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Contact: Dawn Peters
sciencenewsroom@wiley.com
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Lack of vitamin D contributes to pain in black Americans with knee osteoarthritis

A new study reveals that black Americans display lower levels of vitamin D and greater pain sensitivity compared to white Americans. Findings published in Arthritis & Rheumatism, a journal of the American College of Rheumatology (ACR), indicate that vitamin D deficiency may be one of many factors that account for increased pain in older black Americans with knee osteoarthritis (OA).

Those with OA experience painful swelling and stiffness of the joints such as knees, hips and fingers. The National Arthritis Data Workgroup estimates that 27 million Americans over 25 years of age have OA (based on 2005 U.S. census data). A long-term study by researchers from the University of North Carolina—the Johnston County OA Project—suggests that lifetime risk of developing knee OA is roughly 46%.

During the last decade medical evidence has uncovered the importance of vitamin D, not only as a vitamin that aids in calcium absorption, but as a powerful hormone with numerous functions throughout the body. In fact, studies have found that a decreased vitamin D level reduces immunity and may contribute to diseases such as cancer and diabetes.

Most vitamin D in humans comes from exposure to the sun, with research suggesting that a deficiency of this important vitamin may be due to more indoor activities, increased sunscreen use, and need for longer sun exposure for those with dark skin pigmentation. One study estimates that 95% of black Americans compared to 70% of white Americans have low levels of vitamin D.

"People associate vitamin D with good bone health," said lead author Toni Glover, MSN, ARNP, a research nurse practitioner and doctoral candidate at the University of Florida, specializing in the study of pain in older adults. "Yet, not everyone is aware of what factors decrease vitamin D and how low levels could contribute to health issues, including chronic pain."

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 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 OA.

With funding from the National Institute on Aging and the John A. Hartford Foundation and the Mayday Fund, 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 had an average age of 56 years.

In addition, study subjects 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 and forearm.

Despite living in a southern sunny climate, findings indicate that 84% of black participants had vitamin D levels less than 30 ng/mL compared to 51% of white subjects. Furthermore, the average vitamin D level for black Americans was 19.9 ng/mL (deficiency), compared to 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 two races are mediated at least in part by variations in vitamin D levels," concludes Ms. Glover. "However, further studies are needed to fully understand the link between low vitamin D levels and racial disparities in pain. Although rare, vitamin D toxicity is possible and older adults should consult with their primary care provider regarding supplementation. It may be warranted that older black Americans with chronic widespread pain be screened for vitamin D deficiency to reduce disparities in pain." The authors plan to pursue additional research which tests the impact of improving vitamin D status on chronic pain for older black and white Americans.

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This study is published in Arthritis & Rheumatism. Media wishing to receive a PDF of the article may contact sciencenewsroom@wiley.com

Full citation: "Vitamin D, Race, and Experimental Pain Sensitivity in Older Adults with Knee Osteoarthritis." T.L. Glover, B.R. Goodin, A.L. Horgas, L.L. Kindler, C.D. King, K.T. Sibille, C.A. Peloquin, J.L. Riley, III, R. Staud, L.A. Bradley and R.B. Fillingim. Arthritis & Rheumatism; Published Online: November 7, 2012 (DOI: 10.1002/art.37687).

About the Author: Toni L. Glover is a National Hartford Center of Gerontological Nursing Excellence Patricia G. Archbold Scholar, 2011-2013 (formerly known as the John A. Hartford Foundation Building Academic Geriatric Nursing Capacity Scholar) and Mayday Fund awardee.

To arrange an interview with Ms. Glover, please contact Tracy Brown Wright with UF College of Nursing at tracyb@ufl.edu.

About the Journal:
Arthritis & Rheumatism is an official journal of the American College of Rheumatology (ACR) and the Association of Rheumatology Health Professionals (ARHP), a division of the College, and covers all aspects of inflammatory disease. The American College of Rheumatology is the professional organization who share a dedication to healing, preventing disability, and curing the more than 100 types of arthritis and related disabling and sometimes fatal disorders of the joints, muscles, and bones. Members include practicing physicians, research scientists, nurses, physical and occupational therapists, psychologists, and social workers. The journal is published by Wiley on behalf of the ACR. For more information, please visit http://onlinelibrary.wiley.com/journal/10.1002/art.

About Wiley:

Founded in 1807, John Wiley & Sons, Inc. has been a valued source of information and understanding for more than 200 years, helping people around the world meet their needs and fulfill their aspirations. Wiley and its acquired companies have published the works of more than 450 Nobel laureates in all categories: Literature, Economics, Physiology or Medicine, Physics, Chemistry, and Peace.

Wiley is a global provider of content and content-enabled workflow solutions in areas of scientific, technical, medical, and scholarly research; professional development; and education. Our core businesses produce scientific, technical, medical, and scholarly journals, reference works, books, database services, and advertising; professional books, subscription products, certification and training services and online applications; and education content and services including integrated online teaching and learning resources for undergraduate and graduate students and lifelong learners. Wiley's global headquarters are located in Hoboken, New Jersey, with operations in the U.S., Europe, Asia, Canada, and Australia. The Company's Web site can be accessed at http://www.wiley.com. The Company is listed on the New York Stock Exchange under the symbols JWa and JWb.

Media Advisory

2012 ACR/ARHP Annual Meeting Press Registration Now Open.

What: Press registration is now open to journalists planning to attend the 2012 ACR/ARHP Annual Meeting

Where: Walter E. Washington Convention Center; Washington, D.C.

When: November 10 - 14, 2012

Policies: Please make sure to review our press guidelines www.acrannualmeeting.org/Press as they may impact your ability to receive press credentials

Registration: To register for a press pass, please visit www.acrannualmeeting.org/Press

Key dates:

• Press registration closed: Monday, October 29, 2012
• Press conference schedule now available at www.acrannualmeeting.org/Press
• On-site Newsroom opens: Saturday, November 10, 2012
• Opening Lecture/Embargo lifts: 4:30 PM Eastern Time on Saturday, November 10, 2012

Contact:
Suzanne Forte, sforte@rheumatology.org, 404-633-3777

Headquartered in Atlanta, Ga., the American College of Rheumatology is an international professional medical society that represents more than 8,500 rheumatologists and rheumatology health professionals. Rheumatologists are internists or pediatricians who are qualified by training and experience in the diagnosis and treatment of arthritis and other diseases of the joints, muscles and bones. Over 50 million Americans - including nearly 300,000 children - suffer from the painful, disabling and sometimes fatal effects of arthritis and rheumatic diseases. The ACR's mission is to advance rheumatology. Learn more by visiting www.rheumatology.org. or follow ACR on Twitter at www.twitter.com/acrheum.



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