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P120. Vitamin D deficiency is common in Crohn's disease but also in healthy controls: a prospective case-control study

J. de Bruyn1, R. van Heeckeren1, K. Gecse1, C. Ponsioen1, G. van den Brink1, M. Löwenberg1, A.J. Bredenoord1, G. Frijstein2, G. D'Haens1, 1Academic Medical Center, Gastro-enterology, Amsterdam, Netherlands, 2Academic Medical Center, Occupational Health, Safety and Environment, Amsterdam, Netherlands

Background

Vitamin D deficiency is described in a wide range of medical conditions, among which Crohn's Disease (CD). This could be due to different mechanisms, including malabsorption, intestinal loss, decreased dietary intake, or insufficient sunlight exposure. We aim to assess whether CD patients have decreased vitamin D levels compared to healthy controls, and to determine risk factors for vitamin D deficiency.

Methods

We prospectively included CD patients visiting our outpatient clinic in the Netherlands immediately after summer (October and November 2012). Patients with functional oesophageal disorders and healthy hospital employees served as controls. Demographic data, sunlight exposure, dietary vitamin D intake, comorbidities and medication were recorded using validated questionnaires. In CD patients the Harvey–Bradshaw Index, Montreal classification and resections were also evaluated. We measured serum concentrations of 25(OH)D, CRP, calcium, phosphate, alkaline phosphatase and albumin. Based on literature data, we considered 25(OH)D levels >75 nmol/L normal; 50–75 nmol/L suboptimal, 25–50 nmol/L insufficient and <25 nmol/L deficient. Serum 25(OH)D was measured by Chemiluminescent immunoassay technology (DiaSorin Liaison).

Results

76 CD patients (mean age 42.6, IQR 31–52, 35% male) and 35 controls (mean age 35.3, IQR 25–40, 14% male) were included. Mean 25(OH)D level was 54 nmol/L in CD, and 62 nmol/L in controls (p = 0.18). Similar proportions of low 25(OH)D levels (<75 nmol/L) were seen in CD patients and controls (58/76 (76%) vs 25/35 (71%), p = 0.64), also when considering 50 nmol/L as lower limit of normal (39/76 (51%) vs 16/35 (46%), p = 0.68).

A few other variables were associated with vitamin D levels, as shown in Table 1. In multivariate linear regression analysis, not visiting solarium, azathioprine use, and ethnicity (Caucasian) were strongly correlated with vitamin D level (R = 0.56, p = 0.013, 0.03 and 0.014, respectively).

Table 1. Linear regression model of factors independently associated with serum 25(OH)D levels in CD, and in controls
Independent variableCDControls
Ethnicity (caucasian/non-caucasian)R = 0.37, p = 0.001R = 0.33, p = 0.051
Azathioprine use (n = 17)R = 0.24, p = 0.037 
Never visiting solariumR = 0.38, p = 0.001R = 0.44, p = 0.009
Country of birth (northern Europe/outside)R = 0.29, p = 0.012Not significant
Time spent outside, weeklyR = 0.24, p = 0.053Not significant
BMINot significantR = 0.39, p = 0.019

Conclusion

Vitamin D deficiency is common in CD patients, but also in healthy controls. For CD patients, ethnicity, never using a solarium and azathioprine use are associated with vitamin D levels. Appropriate vitamin D screening, the importance of dietary intake and sunlight exposure should be stressed to both patients and the normal population.