Factors related to decreased vitamin D levels in men with spinal cord injury living in a subtropical region

Abstract

AIMS: To evaluate the levels of vitamin D, parathyroid hormone and calcium in individuals with spinal cord injury and to identify related factors. METHODS: A cross-sectional study included men with spinal cord injury, living in the South Region of Brazil. A questionnaire was applied to evaluate socioeconomic data, life habits and health. The time elapsed since the spinal cord injury was considered. Vitamin D was evaluated in plasma via liquid chromatography; calcium and PTH were measured in serum by a colorimetric method and electrochemiluminescence respectively. For data analysis, linear regression and chi-square test were utilized. Values of p < 0.05 were considered significant. RESULTS: The study included 39 paraplegic or tetraplegic men with spinal cord injury. The mean age was 35.52±9.78 years, and the mean time since injury was 6.09±5.55 years. The mean biochemical levels were: 19.0 ±6.98 ng/mL for vitamin D; 9.54±0.52 mg/dL for total calcium; and 34.81±10.84 pg/mL for parathyroid hormone. Individuals with sun exposure for more than two hours daily had higher vitamin D levels than those exposed up to one hour per day (p=0.001). Linear regression identified an inverse relationship between lesion time and vitamin D levels (regression coefficient: -0.424; p=0.029), while the other parameters did not show significant differences regarding the time elapsed since the lesion. Subjects with income above four minimum wages had higher vitamin D values (mean 25.67±5.45 ng/mL) when compared to those with income up to four minimum wages (mean 18.43±6.79 ng/mL) (p=0.021). CONCLUSIONS: Levels of vitamin D were inversely correlated to the time elapsed since the spinal cord injury, probably due to insufficient sun exposure resulting from prolonged limitation of mobility. In addition, lower levels of vitamin D were associated to lower income. These factors may aggravate bone loss associated with decreased mobility resulting from spinal cord injury.