L. Brandi et al., “Vitamin D supplementation in elderly or postmenopausal women: a 2013 update of the 2008 recommendations from the European Society for Clinical and Economic Aspects of Osteoporosis and Osteoarthritis (ESCEO),” Current Medical Research and Opinion, vol. 29, no. 4, pp. 305–313, 2013.

H. A. Bischoff-Ferrari, A. Shao, B. Dawson-Hughes, J. Hathcock, E. Giovannucci, and W. C. Willett, “Benefit-risk assessment of vitamin D supplementation,” Osteoporosis International, vol. 21, no. 7, pp. 1121–1132, 2010.

M. F. Holick et al., “Evaluation, treatment, and prevention of vitamin D deficiency: an endocrine society clinical practice guideline,” The Journal of Clinical Endocrinology and Metabolism, vol. 96, pp. 1911–1930, 2011.

C. L. Benhamou et al., “La vitamine D chez l’adulte : recommandations du GRIO,” La Presse Médicale, vol. 40, pp. 673–682, 2011.

C. A. Hitchon, Y. Sun, D. B. Robinson et al., “Vitamin D receptor polymorphism rs2228570 (Fok1) is associated with rheumatoid arthritis in North American natives,” Journal of Rheumatology, vol. 39, no. 9, pp. 1792–1797, 2012.

M. Cutolo et al., “Circannual vitamin D serum levels and disease activity in rheumatoid arthritis: Northen versus Southern Europe,” Clinical and Experimental Rheumatology, vol. 24, pp. 702–704, 2006.

M. F. Holick, “Vitamin D deficiency,” The New England Journal of Medicine, vol. 357, no. 3, pp. 266–281, 2007.

B. Bouvard, C. Annweiler, A. Sallé et al., “Extraskeletal effects of vitamin D: facts, uncertainties, and controversies,” Joint, Bone, Spine: Revue du Rhumatisme, vol. 78, no. 1, pp. 10–16, 2011.

P. Leventis and S. Patel, “Clinical aspects of vitamin D in the management of rheumatoid arthritis,” Rheumatology, vol. 47, no. 11, pp. 1617–1621, 2008.

H. A. Bischoff-Ferrari, W. C. Willett, J. B. Wong, E. Giovannucci, T. Dietrich, and B. Dawson-Hughes, “Fracture prevention with vitamin D supplementation: a meta-analysis of randomized controlled trials,” Journal of the American Medical Association, vol. 293, no. 18, pp. 2257–2264, 2005.

P. Aguado, M. T. Del Campo, M. V. Garcés et al., “Low vitamin D levels in outpatient postmenopausal women from a rheumatology clinic in Madrid, Spain: Their relationship with bone mineral density,” Osteoporosis International, vol. 11, no. 9, pp. 739–744, 2000.

K. Gopinath and D. Danda, “Supplementation of 1,25 dihydroxy vitamin D3 in patients with treatment naive early rheumatoid arthritis: a randomised controlled trial,” International Journal of Rheumatic Diseases, vol. 14, no. 4, pp. 332–339, 2011.

H. J. Haga, A. Schmedes, Y. Naderi, A. M. Moreno, and E. Peen, “Severe deficiency of 25-hydroxyvitamin D₃(25-OH-D₃) is associated with high disease activity of rheumatoid arthritis,” Clinical Rheumatology, vol. 32, no. 5, pp. 629–633, 2013.

U. J. Haque, J. M. Bathon, and J. T. Giles, “Association of vitamin D with cardiometabolic risk factors in rheumatoid arthritis,” Arthritis Care and Research, vol. 64, no. 10, pp. 1497–1504, 2012.

L. Rejnmark, M. E. Jorgensen, M. B. Pedersen et al., “Vitamin D insufficiency in greenlanders on a westernized fare: ethnic differences in calcitropic hormones between greenlanders and danes,” Calcified Tissue International, vol. 74, no. 3, pp. 255–263, 2004.

M.-H. Gannagé Yared, R. Chemali, N. Yaacoub, and G. Halaby, “Hypovitaminosis D in a sunny country: Relation to lifestyle and bone markers,” Journal of Bone and Mineral Research, vol. 15, no. 9, pp. 1856–1862, 2000.

F. Allali, S. El Aichaoui, H. Khazani et al., “High prevalence of hypovitaminosis D in Morocco: relationship to lifestyle, physical performance, bone markers, and bone mineral density,” Seminars in Arthritis and Rheumatism, vol. 38, no. 6, pp. 444–451, 2009.

N. Seknaji et al., “Prévalence de l’hypovitaminose D chez les patients marocains atteints de polyarthrite rhumatoïde et association avec l’activité de la maladie,” Revue du Rhumatisme, vol. 79, no. S1, p. A248, 2012.

M. Cutolo et al., “Solar light effects on onset/relapses and circannual/circadian symptomatology in rheumatoid arthritis,” Clinical and Experimental Rheumatology, vol. 2, pp. 148–150, 2003.

A.-L. Ponsonby, R. M. Lucas, and I. A. F. Van Der Mei, “UVR, vitamin D and three autoimmune diseases—Multiple sclerosis, type 1 diabetes, rheumatoid arthritis,” Photochemistry and Photobiology, vol. 81, no. 6, pp. 1267–1275, 2005.

M. F. Holick, “High prevalence of vitamin D inadequacy and implications for health,” Mayo Clinic Proceedings, vol. 81, no. 3, pp. 353–373, 2006.

B. Heidari, K. Hajian-Tilaki, and P. Heidari, “The status of serum vitamin D in patients with rheumatoid arthritis and undifferentiated inflammatory arthritis compared with controls,” Rheumatology International, vol. 32, no. 4, pp. 991–995, 2012.

U. J. Haque et al., “Relationship among vitamin D, disease activity, pain and disability in rheumatoid arthritis,” Clinical and Experimental Rheumatology, vol. 28, no. 5, pp. 745–747, 2010.

J. F. Baker et al., “Associations between vitamin D, disease activity, and clinical response to therapy in rheumatoid arthritis,” Clinical and Experimental Rheumatology, vol. 30, no. 5, pp. 658–664, 2012.

E. P. Cherniack, “A ray of hope for tender joints: vitamin D and rheumatoid arthritis,” Journal of Rheumatology, vol. 38, no. 1, pp. 5–7, 2011.

M. Audran and K. Briot, “Critical reappraisal of vitamin D deficiency,” Joint Bone Spine, vol. 77, no. 2, pp. 115–119, 2010.

B. Dawson-Hughes, A. Mithal, J.-P. Bonjour et al., “IOF position statement: vitamin D recommendations for older adults,” Osteoporosis International, vol. 21, no. 7, pp. 1151–1154, 2010.

M. T. Zdrenghea, H. Makrinioti, C. Bagacean et al., “Vitamin D modulation of innate immune responses to respiratory viral infections,” Reviews in Medical Virology, vol. 27, no. 1, 2016.

W. Xiayu et al., “Vitamin D-related gene polymorphisms, plasma 25-Hydroxy-vitamin D, cigarette smoke and non-small cell lung cancer (NSCLC) Risk,” International Journal Of Molecular Sciences, vol. 17, p. 1597, 2016.

L. J. Hoffer et al., “Appropriate vitamin D loading regimen for patients with advanced lung cancer,” Nutrition Journal, vol. 15, p. 84, 2016.

T.-H. Kim, S. J. Choi, Y. H. Lee, G. G. Song, and J. D. Ji, “Combined therapeutic application of mTOR inhibitor and vitamin D₃ for inflammatory bone destruction of rheumatoid arthritis,” Medical Hypotheses, vol. 79, no. 6, pp. 757–760, 2012.

L. A. Merlino, J. Curtis, T. R. Mikuls, J. R. Cerhan, L. A. Criswell, and K. G. Saag, “Vitamin D intake is inversely associated with rheumatoid arthritis: results from the Iowa Women’s Health Study,” Arthritis & Rheumatism, vol. 50, no. 1, pp. 72–77, 2004.

N. Binkley, D. Krueger, C. S. Cowgill et al., “Assay variation confounds the diagnosis of hypovitaminosis D: a call for standardization,” Journal of Clinical Endocrinology and Metabolism, vol. 89, no. 7, pp. 3152–3157, 2004.