Influence of environmental factors on the onset and course of inflammatory bowel disease

Table 3 Environmental factors and onset of inflammatory bowel disease - case control studies

Author	Study setting	Effect on CD	Effect on UC
Ng et al[51], 2014, Asia Pacific	CD - 186	DR with breast feeding for > 12 mo, antibiotic use, having dogs, daily tea intake, daily physical activity	DR with breast feeding for > 12 mo, antibiotic use, daily tea and coffee intake, presence of hot water tap, flushing toilet in childhood
	UC - 256		IR with smoking
	Controls - 940
	Outcome - environmental risk factors and IBD
Sood et al[64], 2014, India	UC- 518		IR with owning a pet and stressful events
	Controls - 188		DR with better toilet facilities and having private bed
	Outcome - environmental risk factors and UC
Chu et al[62], 2013, South Africa	CD - 88	DR - Helminth infection, shared housing, raw beef consumption	DR - Helminth infection, mixed race, smoking, shared housing, raw beef consumption
	UC - 63	IR - Urban dwelling, parental tertiary education	IR -parental tertiary education
	Control - 219
	Outcome - childhood risk factors and IBD
Jakobsen et al[114], 2013, Denmark	CD - 59	IR with bedroom sharing, prior hospitalisation with gastrointestinal infection, family history	IR with prior hospitalisation with gastrointestinal infection, family history
	UC - 56	DR with wholemeal bread consumption	DR with daily vegetable consumption
	Controls - 477 Outcome - environmental risk factors and pediatric IBD
Hlavaty et al[52], 2013, Slovakia	CD - 190	IR with short duration of breast feeding, infrequent childhood sports activity, smoking, infrequent contact with animals in childhood	IR with short duration of breast feeding, infrequent childhood sports activity, smaller family size in childhood
	UC - 148
	Controls - 355
	Outcome - environmental risk factors and IBD
Pugazhendhi et al[45], 2012, India	CD - 200	IR with safe drinking water
	Controls - 200 Outcome - environmental risk factors and CD	DR with regular fish consumption and presence of cattle in house
Castiglione et al[115], 2012, Italy	CD - 468	NA with any factors except IR with smoking and appendectomy	NA with any factors except DR with smoking and appendectomy
	UC - 527
	Controls - 562
	Outcome - environmental risk factors and CD
Hansen et al[44], 2011, Denmark	CD - 123	DR with breast feeding, tonsillectomy,	DR with breast feeding, tonsillectomy, appendectomy, smoking
	UC - 144		IR with pertussis and polio vaccine, measles infection, low fibre and high sugar
	Controls - 267
	Outcome - environmental risk factors and IBD	IR with pertussis and polio vaccine, measles infection, smoking, low fibre and high sugar
López-Serrano et al[61], 2010, Spain	124 CD and 235 controls	IR - Living in urban area, high educational level, social status	IR - Living in urban area, high educational level, social status
	146 UC and 278 controls	DR - Childhood respiratory infection and gastroenteritis	DR - Childhood respiratory infection and gastroenteritis, appendectomy, current smoking
	Outcome - onset of IBD
Gearry et al[39], 2010, New Zealand	Population-based case-control study	IR with smoking, high social class at birth, Caucasian ethnicity	IR with high social class at birth, Caucasian ethnicity, migrant
	CD - 638, UC - 653, Controls - 600 Outcome - risk factors and IBD	DR with breastfeeding and childhood vegetable garden	DR with smoking, breast feeding and childhood vegetable garden
Joseph et al[28], 2009, India	CD - 34	IR - lower levels of Vitamin D
	Controls - 34
	Outcome - vitamin D and CD
Amre et al[32], 2007, Canada	CD - 130	DR - higher consumption of vegetables, fruit, fibre, fish, long chain omega three fatty acid
	Controls - 202
	Outcome - diet and pediatric CD
Baron et al[116], 2005, France	CD - 222	IR - Family history, Breast feeding, BCG vaccination, history of eczema	IR - Family history, disease during pregnancy, bedroom sharing
	UC - 60	DR - Regular drinking of tap water	DR- Appendectomy
	Matched controls
	Outcome - pediatric onset IBD

IR: Increased risk; DR: Decreased risk; NA: No association; CD: Crohn’s disease; UC: Ulcerative colitis; RR: Relative risk; IBD: Inflammatory bowel disease.