%0 Journal Article
%T Environmental risk factors differ between rheumatoid arthritis with and without auto-antibodies against cyclic citrullinated peptides
%A Merete Pedersen
%A S£¿ren Jacobsen
%A Mette Klarlund
%A Bo V Pedersen
%A Allan Wiik
%A Jan Wohlfahrt
%A Morten Frisch
%J Arthritis Research & Therapy
%D 2006
%I BioMed Central
%R 10.1186/ar2022
%X A number of genetic and environmental factors have been implicated in the etiology of rheumatoid arthritis (RA). The only well-established environmental risk factor is tobacco smoking, which has been shown in a number of studies to be associated with increased RA risk [1-4]. Associations between RA and factors such as diet [5-7], coffee intake [8-10], alcohol [11-13], and body mass index [12-14] have also been studied, but the evidence to suggest a causal role of these factors is inconclusive. A widespread theory is that one or more infectious agents might act as initiator in the pathogenesis of RA by having antigens similar to host antigens, a mechanism referred to as molecular mimicry [15], but the evidence in favor of any particular microbe is weak. Because RA is approximately three times as common in women as in men, sex hormones and reproductive factors have been suggested as potentially involved in the etiology [16-18]. Furthermore, a sexually transmitted agent with a higher male-to-female than female-to-male transmission rate might theoretically explain the female predominance in RA, but only few studies have examined sexual behavior and venereal diseases as possible risk factors [19,20].One possible explanation for conflicting results in etiologic studies might be that risk factors differ between subtypes of RA. It was recently demonstrated that smoking is selectively associated with rheumatoid factor (RF)-positive RA [21] or with RA positive for anti-cyclic citrullinated peptide (CCP) antibodies [22,23]. Also, coffee consumption has been found to be selectively associated with RF-positive RA, although the association diminished considerably after adjustment for tobacco smoking [9]. Further supporting the existence of etiologically distinct subtypes of RA, recent case-control studies have shown that measures of low socioeconomic status are predominantly associated with risk of RF-positive RA [24,25]. The aim of the present study was to evaluate both new and
%U http://arthritis-research.com/content/8/4/R133