Breastfeeding and genetic factors in the etiology of inflammatory bowel disease in children

Table 4 Factors affecting development of IBD

Factor	Effect	Findings
Cigarette smoking	Protective factor for UC	Pooled OR for UC = 0.41 (0.34-0.48); χ2 = 11.52 (P < 0.001)[12]
	Risk factor for CD	Pooled OR for CD = 2.0 (1.65-2.47); χ2 = 48.4 (P < 0.001)[12]
Passive cigarette smoke	Uncertain	No effect[2585]
		UC [ψ = 0.50 (0.25-1.00), n = 163][86]
		CD [ψ = 5.32 (1.09-25.9), n = 39 age and sex-matched pairs][87]
		UC [ψ = 2.19 (0.75-6.41), n = 33 age and sex-matched pairs][87]
Oral contraceptive use	Risk factor for UC	Pooled RR for UC = 1.29 [(0.94-1.77) adjusted for smoking]
		Pooled RR for UC = 1.68 [(0.97-2.88) unadjusted for smoking]
	Risk factor for CD	Pooled RR for CD = 1.44 [(1.12-1.86) adjusted for smoking]
		Pooled RR for CD = 1.68 [(0.97-2.88) unadjusted for smoking]
Diet	Protective factor for CD
	Vitamin C	ψ = 0.48 and ψ = 0.23 for medium and high intake, respectively, vs low intake, Ptrend = 0.02[17]
	Risk factors for UC
	Sucrose	[Sucrose] ψ = 2.05 and ψ = 4.22 for medium and high intake, respectively, vs low intake, Ptrend = 0.02
	Animal fat	[Animal fat] ψ = 2.02 and ψ = 4.09 for medium and high intake, respectively, vs low intake, Ptrend = 0.02
	Cholesterol	[Cholesterol] ψ = 2.14 and ψ = 4.57 for medium and high intake, respectively, vs low intake, Ptrend = 0.02
	Soft drinks	[Soft drinks] ψ = 1.84 and ψ = 3.39 for medium and high intake, respectively, vs low intake, vs Ptrend = 0.02[17]
Infections	Risk factor for CD/possible risk factor for UC	CD patients had a higher rate of gastroenteritis than did controls (6/57 vs 1/114, P = 0.005)[8]
		UC patients and controls did not differ (4/51 vs 1/102, P = NS)[8]
	Gastroenteritis	Children with CD were more likely than unaffected siblings to have had diarrheal illness [RR = 2.7 (95% CI 1.5-5.8) P < 0.02, n = 294] Children with UC were more likely than unaffected siblings to have had diarrheal illness [RR = 3.2 (95% CI 1.15-8.75), P = 0.03, n = 231][20]
	Diarrheal illness in infancy
	Risk factor for CD and UC	Recurrent respiratory infections were significantly more common in CD patients and in UC patients than their controls (102/298 vs 156/601 and 73/194 vs 106/393, respectively, both P < 0.01)[7]
	Recurrent respiratory infections	Adults with CD had an increased frequency of childhood infections compared to neighbor controls [ψ = 4.67, (95% CI 2.65-8.23) n = 322 cases, 262 controls][24]
	Childhood infections	Adults with UC had more frequent childhood infections than neighbor controls [ψ = 2.37 (95% CI 1.19-4.71) (n = 181 cases, 141 controls)][24]
Antibiotic use	Risk factor for CD	Patients with CD used antibiotics more frequently than controls (P < 0.01)[7]
		Adults with CD had more frequent treatment with antibiotics for both otitis [ψ = 2.07 (95% CI 1.03-4.14)] and pharyngitis [ψ = 2.14 (95% CI 1.20-3.84)] than controls[24]
Perinatal factors	Risk factor for UC
	Number of older siblings	For UC, the odds ratios for having one, two, and three or more older siblings were 1.08 (1.03-1.14), 1.09 (1.01-1.16), and 1.12 (1.02-1.23), respectively (n = 15823 cases; 79546 controls)[27]
	Protective factor for CD
	Number of younger siblings	For CD, the odds ratios for having one, two, and three or more younger siblings were 0.93 (0.88-0.99), 0.89 (0.82-0.96), and 0.83 (0.75-0.92), respectively (n = 12668 cases; 63035 controls)[27]