Vitamin D, bone mineral density and risk of fracture in patients with intellectual disabilities

Background People with intellectual disabilities (ID) have very high osteoporosis and fractures rates, to which their widespread vitamin D deficiency and other factors could contribute. We aimed to assess in ID people previously treated for vitamin D deficiency 1) long-term adherence to vitamin D supplementation and 2) bone mineral density (BMD), as an indicator for risk of fractures, according to vitamin D supplementation and other factors. Method Height, weight, medical, pharmacological, dietary and lifestyle assessment; blood sample for vitamin D and related analytes; Dual-energy X-ray Absorptiometry (DXA) for BMD. Results Of 51 study participants (mean [SD] age 51.5 [13.6] years, 57 % male), 41 (80.4%) were taking vitamin D and 10 were not. Mean [SD] serum vitamin D was 81.3 [21.3] vs 25.2 [10.2] nmol/L (p<0.0001) respectively. Thirty-six participants underwent a DXA scan, which showed osteoporosis in 23.7% and osteopenia in 52.6%. Participants on vitamin D had higher BMD than those who were not, a statistically significant difference when confounders (lack of mobility, hypogonadism) were removed. BMD was significantly different according to mobility, particularly in wheelchair users, in whom hip BMD was 33% lower (p<0.0001) than in participants with normal mobility. Participants still taking vitamin D showed a 6.1% increase in BMD at the spine (p=0.003) after mean [SD] 7.4 [1.5] years vitamin D treatment. Conclusions In people with intellectual disabilities and previous vitamin D deficiency, bone mineral density increases on long-term vitamin D supplementation. However, additional strategies must be considered for osteoporosis and fracture prevention in this population