Effects of Chronic Spinal Cord Injury and Pressure Ulcer on 25(OH)-Vitamin D Levels

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Abstract
We studied 92 spinal cord injured (SCI) men (50 paraplegics and 42 quadriplegics) with normal renal function, 38 of whom had single or multiple pressure ulcers. The results were compared with those of 28 able-bodied normal controls. Serum concentrations of calcium and magnesium were measured by atomic absorption spectrometry, and 25(OH)-vitamin D was quantitated by a specific competitive binding assay using a sensitive vitamin D binding protein and tritiated 25(OH)-vitamin D. The SCI group exhibited significant reductions in serum 25(OH)-vitamin D and total calcium concentrations as compared to the normal control group. Although the mean serum concentration of 25(OH)-vitamin D in the quadriplegic patients as a whole was lower than that found in the entire paraplegic group, the difference did not attain statistical significance. Similar observations were made when the ulcer-free subgroups of paraplegics and quadriplegics were compared. The SCI subgroup which was least physically active, i.e., those with pressure ulcers, showed the greatest depression of serum 25(OH)-vitamin D, calcium, and magnesium concentrations. The observed reduction in serum 25(OH)-vitamin D in SCI patients appears to be partly related to reduced cutaneous vitamin D biosynthesis from sunlight deprivation occasioned by physical disability and hospitalization. In addition, nutritional deficiency and altered intestinal transport may be involved. The reduction in serum calcium concentration may be related to abnormal vitamin D metabolism and hypoalbuminemia (reduced protein-bound calcium).