AB0198 SMOKING AND POSITIVITY OF RHEUMATOID FACTOR AND ANTI-CYCLIC CITRULLINATED PEPTIDE ANTIBODY IN THE GENERAL POPULATION
Authors: G. Kidoguchi, S. Fukui, T. Nakai, S. Kawaai, H. Ozawa, Y. Ikeda, A. Koido, Y. Ohara, H. Shimizu, K. Yamaguchi, H. Tamaki, M. Okada
Journal: Annals of the Rheumatic Diseases (2020)

Background: It is well known that rheumatoid arthritis (RA) occurs due to environmental risk factors in addition to genetic risk factors. Rheumatoid factor (RF) and anti-cyclic citrullinated peptide antibody (ACPA) are strongly associated with RA, and these biomarkers could turn to be positive before development of clinical symptoms. While smoking, particularly Brinkman index (BI) is well known as a risk factor for RA and ACPA positivity, it is still unclear whether smoking intensity or smoking duration contribute more to positive RF and ACPA. Objectives: This study aims to evaluate risk factors for RF and ACPA positivity in the general population. It also describes whether smoking intensity, duration, and BI are significant. Methods: This is a cross-sectional, observational, single center study. We reviewed the baseline characteristics of the general population who checked RF and ACPA at Preventive Medicine Center in St. Luke’s International Hospital, Tokyo, Japan from January 2004 to December 2018. The data for basic demographics, dietary habit, smoking intensity, smoking duration, BI, and blood tests including RF and ACPA were extracted. The data was analyzed statistically. Results: A total of 127472 people who checked RF are included. Of these 127472 people, 64504 (50.6%) are male and the mean age was 44.9 years. RF was positive in 11477 people (9.0%). Among these, 1667 (1.2%) were checked for ACPA, and 21 people (1.3%) had positive ACPA. None of variables demonstrated significant association with RF positivity. In contrast, BI and smoking duration was significantly associated with an increased risk of ACPA positivity (13.3 years vs 7.49 years, p value = 0.023), although the number of cigarettes smoked was not. The smoking duration for 10 years or more was associated with an increased risk of ACPA positivity even after adjusted for age and sex (adjusted hazard ratio: 2.47 [95% confidence interval: 1.04-5.87]; p=0.04). Conclusion: In this study, no significant risk factor for positive RF was found. Even smoking was not associated with RF positivity. On the other hand, smoking duration, not smoking intensity was significantly associated with an increased risk of ACPA positivity. References: [1]Verpoort KN. 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;56:29138. Table 1. Patient characteristics with RF and ACPA positivity RF positive (n=11477) RF negative (n=115995) p value ACPA positive (n=21) ACPA negative (n=1646) p value Age 44.86 (12.32) 44.94 (12.47) 0.54 37.90 (9.07) 45.26 (12.58) 0.008 Male (%) 5659 (49.3) 57309 (49.4) 0.845 11 (52.4) 834 (50.7) 1 Body Mass Index 22.33 (3.38) 22.35 (3.40) 0.521 21.64 (3.28) 22.34 (3.37) 0.346 Smoker, total (%) 4509 (39.3) 45738 (39.4) 0.772 12 (57.1) 642 (39.0) 0.115 Current smoker (%) 1959 (17.1) 20483 (17.7) 0.114 8 (38.1) 277 (16.8) 0.017 Previous smoker (%) 2550 (22.2) 25255 (21.8) 0.271 4 (19.0) 365 (22.2) 1 Brinkman index 144.8 (299.3) 145.2 (313.8) 0.897 280.9 (409.7) 145.3 (300.3) 0.041 Number of cigarettes (/day) 17.7 (18.5) 17.4 (13.3) 0.166 19.8 (12.0) 17.4 (12.1) 0.511 Smoking Duration (years) 7.43 (11.68) 7.45 (11.66) 0.851 13.33 (14.11) 7.49 (11.68) 0.023 Alcohol Drinker (%) 6972 (60.7) 70010 (60.4) 0.418 10 (47.6) 1005 (61.1) 0.261 Alcohol Intake (g/day) 13.67 (21.88) 13.58 (21.32) 0.676 16.70 (26.89) 14.06 (22.16) 0.59 Exercise ≧3 times/week (%) 2792 (24.3) 28293 (24.4) 0.882 5 (23.8) 402 (24.4) 1 White blood cell (103/μL) 5.32 (1.46) 5.35 (1.50) 0.13 5.59 (2.05) 5.37 (1.54) 0.52 Hemoglobin (g/dL) 13.82 (1.44) 13.82 (1.45) 0.753 14.12 (1.03) 13.83 (1.43) 0.36 Creatinine (mg/dL) 0.73 (0.20) 0.73 (0.25) 0.194 0.76 (0.16) 0.73 (0.18) 0.586 AST (U/L) 21.89 (9.39) 21.93 (11.65) 0.782 20.95 (6.02) 21.68 (8.29) 0.69 LDL cholesterol (mg/dL) 115.41 (30.90) 115.48 (30.77) 0.815 112.62 (33.26) 115.36 (31.03) 0.688 Triglyceride (mg/dL) 97.63 (78.46) 97.70 (80.36) 0.929 100.57 (63.40) 97.85 (78.37) 0.874 Uric Acid (mg/dL) 5.32 (1.42) 5.33 (1.42) 0.623 5.76 (1.34) 5.34 (1.42) 0.172 Disclosure of Interests: None declared