Lack of vitamin D contributes to pain in black Americans with knee osteoarthritis

November 7, 2012, Wiley

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 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 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 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 status on chronic for older black and white Americans.

Explore further: Low levels of vitamin D are associated with mortality in older adults

More information: "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).

Related Stories

Low levels of vitamin D are associated with mortality in older adults

October 2, 2012
Low levels of vitamin D and high levels of parathyroid hormone are associated with increased mortality in African American and Caucasian older adults, according to a new study accepted for publication in The Endocrine Society's ...

Low vitamin D in kids may play a role in anemia

May 2, 2011
Pediatricians from Johns Hopkins Children's Center and elsewhere have discovered a link between low levels of vitamin D and anemia in children.

Study looks at pain processing abnormalities in knee OA

September 17, 2012
(HealthDay)—For patients with knee osteoarthritis (K-OA), the lack of correlation between clinical pain and radiographic evidence of disease severity may be due to central sensitization, according to a study published online ...

Recommended for you

Osteoarthritis could be treated as two diseases, scientists reveal

January 10, 2018
Scientists at The University of Manchester have discovered that most people with osteoarthritis can be subdivided into two distinct disease groups, with implications for diagnosis and drug development.

US arthritis prevalence is much higher than current estimates

November 27, 2017
New research indicates that the prevalence of arthritis in the United States has been substantially underestimated, especially among adults

Maintaining sufficient vitamin D levels may help to prevent rheumatoid arthritis

November 20, 2017
Maintaining sufficient vitamin D levels may help to prevent the onset of inflammatory diseases like rheumatoid arthritis, research led by the University of Birmingham has discovered.

Old World monkeys could be key to a new, powerful rheumatoid arthritis therapy

November 16, 2017
In the quest for a new and more effective treatment for rheumatoid arthritis, researchers from the Keck School of Medicine of USC looked to a primate that mostly roams the land in Asia, the Middle East and Africa. It was ...

Study lists foods for fighting rheumatoid arthritis symptoms and progression

November 8, 2017
A list of food items with proven beneficial effects on the progression and symptoms of rheumatoid arthritis is provided in a new study published today in Frontiers in Nutrition. The authors suggest incorporating these foods ...

Prototype equipment can detect rheumatoid arthritis

September 28, 2017
According to a first clinical study published in the scientific journal Photoacoustics, the University of Twente and various European partners have designed a device that shows the difference between healthy fingers and arthritic ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.