Potential Link Found Between Sodium and Rheumatoid Arthritis

People who smoke and have more sodium in their diets than others could also be more likely to eventually develop rheumatoid arthritis (RA), according to a recent study.

The results of the study were published in Rheumatology and showed that the combination of those two factors could help explain why the condition develops in some patients and not others.

The study was conducted by Björn Sundström, MD, and a team from the Department of Public Health and Clinical Medicine, Rheumatology at Umeå University in Sweden as a follow-up to prior work done involving animal and human cells.

Data was collected from a pool of 386 participants “who had stated their dietary habits as part of a community intervention programme a median of 7.7 years before the onset of RA symptoms,” a statement on the study noted. Their results were compared to 1886 cross controls from the same database.

Factors considered in the patient studies included diet, exercise, and smoking. The patients also provided blood samples. While the results did not show a “significant association” between salt and rheumatoid arthritis, the authors reported that “when the results were stratified for current smokers, sodium intake more than doubled the risk for RA.”

While unable to prove the team’s original hypothesis, Sundström said the results did provide a unique look at the interaction of these factors in this patient population.

“Additive interaction analyses suggested that approximately half (54%) of the increased risk from smoking in the development of RA is due to interaction with sodium intake. A large influence of sodium

intake on smoking as a risk factor for RA is also supported by the fact that we could not identify any significant proportion of risk from smoking in individuals with a low sodium intake,” he said.

Looking at other studies, Sundström said they continue to learn more about the potential causes of RA and how it might be prevented.

“The finding of sodium being a risk factor for the development of RA among smokers is intriguing, as it may explain the discrepancies in previous studies of diet as a risk factor for RA,” he said. “That consumption, of fruit and vegetables is associated with a lower risk for developing RA, while consumption of protein, red meat, and fish with a medium fat content is associated with a higher risk, could be explained by these dietary products being associated with a higher intake of sodium.”

The study was supported by grants from the Swedish Research Council, King Gustaf V’s 80-year Fund, King Gustaf V’s and Queen Victoria’s Fund, the Swedish Rheumatism Association, the Swedish

Controlling Chronic Inflammatory Diseases with Combined Efforts Programme, the Department of Research, Västerbotten County Council and the Swedish Foundation for Strategic Research.