Objective: To perform a meta-synthesis of the evidence for modifiable lifestyle risk factors for inflammatory polyarthritis (IP) and RA.
Methods: We performed a MEDLINE literature search. Case-control and cohort studies and systematic reviews published from 1948 through February 2011 and studying modifiable risk factors for RA were retrieved. The main outcome measure was diagnosis of RA according to the standard criteria.
Results: Smoking contributes up to 25% of the population burden of RA. The risk is dose related, stronger in males and especially strong for anti-citrullinated peptide antibody positive (ACPA(+)) RA through an interaction with the shared epitope. After smoking cessation, there is, however, a latency of up to 20 years to return to baseline risk. Other associations are less definitive; however, prospective studies suggest that dietary antioxidants and breastfeeding may be protective and that high coffee consumption may increase RA risk. An inverse association with alcohol intake (especially in smokers) and with education/social class (especially seropositive RA) and an increased risk with obesity (seronegative RA) is also noted.
Conclusion: There is a need for further large-scale prospective studies with a consistent definition of RA phenotype (undifferentiated IP through to ACPA(+)/RF(+) disease). This will ultimately afford the opportunity to evaluate preventative population strategies for RA akin to the well-established programmes for cardiovascular disease and cancer, targeting common risk factors.