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Table 1 Summary of studies included in the present study

From: Body mass index and the risk of rheumatoid arthritis: a systematic review and dose-response meta-analysis

Author

Year

Country

Study design

Gender (RA/control)

Age (years)

Assessment of BMI

Sample size (RA/control)

Diagnosis criteria

Rates of obesity (RA/control)

BMI categories

Adjustment for covariates

Voigt et al. [21]

1994

USA

Case-Control Study

Female

18-64

Self-reported

349/1,456

Diagnostic Criteria 1958e

29.5%/24.8%

12.94-20.43,

Age, smoking status

Female

20.44-22.51,

22.52-25.82,

25.83-52.86

Symmons et al. [22]

1997

UK

Case-Control Study

Mixed

18-70

Self-reported

90/93

ACR 1987f

17.6%/7.7%

<20, 20-24.9, 25-29.9, >30

Smoking status, social class

Mixed

Uhlig et al. [12]

1999

Norway

Case-Control Study

Mixed

20-79

Self-reported

347/5,725

ACR 1987

7.8%/4.6%

<25, 25-29.9, >30

Age, sex, marital status, employment category, formal education, current smoking status

Mixed

Pedersen et al. [23]

2006

Denmark

Case-Control Study

Mixedb

18-65

Self-reported

505/752

ACR 1987

9.3%/6.8%

<18.5, 18.5-25, 25-30, >30

Birth year, year of RA diagnosis, gender

Mixed

Rodriguez et al. [13]

2009

UK

Case-Control Study

Mixed

20-79

Medical Examination

559/4,234

NA

12.1%/12.5%

<20, 20-24.9, 25-30, >30

Age, gender, referrals, smoking status, alcohol consumption, pregnancy status

Mixed

Wesley et al. [14]

2013

Sweden

Case-Control Study

Mixed Mixed

18-70

Self-reported

2,748/3,444

ACR 1987

13.7%/13.0%

<25, 25-30, >30

Smoking status, alcohol consumption, education level, menopausal status, physical activity, parity, fatty fish consumption

Crowson et al. [24]

2013

USA

Case-Control Study

Mixed

55.9 ± 15.7

Medical Examination

813/813

ACR 1987

40.3%/35.7%

<30, >30

Age, gender, smoking status

Mixed

Cerhan et al. [11]

2002

USA

Cohort Study

Female Female

55-69

Self-reported

31,336c

ACR 1987

25.9%d

<23.4, 23.4-25.8, 25.9-29.2, >29.2

Age

Lu et al.a [27]

2014

USA

Cohort Study

Female

25-55

Medical Examination

218,623

ACR 1987

27.8%d

18.5-24.9, 25-29.9, >30

Age, community median income, smoking status, alcohol consumption, physical activity, parity, breastfeeding status, postmenopausal use Postmenopausal Hormone use.

Female

Harpsoe et al. [26]

2014

Denmark

Cohort Study

Female

27.4- 33.3

Self-reported

75,088

ICD Code

-

<18.5,18.5-25, 25-30, >30

Smoking status, alcohol consumption, parity, socio-occupational status

Female

Lahiri et al. [25]

2014

UK

Cohort Study

Mixed Mixed

40-79

Self-reported

25,271

ACR1987

-

<25, 25-30, >30

Age, gender, smoking status, breastfeeding status, alcohol consumption

  1. aTwo cohorts (NHS1 and NHS2) was included in this study. bThe studies reported the association of BMI and RA risk in both female and male population. cThe total sample size in the cohort studies. dThe prevalence rate of obesity in RA patients. The prevalence rate of obesity in non-RA individuals were not available. eDiagnostic Criteria is a revised version of criteria for rheumatoid arthritis published in 1958 [42]. fACR1987 is the American College of Rheumatology criteria for rheumatoid arthritis published in 1987 [28]. BMI: body mass index; ICD: International Classification of Diseases [43]; NA: No stated; RA: rheumatoid arthritis.