And that's not just because diabetics might be heavier than average, and weight has been linked both to diabetes and to OA, said Dr Georg Schett, who led the group. Instead, he told Reuters Health by email, this study suggests that alterations in glucose metabolism directly promote OA.
"In fact," Dr Schett added, "these data suggest that OA is part of the metabolic syndrome, which would also mean that life-style modification can also change the risk for OA-related arthroplasty."
In an online paper in Diabetes Care, Dr Schett of the University of Erlangen-Nuremberg, Erlangen, Germany, and colleagues cite some similarities between OA and type 2 diabetes: "chronic nature, a high prevalence of end-organ failure, and strong association with age and obesity."
How the study was done
To further investigate this relationship, the team conducted a population-based cohort study with an age and sex-stratified random sample of 927 men and women between the ages of 40 and 80.
Over two decades, the rate of arthroplasty per 1 000 person-years was 17.7 in those with diabetes and 5.3 in those without. Before adjustment, the hazard ratio was 3.8. After adjustment for factors including age and BMI, diabetes continued to be an independent predictor (hazard ratio, 2.1). The probability of arthroplasty increased with duration of diabetes. This was the case for both sexes and in subgroups based on age and BMI.
Moreover, say the researchers, "the link between type 2 diabetes and OA was consistent when using three distinct approaches of OA ascertainment." These were joint failure as determined by arthroplasty, signs and symptoms of OA as quantified by scoring systems and the severity of joint changes as determined by musculoskeletal ultrasound.
Among possible shortcomings of the study are that "subjects with diabetes may receive more medical attention than nondiabetic individuals, leading to increased awareness of or even overtreatment of OA," the authors say. In addition, they add, results are from "a study launched in a small town, in which accessibility to health resources is very high, are not necessarily representative for other Western populations."
More signs of inflammation shown
Turning to the underlying mechanisms, Dr Schett observed, "We think that diabetes creates an inflammatory state in the joint, which exacerbates joint damage." As he pointed out, "The ultrasound data in this study show more signs of inflammation in the knee joint of patients with diabetes than those without diabetes independently of age and BMI."
Given these findings, Dr Schott concluded, "Doctors involved in the management of OA should check for concomitant diabetes and liaise with a diabetologist; vice versa, diabetologists may need to inform their patients that poor management of diabetes may not only increase the risk of cardiovascular events but also joint failure due to severe OA."
(Reuters Health, David Douglas, October 2012)