Vitamin D deficiency in type 1 narcolepsy: a reappraisal.

OBJECTIVES

Narcolepsy type 1 (NT1) is considered to be an immune-mediated disease in which environmental factors, such as vitamin D, might play a major role. The association between NT1 and vitamin D deficiency has previously been reported. The aim of this case-control study was to reassess vitamin D levels in a large clinic-based adult and paediatric population of patients with NT1 by considering several potential confounding factors.

METHODS

The serum level of 25-hydroxyvitamin D (25OHD) was measured in 174 Caucasian patients with NT1 and 174 controls. Demographic and clinical features, body mass index (BMI), Pandemrix® vaccination, age, and season at the time of blood sampling were recorded. Between-group comparisons were made using univariate and multivariate logistic regression analyses. When appropriate, interaction terms were tested using the Wald Chi-squared test.

RESULTS

Age, BMI, and season of blood sampling were different between groups. Conversely, the 25OHD level and fraction of subjects with vitamin D deficiency (serum level <75 nmol/L: 46.6% of patients vs 48.3% of controls; <50 nmol/L: 20.7% vs 17.2%) did not differ between patients with NT1 and controls. Overall, vitamin D deficiency was more frequent in men, obese subjects, and in samples collected in winter, without any association with NT1. In the patients group, no significant association was found between vitamin D deficiency, NT1 duration and severity, treatment, and Pandemrix® vaccination.

CONCLUSIONS

Vitamin D levels were not associated with NT1 in a large case-control population when potential demographic and clinical confounding factors were taken into account.