Cigarette smoking and smoking cessation in relation to risk of rheumatoid arthritis in women

Table 4 Relative risk of rheumatoid arthritis among former smokers by years since quitting and age at quitting cigarette smoking in the Swedish Mammography Cohort, 2003 to 2010

	Person-years¹	Cases, number¹	Age-adjusted relative risk	95% CI	Multivariable relative risk²	95% CI
Never smokers	137,162	79	1.00 (ref)		1.00 (ref)
Years since quitting
1-14	23,297	20	1.45	0.88, 2.38	1.50	0.68, 3.30
≥ 15 (median 24)	35,613	39	1.85	1.25, 2.73	1.99	1.23, 3.20
Age at quitting
≤ 41 (median 32)	31,164	31	1.68	1.09, 2.59	1.94	1.18, 3.18
> 41 (median 50)	27,747	28	1.70	1.11, 2.62	2.02	1.01, 4.07

¹ Numbers do not add up to the totals because of missing values. ²Adjusted for age (continuous), menopausal status (pre- or postmenopausal), parity (0, 1, 2, or ≥ 3 children), alcohol use(none, former, or current), educational level (lower than high school, high school, or university), body mass index (quartiles), and pack-years of smoking (continuous among former smokers). Ref, reference group.

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