Hypovitaminosis D in persons with Down syndrome and autism spectrum disorder

Background Plasma levels of vitamin D have been reported to be low in persons with Down syndrome (DS) and existing data is limited to small and homogenous cohorts. This is of particular importance in persons with DS given the high rates of autoimmune disease in this population and the known relationship between vitamin D and immune function. This study sought to investigate vitamin D status in a multi-center cohort of individuals with DS and compare them to individuals with autism spectrum disorder (ASD) and neurotypical (NT) controls. Methods A retrospective, multi-center review was performed. The three sites were located at latitudes of 42.361145, 37.44466, and 34.05349. Patients were identified by the International Classification of Diseases (ICD)-9 or ICD-10 codes for DS, ASD, or well-child check visits for NT individuals. The first vitamin D 25-OH level recorded in the electronic medical record (EMR) was used in this study as it was felt to be the most reflective of a natural and non-supplemented state. Vitamin D 25-OH levels below 30 ng/mL were considered deficient. Results In total, 1624 individuals with DS, 5208 with ASD, and 30,775 NT controls were identified. Individuals with DS had the lowest mean level of vitamin D 25-OH at 20.67 ng/mL, compared to those with ASD (23.48 ng/mL) and NT controls (29.20 ng/mL) ( p < 0.001, 95% CI: −8.97 to −6.44). A total of 399 (24.6%) individuals with DS were considered vitamin D deficient compared to 1472 (28.3%) with ASD and 12,397 (40.3%) NT controls ( p < 0.001, 95% CI: −5.43 to −2.36). Individuals with DS with higher body mass index (BMI) were found to be more likely to have lower levels of vitamin D ( p < 0.001, 95% CI: −0.3849 to −0.1509). Additionally, having both DS and a neurologic diagnosis increased the likelihood of having lower vitamin D levels ( p < 0.001, 95% CI: −5.02 to −1.28). Individuals with DS and autoimmune disease were much more likely to have lower vitamin D levels ( p < 0.001, 95% CI: −6.22 to −1.55). Similarly, a history of autoimmunity in a first-degree relative also increased the likelihood of having lower levels of vitamin D in persons with DS ( p = 0.01, 95% CI: −2.45 to −0.63). Conclusions Individuals with DS were noted to have hypovitaminosis D in comparison to individuals with ASD and NT controls. Associations between vitamin D deficiency and high BMI, personal autoimmunity, and familial autoimmunity were present in individuals with DS.