A recent study revealed that more than half of the increase in rheumatoid arthritis (RA) in a population of women was due to obesity.

A sample of 813 patients (male and female)with RA and 813 controls was analysed from 1985 to 2007. They found that the incidence of RA increased at a rate of 9.2 per 100,000 women during the period and that obesity accounted for 52% — 4.8 per 100,000 of the increase between 1995 and 2007. This strong association with obesity in women remained after adjustment for smoking status. Following a 40 year period of decline, the incidence of RA has been on the rise since 1995 ; the researchers believe this is due to obesity which has risen dramatically in this time period, although previous research has shown conflicting results for the association.

Statisitcal analysis of the data showed that obesity could explain 52% of the increase in incidence of RA among women observed in 1995-2007. For men, the researchers concluded that the proportion of incidence increase attributable to obesity was much less (2.3 per 100,000).

Although the mechanism for obesity’s association with RA is unknown, chronic inflammation from obesity could be leading to rheumatic problems. Other possibilities include the link between obesity and vitamin D deficiency or the higher levels of estrogen in obese individuals. Another theory is a due to a genetic link between obesity and autoimmune disease.

Arthritis Care Res. Published online April 18, 2012. Abstract