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

Table 4 Environmental factors and course of inflammatory bowel disease

Author	Study setting	Effect on CD	Effect on UC
Ott et al[89], 2014, Germany	Cohort study	IR of EIM	NA
	CD - 161
	UC - 96
	Outcome - Smoking and EIM
Feagins et al[101], 2014, United States	Case-control study	NA with NSAID, antibiotics, stress, smoking, infection and travel in past 3 mo
	Active IBD - 166
	IBD in remission - 68
	Outcome - triggers for flare of IBD
Ananthakrishnan et al[97], 2013, United States	Multi-institutional cohort study, CD - 5405, UC - 5429	IR of surgery with psychiatric comorbidity	NA of surgery with psychiatric comorbidity
	Outcome - psychiatric comorbidity and surgery and hospitalisation in CD and UC
Bernstein et al[93], 2010, Canada	Population-based cohort	IR of flare - High perceived stress
	IBD - 704	NA with flare - NSAID, antibiotics, non-enteric infection
	Outcome - risk factors for flare
	Follow-up - 1 yr
Packer et al[110], 2010	Systematic review, 7 studies	Physical activity significantly increased quality of life and decreased disease activity
	Outcome - Physical activity and course of IBD
Bitton et al[95], 2008, Canada	Cohort study,	IR with stress/avoidance coping, higher CRP, fistulising disease behaviour, disease confined to the colon
	101 patients with CD in remission
	Outcome - biopsychosocial factors and relapse
	Follow-up - 1 yr
Takeuchi et al[25], 2006, United Kingdom	Case series	IR of flare with non-selective NSAID
	IBD - 209
	Outcome - risk of flare with NSAID
Sandborn et al[100], 2006, United States	RCT - Celecoxib vs placebo for 2 wk		No significant difference between celecoxib (3%) and placebo group (4%)
	UC - 222
	Outcome - exacerbation during 2 wk
Persoons et al[96], 2005, Belgium	Cohort study	Major depressive disorder associated with reduced response to infliximab
	CD - 100
	Outcome - major depressive disorder and response to infliximab
Cosnes et al[103], 1999, France	Cohort study	NA between OCP use and disease flare
	CD - 331
	Outcome - OCP and flare of CD
	Follow-up -12 to 18 mo
Cosnes et al[87], 1999, France	Cohort study	IR of flare - Current smokers
	CD - 622	NA with flare - Obesity, dyslipidemia and alcohol consumption
	Outcome - risk factors for flare of CD
	Follow-up -12 to 18 mo
Boyko et al[117], 1998, United States	UC - 209, compared smokers with non-smokers		DR of hospitalisation
	Outcome: Smoking and course of UC		NA with colectomy rates

IR: Increased risk; DR: Decreased risk; NA: No association; CD: Crohn’s disease; EIM: Extraintestinal manifestation; IBD: Inflammatory bowel disease; NSAID: Nonsteroidal anti-inflammatory drug; RCT: Randomised controlled trial, CRP: C reactive protein, OCP: Oral contraceptive pill.