Smokers who eat too much salt have twice the risk of developing rheumatoid arthritis

The interaction between high salt intake and smoking is associated with a more than doubled risk of developing rheumatoid arthritis, says new research published in Rheumatology.
The research team looked at data from 386 people who had outlined their dietary habits before they developed rheumatoid arthritis. The average time from when they gave their information to the onset of symptoms was 7.7 years. They were compared with 1,886 matched controls.
The study did not find any significant association between salt intake and the development of rheumatoid arthritis when all the individuals were included. But when the team looked at current smokers, salt intake more than doubled the risk of rheumatoid arthritis.
“Additive interaction analyses suggested that approximately half (54%) of the increased risk from smoking in the development of rheumatoid arthritis is due to interaction with sodium intake,” says Dr Björn Sundström, who led the work. “A large influence of sodium intake on smoking as a risk factor for rheumatoid arthritis 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.
“The finding of sodium being a risk factor for the development of rheumatoid arthritis among smokers is intriguing, as it may explain discrepancies in previous studies of diet as a risk factor for rheumatoid arthritis. That consumption of fruit and vegetables is associated with a lower risk of developing rheumatoid arthritis, 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.
“These results could have implications for analyses of diet in other conditions in which inflammation is of importance.”

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Image credit: Kevin Dooley