Background The prevalence of both vitamin D (VitD) deficiency and type 1 diabetes mellitus (T1DM) has increased worldwide over the last few decades. The objectives of this study were: (1) to evaluate the prevalence of VitD deficiency and insufficiency among Israeli youth with T1DM and (2) to assess the association between VitD status, seasonality and T1D glycemic control characteristics. Methods This was a multi-centered, cross-sectional study. VitD levels were routinely tested during the years 2008-2011 in T1DM patients aged up to 21 years. Medical records were reviewed for demographic, clinical and laboratory characteristics. Results The study population consisted of 199 participants (53% males), mean age 12.24±4.11 years, mean T1DM duration 3.77±3.43 years. VitD levels were within the normal range in 19.6%, insufficient (15-29 ng/mL, 37-72 nmol/L) in 62.3% and deficient (<15 ng/mL, <37 nmol/L) in 18.1%. Mean VitD level was higher during the summer than during spring, autumn and winter (28.65 ng/mL, 23.16 ng/mL, 21.65 ng/mL, 17.55 ng/mL, respectively, p<0.001). Mean VitD level was higher among secular patients compared to the religious (whole-year heavily dressed) population (23.57 ng/mL, 15.54 ng/mL, respectively, p<0.001). VitD level was negatively associated with body mass index calculation of standard deviation scores (BMI-SDS), high-density lipoprotein (HDL) and age at diagnosis (r=-0.171, p=0.016; r=-0.149, p=0.043; r=-0.150, p=0.037, respectively). No association was demonstrated with disease duration and glycemic control indices and metabolic parameters. Conclusions VitD insufficiency is largely prevalent among Israeli youth with T1DM, as is in Israeli youth in general. The VitD level is associated with seasonality, clothing habits and BMI.
Keywords: glycemic control; type 1 diabetes mellitus; vitamin D.