Plasma vitamin D is associated with insulin sensitivity in youth with Type 1 Diabetes

The identification of modifiable risk factors associated with insulin sensitivity (IS) is critical for improving health outcomes in persons with type 1 diabetes (T1D). Little is known about the association between vitamin D and IS in this population. We examined the prevalence of plasma vitamin D [25(OH)D] deficiency (<50 nmol/L) and its association with IS using data from the SEARCH for Diabetes in Youth Study (n=1,127). Participants had physician‐diagnosed T1D and diabetes autoantibody positive at enrollment (diabetes duration mean=10.0 mo) with data at baseline and 12 months later. IS was estimated using a validated equation. Of these participants, 47% had 25(OH)D deficiency with variation by race and age ( p <0.05). IS was lower in those who had deficient (mean IS=10.2) vs. sufficient (≥75.0 nmol/L) levels of 25(OH)D (mean IS=11.5; p <0.01). Mixed effects models were used to determine the association between 25(OH)D and IS, adjusting for diabetes duration, age, race/ethnicity, gender, insulin regimen, HLA genotype, clinic site, season at time of visit, fasting C‐peptide (FCP), and FCP*diabetes duration. 25(OH)D was positively associated with IS (β=0.008, p =0.001). Further adjustment for BMI z‐score yielded a similar result (β=0.005, p =0.004). Findings highlight the need to increase vitamin D and further examine the role of vitamin D on IS in youth with T1D. Funding: NIH/NIDDK R01 DK077949