Table 1.

Studies of smoking behaviour and appendectomy and the risk of developing ulcerative colitis (UC) or primary sclerosing cholangitis (PSC)

Study	Country	Disease	No of patients (n)	OR* of current smoker having UC/PSC	OR* of former smokers having UC/PSC	OR† of developing UC/PSC after appendectomy
Tobin 19879	UK	UC	280	0.2	1.1‡
Boyko 198710	USA	UC	212	0.6	1.9
Lindberg 198811	Sweden	UC	260	0.6	2.1
Nakamura 199413	Japan	UC	384	0.3	1.67
Rutgeerts 199417	Belgium	UC	174			0.02
Silverstein 199412	USA	UC	100	0.13	1.2‡
Smithson 199518	UK	UC	197			0.2
Loftus 199628	USA	PSC	184	0.13	0.62‡
Van Erpecum 199627	Netherlands	PSC	59	0.37	0.92‡	1.44‡
		UC	130	0.23	2.86	0.64‡
Minocha 199720	USA	UC	193			0.25
Parrello 199719	Italy	UC	536			0.3
Russel 199721	Netherlands	UC	232	0.5		0.36
Duggan 199822	UK	UC	213			0.2
Dijkstra 199923	New Zealand	UC	75			0.32
Koutroubakis 199924	Greece	UC	134			0.6‡
Reif 200047	Israel	UC	273	0.5	1.2‡
Naganuma 200126	Japan	UC	325			0.35
Reif 200136	Israel	UC	271			0.7‡

*Odds ratio of current/former smokers having the disease (UC or PSC) relative to never smokers.

†Odds ratio of patients following appendectomy having the disease (UC or PSC) relative to patients with an appendix in situ.

‡Result is not significant, otherwise all other results are significant (p<0.05).