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Guest commentary: Obesity has ‘complex’ effect on disease outcomes in axial spondyloarthropathy
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In this guest commentary, Vivian P. Bykerk, BSc, MD, FRCPC, discusses the relationship between obesity and disease outcomes in axial spondyloarthropathy following a presentation on the topic at the American College of Rheumatology Annual Meeting. Bykerk is associate attending rheumatologist and director of the Inflammatory Arthritis Center of Excellence at the Hospital for Special Surgery and associate professor of medicine at Weill Cornell Medical College.
The question of whether obesity influences axial spondyloarthropathy outcomes is a chicken and egg problem. Increased pain may lead you to move less, but you may also not make good food choices. Diet is of it; part of it is disease activity, pain and lack of movement. Social disparities need to be considered in these situations, too, because poor people eat a lot of white carbohydrates and they’re not well-nourished; their diet may be not as good.
This study was exploratory, but I think there is truth to the results. When we, as researchers, use composite measures, we’re determining how patients feel generally. If patients are overweight or obese, they tend to feel worse, and that will factor into the outcome measure. That raises the question: Are we measuring only that patients don’t feel well – or is obesity contributing to pain? I think the latter is true, simply because of how you move and feel. It’s not a causal pathway that we know of, per say, although there is some scientific rationale that obesity – or more white adipose tissue – is pro-inflammatory. It’s complex.
In addition, comorbid conditions make you feel worse, and obesity contributes to comorbidities. We recently performed a study that examined patients with early RA; we had a similar study design with 3,000 patients, many who were followed out to 2 years. We looked at the impact of being obese, very obese and morbidly obese in achieving remission. Our results were similar to those from Fitzgerald and colleagues – patients who were obese did not achieve remission. In our study, patients who were obese were 50% less likely to achieve remission.
We also looked at the link between smoking and obesity in a separate study and found that there was an interaction. Some people who are overweight do smoke to keep their weight down, but very obese people aren’t smoking. Smoking is also a psychological comorbidity, to some degree, as patients may have anxiety; some people use nicotine to cope and others use food.
When people have excess weight, they should be referred to specialists, groups and clinics that can help them manage weight. There have been trials demonstrating that bariatric surgery improves outcomes in RA. I don’t know where the trials are in regard to spondylitis, although I don’t think they’re far.
What we also do not know yet is how much weight a patient needs to lose to change the outcomes related to rheumatologic disease. In other words, we don’t have a way to say, “For every 20 pounds, you can improve the symptoms of rheumatologic disease by ‘X’ percent.” I’ve never seen data on this, but it would be a very interesting message to give patients. We could, for example, tell a patient who has osteoarthritis of the knee, “For every 10 pounds you lose, your knee will feel like it’s lost 20 pounds, and your pain will decrease.” Ten pounds is a lot when it comes to stress on the knee; it probably won’t make a difference for elbow joints, but it could be motivational: “Oh, I only need to lose 20 pounds to feel that much better.” However, we don’t yet have specific numbers to give to patients.
Obesity is contributing to numerous issues in health care. It’s become the new smoking.
Disclosure: Bykerk reports serving as a consultant for Amgen, Bristol-Myers Squibb, Gilead Sciences, Pfizer, Sanofi/Regeneron and UCB.