Skip to main content

Table 2 Characteristics of case–control studies for ulcerative colitis and Crohn’s disease studies

From: The relationship between urban environment and the inflammatory bowel diseases: a systematic review and meta-analysis

Study characteristics and demographics

Study quality characteristics

Author (year)

Country

No. of cases

No. of controls

Source of controls

Controls matched for:

Methods of diagnosis defined

Diagnosis based on recognized criteria

Urban/rural defined

Urban population >10,000

Time of exposure

Multiple levels of exposure

Ulcerative Colitis

Parrello 1997[26]

Italy

509

657

Attending orthopedic and surgical clinics

Sex, age, year of diagnosis

Yes

Yes

No

No

Time of data collection

No

Feeney 2002[17]

UK

137

137

Functional GI Disorders

Sex, age

Yes

Yes

No

No

Childhood (age 0–5)

No

Bernstein 2007[27]

Canada

137

310

Manitoba Health Population Registry

Sex, age

No

N/A

No

No

N/A

No

Jiang 2007[28]

China

177

177

Neighbours or colleagues

Sex, age

Yes

Yes

No

No

Childhood

No

Radon 2007[54]

Germany

304

1481

Strabismus surgery

Age

No

N/A

No

No

Time of data collection

No

Martinez Salmeron 1994[46]

Spain

63

63

Hospital

Sex, age

Yes

Yes

Yes

No

Time of data collection

No

Ekbom 1990[8]

Sweden

164

328

Live births between 1924–1957 in Uppsala County

Date of birth, sex, and maternal age or parity

Yes

Yes

Yes

No

Time of birth

No

Crohn’s Disease

Feeney 2002[17]

UK

139

139

Functional GI disorders

Sex, age

Yes

Yes

No

No

Childhood (age 0–5)

No

Bernstein 2007[27]

Canada

235

310

Manitoba Health Population Registry

Sex, age

No

N/A

No

No

N/A

No

Ponsonby 2009[53]

Australia

278

998321

Live births from 1983–1998 in Victoria

Age

Yes

No

Yes

No

Childhood (age 0–6)

No

Malekzadeh 2009[16]

Iran

196

207

IBS treated by an expert gastroenterologist

Age

Yes

Yes

No

No

Childhood (before 16th birthday)

No

Radon 2007[54]

Germany

444

1481

Strabismus surgery

Age

No

N/A

No

No

Time of data collection

No

Thompson 1998[29]

England, Wales

291

1682

Same GP

Sex, age

No

N/A

No

No

N/A

No

Wurzelmann 1994[13]

United States

322

262

Closest neighbour

Sex, age, race

No

N/A

No

No

Childhood (age 0–5)

Yes

Martinez Salmeron 1994[46]

Spain

30

30

Hospital

Sex, age

Yes

Yes

Yes

No

Time of data collection

No

Ekbom 1990[8]

Sweden

93

186

Live births between 1924–1957 in Uppsala County

Date of birth, sex, and maternal age or parity

Yes

Yes

Yes

No

Time of birth

No