Using lifestyle factors to identify individuals at higher risk of inflammatory polyarthritis (results from the European Prospective Investigation of Cancer-Norfolk and the Norfolk Arthritis Register-the EPIC-2-NOAR Study)

Abstract

Objectives To investigate the association of lifestyle factors with risk of inflammatory polyarthritis (IP) and rheumatoid arthritis (RA). Methods The European Prospective Investigation of Cancer, Norfolk, UK (EPIC-Norfolk) gathered lifestyle data from participants aged 40-79 years from 1993 to 1997. Individuals who subsequently developed IP were identified by linkage with the Norfolk Arthritis Register. A Cox proportional hazard model was developed, and a score assigned to each risk factor to calculate the odds of developing IP. Results 25 455 EPIC participants were followed for a median (IQR) of 14.2 (12.9, 15.3) years; 184 developed incident IP (138 cumulatively fulfilled criteria for RA; 107 were seropositive). Pack-years of smoking were associated with increased risk of IP and RA in men (HR 1.21 (95% CI 1.08 to 1.37) per 10-pack-years) and seropositive IP (HR 1.24 (95% CI 1.10 to 1.41)) for all. Diabetes mellitus was associated with increased risk of IP (HR 2.54 (95% CI 1.26 to 5.09)), while alcohol (HR 0.86 (95% CI 0.74 to 0.99) per unit/day) and higher social class (HR 0.36 (95% CI 0.15 to 0.89) for professionals vs manual workers) were associated with reduced risk. Body mass index was associated with seronegative IP (HR 2.75 (95% CI 1.39 to 5.46) for obese vs normal-weight participants). In women, parity (HR 2.81 (95% CI 1.37 to 5.76) for ≥2 vs no children) was associated with increased risk, and breast feeding (HR 0.66 (95% CI 0.46 to 0.94) for every 52 weeks of breast feeding) was inversely associated with risk. Risk factors from the model were used to generate a 'risk score'. A total of 1159 (8.4%) women had scores reflecting a >3-fold increased risk of IP over those with a score of 0. Conclusions Several easily ascertained clinical and lifestyle factors can be used to stratify populations for risk of IP.