A recent study links the interaction between high sodium intake and smoking to a more than doubled risk of developing rheumatoid arthritis (RA).

The study appears in Rheumatology

 An Oxford University Press (OUP) news release reports that Dr. Björn Sundström and colleagues from the department of Public Health and Clinical Medicine, Rheumatology at Umeå University, Sweden, carried out the research. The study’s goal centered on determining whether recent animal and human cell study results that indicated a link between high sodium intake and RA would yield similar results in a nested case-control study of data from the Västerbotten Intervention Programme (VIP).

The release notes that the study encompassed a total of 386 individuals who had stated their dietary habits as part of a community intervention program a median of 7.7 years before the onset of RA symptoms. Additionally, 1,886 matched controls were identified from the same database and co-analyzed for comparison.

As part of the VIP, health-screening data, which included dietary habits, physical exercise, smoking, and other social factors, were collected along with blood samples. The study, the release says, did not find any significant link between sodium intake and the development of RA when all individuals were included, and as a result the researchers were unable to confirm their original stated hypothesis. Yet, when the results were stratified for current smokers, sodium intake more than doubled the risk for RA.

Sundström explains in the release that the addictive interaction analyses indicated that 54% of the increased risk from smoking in the development of RA is a result of 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,” Sundström says.

Sundström adds that the study’s findings will offer new insights into the aetiopathogenic process leading to the development of RA among smokers.

“The finding of sodium being a risk factor for the development of RA among smokers is intriguing, as it may explain discrepancies in previous studies of diet as a risk factor for RA,” Sundström notes, “That consumption of fruit and vegetables is associated with a lower risk of 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.”

Source: Oxford University Press