Prevalence of Vitamin D Deficiency in Patients with Lumbar Spinal Stenosis and its Relationship with Pain

Background: Patients with lumbar spinal stenosis (LSS) are at a great risk of a fall and fracture,which vitamin D protects against. Vitamin D deficiency is expected to be highly prevalent in LSSpatient, and pain is thought to have a profound effect on vitamin D status by limiting activity andsunlight exposure.Objective: To identify the prevalence of vitamin D deficiency (serum 25-hydroxyvitamin D [25-OHD]< 20ng/mL) and its relationship with pain.Study Design: Nonblinded, cross-sectional clinical study.Setting: University-based outpatient clinic of the Department of Orthopedic Surgery, YonseiUniversity College of Medicine, Korea.Methods: Consecutive patients who visited the orthopedic outpatient clinic for chronic low back painand leg pain and were diagnosed as LSS between May 2012 and October 2012 were included. Painwas categorized into 4 groups based on location and severity: 1) mild to moderate back or leg pain; 2)severe back pain; 3) severe leg pain; and 4) severe back and leg pain. Covariates for vitamin D deficiencyincluded age, sex, body mass index, level of education, medical history, season, region of residence,sunlight exposure score and functional disability. 25-OHD level was measured by radioimmunoassay,and bone metabolic status including bone mineral density and bone turnover markers was alsomeasured. Multivariable logistic regression modeling was used to adjust all risk estimates for covariates.Results: The study had 350 patients enrolled. Mean serum 25-OHD level was 15.9 ± 7.1 ng/mL(range, 2.5 ~ 36.6). of the 350 patients, 260 patients out of 350 (74.3%) were vitamin D deficient.Univariate logistic regression analysis showed a significantly higher prevalence of vitamin D deficiencyin the following patients: 1) medical comorbidity; 2) urban residence rather than rural; 3) lower scorefor sunlight exposure; and 4) severe leg pain, or severe back and leg pain rather than mild to moderatepain. Pain category was significantly associated with lower sunlight exposure; however, the associationbetween pain category and vitamin D deficiency remained significant even after adjustment for thesunlight exposure. Furthermore, severe back pain, and severe back and leg pain were also associatedwith higher incidence of osteoporosis and higher level of bone resorption marker (serum CTx).Limitations: The limitation of our study is that due to its cross-sectional design, causal relationshipsbetween pain and vitamin D deficiency could not be established.Conclusion: Vitamin D deficiency was highly prevalent in LSS patients (74.3%), and severe painwas associated with higher prevalence of vitamin D deficiency and osteoporosis which could bepotential risk factors or a fall and fracture. As evidenced by the present study, assessment of serum25-OHD and bone mineral density are recommended in LSS patients with severe pain, and activetreatment combining vitamin D, calcium, or bisphosphonate should be considered according to thestatus of the bone metabolism.Key words: Vitamin D, lumbar spinal stenosis, pain, bone mineral density