Supplement:

Table A: Smoking habits across level of education for both cases and controls.

Case / Control
Never-smoker
n (%) / Ever-smoker
n (%) / Never-smoker
n (%) / Ever-smoker
n (%)
No formal education / 76 (8 %) / 4 (5 %) / 44 (4 %) / 1 (2 %)
Primary school / 207 (23 %) / 25 (32 %) / 256 (21 %) / 19 (30 %)
Lower secondary / 176 (19 %) / 16 (21 %) / 219 (18 %) / 14 (22 %)
Higher secondary / 261 (29 %) / 23 (29 %) / 417 (34 %) / 16 (25 %)
College/University / 130 (14 %) / 8 (10 %) / 252 (20 %) / 10 (16 %)
Other / 53 (6 %) / 2 (3 %) / 49 (4 %) / 4 (6 %)

Table B: Smoking habits across level of education for both cases and controls by gender.

Men / Women
Case / Control / Case / Control
Never-smoker
n (%) / Ever-smoker
n (%) / Never-smoker
n (%) / Ever-smoker
n (%) / Never-smoker
n (%) / Ever-smoker
n (%) / Never-smoker
n (%) / Ever-smoker
n (%)
No formal education / 1 (2 %) / 3 (4 %) / 1 (1 %) / 0 (0 %) / 75 (9 %) / 1 (11 %) / 43 (4 %) / 1 (17 %)
Primary school / 9 (16 %) / 22 (32 %) / 20 (20 %) / 17 (29 %) / 198 (23 %) / 3 (33 %) / 236 (21 %) / 2 (33 %)
Lower secondary / 13 (23 %) / 15 (22 %) / 17 (17 %) / 14 (24 %) / 163 (19 %) / 1 (11 %) / 202 (18 %) / 0 (0 %)
Higher secondary / 24 (43 %) / 21 (30 %) / 35 (35 %) / 14 (24 %) / 237 (28 %) / 2 (22 %) / 382 (34 %) / 2 (33 %)
College/University / 6 (11 %) / 7 (10 %) / 21 (21 %) / 10 (17 %) / 124 (15 %) / 1 (11 %) / 231 (20 %) / 0 (0 %)
Other / 3 (5 %) / 1 (2 %) / 7 (7 %) / 3 (5 %) / 50 (6 %) / 1 (11 %) / 42 (4 %) / 1 (17 %)
Table C Odd ratios (OR) with 95% confidence interval (95% CI) of developing ACPA-positive RA, ACPA-negative RA and overall RA for ever-smokers compared with never-smokers among Malays.
Overall RA / ACPA-positive RA / ACPA-negative RA
Ca/Coa / ORb / 95% CIb / ORc / 95% CIc / Ca/Co / ORb / 95% CIb / ORc / 95% CIc / Ca/Co / ORb / 95% CIb / ORc / 95% CIc
Never-smokers / 401/806 / 1.0 / - / 1.0 / - / 242/806 / 1.0 / - / 1.0 / - / 159/806 / 1.0 / - / 1.0 / -
Ever-smokers / 37/40 / 2.3 / 1.2 – 4.4 / 2.4 / 1.3 – 4.5 / 27/40 / 3.4 / 1.6 – 7.2 / 3.4 / 1.6- 7.2 / 10/40 / 1.3 / 0.5 – 3.3 / 1.4 / 0.6 – 3.3
a A total of 61 controls and 23 cases lacked smoking information.
b OR and 95% CI for crude unconditionalanalyses (adjusted for age and sex).
c OR and 95% CI with additional adjustment for formal education and residential place.
Ca/Co number of cases and controls.
Table D Odd ratios (OR) with 95% confidence interval (95% CI) of developing ACPA-positive RA, ACPA-negative RA and overall RA for ever-smokers compared with never-smokers among Chinese.
Overall RA / ACPA-positive RA / ACPA-negative RA
Ca/Coa / ORb / 95% CIb / ORc / 95% CIc / Ca/Co / ORb / 95% CIb / ORc / 95% CIc / Ca/Co / ORb / 95% CIb / ORc / 95% CIc
Never-smokers / 182/162 / 1.0 / - / 1.0 / - / 113/162 / 1.0 / - / 1.0 / - / 69/162 / 1.0 / - / 1.0 / -
Ever-smokers / 22/13 / 1.7 / 0.7 – 4.2 / 1.8 / 0.7 – 4.5 / 18/13 / 2.5 / 1.0 – 6.3 / 2.4 / 0.9 – 6.1 / 4/13 / 0.7 / 0.2 – 2.9 / 0.8 / 0.2 – 3.2
a A total of 7 controls and 14 cases lacked smoking information.
b OR and 95% CI for crude unconditionalanalyses (adjusted for age and sex).
c OR and 95% CI with additional adjustment for formal education and residential place.
Ca/Co number of cases and controls.
Table E Odd ratios (OR) with 95% confidence interval (95% CI) of developing ACPA-positive RA, ACPA-negative RA and overall RA for ever-smokers compared with never-smokers among Indians.
Overall RA / ACPA-positive RA / ACPA-negative RA
Ca/Coa / ORb / 95% CIb / ORc / 95% CIc / Ca/Co / ORb / 95% CIb / ORc / 95% CIc / Ca/Co / ORb / 95% CIb / ORc / 95% CIc
Never-smokers / 299/230 / 1.0 / - / 1.0 / - / 195/230 / 1.0 / - / 1.0 / - / 104/230 / 1.0 / - / 1.0 / -
Ever-smokers / 14/7 / 2.7 / 0.9 – 7.9 / 2.7 / 0.9 – 8.2 / 14/7 / 4.7 / 1.5 – 14.4 / 4.8 / 1.5 – 15.3 / 0/7 / - / - / - / -
a A total of 15 controls and 11 cases lacked smoking information.
b OR and 95% CI for crude unconditionalanalyses (adjusted for age and sex).
c OR and 95% CI with additional adjustment for formal education and residential place.
Ca/Co number of cases and controls.
Table F Odd ratios (OR) with 95% confidence interval (95% CI) of developing ACPA-positive RA, ACPA-negative RA and overall RA for ever-smokers compared with never-smokers among men.
Overall RA / ACPA-positive RA / ACPA-negative RA
Ca/Coa / ORb / 95% CIb / ORc / 95% CIc / Ca/Co / ORb / 95% CIb / ORc / 95% CIc / Ca/Co / ORb / 95% CIb / ORc / 95% CIc
Never-smokers / 60/104 / 1.0 / - / 1.0 / - / 32/104 / 1.0 / - / 1.0 / - / 28/104 / 1.0 / - / 1.0 / -
Ever-smokers / 70/59 / 2.2 / 1.2 – 4.2 / 2.4 / 1.2 – 5.0 / 56/59 / 4.1 / 1.6 – 10.0 / 5.2 / 1.7 – 16.1 / 14/59 / 0.8 / 0.3 – 2.3 / 0.9 / 0.2 – 3.5
a A total of 50 controls and 19 cases lacked smoking information
b OR and 95% CI for crude matched analyses
c OR and 95% CI with additional adjustment for formal education and ethnicity
Ca/Co number of cases and controls
Table G Odd ratios (OR) with 95% confidence interval (95% CI) of developing ACPA-positive RA, ACPA-negative RA and overall RA for ever-smokers compared with never-smokers among women.
Overall RA / ACPA-positive RA / ACPA-negative RA
Ca/Coa / ORb / 95% CIb / ORc / 95% CIc / Ca/Co / ORb / 95% CIb / ORc / 95% CIc / Ca/Co / ORb / 95% CIb / ORc / 95% CIc
Never-smokers / 867/1156 / 1.0 / - / 1.0 / - / 545/1156 / 1.0 / - / 1.0 / - / 322/1156 / 1.0 / - / 1.0 / -
Ever-smokers / 9/6 / 2.2 / 0.7 – 6.9 / 1.9 / 0.6 – 6.1 / 8/6 / 5.3 / 1.1 – 26.0 / 3.6 / 0.7 – 18.4 / 1/6 / 0.4 / 0.04 – 3.8 / 0.5 / 0.05 – 4.7
a A total of 41 controls and 25 cases lacked smoking information
b OR and 95% CI for crude matched analyses
c OR and 95% CI with additional adjustment for formal education and ethnicity
Ca/Co number of cases and controls