Background: Chronic low back pain (LBP) is an extremely common problem in society. The prevalence of this disease is different in countries. Due to the importance of LBP and vitamin D key role in its manifestation, this research was done to determine the prevalence of osteomalacia and the relevant factors in idiopathic low back pain patients at Kashan in 2005-2006.

Materials & Methods: This cross sectional study was carried out on 100 patients diagnosed with LBP referring to Kashan specialty medical clinics. The second etiology of LBP was ruled out through history, physical examination and imaging methods. A biochemical assay of serum calcium, phosphate, alkaline phosphates (ALP), parathyroid hormone (PTH), 25-hydroxy vitamin D level, and 24 hours urine calcium were considered. Serum 25-hydroxy vitamin D test was used to confirm the osteomalacia diagnosis. Patients information including age, gender, vitamin D consumption, sun light exposure time periods and vitamin D deficiency (mild, moderate, severe) were also considered. The data were analyzed using statistical tests x² and t-test.

Results: The average (12% male and 88% female) patient age was 41.2±6. Fifty percent of patients were diagnosed by osteomalacia of which 42(84%) were females and 8 (16%) males. Fifty four percent of osteomalacia patients had not been exposed to the sun light effectively while they had consumption of vitamin D. The most and least prevalence of osteomalacia were found in age range of 40-49 years old and under 20 years old, respectively. The mean of 25 hydroxy-vitamin D in patients with osteomalacia was 10.5ng/ml and 58.5 ng/ml in others (p<0.0001). Vitamin D deficiency was reported mild in 50%, moderate in 24%, and severe in 26% of patients.

Conclusion: Due to the high prevalence of vitamin D deficiency in LBP patients, using different methods like food fortification and patient education to have enough sun light exposure are recommended.