11/6/12 Age and body mass index – the relationship of weight to height – are two well-recognized risk factors for the development of osteoarthritis, or OA. Now, a new study out of Europe adds type 2 diabetes to the list. The study, published recently online in Diabetes Care, finds that type 2 diabetes doubles the risk of developing osteoarthritis that is severe enough to require joint replacement.

“Data from this study show that age, body mass index and diabetes constitute three independent and strong risk factors for joint failure,” says study co-author Georg Schett, MD, chief of rheumatology and director of the department of internal medicine at the University of Erlangen-Nuremberg in Germany. 

Dr. Schett says one of the strengths of the study is that it was based on comprehensive and lengthy patient follow-up. The researchers analyzed the medical records of more than 900 diabetic and nondiabetic people over 20 years. The sample came from the Italian town of Bruneck, in which there is one single hospital and very little relocation of residents out of the area.

The study participants, recruited in 1990 and followed until 2010, were examined every five years. The number of diabetic patients in the study was comparatively small: 69 patients in all. The nondiabetic patients numbered 858.

The outcome the study focused on was joint replacement surgery. During the 20-year period, the researchers found 13 people in the diabetic group and 73 people in the nondiabetic group needed either a knee or hip replaced because of severe OA. The so-called “intervention rate” – the number of people who required total joint replacement, or arthroplasty – for the nondiabetic group was 5.3 percent. But for the diabetic group, it was 17.7 percent – more than three times greater. When age, body mass index and several other factors were taken into account, participants with type 2 diabetes were about twice as likely to need joint replacement surgery than those without type 2 diabetes.

“High BMI, like age, is indeed independently associated with an increased risk of arthroplasty. Diabetes, however, is an independent risk factor as well,” says Dr. Schett. “This finding means that diabetes, when present, increases the risk for arthroplasty, and thus also in a younger person and also in those with normal body weight.”  

Arthritis and diabetes experts alike welcome the study findings. “I don’t know that [the study] is exactly a surprise, but they are one of the first to look at this in a systematic way over time,” says Joanne Marie Jordan, MD, director of the Thurston Arthritis Research Center at the University of North Carolina at Chapel Hill. “One of the really nice parts about the study is that they looked at [an objective, measurable] outcome, which is joint replacement.”

“I think it is a very important study because it clearly establishes that severe osteoarthritis is a component of diabetes complications,” says George King, MD, research director of the Joslin Diabetes Center in Boston, and a professor of medicine at Harvard Medical School. “This has been talked about before – that arthritis and other musculoskeletal problems are increased in diabetics. But I think, as the authors point out, this is a population-based study that clearly establishes a link.”

The study authors say their research calls into question the commonly held view that osteoarthritis is a biomechanical – “wear and tear” – disorder and raises the proposition that it is also a metabolic one. How might diabetes raise the risk for developing osteoarthritis? The authors suggest it’s possible high blood sugar levels promote the destruction of collagen (one of the main components of cartilage) or perhaps stimulate the production of inflammatory substances that ultimately damage the joint.

Dr. Schett says the study suggests that osteoarthritis may be one manifestation of metabolic syndrome – a group of risk factors, such as obesity, high cholesterol and high blood pressure, that raise the chances of developing cardiovascular disease, stroke and type 2 diabetes. “Effective management of the metabolic syndrome may help to prevent development of symptomatic joint disease,” he adds.

Dr. Jordan says this is a fertile area for study. “We’ve become increasingly aware of the fact that osteoarthritis and diabetes are conditions that may be part of one syndrome, or that at least travel together,” she says. “It is critical for the public and health care providers to recognize this linkage and work together to break the cycle.”