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Vitamin D deficiency could mean back pain for some postmenopausal women, according to a study from China.

In a retrospective analysis, postmenopausal women with severe vitamin D deficiency -- serum levels under 10 ng/mL -- had lower average bone mineral density T-scores (-1.92 vs -0.7) and greater lower back pain scores (visual analog scale 4.07 vs 3.03) versus women with normal vitamin D levels, reported Hao-Wei Xu, MD, of the Tongji University School of Medicine in Shanghai, and colleagues.

Several preexisting factors predisposed women to a higher risk of moderate-to-severe lower back pain, although severe vitamin D deficiency was the strongest (odds ratio 5.791, 95% CI 1.57-21.38, P=0.008), they noted in :

• Smoking: OR 4.18 (95% CI 1.12-19.89)
• Osteoporosis: OR 3.33 (95% CI 1.39-7.94)
• Lack of vitamin D supplementation: OR 2.85 (95% CI 1.29-6.26)
• Moderate vitamin D deficiency (10 to <30 ng/mL): OR 3.03 (95% CI 1.10-8.31)
• Higher BMI: OR 1.18 per point (95% CI 1.06-1.32)

Severe vitamin D deficiency was also tied to a higher grade of lumbar disc degeneration in the lower back, specifically the lumbosacral region of the L4/L5, L5/S1, and L1/S1 vertebrae.

Those with severe vitamin D deficiency also had a higher grade of disc degeneration in the upper lumbar region, but this didn't reach statistical significance.

"This study shows that very low vitamin D levels were linked to a greater likelihood of moderate to severe lower back pain and more severe lumbar disc degeneration, possibly because of the beneficial effects vitamin D has on nerve and muscle pain sensitivity, muscle strength and mass, and inflammation," commented Stephanie Faubion, MD, MBA, medical director of the North American Menopause Society, in a statement.

"Although not all women need vitamin D supplementation, this speaks to the importance of avoiding severe vitamin D deficiency states," Faubion stated.

This analysis included data on 232 postmenopausal women who attended the spinal surgery unit at a single hospital due to lower back pain. Based on MRIs, all women had some degree of lumbar disc degeneration, including intervertebral disc herniation, spinal canal stenosis, or spinal instability. Serum 25(OH)D levels were measured with overnight fasting blood samples. With the average vitamin D level of 19.38 ng/mL, 75% of this cohort had a vitamin D deficiency, while another 13% were considered severely vitamin D deficient. Only 12.5% of these women had normal vitamin D levels over 30 ng/mL.

However, Xu's group pointed out that the associations between lumbar disc degeneration and low vitamin D levels were only significant in those severely deficient -- not with simply just a vitamin D insufficiency or mild deficiency from 10 ng/mL to less than 30 ng/dL.

"Therefore, we speculate that only extremely low vitamin D levels affect disc degeneration," they stated, and suggested that a clinical trial assessing the effect of vitamin D supplementation on the prevention and treatment of disc degeneration and lower pain back is warranted.

Study limitations included the small sample size and the exclusive inclusion of only Chinese women.

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