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Published: 2014-09-11

Smokers with high salt intake are at 'double the risk' of rheumatoid arthritis

NEWS Smokers who also have a high sodium intake may be at double the risk of developing rheumatoid arthritis (RA), according to a new study published in the journal Rheumatology.

"Our findings suggest that more than half (54 percent) of the increased risk from smoking in the development of rheumatoid arthritis is due to interaction with sodium intake," says Björn Sundström from department of public health and clinical medicine at Umeå University, Sweden.

The study, carried out by Björn Sundström and colleagues from the Department of Public Health and Clinical Medicine, Rheumatology, was carried out to see whether recent animal and human cell study results that showed a link between a high sodium intake and RA would yield similar results in a nested case-control study of data from the Västerbotten Intervention Programme (VIP). It focused on 386 individuals 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. For comparison, 1886 matched controls were identified from the same database and co-analysed.

As part of the VIP, health-screening data (dietary habits, physical exercise, smoking, and other social factors) were collected, along with blood samples. The study did not find any significant association between sodium intake and the developed of RA when all the individuals were included, and so the researchers were not able to confirm their original stated hypothesis. However, when the results were stratified for current smokers, sodium intake more than doubled the risk for RA.

"The 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,’"stated Sundström.

Sundström adds that the reason why eating fruit and vegetables is associated with a lower risk of developing rheumatoid arthritis - while eating protein, red meat and some fish is associated with a higher risk - could be that fruit and vegetables are lower in sodium.

"These results could have implications for analyses of diet in other conditions in which inflammation is of importance," says Sundström.

For more information, please contact:

Björn Sundström, Postdoctoral researcherDepartment of Public Health and Clinical Medicine, Umeå UniversityPhone:+ 46 (0)90-785 86 58
Email: bjorn.sundstrom@medicin.umu.se

Read the study in the journal Rheumatology

Editor: Mattias Grundström Mitz