Jacques et al.10 asserted that homebound elderly persons who have no specific disease and stay at home have high prevalence of vitamin D deficiency and thus, vitamin D supplementation is required. Kim et al.8 reported a high prevalence of vitamin D deficiency in elderly patients who find substantial difficulties to go outside due to claudication attributable from LSS. Therefore, they said that even supplementation of vitamin D alone can maintain a stable health status by increasing muscle strength to some extent and keeping balance of muscle strength3, 11 and Bischoff-Ferrari12 stated that vitamin D supplementation would reduce the falling accidents of the elderly by about 22%.
Although healthy adults are not deficient through sufficient meals and sunlight, others are recommended that 25(OH)D level in serum maintains 20 ng/ml or more. However, Tangpricha et al.13 reported that vitamin D deficiency occurs even in healthy young adults; 11% in summer and 26% in winter. Kim et al.8 reported that the elderly patients with LSS showed increasing prevalence of vitamin D deficiency, and about 74.3% of them had vitamin D deficiency. The authors of this paper also stated that a prevalence of 76.5% (78/102 patients) was exhibited in patients with LSS who require surgery. The authors supposed the cause of vitamin D deficiency was the walking problems due to intermittent neurogenic claudication, and then restriction of going out, but did not make an accurate investigation.
For patients with LSS, surgical treatment has better results than palliative treatment in terms of physical function, pain, and QoL . As described by Kim et al.7, decompression surgery for patients with LSS showed elevated vitamin D levels, and after one year, the levels increased from 11.1 ng/ml to 14.2 ng/ml in the depletion group and 23.2 ng/ml to 23.1 ng/ml in deficiency group, but neither of the two groups recovered normal levels. The authors of this paper believed that vitamin D supplementation for the vitamin D deficient group before surgery would be reasonable, and concluded that supplementation of vitamin D for the vitamin D deficient group before surgery would result in better functional result of spine and improve QoL.
In our results, ODI after 12month after surgery was improved in vitamin D supplementation group. RMDQ was not different between preoperative and all postoperative periods. However, both SF-36 MCS and SF-36 PCS improved in vitamin D supplementation group from 12 month after surgery. Although there is a growing body of literature suggesting a possible negative influence of preoperative vitamin D deficiency upon surgical outcomes in spine surgery, the vast majority of the literature focuses on the causative link between vitamin D deficiency and pseudoarthrosis15 or new vertebral fractures16.
The effect of vitamin D on the functional outcome and QoL of patients with LSS has not been elucidated but may be deduced from several studies. There is much debate about the pain relief effect of Vitamin D. Although it is a study of idiopathic chronic LBP, Cannell et al.17 have reported on the pain relief effect of vitamin D. Helde-Frankling et al.18 have commented on the pain reducing effect of Vitamin D, Cakar et al.19 said that in a cohort of 149 patients, the authors found that serum vitamin D concentration was not associated with knee pain in patients with osteoarthritis, and Heuch et al.20 said that after analyzing a data set including 1685 individuals with LBP and 3137 controls without LBP, the authors found no association between vitamin D status and risk of LBP. In addition, it appears that vitamin D may have an effect to enhance mood, but there are not sufficient studies regarding accurate mechanism21. The results of this study showed that both ODI and the QoL after twelve months were improved. In this regard, supplementation of vitamin D would improve functional outcome and enhance QoL in a long-term perspective, if the normal level of vitamin D is maintained. However, authors of this study could not figure out the mechanism.
The limitations of this study are as follows: First, there was a lack of research on socio-demographic characteristics. As Kim et al.8 pointed out, there was a lack of consideration of level of education22, season23 as well as medical comorbidity, urban residence and sunlight exposure. However, this study evaluated serial changes in the same patient. There was no significant difference in the degree of education level, seasonal exposure, medical comorbidity, urban residence, and sunlight exposure. Second, there are many studies on LSS associated with various chronic diseases such as diabetes, hypertension, chronic obstructive pulmonary disease and gout, but there has been no study on mutual causal relationship24. In addition, several authors have shown that vitamin D itself has the effect of preventing the deterioration of the physical function of a patient by preventing the chronic disease such as cancer, osteoarthritis, diabetes and cardiovascular diseases4, 7, 25, 26. This study showed a drawback that errors due to factors related to chronic diseases of patients who needed surgery could not be completely eliminated. Third, only the results of improvement of functionality and QoL were obtained. Forth, the number of patients in each group was too small (27 patients in group A and 27 patients in group B) to analyze the mechanism and related factors, although this was a randomized method. In addition, there was limited data about how long was vitamin D administrated before surgery and how long did it take to normalize the vitamin D serum levels postoperatively.