Smoking increases the risk of extraintestinal manifestations in Crohn's disease

Table 4 Univariate analysis and logistic regression model (outcome variable = extraintestinal manifestation during observation period) for Crohn's disease n (%)

Variable	Category (n)	With EIM	Univariate analysis		Logistic regression analysis
			P value	RR (95%CI)	P value	RR (95%CI)
Surgery	Yes (27)	19 (70.4)	0.015	2.93 (1.20-7.16)	0.015	3.19 (1.26-8.02)
	No (134)	60 (44.8)
Smoking	Yes (55)	33 (60.0)	0.046	1.96 (1.01-3.74)	0.023	2.36 (1.13-4.93)
	No (106)	46 (43.4)
Age	≤ 40 yr (126)	62 (49.2)	0.026	2.40 (1.01-5.23)	0.011	2.94 (1.28-6.76)
	> 40 yr (35)	22 (62.9)
Family history	Yes (35)	20 (57.1)	0.510	1.29 (0.61-2.75)	0.260	1.59 (0.71-3.55)
	No (126)	64 (50.8)
Sex	Female (90)	46 (51.1)	0.870	0.9 (0.49-1.69)	0.070	0.52 (0.25-1.05)
	Male (71)	38 (53.3)

EIM: Extraintestinal manifestation.