From the Journals

Lower BMI linked with better knee osteoarthritis outcomes


 

FROM ARTHRITIS & RHEUMATOLOGY

Losing weight and lowering body mass index may help people slow, delay, or even prevent the structural defects of knee osteoarthritis, especially on the medial side of the knee, results of a prospective multicohort study from Australia suggest.

“We showed that the more weight that is lost, the greater the apparent benefit for delaying or preventing knee joint degradation in osteoarthritis,” senior study author Amanda Sainsbury, PhD, professor of obesity research at the University of Western Australia, Perth, said in an interview. “For example, a person weighing 100 kilograms [220 pounds] who loses 10 kilograms [22 pounds] is likely to have double the benefit compared to losing 5 kilograms [11 pounds].”

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“We showed evidence of association, not causality,” she and her colleagues wrote in Arthritis & Rheumatology. “Future randomized, controlled trials are required to demonstrate causality.”

Dr. Sainsbury and colleagues analyzed radiographs of knees from three independent cohort studies from the United States and the Netherlands – the Osteoarthritis Initiative (OAI), the Multicenter Osteoarthritis Study (MOST), and the Cohort Hip and Cohort Knee (CHECK) study – at baseline and again 4-5 years later.

The authors created two groups of knees at baseline: the “incidence cohort” of 9,683 knees from 5,774 participants without OA structural defects (Kellgren-Lawrence grade 0 or 1) and the “progression cohort” of 6,075 knees from 3,988 participants with OA structural defects (KL grade 2 or higher). After 4-5 years, they determined OA incidence (KL grade 2 or higher in participants without baseline knee OA) and progression (increase of one or more KL grades in those with baseline knee OA).At baseline, the mean patient age in both groups was around 60, and around 60% of participants were female. In the incidence and progression groups, respectively, White patients comprised 87.5% and 80.4% of participants; mean body mass index was 28.2 and 30.4 kg/m2; and 32.6% and 48.4% of participants were obese (BMI, 30 or higher). The authors combined data from the three studies and used logistic regression and generalized estimating equations, with clustering of both knees within individuals. On multivariable analysis, they found that change in BMI 4-5 years post baseline was positively linked with both incidence and progression of knee OA structural defects.

Dr. Amanda Sainsbury (left), professor of obesity research at the University of Western Australia in Perth, and Zübeyir Salis, BEng, a PhD student in Public Health at the University of New South Wales in Kensington

Dr. Amanda Sainsbury (left) and Zübeyir Salis

In the incidence group, BMI decreased 1 or more units in 1,101 patients and increased 1 or more units in 1,611. In the progression group, BMI decreased 1 or more units in 798 patients and increased in 1,008.

The adjusted odds ratio for overall structural defects in the incidence group was 1.05 (95% confidence interval, 1.02-1.09) and 1.05 (95% CI, 1.01-1.09) in the progression group was. A 1-unit decrease in BMI was linked with a nearly 5% drop in odds of incidence and progression of knee OA, and a 5-unit decrease was linked with a more than 21% drop in odds of incidence and progression.

In the incidence group, change in BMI was positively linked with medial, but not lateral, joint space degeneration (narrowing; OR, 1.08; 95% CI, 1.04-1.12) and with medial femoral surface degeneration indicated by osteophytes (OR, 1.07; 95% CI, 1.03-1.12).

In the progression group, change in BMI was positively linked with overall structural defects (OR, 1.05; 95% CI, 1.01-1.09) as well as medial, but not lateral, joint space degeneration (OR, 1.08; 95% CI, 1.03-1.12).

“Previous research showed that weight loss helps reduce symptoms of knee osteoarthritis, such as pain and impaired physical function,” said lead study author Zübeyir Salis, BEng, a PhD student in public health at the University of New South Wales, Kensington, Australia. “Weight loss is emerging as a suitable strategy for potentially delaying and preventing osteoarthritic knee joint degeneration.”

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