study reveals that black Americans display lower levels of vitamin D and greater
pain sensitivity than do white Americans. A Vitamin D deficiency may be a risk
factor for increased knee osteoarthritic pain in black Americans, the authors conclude.
Clinical practice guidelines state that vitamin D
levels less than 20 ng/mL represent deficiency, and levels between 21 and 29
ng/mL represent insufficiency. Given that low levels of vitamin D are linked to
chronic pain and other health conditions, especially in black Americans, the
research team set out to investigate if variations in vitamin D levels
contribute to racial differences in patients with knee pain caused by
Researchers at the University of Florida and the University
of Alabama at Birmingham recruited 94 participants—45 black and 49 white
patients with symptomatic knee OA—to complete questionnaires regarding their
symptoms. The study group was 75% female and an average 56 years old.
In addition, study participants underwent testing that
included sensitivity to heat and mechanical pain on the affected knee and the
forearm. Researchers measured heat pain threshold as the point when patients
indicate the sensation "first becomes painful" and pain tolerance
when patients "no longer feel able to tolerate the pain." Mechanical
pain measures were determined by the patients' response to pressure in the knee
that despite living in a southern sunny climate, 84% of black participants had
vitamin D levels less than 30 ng/mL compared with 51% of white subjects.
Furthermore, the average vitamin D level for black Americans was 19.9 ng/mL
(deficiency), compared with white Americans who averaged 28.2 ng/mL
(insufficiency). Black participants reported greater overall knee
osteoarthritis pain, and those with lower vitamin D levels displayed greater
sensitivity to heat and mechanical pain (experimental pain).
"Our data demonstrate that differences in
experimental pain sensitivity between the 2 races are mediated at least in part
by variations in vitamin D levels," said lead author Toni Glover, MSN, ARNP. "However, further studies are needed to fully
understand the link between low vitamin D levels and racial disparities in
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