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 LSS patient, and pain is thought to have a profound effect on vitamin D status by limiting activity and sunlight 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, Yonsei University College of Medicine, Korea.
METHODS: Consecutive patients who visited the orthopedic outpatient clinic for chronic low back pain and leg pain and were diagnosed as LSS between May 2012 and October 2012 were included. Pain was 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 deficiency included 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 also measured. 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 deficiency in the following patients: 1) medical comorbidity; 2) urban residence rather than rural; 3) lower score for sunlight exposure; and 4) severe leg pain, or severe back and leg pain rather than mild to moderate pain. Pain category was significantly associated with lower sunlight exposure; however, the association between pain category and vitamin D deficiency remained significant even after adjustment for the sunlight exposure. Furthermore, severe back pain, and severe back and leg pain were also associated with 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 relationships between pain and vitamin D deficiency could not be established.
CONCLUSION: Vitamin D deficiency was highly prevalent in LSS patients (74.3%), and severe pain was associated with higher prevalence of vitamin D deficiency and osteoporosis which could be potential risk factors or a fall and fracture. As evidenced by the present study, assessment of serum 25-OHD and bone mineral density are recommended in LSS patients with severe pain, and active treatment combining vitamin D, calcium, or bisphosphonate should be considered according to the status of the bone metabolism.