Obese men at lower risk of rheumatoid arthritis

A high body mass index (BMI) could reduce the risk of rheumatoid arthritis in men, but not in women, a new study in Sweden has found.
Scientists analysed data from 383 patients, taken from two population based health surveys with a total of 50,705 participants, to discover that there is a strong association between a high BMI in men and a lower risk of developing rheumatoid arthritis (RA).
However, this association was not found in women.
The results were based on the Malmo Diet Cancer Study (MCDS) and Malmo Preventative Medicine Programme (MPMP) data sets.
After the results had been adjusted for smoking, as that has been found to be negatively associated with obesity in men, men with a BMI over 25 kg per square metre were estimated to be 63 per cent less likely to develop RA in the MDCS, and 40 per cent less likely in the MPMP.

When looking into why a high BMI would reduce the risk of men developing RA in the future, the scientists suggested that a high BMI more often reflects increased abdominal obesity or visceral fat in men compared with women, which could be protective against the development of RA.

They have previously described a connection between high BMI and hormones, where metabolic pathways related to the adipose tissue and hormone-related factors could have a protective effect against RA.
"To our knowledge, this is the first nested case-control study to investigate this issue in men," said lead study author Carl Turesson, from Lund University in Sweden.

"The effect of obesity on the risk of RA did not appear to be substantially different from that of overweight. However, a differential effect of very high BMI cannot be ruled out," Turesson said.
The study was published in the journal Rheumatology.