The Association Between Inflammatory Bowel Disease and Exposure to Tobacco Smoking: A Case-Control Study in Qatar

Figures & data

Table 1 Comparison of Demographic Characteristics Between Ulcerative Colitis Cases and Controls

Factor	Level	UC Control	UC Cases	p-value
N		362	362
Age, median (IQR)		35.0 (28.0, 44.0)	35.0 (28.0, 44.0)	0.98
Gender	Male	134 (37.0%)	134 (37.0%)	1.00
	Female	228 (63.0%)	228 (63.0%)
Nationality	Qatari	292 (80.7%)	298 (82.8%)	0.46
	Non-Qatari	70 (19.3%)	62 (17.2%)
BMI, mean (SD)		30.1 (6.9)	28.9 (5.9)	0.009
Education	Primary & secondary	171 (47.2%)	207 (57.2%)	0.016
	Undergraduate	170 (47.0%)	143 (39.5%)
	Postgraduate	21 (5.8%)	12 (3.3%)
Employment	Employed	240 (66.3%)	247 (68.2%)	0.58
	Unemployed	122 (33.7%)	115 (31.8%)
Income	<10,000	84 (23.3%)	74 (20.4%)	0.48
	10,000–80,000	235 (65.1%)	246 (68.0%)
	>80,000	8 (2.2%)	13 (3.6%)
	Do not know	34 (9.4%)	29 (8.0%)
Hypertension	No	310 (86.1%)	328 (90.6%)	0.060
	Yes	50 (13.9%)	34 (9.4%)
Diabetes Mellitus	No	301 (83.6%)	322 (89.0%)	0.037
	Yes	59 (16.4%)	40 (11.0%)
Hypercholesterolemia	No	278 (77.2%)	291 (80.4%)	0.30
	Yes	82 (22.8%)	71 (19.6%)

Table 2 Comparison of Demographic Characteristics Between Crohn’s Disease Cases and Controls

Factor	Level	CD Control	CD Cases	p-value
N		89	89
Age, median (IQR)		37.0 (29.0, 47.0)	37.0 (29.0, 47.0)	1.00
Gender	Male	49 (55%)	49 (55%)	1.00
	Female	40 (45%)	40 (45%)
Nationality	Qatari	71 (80%)	74 (83%)	0.56
	Non-Qatari	18 (20%)	15 (17%)
BMI, mean (SD)		32.0 (6.9)	28.5 (5.3)	<0.001
Education	Primary & secondary	40 (45%)	41 (47%)	0.70
	Undergraduate	41 (46%)	42 (48%)
	Postgraduate	8 (9%)	5 (6%)
Employment	Employed	63 (71%)	64 (73%)	0.77
	Unemployed	26 (29%)	24 (27%)
Income	<10,000	26 (29%)	16 (18%)	0.18
	10,000–80,000	56 (63%)	59 (66%)
	>80,000	2 (2%)	3 (3%)
	Do not know	5 (6%)	11 (12%)
Hypertension	No	74 (83%)	80 (90%)	0.19
	Yes	15 (17%)	9 (10%)
Diabetes Mellitus	No	75 (84%)	80 (90%)	0.26
	Yes	14 (16%)	9 (10%)
Hypercholesterolemia	No	62 (70%)	70 (79%)	0.17
	Yes	27 (30%)	19 (21%)

Table 3 Association Between Smoking Exposure and Ulcerative Colitis

Factor	Level	UC Controls, n (%)	UC Cases, n (%)	Univariable Analysis OR (95% CI)	p-value	Multivariable Analysis OR (95% CI)^a	p-value
Childhood Passive Smoking	No	198 (54.8%)	194 (53.6%)	Base	Base	Base	Base
	Yes	126 (34.9%)	113 (31.2%)	0.91 (0.65–1.27)	0.578	0.86 (0.61–1.20)	0.371
Adulthood Smoking	Never	268 (74.9%)	263 (72.7%)	Base	Base	Base	Base
	Former	27 (7.5%)	26 (7.2%)	1.00 (0.57–1.78)	0.987	0.98 (0.55–1.74)	0.932
	Current	63 (17.6%)	73 (20.2%)	1.19 (0.80–1.76)	0.387	1.13 (0.75–1.69)	0.557
Ever Smoked	No	268 (74.9%)	263 (72.7%)	Base	Base	Base	Base
	Yes	90 (25.1%)	99 (27.3%)	1.13 (0.80–1.60)	0.480	1.10 (0.78–1.56)	0.590

Note: ^aAdjusted for nationality and income.

Abbreviation: UC, Ulcerative colitis.

Figure 1 Comparison of proportions of smoking exposure between Ulcerative colitis cases and controls.

Table 4 Association Between Smoking Exposure and Crohn’s Disease

Factor	Level	CD Cases, n (%)	CD Controls, n (%)	Univariable Analysis OR (95% CI)	p-value	Multivariable Analysis OR (95% CI)^a	p-value
Childhood Passive Smoking	No	49 (55%)	46 (52%)	Base	Base	Base	Base
	Yes	25 (28%)	30 (34%)	1.23 (0.66–2.30)	0.517	1.18 (0.59–2.36)	0.641
Adulthood Smoking	Never	69 (79%)	67 (75%)	Base	Base	Base	Base
	Former	10 (11%)	8 (9%)	0.78 (0.27–2.25)	0.642	0.99 (0.30–3.24)	0.981
	Current	8 (9%)	14 (16%)	1.69 (0.67–4.31)	0.269	2.51 (0.85–7. 37)	0.095
Ever Smoked	No	69 (79%)	67 (75%)	Base	Base	Base	Base
	Yes	18 (21%)	22 (25%)	1.21 (0.60–2.46)	0.591	1.33 (0.63–2.83)	0.453

Note: ^aAdjusted for nationality, income, and education.

Abbreviation: CD, Crohn’s disease.

Figure 2 Comparison of proportions of smoking status between Crohn’s disease cases and controls.