Did you know these weighty facts about Psoriatic Arthritis?

By Dr Irwin Lim, Rheumatologist

2 weekends ago, 11 from our clinic were in Hobart attending the Australian Rheumatology Association's Annual Scientific Meeting.

It's always an enjoyable meeting where familiar faces and a general sense of camaraderie abound.

There was a great session updating us on Psoriatic Arthritis (PsA). There is a lot of scientific buzz around psoriasis and psoriatic arthritis, with a range of interesting and useful-looking medication therapies in the pipeline.

What I want to highlight however is a range of facts I gleaned from the talk by Professor Christopher Ritchlin. He hails from Rochester, USA and is a world expert.

His talk focussed on the link between obesity and psoriatic arthritis. Here are some interesting tidbits:

• Using a definition of body mass index (BMI) >30 kg/sq.m, around 37% of those suffering with PsA are obese while 29% with psoriasis are obese.
• Obesity seems to be a state of non-resolving inflammation. Adipocytes (fat cells) release chemicals called cytokines which seem to draw immune cells into the adipose tissues from the blood stream. This in turn leads to an increase in pro-inflammatory cytokines, driving the inflammatory process.
• Having a higher BMI seems to also lead to a higher incidence of Psoriatic Arthritis. BMI > 35 leads to a relative risk of between 1.48 - 2.7 of developing PsA.
• PsA seem to be an independent risk factor for cardiovascular risks. This means that having PsA increases your risk of heart attacks or strokes over and above the standard risk factors of high lipids or high blood pressure, diabetes, etc.
• Rheumatoid arthritis (RA) is known to increase cardiovascular risks significantly. The CVS risk of PsA is thought to be similar to that of RA.
• Metabolic Syndrome (the combination of insulin resistance, obesity, dyslipidemia and hypertension) is found in twice as many patients with PsA compared to RA.
• Obese patients are significantly less likely to achieve a state of Minimal Disease Activity.
• Importantly, weight loss actually improves the ability to control disease activity. In a study involving 138 obese PsA patients starting TNF-inhibitor therapy, those patients who managed to lose >10% of weight at 6 months, were 4.8 times more likely to achieve a Minimal Disease Activity state. Therefore, weight loss enhances the response to TNF inhibitor therapy.

It's easy to link excess weight to back, knee and lower limb pain. Patients understand the physics of carrying this extra baggage and it's biomechanical load on these areas. I think it's widespread knowledge that obesity predisposes to cardiovascular risks. But in many, this information still does not seem enough to engender lifestyle change.

Maybe, we rheumatologists need to spend more time explaining how weight affects the actual disease process in PsA. Maybe we need to highlight that reducing weight improves response to treatment.

So much attention is placed on therapeutics and rightfully so, given the disease process needs to be controlled. But we just don't seem to address obesity effectively in our patients with rheumatic disease.

We can do better. We need to do better.

What do you think I could say or do to help this process?