Table 1 Study and patient characteristics

Zamir (1998) [7]

Israel

Case control

Pediatric rheumatology clinic

JRA: 16

12 (4)

69

Olig: 4

4.5 (3.4)

Controls: 9

Poly: 12

Bloom (2002) [25]

USA

Case control

Hasbro Children's Hospital, Pediatric Rheumatology Clinic

JRA: 25

8.7

80

Syst: 5

3.1 (range: 0.2-5.5 )

Controls: 45

Range: 6-12

Olig: 9

Poly: 11

Palermo (2005) [26]

USA

Cross- sectional

Outpatient pediatric rheumatology clinics (NS)

JIA: 20

NR

67

Syst: 2

4.49 (NR)

Olig: 5

Poly: 7

ERA: 2

NS: 4

Passarelli (2006) [27]

Brazil

Case-control

NR

JRA: 21

13 (2)

57

Syst: 9

NR

Controls: 20

Poly: 12

Long (2008) [1]

USA

Cross sectional

Four clinical sites during specialty care visits (NS)

JIA: 30

Range: 8-12

56

Syst: 3

NR

Olig:21

Poly: 6

Ward (2008) [3]

USA

Cross sectional

Children's Hospital and Regional Medical Centre- Paediatric Rheumatology Clinic

JRA: 70

8.5 (1.9)

84

Syst: 4

Inactive JRA: 3.8 (1.7)

Olig: 26

Poly: 40

Active JRA: 3.4 (3.0)

Ward (2010) [28]

USA

Cross sectional

Seattle Children's Hospital and University of Washington School of Nursing sleep laboratory

JIA: 69

8.5 (1.9)

84

Sys: 3

NR

Olig: 26

Poly: 40

Butbul Aviel (2011) [29]

Canada

Cross sectional

The Hospital for Sick Children

JIA: 92

12.7 (0.4)

66

Syst: 28

NR

Olig: 31

Poly: 33

Ward (2011) [30]

USA

Case control

Seattle Children's Hospital Paediatric Rheumatology Clinic

JIA: 70

8.5 (1.9)

76

Sys: 4

NR

Controls: 46

Olig: 26

Poly: 40

Bromberg (2012) [31]

USA

Cohort

Pediatric Rheumatology Clinic

JIA: 51

12.4 (2.8)

65

Poly: 51

NR