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• Potential confounding effects of smoking on Body Mass Index in Rheumatoid Arthritis
  Jenny H Scott
  Published on: 7 July 2008

• Published on: 7 July 2008

  Potential confounding effects of smoking on Body Mass Index in Rheumatoid Arthritis

  • Jenny H Scott, Medical practitioner
  • Other Contributors:
    • Cristina Estrach, Nicola Goodson

  Dear Editor,

  We read with interest the article by van der Helm, which explores the relationship between Body Mass Index (BMI) and radiological damage in early rheumatoid arthritis (RA). We were particularly interested in the finding that patients with baseline BMI lesser than 25 developed more erosive disease during follow-up than those with increased BMIs. This association was only observed in those patients who were...

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  Dear Editor,

  We read with interest the article by van der Helm, which explores the relationship between Body Mass Index (BMI) and radiological damage in early rheumatoid arthritis (RA). We were particularly interested in the finding that patients with baseline BMI lesser than 25 developed more erosive disease during follow-up than those with increased BMIs. This association was only observed in those patients who were positive for anti-cyclic citrullinated peptide (anti-CCP) antibodies.

  We wonder whether this finding may be confounded by cigarette smoking. We note from table 1 that smoking was more prevalent in the group of patients with a lower BMI. A recent study has highlighted that cigarette smoking is associated with low body mass index in rheumatoid arthritis and an inverse relationship exists between pack years of smoking and percentage body fat(1). As cigarette smoking is also associated with more severe RA disease(2) we wonder whether adjusting for smoking in the multivariate analysis might reduce the observed association between BMI and the development of erosions.

  Smoking has been identified as a predictor of erosive disease in RA cohorts(2), although other studies have failed to observe an association(3). Cigarette smoking and increasing pack years of smoking are strongly associated with the development of RA and rheumatoid factor (RF) positive disease(4). Anti-CCP positive status, like RF, is a poor prognostic marker in RA and these patients are more likely to experience a more severe disease course(5). In addition an association has been identified between anti-CCP positivity and smoking(6). A number of studies have gone on to postulate a gene-environment interaction in this group. They hypothesise that in genetically susceptible patients, who carry the HLA-DRB1 shared-epitope alleles, smoking may trigger RA-specific immune reactions to citrullinated protein(6,7).

  Most studies exploring the effect of smoking on radiological outcome have done so in patients with established RA, and there is little literature relating to smoking as a predictor of erosive disease in the early years of the RA process. Therefore, we feel that it is important to explore the potential effect of smoking on the development of erosions in early RA and suggest that smoking may confound the observed association between low BMI and radiological outcome in this cohort.

  References

  1. Stavropoulos-Kalinoglou A, Metsios GS, Panoulas VF, Douglas KMJ, Nevill AM, Jamurtas AZ, Kita M, Koutedakis Y, Kitas GD. Cigarette smoking associates with body weight and muscle mass of patients with rheumatoid arthritis: a cross-sectional, observational study. Arthritis Research & Therapy 2008;10:R59 (20 May 2008).

  2. Saag KG, Cerhan JR, Kolluri S, Ohashi K, Hunninghake GW, Schwartz DA. Cigarette smoking and rheumatoid arthritis severity. Ann Rheum Dis 1997;56:463-9.

  3. Finckh A, Dehler S, Costenbader KH, Gabay C. Cigarette smoking and radiographic progression in rheumatoid arthritis. Ann Rheum Dis 2007;66:1066-71.

  4. Manfredsdottir VF, Vikingsdottir T, Jonsson T, Geirsson AJ, Kjartansson O, Heimisdottir M, Sigurdardottir SL, Valdimarsson H, Vikingsson A. The effects of tobacco smoking and rheumatoid factor seropositivity on disease activity and joint damage in early rheumatoid arthritis. Rheumatology 2006;45:734-40.

  5. Forslind K, Ahlmén M, Eberhardt K, Hafström I, Svensson B. Prediction of radiological outcome in early rheumatoid arthritis in clinical practice: role of antibodies to citrullinated peptides (anti-CCP). Ann Rheum Dis 2004;63(9):1090-5.

  6. Verpoort KN, Papendrecht-van der Voort, van der Helm-van Mil, Jol-van der Zijde CM, van Tol MJD, Drijfhout JW, Breedveld FC, Vries RRP, Huizinga TWJ, Toes REM. Association of smoking with the constitution of the anti-cyclic citrullinated peptide response in the absence of HLA-DRB1 shared epitope alleles. Arthritis Rheum 2007;56:2913-8.

  7. Klareskog L, Stolt P, Lundberg K, Källberg H, Bengtsson C, Grunewald J, Rönnelid J, Harris HE, Ulfgren AK, Rantapää-Dahlqvist S, Eklund A, Padyukov L, Alfredsson L. A new model for an etiology of rheumatoid arthritis: smoking may trigger HLA-DR (shared epitope)-restricted immune reactions to autoantigens modified by citrullination. Arthritis Rheum 2006:54(1):38-46.

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  Conflict of Interest:
  None declared.

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