DENVER – Metabolic syndrome in both early and mid-adulthood is associated with symptoms of knee osteoarthritis, according to a study presented at the OARSI 2023 World Congress.
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To supplement existing evidence on the association between metabolic syndrome and joint pain in older adults, the researchers investigated the association in middle-aged adults over a 10- to 13-year period.
The researchers analyzed data from the Childhood Determinants of Adult Health study, which enrolled 2,447 adults with an average age of 31 between 2004 and 2006 and conducted follow-up in 1,549 participants with an average age of 44, during 2014-2019. The Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) was used at follow-up only to assess knee symptoms of pain, stiffness, and dysfunction, as well as the overall score.
Data at both time points included fasting blood biochemistry, waist circumference, and blood pressure measures. The criteria for metabolic syndrome requires presence of central obesity (a waist circumference of at least 94 cm in males or 80 cm in females) and two of the following four factors:
- Raised triglycerides (at least 150 mg/dL) or specific treatment for this lipid abnormality.
- Reduced HDL cholesterol (below 40 mg/dL in males and below 50 mg/dL in females) or treatment for this.
- Raised blood pressure (at least 130 mm Hg systolic or at least 85 mm Hg diastolic) or treatment of previously diagnosed hypertension.
- Raised fasting blood glucose (at least 100 mg/dL) or previously diagnosed type 2 diabetes.
The researchers grouped the participants on the basis of having no metabolic syndrome at either life stage, having metabolic syndrome in young adulthood but not at follow-up (improved), having developed metabolic syndrome at follow-up (incident), and having metabolic syndrome at both time points (persistent). Most of the participants did not have the metabolic syndrome at either time point (85%), whereas 2% improved in mid-adulthood, 9% developed incident metabolic syndrome in mid-adulthood, and 4% had persistent metabolic syndrome.
At follow-up, 43% of the participants reported pain on the WOMAC, and the average WOMAC score was 10. Prevalence of metabolic syndrome increased from 8% in young adulthood to 13% in mid-adulthood, with an increase in abdominal obesity prevalence from 29% to 47%. Metabolic syndrome at any time point – whether improved later, developed later, or persistent – was associated with more knee symptoms, compared with no metabolic syndrome.
Presence of metabolic syndrome in mid-adulthood was associated with knee symptoms from the total WOMAC score (ratio of means, 1.33; P < .001) after adjustment for age, sex, and body mass index (BMI). Metabolic syndrome was also independently associated in mid-adulthood with knee pain (RoM, 1.29; P < .001) and poor function (RoM, 1.37; P < .001).
Those who developed incident metabolic syndrome in mid-adulthood had the greatest association with overall knee symptoms (RoM, 1.56; P < .001) and with knee pain (RoM, 1.52; P < .001). Although improved and persistent metabolic syndrome were both significantly associated with total WOMAC score, neither was significantly associated with knee pain after adjustment for age, sex, and BMI.
The three individual metabolic criteria independently associated with overall WOMAC score were abdominal obesity (RoM, 1.09), hypertension (RoM, 1.44), and low HDL (RoM, 1.17; P < .001 for all).
Leigh F. Callahan, PhD, a professor of medicine and associate director of the Thurston Arthritis Research Center at the University of North Carolina at Chapel Hill, said in an interview that this topic is especially important because there’s so little understanding of the role of comorbid conditions and osteoarthritis.
“There were some key things that I thought were wonderful about this study – the longitudinal nature and the fact that they had collected metabolic syndrome [criteria] at multiple time points and were able to look at persistent versus incident metabolic syndrome,” Dr. Callahan said. “We frequently don’t have that kind of trajectory.”
Jaqueline Lourdes Rios, PhD, an assistant professor of orthopedics at University Medical Center Utrecht (Netherlands), said in an interview that the study raised questions about whether treating metabolic syndrome could help prevent the progression of osteoarthritis to some extent. “Although, if you already have damage in your cartilage, and if you have a lot of inflammation that’s local, it might be a bit trickier than just treating metabolic syndrome,” Dr. Lourdes Rios added. “Then, it might help, it might not.” Either way, she said, it’s certainly worthwhile for physicians to spend time discussing interventions to address metabolic syndrome “because you treat the patient, not a knee.”
Dr. Ding, Dr. Lourdes Rios, and Dr. Callahan had no relevant financial relationships to disclose. The researchers did not note any external funding.