No Association Between Knee Osteoarthritis and Metabolic Syndrome

Investigators found no association between metabolic syndrome (MetS), its components, and incident knee osteoarthritis (OA), according to research recently published in Arthritis & Rheumatology.

David T. Felson, MD, MPH, from the Clinical Epidemiology Research and Training Unit at the Boston University School of Medicine in Massachusetts, and colleagues evaluated 991 patients from the Framingham Offspring Cohort for OA between 1992 and 1995, and again between 2002 and 2005. The cohort consisted of 55.1% women (mean age, 54.2 years), with 26.7% of men and 22.9% of women having MetS according to Adult Treatment Panel III criteria for MetS.

Dr Felson and colleagues assessed MetS near baseline, and knees were excluded if baseline prevalent radiographic OA (ROA) and prevalent symptomatic OA (SxOA) were present. The researchers defined ROA at follow-up as a knee having Kellgren and Lawrence grade ≥2 and SxOA as knee pain in addition to ROA.

Men in the study had ROA in 9.8% of cases (n = 78), whereas women had ROA in 10.5% of cases (n = 105), after excluding patients with initial ROA or SxOA at baseline. After adjusting for body mass index (BMI), Dr Felson and colleagues used the Adult Treatment Panel III criteria to determine whether MetS or its components were related to incident ROA or SxOA.

“Before adjustment for BMI and body weight, MetS was associated with an increased incidence of ROA in men and increased incidence of SxOA in women, while the association between count of components of MetS and incidence OA was consistent in both genders and for both ROA and SxOA,” Dr Felson and colleagues wrote in their study. “After controlling for BMI or weight, the associations of these measures with OA were all markedly attenuated and almost all became nonstatistically significant. Only [diastolic blood pressure] remained to be associated with an increased incidence of SxOA in both men and women after adjusting for body weight.”

Summary and Clinical Applicability

Dr Felson and colleagues said one area that needs further research is the association between an increase in blood pressure level and higher incidence of symptomatic OA.

“While we found that [diastolic blood pressure] was related to incident SxOA even after adjustment for BMI, the relation of [systolic blood pressure] and incident SxOA was nearly significant also, suggesting that both might be related to SxOA,” the investigators wrote. “Any cross-sectional analyses of this relationship would be challenging to interpret since treatment for SxOA includes [nonsteroidal anti-inflammatory drugs,] which can raise blood pressure.”

Study Limitations

• The researchers noted they were unable to account for misclassification of MetS as a result of having no data on the change in MetS in the 10-year follow-up period.
• Data linking high blood pressure as a significant risk factor for OA may be a result of the large number of incident tibiofemoral OA cases in the study, but the researchers were unable to confirm whether this link existed for patellofemoral OA cases as well.

Reference

Niu J, Clancy M, Aliabadi P, et al. The metabolic syndrome, its components and knee osteoarthritis (OA): The Framingham OA study [published online March 3, 2017]. Arthritis Rheumatol. doi: 10.1002/art.40087

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