Background/Purpose: Recent studies using animal models and human cells ex vivo have indicated that sodium chloride may affect the immune system by the inducting of pathogenic Th17 cells mediated through a salt–sensing kinase (SGK1) leading to autoimmune disease. Since Th17 cells may play a role in the early stages of disease development in rheumatoid arthritis (RA), the dietary intake of sodium is of interest to analyse as a risk factor for the development of RA.

Methods: A nested case–control study was performed using the population based prospective data from the Västerbotten Intervention Programme collected between 1991 and 2011. The study included 386 individuals who later developed RA according to the 1987 ACR criteria. These 386 individuals (271 women, 115 men) had stated their dietary habits in a food frequency questionnaire (FFQ) as part of the community intervention programme before the onset of symptoms of RA (pre–symptomatic individuals). The pre-symptomatic individuals were compared using conditional logistic regression analyses with 1886 controls – matched for age, sex, time point of examination and version of the FFQ – drawn from the same database.

Results: Among current smokers with higher sodium consumption an increased odds ratio (OR) for developing RA was observed (OR) 2.26 (95% CI 1.06–4.81). Restriction of analyses to current smokers examined within the tertile closest to the onset of symptoms, the OR increased to 7.82 (95% CI 1.48–41.3). These associations were not found among non-smokers.  Among current smokers with the lowest consumption of sodium, no significantly increased risk for developing RA could be identified. An interaction between high sodium intake and being current smoker was found.

Conclusion: Higher sodium consumption among smokers yielded an increased OR for development of RA. An interaction between smoking and sodium was found. These results provide new insights into the pathogenesis of RA. Furthermore, since sodium intake is related to the consumption of foods that are suggested to have an impact on health, i.e. meat, fruit, and vegetables, these results may have implications for studies of the effect of diet in RA, as well as in other diseases.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/dietary-sodium-increases-the-risk-for-rheumatoid-arthritis-among-smokers-results-from-a-nested-case-control-study/