How Fat Affects PsA
Learn how excess body fat can worsen psoriatic arthritis ( PsA) symptoms and affect how well arthritis drugs work.
Ten to 30 percent of people with psoriasis eventually develop psoriatic arthritis (PsA) – often about a decade after skin symptoms appear. The biggest risk factor is obesity (defined as a body mass index or BMI of 30 or more), according to Dafna Gladman, MD, professor of medicine at the University of Toronto and a noted PsA expert. Studies show that psoriasis patients who are obese are far more likely to develop PsA than those who weigh less.
Why Obesity Matters
Psoriasis and PsA share some of the same inflammatory proteins (cytokines) produced by fat tissue. The more fat cells you have, the more inflammation you have, too. And the damage can start when you’re young. One study found that people with psoriasis who were obese at age 18 were three times more likely to develop PsA than their normal-weight peers.
Why Weight Loss Matters
Weight loss can change the picture. A study of more than 90,000 patients with psoriasis found that shaving 5 points off their BMI cut the risk of PsA by 13 percent and losing13 points from their BMI over 10 years reduced the risk by 30 percent. Healthy weight loss also makes it more likely you can reduce disease activity, your blood pressure and your risk of diabetes and heart disease.
Disease Severity and Treatment Response
Most studies suggest that people with PsA who are obese or overweight (BMI of 25 to 29) have more pain, more widespread skin disease and more disability than those who aren’t as heavy. Dr. Gladman and colleagues also reported that obese and overweight patients were less likely to achieve minimal disease activity (MDA) – a common goal for PsA treatment.
In Dr. Gladman’s study, MDA was defined as improvement in five or more PsA domains (such as skin, enthesitis, and tender and swollen joint counts) for at least one year. The heavier people were, the less likely they were to respond to treatment with conventional disease-modifying anti-rheumatic drugs (DMARDs) like methotrexate. In other studies, obese patients treated with tumor necrosis factor (TNF) blockers, such as etanercept (Embrel) and adalimumab (Humira) didn’t do as well as healthy-weight people who got the same drugs. They were also more likely to stop treatment.
Other Health Problems
More than half of people with PsA have at least one other health problem – what doctors call a comorbidity. Many have three or more comorbid conditions. The most common are heart disease, diabetes and metabolic syndrome. Metabolic syndrome is a combination of fat around your middle, high blood pressure, insulin resistance, high triglycerides and high “bad” cholesterol. When you carry too much weight, your chance of developing these conditions is even higher than for PsA patients in general. That’s because all are caused by inflammation, and overweight people have more of it. “Fat tissue is an endocrine organ that produces a variety of inflammatory chemicals that can add to your overall level of systemic inflammation,” says Alexis Ogdie-Beatty, MD, a rheumatologist and director of the Penn Psoriatic Arthritis Clinic at the University of Pennsylvania in Philadelphia.
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