SAN DIEGO – A new study offers a double message about the potential impact of obesity on systemic lupus erythematosus (SLE) in women: Excess pounds are linked to a higher risk of patient-reported outcomes such as pain and fatigue, and body mass index may be an appropriate tool to study weight issues in this population.
Researchers found “a strong relationship between body composition and worse outcomes,” Sarah Patterson, MD, a fellow in rheumatology at the University of California, San Francisco, and the lead study author, said at the annual meeting of the American College of Rheumatology.
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For the new study, Dr. Patterson and her colleagues analyzed findings from surveys of 148 participants in the Arthritis Body Composition and Disability study. All participants were women with a verified SLE diagnosis.
About two-thirds of the sample were white, 14% were Asian, and 13% were African American. The average age was 48 years, the average disease duration was 16 years, and 45% took glucocorticoids.
Researchers used two measurements of obesity: BMI of 30 kg/m2 or greater and fat mass index (FMI) of 13 kg/m2 or greater.
They calculated FMI with data collected via whole dual x-ray absorptiometry. Of the participants, 32% and 30% met criteria for obesity under FMI and BMI definitions, respectively.
Researchers also collected survey data regarding measurements of disease activity, depressive symptoms, pain and fatigue.
The study authors controlled their results to account for factors such as age, race, and prednisone use. They found that those defined as obese via FMI had more disease activity and depression than did nonobese women: 14.8 versus 11.5, P = .010, on the Systemic Lupus Activity Questionnaire scale, and 19.8 versus 13.1, P = .004, on the Center for Epidemiologic Studies Depression scale.
On two other scales of pain and fatigue, obese patients scored lower – a sign of worse status – compared with nonobese women: 38.7 versus 44.2, P = .004, on the Short Form 36 (SF-36) Health Survey pain subscale and 39.6 versus 45.2, P = .010, on the SF-36 vitality subscale. The researchers reported similar findings when using BMI to assess obesity.
It’s not clear why obesity and lupus may be linked, Dr. Patterson said, though she noted that inflammation is a shared factor. “People with lupus have arthritis and chronic pain, so there may be this vicious feedback cycle with hindrances to be able to live healthy lifestyles,” she added.
The study has limitations, including that the sample is largely white, while lupus is more common among minority women. In addition, the study does not include underweight patients or track patients over time. “It will be important to look at obesity and patient-reported outcomes to determine whether weight loss results in better outcomes,” Dr. Patterson said.
The study does provide an extra benefit by suggesting that BMI is not an inferior tool to measure the effects of obesity in the SLE population, Dr. Patterson said. BMI has been criticized as a misleading measurement of obesity. But the BMI and FMI measures produced similar results in this study. “That’s really good news in a way for the practicalities of using this information,” she said.
But FMI may still be a better measurement of obesity in the general population, where BMI may be more likely to be thrown off by high muscle mass.
It may seem obvious that obesity is linked to worse lupus outcomes, but rheumatologist Bryant England, MD, of the University of Nebraska, Omaha, said that this research is noteworthy because it highlights the importance of focusing on obesity in the clinic.
Rheumatologists shouldn’t leave obesity to primary care physicians but instead confront it themselves, said Dr. England, who moderated a discussion of new research at an ACR annual meeting press conference. But he cautioned that prudence is especially important when talking about obesity with lupus patients because they may be sensitive about medication-related weight gain.
Dr. Patterson and the other study authors reported having no relevant disclosures. Dr. England also reported no relevant disclosures. The study was funded by the National Institute of Arthritis and Musculoskeletal and Skin Diseases.