Vitamin D status and optimal supplementation in institutionalized adults with intellectual disability

Background Adults with intellectual disability (ID) have several risk factors for osteoporosis. Feeding problems with consequent nutritive deficiencies, and lack of sunshine exposure may lead to vitamin D deficiency. The purpose of this study was to evaluate vitamin D status in adults with ID living in nursing homes and to compare two different means to administer vitamin D in adults with ID. Methods The study included 138 adults (95 males and 43 females) with ID living in nursing homes of Paajarvi Inter-Municipal Association. Clinical data on the etiology and severity of ID, other illnesses, medications, anthropometry and fractures during the preceding 5 years were collected from medical records. The participants were alternately allocated to receive vitamin D3 either per orally 800 IU daily for 6 months (PO group, n = 72) or as a single intramuscular injection of 150 000 IU (IM group, n = 66). Blood samples were obtained at baseline and at 6 months for parameters of calcium homeostasis, including serum concentrations of 25-hydroxyvitamin D (S-25-OHD) and parathyroid hormone (P-PTH). Results At baseline, the mean S-25-OHD was low, 40 nmol/L in the PO group and 41 nmol/L in the IM group. The low vitamin D levels were associated with secondary hyperparathyroidism in 17%. At 6 months the mean S-25-OHD was 82 nmol/L in the PO group (P < 0.001 for the difference from baseline) and 62 nmol/L in the IM group (P < 0.001). P-PTH decreased in both groups: from 51 ng/L to 33 ng/L in the PO group (P < 0.001) and from 54 ng/L to 34 ng/L in the IM group (P < 0.001). With daily dosing (800 IU/day) the recommended level (> 80 nmol/L) was attained in 42%, but with intramuscular dose only in 12%. S-25-OHD was > 100 nmol/L in 14 participants in the PO group and in one participant in the IM group; these high values were associated with hypercalcemia in two and hyperphosphatemia in six participants. Participants with S-25-OHD > 100 nmol/L at 6 months were lighter (51.9 kg vs. 67.5 kg, P = 0.002) and had smaller body mass index than participants with lower S-25-OHD (20.5 kg/m2 and 24.4 kg/m2, P = 0.017). Conclusions Vitamin D insufficiency was common in adults with ID living in nursing homes. Both oral and intramuscular administrations of vitamin D3 improved vitamin D status without adverse effects. The treatment response at 6 months was better in the PO group. High-dose intramuscular vitamin D3 injections may be a convenient way to maintain sufficient vitamin D status in adults with ID but further studies are needed to establish the optimal dose and interval as well as subsequent potential health benefits in these patients. Based on this study, vitamin D supplementation with per oral 800 IU/day is recommended to all adults with ID living in nursing homes.