Worse RA with Obesity

Obese rheumatoid arthritis patients may have worse outcomes than non obese patients

(RxWiki News) In study after study, researchers have shown that being obese is unhealthy. Obesity can both cause and worsen disease. Rheumatoid arthritis is one disease that seems to get worse with obesity.

A recent study showed that obese patients with rheumatoid arthritis had worse outcomes and higher rates of other health problems compared to those who were not obese. Obese patients had higher odds of being diagnosed with high blood pressure, diabetes and chronic pulmonary disease.

According to the authors, taking body size measurements may help doctors better predict the course of rheumatoid arthritis in their patients.

"Control your weight to help improve rheumatoid arthritis."

Sofia Ajeganova, of Karolinska Institutet at Karolinska University Hospital in Sweden, and colleagues set out to better understand the links between obesity and disease activity and severity of rheumatoid arthritis. They also looked at the relationship between obesity and other conditions in patients with rheumatoid arthritis.

For this study, obesity was defined by the researchers as a body mass index (BMI) of at least 30, at least 28 or by waist size.

BMI is a measure of body fat using height and weight. A BMI between 18.5 and 25 is considered normal weight. A BMI of 30 or more is typically considered obese.

This study used two cutoff points for obesity. The lower cutoff (BMI of 28) is not the official cutoff for obesity. However, using it as part of the analysis could show how the impact of obesity on rheumatoid arthritis affects those who are not usually considered obese.

The study included 1,596 patients with early rheumatoid arthritis who were part of the Better Anti-Rheumatic Farmacotherapy observational study from 1992 to 2006. In 2010, researchers sent out a questionnaire through the mail that asked about lifestyle and the presence of conditions other than rheumatoid arthritis. A total of 1,391 patients answered the questionnaire.

The researchers wanted to find out if obesity affected the outcomes of rheumatoid arthritis patients. Outcomes included Disease Activity Score in 28 joints (DAS-28), sustained remission (long-term reduction or disappearance of symptoms), physical function, pain and overall health.

DAS-28 is a measure of rheumatoid arthritis disease activity that counts the total number of tender or swollen joints out of a total of 28 joints. DAS-28 scores range from 0 to 10. A score below 2.6 is considered remission while a score over 5.1 is considered high disease activity.

To measure physical function, researchers used the Health Assessment Questionnaire (HAQ). A higher HAQ score is a sign of higher disability.

At the beginning of the study, 12.9 percent of participants were obese, with a BMI of 30 or more. At follow-up, 15.8 percent of participants had a BMI of 30 or more.

Results showed that obesity - defined by the researchers as BMI of either at least 30 or at least 28 - was associated with higher disease activity, fewer patients in sustained remission, higher HAQ scores, more pain and worse global health. In other words, obese rheumatoid arthritis patients appeared to have more disease activity, lower odds of remission, poorer physical function, more pain and worse overall health.

Obese patients were also more likely to be diagnosed with hypertension (high blood pressure), diabetes and chronic pulmonary disease. 

What's more, patients' BMI and waist size were linked to angina (chest pain due to restricted blood flow to the heart), heart attack or coronary revascularization (procedures to restore blood flow to the heart).

More specifically, rheumatoid arthritis patients with a BMI of 30 or more at the beginning of the study had:

  • 2.40 times the odds of developing hypertension compared to those who were not obese
  • 2.09 times the odds of developing diabetes
  • 1.33 times the odds of angina, heart attack or coronary revascularization

At the time the questionnaire was sent out, patients with a BMI of 30 or more had:

  • 2.17 times the odds of developing hypertension
  • 3.23 times the odds of diabetes
  • 1.24 times the odds of angina, heart attack or coronary revascularization

Patients with a BMI of 28 or more also faced these increased odds, suggesting that even patients with a BMI not usually considered obese may face the same risks as those who are typically considered obese.

"Irrespective of which of the two definitions of obesity was used (BMI of 30 or more or 28 or more), analyses of associations with disease severity produced similar results, implying that with the lower cutoff point, more patients with an unfavorable body composition were detected," the authors wrote.

They concluded that the study's results show that obesity and central adiposity (fat in a person's midsection) both at the beginning and during the course of disease were associated with worse arthritis outcomes and higher rates of other health problems.

"BMI with an appropriate cutoff to assess obesity and waist circumference measurements should both be used and encouraged in the rheumatoid arthritis population and might aid in prediction of the disease course," they wrote.

The study was published December 27 in Arthritis Care & Research. The research was funded by The Swedish Rheumatism Association, King Gustaf V's 80-Year Fund, Stockholm County Council and Karolinska Institutet. No conflicts of interest were reported by the authors.

Review Date: 
January 29, 2013