NEW YORK – Obesity appears to reduce response to anti–tumor necrosis factor–alpha treatment in individuals with psoriatic arthritis, but weight loss can improve it, according to a review of two studies by Dr. Christopher T. Ritchlin.
"These data convincingly show that if we talk to our patients and tell them to lose weight, it can have an impact on how their PsA [psoriatic arthritis] therapies are going to work," Dr. Ritchlin, director of the Translational Immunology Research Center at the University of Rochester (N.Y.), said at a meeting sponsored by New York University.
Dr. Christopher Ritchlin
Dr. Ritchlin said these results fit in with previous epidemiologic studies that show that as body mass index goes up, so does the risk for both psoriasis and PsA (Arch. Intern. Med. 2009;167:1670-5 and Ann. Rheum. Dis. 2012;71:1273-7).
These data support a link between obesity-related chronic tissue inflammation and development of some rheumatic diseases, such as arthritis in psoriatic patients. These same inflammatory processes may also interfere with good clinical response to biologic agents.
In a study published by Dr. Matteo Nicola di Minno of Federico II University in Naples, Italy, and his colleagues, individuals with a BMI in the 30-35 kg/m2 range with PsA had a nearly fourfold increased risk of not responding well to treatment with tumor necrosis factor–alpha inhibitors (TNFis). The risk of a poor response rose more than fivefold for those whose BMIs greater than 35 kg/m2 (Arthritis Care Res. 2013;65:141-7).
The study prospectively followed PsA patients with active disease for 24 months who were starting TNFi therapy (30% adalimumab, 41% etanercept, 29% infliximab). The group comprised 135 obese patients (BMI greater than 30 kg/m2) and 135 controls of normal weight. The primary outcome was achievement of minimal disease activity (MDA), which meant they fulfilled five of seven outcome measures: one or fewer tender joints, one or fewer swollen joints, a score of 1 or less on the Psoriasis Area and Severity Index or body surface area = 3, a score of 15 or less on a visual analog scale (VAS) for pain, a score of 20 or less on a patient global disease severity VAS score, a score on the Health Assessment Questionnaire of 0.5 or less, or one or fewer tender entheseal points.
After 12 months, only 98 (36%) of the total group reached MDA. "What the results showed was that the odds of not achieving MDA were directly related to increased BMI," Dr. Ritchlin said.
Significantly more of the patients who did not achieve MDA were obese (64% vs. 25.5%, P less than .001). After adjustment for other variables, obesity was found to incur a nearly fivefold risk of poor response to therapy (hazard ratio 4.90, 95% confidence interval [CI] 3.04-7.87). The hazard ratios were 3.98 for those with BMI of 30-35 kg/m2 and 5.4 for those with BMI greater than 35 kg/m2 (both P less than .001). Among the 98 PsA patients who had achieved MDA by 12 months, those who were obese had a poor probability of sustaining MDA when tested at 24 months, according to Dr. di Minno.
In a follow-up study presented at the 2012 EULAR meeting (Ann. Rheum. Dis. 2012;71[Suppl. 3]:109), Dr. di Minno addressed the question of whether weight loss in obese PsA patients would improve treatment response. In this study, 138 obese PsA patients were divided into two groups of 69 patients each. One group received a hypocaloric diet and the controls followed a normal diet.
After 6 months, those who lost 10% of their BMI or more were almost five times more likely to achieve MDA (HR 4.79, P = .002). Those who lost 5%-10% of their BMI were twice as likely as were controls to reach MDA.
Dr. Ritchlin said that he had no relevant disclosures.